JP2006261801A - Multiband compatible microstrip antenna, and module and system employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small antenna structure capable of improving an isolation characteristic of a switch and suppressing reflection in a switch section in a multiband compatible antenna adapted to a plurality of frequency bands. <P>SOLUTION: A rectangular feeding element 13 arranged on the top surface of a first dielectric 10 and rectangular parasitic elements 12 surrounding the feeding element 13 are arranged in a matrix. First switches 11 each connect the feeding element 13 and each of parasitic elements 12 and the adjacent parasitic elements 12 to form a rectangular radiation element. The first switch 11 has an insulating film 24 for covering the end of the adjacent feeding element 13 or the parasitic element 12. A movable electrode 17 held in the air is provided on the insulating film 24, and the adjacent feeding element 13 and the parasitic element 12 and the movable electrode 17 can apply DC biases. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a small antenna and a small wireless module and a system that can support a plurality of frequency standards, and more particularly to a multiband antenna, a small wireless module, and a small wireless system in which rectangular parasitic elements surrounding a feeding element are arranged in a matrix. It is about.

Conventionally, PDC, FOMA, CDMA2000, PHS, etc. for mobile phones, IEEE802.11a, 802.11b, 802.11g, Bluetooth, etc. for wireless LAN, ITS GPS, VICS, ETC etc. In the future, it is expected that an environment in which multiple frequencies coexist will continue.
In conventional wireless communication, a single-frequency antenna is used, and a wireless device corresponding to a plurality of frequencies needs to be provided with a plurality of antennas, which has been increased in size. In addition, the area where radio waves can be transmitted and received satisfactorily on the surface of the wireless device is limited, and there is a limit to installing all antennas in a favorable radio wave environment. Thus, in recent years, multi-frequency (multi-band) compatible antennas that can handle a plurality of frequencies with one antenna have attracted attention.

As a conventional example of a multiband antenna, one has a structure in which a radiation element corresponding to a plurality of frequencies is provided in the antenna. For example, as a structure using a plurality of radiating elements with different resonance lengths, “Design and measurement results of a three-frequency resonant antenna with a multilayer plate configuration (Technical Report of IEICE, AP2002-141, p41-46, 2003)” (See Non-Patent Document 1), “Multifrequency Microstrip Patch Antenna Using Multiple Stacked Elements (IEEE Microwave and Wireless Components Letters, vol. 13, No. 3, p123-124, 2003)” (see Non-Patent Document 2), “ This is disclosed in a study of a dual-frequency microstrip antenna configuration method (2003 IEICE Communication Society Conference, Lecture No. B-1-161) (see Non-Patent Document 3).
However, the above antenna has a structure in which a plurality of antennas are arranged in one place, and since the area where radio waves can be transmitted and received satisfactorily on the surface of the wireless device is limited, it is difficult to transmit and receive all desired radio waves satisfactorily. there were.

In addition, a structure in which one radiating element has a plurality of resonance lengths has been proposed. For example, “A study on radiation characteristics of a modified Sirpinski-type microstrip antenna (2003 IEICE Communication Society Conference, Lecture) No. B-1-162) (see Non-Patent Document 4), “Dual Frequency Slot Bowtie Antenna (2003 IEICE Communication Society Conference, Lecture No. B-1-176)” (see Non-Patent Document 5), etc. There is.
However, the modified Sirpinski-type microstrip antenna has a problem in that the radiation pattern is different in the three bands, and three frequencies cannot be transmitted and received in the same area under the same conditions. In addition, it seems that the dual-frequency slot bow tie antenna can only handle up to about three frequencies.
Therefore, a method of switching the resonance length of the antenna with a switch has been proposed. For example, JP-A-2000-236209 (see Patent Document 1), JP-A-2002-261533 (see Patent Document 2), JP-A-2003-124730 (see Patent Document 3), and US Patent 6198438 ( Patent Document 4).

  In Japanese Patent Laid-Open No. 2000-236209, as shown in FIG. 13, a metal piece 56 is connected by a PIN diode 57 to form a dipole antenna. A bias is applied to the PIN diode 57 to switch the conduction / cutoff of the PIN diode 57 to change the resonance length. The dipole antenna used in JP 2000-236209 needs to be excited with a balanced current. However, the line used in the RF circuit often uses an unbalanced current such as a microstrip line or a coplanar line. When the balanced current 58 is required, a balun must be provided between the antenna and the line. In general, since the balun has a narrow band, it cannot cope with a plurality of frequencies, and one balun is required for each frequency. Therefore, in order to support multiband, it is necessary to arrange baluns in the vicinity of the feeding point of the dipole antenna by the number of multibands, and the number of multibands is limited by the installation area of the baluns. Therefore, the one described in Japanese Patent Laid-Open No. 2000-236209 can be used when there are few frequency bands such as a dual band, but it cannot be applied to multibands with many frequency bands.

  Next, as described in JP 2002-261533 A, as shown in FIG. 14, an antenna element 18A is provided with one feeding point 19A and a plurality of grounding points 20a, b, c, d. The resonance length is changed by switching 20a-d with the switches 21a, b, c, d. However, in Japanese Patent Laid-Open No. 2002-261533, since the short-circuit point is switched by the switches 21a-d, the input impedance of the antenna changes at each frequency. Therefore, the ground point can be moved only within the matching range, and it seems that the frequency range that can be varied in multiband cannot be increased. Actually, the variable frequency band disclosed in JP-A-2002-261533 is 1.55 to 2.2 GHz, which is as small as 30% with respect to the center frequency of 1.8 GHz. Therefore, it is possible to cope with the case of using a relatively close frequency band such as a mobile phone, but it is not possible to cope with the case of using the 2.4 GHz band and the 5 GHz band like a wireless LAN.

  As disclosed in Japanese Patent Laid-Open No. 2003-124730, as shown in FIGS. 15 (a) and 15 (b), the three radiating elements 102, 103, and 105 share a short-circuit point with a feed point 106-111 that can be switched. Four frequency bands are realized by switching the feeding point 106-111 and the short-circuit point by SW180 and SW182. However, in Japanese Patent Laid-Open No. 2003-124730, it is necessary to arrange the three radiating elements 102-103 on the same plane, and the area where radio waves can be transmitted and received satisfactorily on the surface of the wireless device is limited. It is difficult to transmit / receive data well.

As shown in FIG. 16, the element described in US Pat. No. 6198438 has a structure in which element elements arranged in a matrix are connected by MEMS switches. When all the MEMS switches are turned off (shut off state), one side of each element element has a resonance length and corresponds to a high frequency. On the other hand, when all the MEMS switches are turned on (conductive state), the individual element elements are connected to form one rectangular radiating element and resonate at a low frequency.
The US patent 6198438 does not describe the details of the MEMS switch for connecting the element elements, so the operation of the US patent 6198438 will be described by taking a general MEMS switch structure (see FIG. 17) as an example.
A lead 201 is provided on each side of the element element 203, and a MEMS switch 202 is provided between the leads 201 of the adjacent element elements 203. The MEMS switch 202 includes a lead 201 of an element element 203 provided on a substrate 213, a fixed electrode 212, and a movable electrode provided thereon, and the movable electrode is held in the air by a hinge 205. A contact electrode 204 and an upper electrode 206 are formed on the movable electrode and separated by an insulating layer 207.

  When the MEMS switch 202 is turned ON, a reverse polarity bias is applied to the upper electrode 206 and the fixed electrode 212 to generate an electrostatic attractive force between the electrodes, and the movable electrode is driven downward to contact the contact electrode 204 and the element element 203. The lead 201 is brought into contact. As a result, the leads 201 of the adjacent element elements 203 are electrically connected via the contact electrode 204, and the adjacent element elements 203 are connected. On the other hand, when the MEMS switch 202 is turned off, if the bias of the upper electrode 206 and the fixed electrode 212 is cut off to eliminate the electrostatic attractive force, the movable electrode returns upward due to the rigidity of the hinge 205, and the contact electrode 204 and the element element 203 The lead 201 is blocked. For this reason, the leads 201 of the adjacent element elements 203 are blocked, and the element elements 203 are cut off.

  In the above structure, it is necessary to arrange the lead 201 and the fixed electrode 212 for driving the movable electrode (generating the electrostatic attraction with the upper electrode 206) between the adjacent element elements 203. For this reason, the adjacent element elements 203 cannot be connected over the entire surface of the opposing sides, and the element elements 203 are connected by leads 201 having a narrow line width. As a result, when all the MEMS switches 202 are turned on to form one rectangular radiating element, a large gap is generated inside the radiating element. The current flowing through the radiating element is limited by the air gap, and there is a problem that the bandwidth is reduced when operating at a low frequency. When the number of MEMS switches 202 is extremely large, a bandwidth necessary for communication cannot be secured if operated at a low frequency, and there is a problem that the number of multibands is limited.

  In order not to reduce the bandwidth, it is desirable that adjacent element elements 203 are conductive on the entire surface of the opposing sides. For example, a MEMS switch 202 using a movable electrode in which an upper electrode 206 and a contact electrode 204 are stacked can be considered (see FIG. 18). In the MEMS switch 202 of FIG. 18, only the fixed electrode 212 is provided between adjacent element elements 203, and a movable electrode in which an upper electrode 206 and a contact electrode 204 are stacked is provided above the fixed electrode 212 by a hinge 205. The structure is supported in the air. The width of the contact electrode 204 is almost the same as the side of the element element 203. The upper electrode 206 and the contact electrode 204 are insulated by an insulating layer not shown.

  When the MEMS switch 202 is turned ON, a reverse polarity bias is applied to the upper electrode 206 and the fixed electrode 212 to generate an electrostatic attractive force between the electrodes, and the movable electrode is moved downward to move the contact electrode 204 and the element element 203. Make contact. Since the width of the contact electrode 204 is substantially equal to one side of the element element 203, when the MEMS switch 202 is turned on, the adjacent element element 203 is connected to the entire surface of the opposite side via the contact electrode 204. It becomes. On the other hand, when the MEMS switch 202 is turned off, when the bias of the upper electrode 206 and the fixed electrode 212 is cut off to eliminate the electrostatic attraction, the movable electrode returns upward due to the rigidity of the hinge 205, and the contact electrode 204 and the element element 203 are The element elements 203 adjacent to each other are cut off and put into a cut-off state.

In the above structure, the adjacent element elements 203 can be connected over the entire surface of the opposite sides. Therefore, even when all the MEMS switches 202 are turned on to form one rectangular radiating element, the inside of the radiating element There are no large voids. Therefore, the current flowing through the radiating element is not limited by the air gap, and the bandwidth is unlikely to decrease even when operated at a low frequency.
However, in the above structure, the fixed electrode 212 is disposed between the adjacent element elements 203, and the sides of the fixed electrode 212 are close to each other over the entire length of the element element 203. There is a relatively large parasitic capacitance Cp between them. For this reason, even when the MEMS switch 202 is turned off, the RF signal leaks due to Cp between the element element 203 and the fixed electrode 212, and it is difficult to obtain sufficient isolation characteristics.

In the state where the MEMS switch 202 is turned on, the contact electrode 204 also functions as a part of the radiating element, but in the region of the contact electrode 204, the fixed electrode 212 and the upper electrode 206 act as a ground plane. Usually, a thin insulating film of several μm or less is formed between the contact electrode 204 and the upper electrode 206, and the contact electrode 204 and the fixed electrode 212 are also very close to each other. The effective dielectric constant and the dielectric thickness of the element greatly differ from the effective dielectric constant and thickness of the substrate on which the element element 203 is formed, and a large reflection loss occurs in the MEMS switch 202 portion.
In order to suppress reflection loss, it is conceivable that the upper electrode 206 and the contact electrode 204 are integrated and a ground plane provided at the lower part of the substrate is used as the fixed electrode 212. Is about 0.5 to 2 mm, and a very large DC bias is required to generate an electrostatic attractive force for moving the movable electrode between the upper electrode 206 and the fixed electrode 212. In a practical voltage range, the MEMS switch 202 Cannot be turned ON / OFF.

Furthermore, US patent 6198438 uses different feed points for high and low frequencies to match the characteristic impedance of the line (usually 50Ω). Therefore, there is a drawback that the number of multibands that can be handled is limited by the number of feeding points that can be arranged in the array antenna arranged in a matrix.
Further, there is a drawback that it is difficult to provide a feeding point on the MEMS switch 202. In the example of FIG. 16, a feeding point that resonates with one element element 203 (High frequency feed point) and a feeding point that resonates with a 3 × 3 array (Low frequency feed point) can be arranged on the element element, but 2 × If you want to resonate the two arrays, the feed point comes on the MEMS switch, so even if you use a 3x3 array, you can only handle two frequencies.

  On the other hand, the present applicant has made a proposal regarding a tapered slot antenna. (For example, JP-A-10-13141 (see Patent Document 5), JP-A-10-13143 (see Patent Document 6), JP-A-10-173432 (see Patent Document 7), JP-A-11-163626 (See Patent Document 8). The tapered slot antenna has a constant input impedance over a wide band, and is classified into a wide band antenna. Although transmission / reception is possible in a relatively wide frequency band, the bandwidth is limited, and is generally used in a frequency band several times higher.

JP 2000-236209 A JP 2002-261533 A Japanese Patent Laid-Open No. 2003-124730 US Patent 6198438 Japanese Patent Laid-Open No. 10-13141 Japanese Patent Laid-Open No. 10-13143 Japanese Patent Laid-Open No. 10-173432 JP-A-11-163626

"Design and measurement results of multi-frequency resonant antenna with multi-layer plate configuration (Technical Report of IEICE, AP2002-141, p41-46,2003)", `` Multifrequency Microstrip Patch Antenna Using Multiple Stacked Elements (IEEE Microwave and Wireless Components Letters, vol.13, No.3, p123-124, 2003) '', "A study on a dual-frequency microstrip antenna configuration method (2003 IEICE Communication Society Conference, Lecture No. B-1-161)" "A Study on Radiation Characteristics of Modified Sirpinski Type Microstrip Antenna (2003 IEICE Communication Society Conference, Lecture No. B-1-162)" “Dual Frequency Slot Bowtie Antenna (2003 IEICE Communication Society Conference, Lecture Number B-1-176)

  As mentioned above, various multi-frequency antennas have been proposed in the past, but most of them can be used when there are few frequency bands such as dual bands, but many are not compatible with multi-bands with many frequency bands, In addition, the matrix antenna also has a drawback that the number of multibands that can be handled is limited by the number of feed points that can be arranged in the array antenna arranged in a matrix. In the case of a tapered slot antenna, transmission / reception is possible in a relatively wide frequency band, but the bandwidth is limited.

(the purpose)
An object of the present invention is to eliminate the above-described conventional problems. That is,
The purpose of claims 1 and 2 is to form a radiating element by connecting a plurality of elements (feeding element, parasitic element) by a switch, and in a multiband antenna corresponding to a plurality of frequency bands, the isolation characteristics of the switch And providing a small antenna structure that can suppress reflection at the switch portion.
The purpose of claims 3 and 4 is to provide a control method for using the multiband microstrip antenna according to claims 1 and 2 in a plurality of frequency bands.
The purpose of claims 5 and 6 is to provide a multiband-compatible antenna structure capable of good transmission and reception in a plurality of frequency bands in an antenna having one feeding point in addition to the objects of claims 1 and 2. is there.

Further, the purpose of claims 7 and 8 is to provide a structure capable of improving the bandwidth when the antenna is used at a low frequency or a medium frequency in the multiband antennas according to claims 1, 2, 5, and 6. It is.
An object of claim 9 is to provide a structure capable of realizing directivity control in the multiband antenna according to claims 1, 2, 5 to 8.
An object of claim 10 is to provide an inexpensive and small-sized wireless module structure capable of supporting a plurality of frequency standards.
An object of claim 11 is to provide an inexpensive and small-sized radio system structure capable of supporting a plurality of frequency standards.

The features of the multiband microstrip antenna of the present invention are as follows.
In the multiband-compatible microstrip antenna according to claim 1, a rectangular feeding element and a rectangular parasitic element surrounding the feeding element are arranged in a matrix on the upper surface of the first dielectric, and the feeding element and the parasitic element, and Adjacent parasitic elements are connected by a first switch to form a rectangular radiating element, and the first switch covers the end of an adjacent element (feed element or parasitic element). And there is a movable electrode held in the air on the insulating film, and the adjacent element (feeding element or parasitic element) and the movable electrode have a structure to which a DC bias can be applied. Yes.
In the multiband microstrip antenna according to claim 2, the adjacent element (feeding element or parasitic element), a structure that can apply a DC bias provided to the movable electrode includes a via hole and an inductor, and the inductor is It has an inductance that is almost insulative at the frequency used in a multi-band microstrip antenna.

In the control method of the multiband microstrip antenna according to claim 3, when the first switch is turned on, an element (feeding element or parasitic element) adjacent to the first switch and a movable electrode Since a reverse polarity DC bias is applied, the movable electrode and the element are reversed in polarity, an electrostatic attractive force is generated between the element and the movable electrode, and the movable electrode is deformed to cover the end portion of the element. Contact.
5. The method for controlling a multi-band microstrip antenna according to claim 4, wherein when the first switch is turned on, an element (feeding element or parasitic element) adjacent to the first switch and a movable electrode Since 0V is applied to one side and a positive or negative DC bias is applied to the other side, a large potential difference occurs between the movable electrode and the element, an electrostatic attractive force is generated between the element and the movable electrode, and the movable electrode is deformed. Contact with the insulating film covering the element end.

The multiband microstrip antenna according to claim 5 is provided with a matching circuit connected to the feeding point by a changeover switch. Therefore, when the antenna of the present invention is used at two frequencies, a high frequency and a low frequency, matching can be realized at both frequencies and good transmission / reception can be performed.
For example, if the position of the feed point is set so that the antenna input impedance matches the output impedance of the RF circuit when all the first switches are in the OFF state and are compatible with high frequencies, all the first switches are in the ON state. The constant of the matching circuit is set in advance so that the input impedance of the antenna when the element is connected to become low frequency compatible is matched with the output impedance of the RF circuit by the matching circuit.

In the multiband microstrip antenna according to claim 6, a matching circuit capable of changing a constant is provided at a feeding point of the feeding element.
In the multiband-compatible microstrip antenna according to claim 7, the first switch is configured to be connected over almost the entire surface of the adjacent element (feeding element or parasitic element) facing each other. Therefore, when a rectangular radiating element is formed by connecting a feeding element and a parasitic element by a combination of ON / OFF of the first switch, the gap surrounded by the four first switches generated inside the radiating element is Get smaller.
9. The multiband microstrip antenna according to claim 8, wherein the first switch extends in a V-shape at the tip portion facing the other first switch, and the interval between the four first switches facing each other. Is X-shaped.

In the multiband microstrip antenna according to claim 9, at least a part of the parasitic element is provided with a second switch that is short-circuited to the ground plane by capacitive coupling.
Consider a case in which all the first switches are turned OFF and only the power feeding element is operated.
When the feed element and the parasitic element are close to each other, a large mutual coupling occurs between the feed element and the parasitic element, and the parasitic element receives the polarized wave radiated from the feed element and has the same resonance frequency as that of the feed element. This produces a polarized wave.
Here, if only the second switch connected to the parasitic element in the + X direction with respect to the feeding element among the plurality of parasitic elements is turned OFF and the other second switch is turned ON, Only certain parasitic elements are opened to the ground plane, and other parasitic elements are short-circuited to the ground plane. Since the parasitic element short-circuited with the ground plane has a smaller voltage excited by mutual coupling with the feeder element, the radiation pattern is mainly determined by the feeder element and the parasitic element on the + X side. It begins to lean in the direction.

Since the radio module of claim 10 uses any of the multiband-compatible microstrip antennas of claims 1, 2, 5 to 9, one radio module can support a plurality of frequency standards.
The radio system according to claim 11 uses the radio module according to claim 10.

According to the present invention, the following effects can be obtained.
(Claim 1)
When a DC bias is applied so that the element (feeding element, parasitic element) and the movable electrode have the same potential, no electrostatic attractive force is generated between the element (feeding element and parasitic element) and the movable electrode. For this reason, the movable electrode is disposed with an air gap maintained between the movable film and the insulating film, and the power feeding element and the parasitic element are cut off. Similarly, when all the first switches are in the OFF state, the feed element is separated from all the parasitic elements, and the antenna operates only with the feed element, corresponding to the high frequency.

On the other hand, when a reverse polarity potential or OV and positive / negative DC bias are applied to the element (feeding element, parasitic element) and the movable electrode, electrostatic attraction is generated between the element (feeding element and parasitic element) and the movable electrode. And the movable electrode is deformed to come into contact with the insulating film and the air gap disappears. As a result, the movable electrode and the element are brought into conduction by capacitive coupling, and the adjacent elements (feeding element and parasitic element) are connected via the first switch. Similarly, when all the first switches are turned on, all the feeding elements and the parasitic elements are connected to form one rectangular radiating element, which can cope with a low frequency.
Further, when only a part of the first switches are turned on and the feed element and a part of the parasitic element are connected to form a rectangular radiating element, it is possible to operate at an intermediate frequency.
As described above, when the structure of claim 1 is adopted, it is possible to cope with multiband by combining ON / OFF of the first switch.

Further, in the structure of claim 1, since there is no fixed electrode between adjacent elements (feeding element or parasitic element), the parasitic capacitance Cp can be sufficiently reduced by separating the adjacent elements to some extent, which is seen in the conventional MEMS. The leakage of the RF signal through the fixed electrode can be suppressed. As a result, it is possible to improve the isolation characteristics of the switch that connects the feed element and the parasitic element (that is, the first switch), reduce the loss when the first switch is all turned off and operated at high frequency, and receive When used as an antenna, large received power is obtained, and when used as a transmit antenna, large transmitted power is obtained.
Furthermore, when the first switch is turned on and the movable electrode also functions as a part of the radiating element, the member corresponding to the dielectric with respect to the movable electrode is the first substrate and the insulating film, but the insulating film is Since it is very thin with respect to the first substrate, the effective dielectric constant and thickness of the dielectric in the region of the first switch are almost the same as the effective dielectric constant and thickness of the substrate on which the feed element or parasitic element is formed. This is the same, and reflection at the first switch portion can be suppressed.

(Claim 2)
According to claim 2, a DC bias can be applied to the element (feeding element, parasitic element) and the movable electrode via the inductor and the via hole, but the RF signal is blocked by the inductor. As a result, since no RF signal is input to the control circuit to which the inductor is connected, it is difficult for the control circuit to malfunction, and the ON / OFF malfunction of the first switch can be suppressed.

(Claims 3 and 4)
According to the third and fourth aspects, since the element and the movable electrode are brought into conduction by capacitive coupling, the elements can be conducted through the first switch.
(Claim 5)
For high-frequency support (when the first switch is turned off and only the feed element operates), when the changeover switch is set so that the RF circuit and the antenna are directly connected, the antenna input impedance matches the output impedance of the RF circuit, so reflection occurs. Can be suppressed. On the other hand, in the case of low frequency support (one radiating element is formed with all the first switches in the ON state), if the changeover switch is set so that the matching circuit is inserted between the RF circuit and the antenna, the antenna Since the input impedance is matched to the output impedance of the RF circuit by the matching circuit, reflection can be suppressed even for low frequencies.
As described above, when the structure of the present invention is employed, even when a single feeding point is used, matching can be performed at both low and high frequencies, and satisfactory transmission and reception at two frequencies can be realized.

(Claim 6)
According to claim 6, when a plurality of rectangular radiating elements having different excitation lengths are formed by connecting a feeding element and a parasitic element by a combination of ON / OFF of the first switch, the matching circuit constant is appropriately set. Therefore, the input impedance of each radiating element can be matched with the output impedance of the RF circuit, reflection can be suppressed in all frequency bands, and good transmission / reception can be performed.
As a result, more frequency bands than the antenna of claim 5 can be supported.
(Claim 7)
According to claim 7, the current flowing through the radiating element is less likely to be limited by the air gap, and the rectangular element is formed by connecting the feeding element and the parasitic element by the first switch rather than the antenna of claims 1, 2, 5, and 6. The bandwidth when the radiating element is formed can be improved.

(Claim 8)
According to claim 8, when a rectangular radiating element is formed by connecting a feeding element and a parasitic element by a combination of ON / OFF of the first switch, four first switches generated inside the radiating element There are almost no voids surrounded by. Therefore, the current flowing through the radiating element is more difficult to be limited, and the bandwidth when the rectangular radiating element is formed by connecting the feeding element and the parasitic element by the first switch than the antenna of claim 7 can be improved. .

(Claim 9)
According to claim 9, when all the first switches are turned off and operated with only the feed element (high frequency support), the radiation pattern is tilted from the zenith by the combination of ON / OFF of the second switches. And directivity control can be realized.
In addition, when the first switch is turned on and off, the feed element and some parasitic elements are connected to form a rectangular radiating element to support intermediate frequencies. By connecting the elements to each other to form a parasitic element having the same excitation length as the rectangular radiating element, and turning on / off the second switch connected to the parasitic element, it is possible to cope with medium frequencies. Directivity control is also possible.
As a result, the gain can be increased with respect to the direction of the desired wave, and better transmission / reception can be performed.

(Claim 10)
According to claim 10, the cost of the wireless module can be reduced. Further, when the antenna of claim 9 is used, a large gain can be realized by directing the maximum radiation angle of the antenna in the direction of the desired wave, and further satisfactory transmission / reception can be performed. Furthermore, since the antennas of claims 1, 2, 5 to 9 have a microstrip antenna structure and a planar structure, the radio module can be miniaturized.
(Claim 11)
According to the eleventh aspect, a single radio system can cope with a plurality of frequency standards, and the cost of the radio system can be reduced. In addition, when the wireless module using the antenna of claim 9 is used, a large gain can be realized by directing the maximum radiation angle of the antenna in the direction of the desired wave, so that even better transmission / reception can be performed. In addition, since the antenna of the present invention is a microstrip antenna and has a planar structure, the radio system is also small.

Embodiments of the present invention will be described below in detail with reference to the drawings.
(Example 1)
FIGS. 1A and 1B are structural views of a multiband microstrip antenna according to Embodiment 1 of the present invention. (a) is a top view and (b) is a cross-sectional view.
The multiband microstrip antenna of Example 1 supports two frequencies of 17 GHz and 63 GHz, and a ground plane made of Cu on the lower surface of the first substrate 10 made of a quartz substrate having a relative dielectric constant of 3.9 and a thickness of 525 μm. 25 is formed, and an insulating layer 26 made of SiO 2 is formed under the base plate 25. Further, on the upper surface of the first substrate 10, one rectangular feed element 13 made of an Au / Cu pattern and eight rectangular parasitic elements 12 surrounding the feed element 13 are arranged in a matrix. The sizes of the feed element 13 and the parasitic element 12 are the same, and the length in the excitation direction (Y direction) is L1, and the length in the direction orthogonal to the excitation direction (X direction) is W1, L1 = W1 = 1.1mm.

In addition, the feed element 13 and the parasitic element 12, and the adjacent parasitic element 12 can be connected by the first switch 11. When all the switches are turned on, the excitation length is L3. A rectangular radiating element is formed. The first switch 11 has a movable electrode made of Au / Cu whose end of an adjacent element (feeding element 13 or parasitic element 12) is covered with SiO2 and held in the air on the insulating film 26. 17 is provided. Note that the width of the movable electrode 17 (the length in the short direction) overlaps with the end of the element (feeding element 13 or parasitic element 12) adjacent to the first switch 11.
Further, the element adjacent to the first switch 11 (feed element 13 or parasitic element 12) and the movable electrode 17 are provided with via holes (via hole 14 of the movable electrode 17, via hole 16 of the elements 12, 13), The via holes 14 and 16 are connected to an inductor (see FIG. 2) formed on an insulating layer 26 under the ground plane 25, and are movable with an element adjacent to the first switch 11 by a control circuit (see FIG. 2). Each electrode 17 has a structure in which a different DC bias can be applied.

FIG. 2 is a diagram illustrating details of a first switch provided between the power feeding element and the parasitic element in FIG.
End portions of the feeding element 13 and the parasitic element 12 are covered with an insulating film 19 (thickness 0.3 μm) made of SiO 2, and the insulating film 19 is also formed between the elements. At both ends of the insulating film 19, a quadrangular columnar movable electrode support portion 18 made of Si3N4 (thickness 3um) is provided, and a movable electrode made of Au / Cu is formed on the insulating film 19 through a 3um air gap. It has a structure that holds 17 in the air.
The movable electrode 17 is connected to a via hole having a diameter of 50 μm (via hole 14 of the movable electrode) penetrating the movable electrode support 18, the insulating film 19, the first substrate 10, and the insulating layer 26. The via hole 14 is a meander. A DC bias is applied to the movable electrode 17 by a control circuit 30 connected to an inductor 29 composed of a line. The inductor 29 connected to the via hole 14 of the movable electrode 17 has an inductance that is substantially insulative in the frequency bands (17 GHz and 63 GHz) used in the antenna of the first embodiment.

Also, the feed element 13 and the parasitic element 12 are connected to a via hole having a diameter of 50 μm (element via hole 16) penetrating the first substrate 10 and the insulating layer 26, and the via hole 16 is connected to an inductor 29 formed of a meander line. The DC bias is applied to the feeding element 13 and the parasitic element 12 by the control circuit 30. The inductor 29 has a shape having an inductance that is substantially insulative in the frequency bands (17 GHz and 63 GHz) used in the antenna of the first embodiment.
FIG. 3 is an explanatory diagram illustrating an example of ON / OFF operation of the first switch.
In order to turn off the first switch 11, the control circuit 30 applies OV to the feeding element 13 and the parasitic element 12 via the inductor 29 and the via hole, and applies 0V to the movable electrode 17. As a result, the elements (feed element 13 and parasitic element 12) and the movable electrode 17 are at the same potential, and no electrostatic attractive force is generated. As a result, the movable electrode 21 is disposed with the air gap of 3 μm between the movable film 21 and the insulating film 24, and the feeding element 13 and the parasitic element 12 are cut off. Similarly, when all the first switches are turned off, the feed element 13 is separated from all the parasitic elements 12, and the multiband-compatible microstrip antenna of the first embodiment operates with only the feed element 13. As a result, the resonance length is L1, and high frequency (63 GHz) can be supported.

On the other hand, in order to turn on the first switch 11, the control circuit 30 applies + 15V to the feeding element 13 and the parasitic element 12 via the inductor 29 and the via holes 14 and 16, and the movable electrode 17 Apply -15V. As a result, the elements (feed element 13 and parasitic element 12) and the movable electrode 17 are reversed in polarity and electrostatic attraction is generated, and the movable electrode 17 is deformed into a concave shape at the center in the longitudinal direction and contacts the insulating film 19. Air gap disappears. Here, since the width of the movable electrode 17 overlaps the end portions of the feeding element 13 and the parasitic element 12, the movable electrode 17 and the elements 12, 13 are electrically connected by capacitive coupling. As a result, adjacent elements (feed element 13 and parasitic element 12) are connected via the first switch 11. Similarly, when all the first switches 11 are turned on, the feed element 13 and the parasitic element 12 are all connected to form one rectangular radiating element. The strip antenna has a resonance length of L3 and can handle low frequencies (17 GHz).
As described above, when the structure of the first embodiment is adopted, two frequencies can be handled by the combination of ON / OFF of the first switch 11.

  Further, the ON / OFF ratio of the first switch 11 of Example 1 was about 40, and a good ON / OFF ratio was obtained at both 17 GHz and 63 GHz. In the first switch 11 of the first embodiment, there is no fixed electrode between adjacent elements (feeding element 13 or parasitic element 12), and the elements (feeding element 13, parasitic element 12) themselves are used as fixed electrodes. Therefore, the parasitic capacitance Cp can be sufficiently reduced by separating the adjacent elements to some extent, and the leakage of the RF signal through the fixed electrode as seen in the conventional MEMS switch (see FIG. 18) can be suppressed. As a result, the isolation characteristics of the switch connecting the feed element 13 and the parasitic element 12 (that is, the first switch 11) are improved, and even when the first switch 11 is all turned off and operated at a high frequency, the loss is reduced. When it is used as a receiving antenna, a large received power can be obtained, and when used as a transmitting antenna, a large transmitted power can be obtained.

Further, when the first switch 11 is turned on and the movable electrode 21 functions as a part of the radiating element, the members corresponding to the dielectric with respect to the movable electrode 21 are the first substrate 10 and the insulating film 19. However, since the insulating film 19 is very thin with respect to the first substrate 10, only the first substrate 10 may be considered as a dielectric. Therefore, in the ON state, the effective dielectric constant and thickness of the dielectric in the region of the first switch 11 are substantially the same as the effective dielectric constant and thickness of the substrate on which the feed element 13 or the parasitic element 12 is formed. Reflection at the part of the switch 11 can be suppressed.
In addition, the inductor 29 connected to the via holes 14 and 16 used in the first embodiment shows almost insulation at the frequency used in the antenna of the first embodiment. A DC bias can be applied to the movable electrode 17, but the RF signal is blocked by the inductor 29. Therefore, since no RF signal is input to the control circuit 30 to which the inductor 29 is connected, malfunction does not easily occur in the control circuit 30, and ON / OFF of the first switch 11 can be executed in accordance with instructions of an arithmetic circuit such as a CPU. .

  In the first embodiment, a reverse polarity DC bias is applied to the elements 12, 13 and the movable electrode 17 in order to turn on the first switch 11, but 0V is applied to one electrode and the other electrode is applied. Alternatively, a positive or negative DC bias may be applied to the device to bring the drive electrode into contact with an insulating film covering the end portion of the device by electrostatic attraction between the drive electrode and the device, and the devices may be electrically connected by capacitive coupling. For example, when OV is applied to the feeding element 13 and the parasitic element 12 and +30 V is applied to the movable electrode 21, an equivalent electrostatic attractive force is generated between the element (the feeding element 13 and the parasitic element 12) and the movable electrode 21. Therefore, the movable electrode 21 is deformed into a concave shape at the center in the longitudinal direction so that the movable electrode 21 comes into contact with the insulating film 24 and there is no air gap. Similarly, the ON operation is possible even when −3 OV is applied to the feeding element 13 and the parasitic element 12 and 0 V is applied to the movable electrode 21.

(Example 2)
FIG. 4 is a structural diagram of the multiband-compatible microstrip antenna according to the second embodiment of the present invention.
The multiband-compatible microstrip antenna according to the second embodiment is provided with a matching circuit 22 connected to the feeding point 15 of the antenna according to the first embodiment by a changeover switch 23. The matching circuit 22 is a π-type matching circuit using capacitors, inductors and capacitors (C, L, C) by stubs.
The antenna of Example 1 can support high frequency (63 GHz) and low frequency (17 GHz) by the combination of ON / OFF of the first switch 11, but since the feeding point 15 is one place, it can be used only in one band. Matching cannot be achieved, and a large reflection loss occurs in the other band. In the second embodiment, since the matching circuit 22 connected to the feeding point 15 by the changeover switch 23 is provided, matching can be realized at both high frequency and low frequency.

For example, if the position of the feeding point 15 is set so that the input impedance of the antenna when the first switch 11 is all in the OFF state and is 63 GHz compatible, the output impedance of the RF circuit 36 matches, The input impedance of the antenna when the L and C constants are adapted to low frequency (all the first switch 11 is turned on) is set in advance so as to match the output impedance of the RF circuit 36.
For 63 GHz support (when the first switch 11 is all OFF and only the feed element 13 operates), when the changeover switch 23 is set so that the RF circuit 36 and the antenna are directly connected, the input impedance of the antenna of the second embodiment is RF Since it matches the output impedance of the circuit 36, reflection can be suppressed.
On the other hand, in the case of 17 GHz support (all the first switch 11 is turned on to form one radiating element), setting the changeover switch 23 so that the matching circuit 22 is inserted between the RF circuit 36 and the antenna. Since the input impedance of the antenna is matched to the output impedance of the RF circuit 36 by the matching circuit 22 of the second embodiment, reflection can be suppressed even for low frequencies.

As described above, when the structure of Example 2 is adopted, even when the number of feeding points 15 is one, matching is possible at both low frequency (17 GHz) and high frequency (63 GHz), and good transmission and reception at two frequencies is possible. It becomes possible.
In the second embodiment, a π-type matching circuit is used. However, as a matching circuit 22 that can be used in the present invention, a lumped constant element of a capacitor or an inductor is configured in an L type, a π type, or a T type when the frequency is relatively low. A circuit can be used, and in the case of high frequency, a circuit in which distributed constant circuits such as stubs are configured in L-type, π-type, and T-type, or a λ / 4 transformer can be used. Further, the matching circuit 22 may be configured by a phase shifter and a capacitor, and a generally known matching circuit 22 may be used in accordance with the resonance frequency of the antenna.

(Example 3)
FIG. 5 is a structural diagram of a multiband-compatible microstrip antenna according to Example 3 of the present invention.
The antenna according to the third embodiment corresponds to three frequencies (17 GHz, 28 GHz, and 63 GHz) and can be matched in all frequency bands.
The multiband microstrip antenna of the third embodiment is an antenna provided with a matching circuit 35 whose constant can be varied at the feeding point 15 of the antenna of the first embodiment, and the matching circuit 35 includes a variable phase shifter and a varactor diode. Has been.
When all the first switches 11 are turned off, only the feed element 13 operates. If the radiating element at that time is radiating element A (region surrounded by a dotted line in the drawing) 32, the radiating element A resonance length corresponds to 63 GHz at L1.

When a rectangular radiating element B (region surrounded by a one-dot chain line in the figure) 33 is formed by connecting a 3 × 2 element array including the feeding element 13 by a combination of ON / OFF of the first switch 11, The resonance length is L2, and the resonance frequency is 28 GHz. When all the first switches 11 are turned on, the 3 × 3 element array is connected to form a rectangular radiating element C (a region surrounded by a two-dot chain line in the drawing) 34. The resonance length of the radiating element C is L3, and the resonance frequency is 17 GHz.
In the third embodiment, since the constants of the variable phase shifter and the varactor diode constituting the matching circuit 35 can be made variable, even when the radiating elements A to C are formed by the combination of ON / OFF of the first switch 11, By appropriately selecting the constants of the variable phase shifter and the varactor diode, the input impedance of each radiating element can be matched with the output impedance of the RF circuit 36, reflection can be suppressed at three frequencies, and good transmission and reception can be performed.

As described above, when the structure of the third embodiment is adopted, more frequency bands can be accommodated than the antenna of the second embodiment. In the third embodiment, since a 3 × 3 element array is used, it corresponds to three frequencies, but more parasitic elements 12 are arranged around the feeding element 13, and the first switch 11 feeds the feeding elements 13, The structure that can connect the parasitic element 12 can realize a multi-band antenna that can handle more frequency bands, and the number of frequencies that can be supported is limited by the number of feeding points 15 as in US Patent No. 6198438. There is nothing.
In the third embodiment, the matching circuit 35 is configured by a variable phase shifter and a varactor diode. However, as an element capable of changing a constant, a variable capacitor and a variable inductor by MEMS have been intensively studied in recent years. If the variable range of the MEMS-based variable capacitor and variable inductor satisfies the range required for the matching circuit, the variable capacitor and variable inductor can also be used in the matching circuit 35 of the present invention.

(Example 4)
The multiband microstrip antenna of the fourth embodiment has the same structure as that of the third embodiment, and the first switch 11 is connected to almost the entire side of the adjacent element (feeding element 13 or parasitic element 12) facing each other. The antenna has a structure that can be used.
The multi-strip microstrip antenna of Example 4 supports three frequencies of 18 GHz, 29 GHz, and 63 GHz, and Cu is formed on the lower surface of the first substrate 10 made of a quartz substrate having a relative dielectric constant of 3.9 and a thickness of 525 μm. A base plate 25 is formed, and an insulating layer 26 made of SiO 2 is formed under the base plate 25.
Further, on the upper surface of the first substrate 10, one rectangular feed element 13 made of an Au / Cu pattern and eight rectangular parasitic elements 12 surrounding the feed element 13 are arranged in a matrix. The sizes of the feed element 13 and the parasitic element 12 are the same, the length (L1) in the excitation direction is 1.1 mm, and the length (W1) in the direction orthogonal to the excitation direction is also 1.1 mm.

The feed element 13 and the parasitic element 12, and the adjacent parasitic element 12 are connected by the first switch 11, and the first switch 11 is connected to the adjacent element (feed element 13 or parasitic element 12). ) Is covered with SiO 2, and a movable electrode 17 made of Au / Cu held in the air is provided on the insulating film 24. The width (length in the short direction) of the movable electrode 17 overlaps the end of the element (feeding element 13 or parasitic element 12) adjacent to the first switch 11.
In addition, via holes 14 and 16 are provided in the element (feed element 13 or parasitic element 12) adjacent to the first switch 11 and the movable electrode 17, and the via hole 14 is an insulating layer under the ground plane 25. It is connected to a spiral inductor 29 formed on 26, and has a structure in which a separate DC bias can be applied to the element adjacent to the first switch 11 and the movable electrode 17 by the control circuit 30.
In addition, a matching circuit composed of a variable phase shifter and a varactor diode is connected to the feed point, and matching of all three frequencies is possible by appropriately selecting constants of the variable phase shifter and the varactor diode.

FIG. 6 is a detailed structural diagram of the first switch according to Embodiment 4 of the present invention.
End portions of the feeding element 13 and the parasitic element 12 are covered with an insulating film 24 (thickness 0.3 μm) made of SiO 2, and the insulating film 24 is also formed between the elements 12 and 13. At both ends of the insulating film 24, a quadrangular columnar movable electrode support portion 18 made of Si3N4 (thickness 3 um) is provided, and a movable electrode 17 made of Au / Cu is formed on the insulating film 24 through a 3 um air gap. Is held in the air. Here, the overlapping area of the movable electrode 31 and the element is 5 × 1100 μm, which is the same length as one side of the adjacent elements 12 and 13.
Further, the movable electrode 17, the feeding element 13, and the parasitic element 12 are connected to via holes having a diameter of 50um (the movable electrode via hole 16 and the element via hole 14), and the via holes 14 and 16 are connected to the spiral inductor 29, The control circuit 30 applies a DC bias to the movable electrode 17 and the elements 12 and 13. The spiral inductor 29 has an inductance value that is substantially insulative in the frequency bands (18 GHz, 29 GHz, 63 GHz) used in the antenna of the fourth embodiment.

The control circuit 30 applies +15 V to the feeding element 13 and the parasitic element 12 and applies -15 V to the movable electrode 17. As a result, the elements (feed element 13 and parasitic element 12) and the movable electrode 17 are reversed in polarity and electrostatic attraction is generated, and the movable electrode 17 is deformed into a concave shape in the center in the longitudinal direction and contacts the insulating film 24. Air gap disappears. Here, since the overlapping length of the element adjacent to the movable electrode 17 is equal to the length of one side of the element, the movable electrode 31 and the elements 12, 13 are electrically connected to all of the element sides by capacitive coupling. Adjacent elements 12 and 13 are connected to almost the entire surface of the opposing sides via the first switch 11.
As a result, the antenna of the fourth embodiment is compatible with low frequencies (3 × 3 elements are connected by the first switch 11, the resonance frequency is 18 GHz), or is compatible with medium frequencies (3 × 2 elements are connected by the first switch). When the resonance frequency is 29 GHz), the gap surrounded by the four first switches generated inside the rectangular radiating element formed by the connected elements is smaller than that of the third embodiment. Therefore, the current flowing through the rectangular radiating element formed by ON / OFF of the first switch 11 is less likely to be limited by the air gap inside the radiating element, and the bandwidth in the lower frequency band and the middle frequency band than in Example 3. Can be improved.

(Example 5)
FIG. 7 is a structural diagram of the multiband-compatible microstrip antenna according to the fifth embodiment of the present invention.
The multiband microstrip antenna according to the fifth embodiment is an antenna obtained by further improving the fourth embodiment. The first switch 11 extends the shape of the tip portion facing the other first switch 11 into a V-shape. In addition, the interval between the four first switches 11 facing each other is X-shaped.
The ends of the feed element 13 and the parasitic element 12 are covered with an insulating film 24 made of SiO2. At both ends of the insulating film 24, a quadrangular columnar movable electrode support portion 20 made of Si3N4 is provided, and the movable electrode 17 made of Au / Cu is held in the air via an air gap of 3um on the insulating film 24. is doing. Here, in the movable electrode 17, the shape of the tip portion facing the other first switch is extended in a V shape, and the interval between the four first switches facing each other is an X shape.

  When + 15V is applied to the feeding element 13 and the parasitic element 12 by the control circuit 30 and -15V is applied to the movable electrode 17, the elements (feeding element 13 and parasitic element 12) and the movable electrode 17 are reversed in polarity and static. An electric attractive force is generated, and the movable electrode 17 is deformed into a concave shape at the center in the longitudinal direction, and comes into contact with the insulating film 24 to eliminate an air gap. Here, the shape of the tip of the movable electrode 17 facing the other first switch 11 is extended in a V shape, and the interval between the four first switches 11 facing each other is an X shape. Therefore, a space surrounded by the four first switches 11 hardly occurs in the rectangular radiating element formed by the ON / OFF combination of the first switches 11. As a result, the antenna of the fifth embodiment is compatible with low frequencies (3 × 3 elements are connected by the first switch 11, the resonance frequency is 18 GHz), and is compatible with medium frequencies (3 × 2 elements are connected by the first switch 11; When used at a resonance frequency of 29 GHz, the current flowing in the rectangular radiating element is further limited by the air gap, and the bandwidths in the low frequency band and the medium frequency band can be further improved as compared with the fourth embodiment.

(Example 6)
FIGS. 8A and 8B are structural views of a multiband-compatible microstrip antenna according to Example 6 of the present invention. (a) is a top view and (b) is a cross-sectional view.
In the six antennas of the present embodiment, in addition to the structure of the third embodiment, each parasitic element 12 is provided with a second switch 21 that is short-circuited to the ground plane 25 by capacitive coupling.
Explaining the structure of the antenna, a ground plate 25 made of Cu is formed on the lower surface of the first substrate 10 made of a quartz substrate having a relative dielectric constant of 3.9 and a thickness of 525 um, and an insulating layer made of SiO2 is formed under the ground plate 25 26 is formed. Further, on the upper surface of the first substrate 10, one rectangular feed element 13 made of an Au / Cu pattern and eight rectangular parasitic elements 12 surrounding the feed element 13 are arranged in a matrix. The sizes of the feed element 13 and the parasitic element 12 are the same, and both the excitation direction (L1) and the direction (W1) orthogonal to the excitation direction are 1.1 mm. The pitch between the feeding element 13 and the parasitic element 12 is 0.40λo at a wavelength λo corresponding to 63 GHz.
In addition, a matching circuit (not shown) composed of a variable phase shifter and a varactor diode is provided at the feed point 15 of the feed element 13, and by appropriately selecting constants of the variable phase shifter and the varactor diode, Matching can be achieved at all three frequencies (17, 28, 63 GHz).

Adjacent elements (feeding element 13 or parasitic element 12) can be connected by the first switch 11, and when all the first switches 11 are OFF, the resonance length is L1. When a 3 × 2 element array is connected including the power feeding element 13 by the ON / OFF combination of the element A and the first switch 11, the rectangular radiating element B having a resonance length of L2 and all the first switches 11 are When the 3 × 3 element array is turned on and connected, a rectangular radiating element C having a resonance length of L3 is formed.
As in Example 3, the first switch 11 has the end portions of adjacent elements covered with an insulating film A24 made of SiO2, and on the insulating film A24, two quadrangular columnar movable electrodes made of Si3N4 There is a support portion A (not shown), and both ends of the movable electrode A17 made of Au / Cu are held in the air. The width (length in the short direction) of the movable electrode A17 overlaps the end of the element adjacent to the first switch 11.

The element adjacent to the first switch 11 and the movable electrode A17 are provided with via holes (the via hole 14 of the movable electrode A, the via hole 16 of the element), and the via holes 14 and 16 are insulated as in the third embodiment. A DC bias is applied to the element adjacent to the first switch 11 and the movable electrode A17 by a control circuit (not shown) connected to an inductor (not shown) made of meander lines formed on the layer 26. It has a structure that can be done. Note that the inductor has an inductance value substantially showing insulation in the frequency bands (17 GHz, 28 GHz, 63 GHz) used in the antenna of the sixth embodiment.
Further, the parasitic element 12 is provided with a second switch 21 that is short-circuited to the ground plane 25.

FIG. 9 is a detailed structural diagram of the second switch 21. (a) is a front view, (b) is an AA ′ sectional view, and (c) is a BB ′ sectional view.
The second switch 21 includes a fixed electrode B46 made of Au / Cu formed on the insulating layer 26, a lead B42 connected to the parasitic element 12 by a via hole 44 of the second switch, and a via hole of the second switch. From the lead B42 connected to the ground plane 25 by 44, the insulating film B24 made of SiO2 covering the ends of the leads B42 and B, and the movable electrode B17 held on the insulating film B24 through a 2 um air gap It is configured. The movable electrode B17 has a contact electrode B41 and an upper electrode B45 connected via an insulating layer B24, and is held in the air by a hinge B47.

Here, the contact electrode B41 is formed so as to overlap the leads B42 and B′43.
In addition, the upper electrode B45 and the fixed electrode B46 of the movable electrode B17 are disposed so as to face each other, so that different DC biases can be applied by different DC bias lines (not shown).
Next, the operation of turning on / off the second switch 21 will be described.
When + 15V is applied to the upper electrode B45 and -15V is applied to the fixed electrode B46, the upper electrode B45 and the fixed electrode B46 have opposite polarities, and electrostatic attraction is generated. As a result, the hinge B47 is deformed, the contact electrode B41 contacts the insulating film B24, and the air gap disappears. Here, since the contact electrode B41 and the leads B42 and B′43 overlap, they are conducted by capacitive coupling. Therefore, the parasitic element 12 connected to the lead B42 is short-circuited by the capacitive coupling with the ground plane 25 connected to the lead B42. On the other hand, if 0V is applied to the upper electrode B45 and 0V is applied to the fixed electrode B46, there is no potential difference between the upper electrode B45 and the fixed electrode B46, and no electrostatic attractive force is generated between the upper electrode B45 and the fixed electrode B46. As a result, the movable electrode returns to the original state, a 2 um air gap is generated between the contact electrode B41 and the insulating film B24, the second switch 21 is turned OFF, and the parasitic element 12 connected to the lead B42 is connected to the lead B42. It becomes an open state with the ground plate 25.
Since the second switch 21 is turned ON / OFF by capacitive coupling through the insulating film B24, a DC bias (no charge) for turning ON / OFF the first switch 11 supplied to the parasitic element 13 is used. The DC bias (which is supplied to the parasitic element 12 through the via hole 14 of the feeding element) is not affected.

Here, it is considered that all the first switches 11 are turned OFF and operated only by the power feeding element A13. Since the feed element 13 and the parasitic element 12 are arranged at 0.40λo, a large mutual coupling occurs between the feed element 13 and the parasitic element 12, and the parasitic element 12 is radiated from the feed element 13 in the Y direction. Upon receiving the linearly polarized wave, it is excited in the Y direction, and a linearly polarized wave in the Y direction having the same resonance frequency as that of the feed element 13 is generated. When the pitch between the feeding element 13 and the parasitic element 12 is 0.40λo, the voltage of the parasitic element 13 is delayed in phase from the voltage of the feeding element 13, and the parasitic element 12 acts as a waveguide.
Here, when all the second switches 21 are OFF, the eight parasitic elements 12 surrounding the feeding element 13 are arranged symmetrically with the feeding element 13, so the influence of each parasitic element 12 is canceled out. The radiation pattern of the antenna of Example 6 faces the zenith direction.

FIG. 10 is an explanatory diagram of antenna directivity control according to the sixth embodiment of the present invention.
As shown in FIG. 10, among the eight parasitic elements 12, only the second switch 21 connected to the parasitic element 12 in the + X direction with respect to the feeder element 13 is turned OFF, and the other second switches 21 are turned off. When is turned ON, only the parasitic element 12 on the + X side of the feeding element 13 is opened to the ground plane 25, and the other parasitic elements 12 are short-circuited to the ground plane 25. Since the parasitic element 12 short-circuited to the ground plane 25 has a small voltage excited by mutual coupling with the feeding element 13, the radiation pattern of the antenna of the sixth embodiment is mainly the parasitic element on the + X side with the feeding element 13. It is determined only by the element 12, and the radiation pattern is inclined 20 to 30 ° toward the + X side from the zenith.
As described above, when the structure of the sixth embodiment is adopted, the second switch 21 can be used for high frequencies (when all the first switches 11 are turned off and only the feed element 13 is operated and the resonance frequency is 63 GHz). The ON / OFF combination can tilt the radiation pattern from the zenith, realize directivity control, increase the gain with respect to the desired wave direction, and perform better transmission / reception.

In the sixth embodiment, since the 3 × 3 element array is used, directivity control can be realized by the second switch 21 only in the case of high frequency support, but the matrix is formed by more parasitic elements 12 around the feeding element 13. When the second switch 21 is provided on the parasitic element 12, the first switch 11 connects the feeding element 13 and the parasitic element 12 to form a rectangular radiating element so that the intermediate frequency is supported. In this case, the parasitic elements are connected by the first switch 11 to form the parasitic element 12 having the same excitation length as the rectangular radiating element, and the second switch connected to the parasitic element 12 By turning ON / OFF the switch 21, directivity control is possible even in the middle frequency range.
Furthermore, in the sixth embodiment, the second switch 21 is provided for all the eight parasitic elements, but even if the second switch 21 is provided for only a part of the parasitic element 12, a certain degree of directivity control can be achieved. Since it is possible, it shall be included in the present invention.

(Example 7)
FIG. 11 is a structural diagram of a wireless module according to Embodiment 7 of the present invention.
The wireless module of the seventh embodiment uses the multiband-compatible microstrip antenna of the sixth embodiment. In addition, a second substrate 40 made of a GaAs substrate is laminated below the insulating layer 25 constituting the antenna, and the front end corresponding to 17, 28, 63 GHz is provided on the second substrate 40. A circuit 39 is configured, and the front end circuit 39 and the power feeding element 13 are connected by a via hole 38 penetrating the insulating layer 26 and the second substrate 40.
Since the radio module of the seventh embodiment uses the antenna of the sixth embodiment, it can cope with three frequencies (17, 28, 63 GHz) by turning on / off the first switch 11. In 17GHz, directivity can be controlled in two dimensions, X and Y.

Therefore, a single wireless module can support a plurality of frequency standards, and the cost of the wireless module can be reduced. In addition, in the 17 GHz standard, a large gain can be realized by directing the maximum radiation angle of the antenna in the direction of the desired wave, and even better transmission and reception can be performed. The antenna has a microstrip antenna structure and has a planar structure, so that the wireless module can be reduced in size. Furthermore, since the second substrate is stacked below the antenna and the front end circuit is provided on the second substrate, a further compact wireless module can be realized.
In the seventh embodiment, only the front end circuit 39 is mounted on the second substrate 40. However, both the front end circuit 39 and the baseband circuit may be mounted. Even if the unit is mounted, the wireless module can be similarly reduced in size.

FIG. 12 is a diagram illustrating an example of a wireless system according to the present invention.
In this embodiment, the wireless module shown in FIG. 11 is used, and the antenna 50 is connected to a transmission / reception changeover switch 56 for switching between a transmission system and a reception system. The control circuit 53 sets the ON / OFF combination of the first and second switches according to the desired frequency and directivity. Thereafter, a control signal A is supplied from the control circuit 53 to the bias generation circuit 51 of the first switch to generate a predetermined bias, and the first switch is turned ON / OFF to connect the feeding element 13 and the parasitic element 12 / Performs blocking and forms a rectangular radiating element that resonates at a desired frequency. In the case of 17 GHz, a control signal B is supplied from the control circuit 53 to the bias generation circuit 52 of the second switch to generate a predetermined bias, and the second switch is turned ON / OFF, and a desired parasitic element Short circuit 12 to the ground plane. Further, a control signal C is supplied from the control circuit 53 to the transmission / reception changeover switch 56, and a desired circuit is selected from the 17, 28, and 63 GHz transmission / reception circuits.

  As described above, the wireless system of the present embodiment can support three frequencies by the combination of ON / OFF of the first and second switches, and can also implement two-dimensional directivity control when supporting 17 GHz. Therefore, one radio system can support three frequency standards, and the cost of the radio system can be reduced. Furthermore, the 17 GHz standard can achieve a high gain and can perform good transmission and reception. Further, the wireless system of this embodiment can be miniaturized because it uses a small wireless module composed of a microstrip antenna.

1 is a structural diagram of a multiband-compatible microstrip antenna according to Example 1 of the present invention. FIG. 3 is a structural diagram illustrating details of a first switch according to the first embodiment. FIG. 3 is a diagram for explaining an ON / OFF operation of a first switch according to the first embodiment. FIG. 6 is a structural diagram of a multiband-compatible microstrip antenna according to Example 2 of the present invention. FIG. 6 is a structural diagram of a multiband-compatible microstrip antenna according to Example 3 of the present invention. FIG. 6 is a structural diagram showing details of a first switch according to Embodiment 4 of the present invention. FIG. 10 is a structural diagram showing details of a first switch according to Embodiment 5 of the present invention. FIG. 10 is a structural diagram of a multiband-compatible microstrip antenna according to Example 6 of the present invention. 12 is a detailed structural diagram of a second switch according to Embodiment 6. FIG. FIG. 10 is an explanatory diagram of directivity control according to a sixth embodiment. FIG. 9 is a structural diagram of a wireless module according to Embodiment 7 of the present invention. FIG. 10 is a structural diagram of a radio system according to embodiment 8 of the present invention. It is explanatory drawing of a prior art example (Unexamined-Japanese-Patent No. 2000-236209). It is explanatory drawing of a prior art example (Unexamined-Japanese-Patent No. 2002-261533). It is explanatory drawing of a prior art example (Unexamined-Japanese-Patent No. 2003-124730). It is explanatory drawing of a prior art example (US patent 6198438). It is a figure which shows an example of the structure of the conventional MEMS switch. It is a figure which shows another example of the structure of the conventional MEMS switch.

Explanation of symbols

10 First board
11 First switch
12 Parasitic element
13 Feeding element
14 Via hole of movable electrode
15 Feed point
16 element via holes
17 Movable electrode
18 Movable electrode support
21 Insulating film B
22 Matching circuit
23 selector switch
24 Insulating film
25 Ground plane
26 Insulation layer
27 First board
28 Feed line
29 Inductor on insulation layer
30 Control circuit
32 Radiating element A
33 Radiating element B
34 Radiating element C
35 Matching circuit with variable constant
36 RF circuit
37 Matching circuit
38 Beer Hall
39 Front-end circuit
40 Second board
41 Contact electrode B
42 Lead B
43 Lead B '
44 Second switch via hole
45 Upper electrode B
46 Fixed electrode B
47 Hinge B
48 Parasitic element
49 element via hole
50 antenna
51 First switch bias generation circuit
52 Second switch bias generation circuit
53 Control circuit
54 Reception system
55 Transmission system
56 Transmission / reception selector switch

Claims (11)

A rectangular feeding element disposed on the upper surface of the first dielectric and a rectangular parasitic element surrounding the feeding element are arranged in a matrix, the feeding element and the parasitic element, and the adjacent parasitic element In the multiband-compatible microstrip antenna having a structure in which the elements are connected by a first switch to form a rectangular radiating element,
The first switch includes an insulating film that covers an end of an adjacent feeding element or parasitic element, and a movable electrode held in the air on the insulating film,
Furthermore, the adjacent feeding element or parasitic element and the movable electrode have a structure to which a DC bias can be applied. The multi-band microstrip antenna according to claim 1,
The adjacent feeding element or parasitic element, and a structure capable of applying a DC bias provided on the movable electrode is composed of a via hole and an inductor, and the inductor is substantially insulative at a frequency used in a multiband microstrip antenna. A multi-band microstrip antenna characterized by having an inductance of The method for controlling a multiband microstrip antenna according to claim 1 or 2,
When the first switch is turned on, a DC bias having a reverse polarity is applied to a feeding element or a parasitic element adjacent to the first switch and the movable electrode, and electrostatic attraction between the movable electrode and the element is applied. A control method for a multiband microstrip antenna, characterized in that the movable electrode is brought into contact with an insulating film covering an end portion of the element, and the elements are electrically connected by capacitive coupling. The method for controlling a multiband microstrip antenna according to claim 1 or 2,
When turning on the first switch, 0V is applied to one of the feeding element or parasitic element adjacent to the first switch and the movable electrode, and a positive or negative DC bias is applied to the other, A method for controlling a multi-band microstrip antenna, wherein the movable electrode is brought into contact with an insulating film covering the end portion of the element by electrostatic attraction between the movable electrode and the element, and the elements are electrically connected by capacitive coupling. The multiband microstrip antenna according to claim 1 or 2,
A multi-strip microstrip antenna characterized in that a matching circuit connected to the feed point by a changeover switch is provided at the feed point of the feed element. The multiband microstrip antenna according to claim 1 or 2,
A multi-band microstrip antenna, characterized in that a matching circuit capable of changing a constant is connected to a feeding point of the feeding element. The multiband microstrip antenna according to any one of claims 1, 2, 5, and 6,
The multi-band microstrip antenna, wherein the first switch has a structure in which the first switch is connected over almost the entire surface of the adjacent feeding element or parasitic element facing each other. The multiband microstrip antenna according to claim 7,
The first switch is characterized in that the shape of the tip portion facing the other first switch is extended to a V shape, and the interval between the four first switches facing each other is an X shape. Multi-band compatible microstrip antenna. The multiband microstrip antenna according to any one of claims 1, 2, 5 to 8,
At least a part of the parasitic element is provided with a second switch that is short-circuited to the ground plane by capacitive coupling.   A wireless module using the multi-band microstrip antenna according to claim 1.   A wireless system using the wireless module according to claim 10.

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