JPH09307331A - Matching circuit and antenna system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a matching circuit and an antenna system using it, which can be used for a radio equipment transmitting/receiving frequency in a wide range even by a small antenna system. SOLUTION: The matching circuit 10 consists of and inductance element 12 consisting of a chip inductor serially connected with an antenna main body 11, a first capacitance element 13 consisting of a trimmer capacitor parallelly connected with the antenna main body 11 and a second capacitance element 14 consisting of a chip capacitor. At this time one terminal of the inductance element 12 is connected to the power feeding terminal 15 of the antenna main body 11 and the other terminal is connected with a power feeding source V for feeding voltage. In addition, the first capacitance element 13 is connected between the connecting point A of the power feeding terminal 15 and the inductance element 12 and the ground, and the second capacitance element 14 is connected between the connecting point B of the inductance element 12 and the power feeding source V and the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matching circuit and an antenna device using the matching circuit, and more particularly to a matching circuit used in a radio device for transmitting and receiving a wide range of frequencies, such as a television, a radio, a pager and the like. The present invention relates to an antenna device.

[0002]

2. Description of the Related Art Generally, radio equipment for transmitting and receiving a wide range of frequencies, for example, a television (90 MHz to 800 MHz)
The antenna main body used for the antenna includes a Yagi-Uda antenna, a whip antenna and the like. However, in the case of the Yagi-Uda antenna and the whip antenna, the antenna becomes very large because the bandwidth is widened so that radio waves of a wide range of frequencies can be received.

On the other hand, in order to realize miniaturization, an antenna device 50 as shown in FIG. 10 has been proposed.
In FIG. 10, 51 is an antenna main body, 52 is a mounting board for mounting the antenna main body 51, and 53 is a mounting board 5.
Reference numeral 54 is a ground pattern formed on the mounting board 52, and 54 is a transmission line also formed on the mounting board 52. The ground pattern 53 is connected to the ground. In addition, the transmission line 54
Is connected to the power supply V, and the power supply V is connected to the ground.

For example, this antenna body 51 is shown in FIG.
As shown in FIG. 5, a rectangular parallelepiped insulator 55 in which an insulator layer (not shown) made of an insulator powder such as alumina or steatite is laminated, and an insulator 5 made of silver, silver-palladium, or the like.
5, a conductor 56 formed in a coil shape, and a magnetic material 57 made of a magnetic material powder such as a ferrite powder, and formed inside the insulator 55 and the coiled conductor 56, and the insulator 55 are fired. Then, a lead end of the conductor 56 (not shown)
External connection terminals 58a and 58 to be adhered and baked
b.

[0005]

However, the above-mentioned miniaturized conventional antenna device has a problem that it cannot be used in an antenna device used for a radio device that transmits and receives a wide range of frequencies because of its narrow bandwidth. .

The present invention has been made in order to solve such a problem, and a matching circuit which can be used in a radio device for transmitting and receiving a wide range of frequencies even with a small antenna device, and an antenna device using the matching circuit. The purpose is to provide.

[0007]

In order to solve the above-mentioned problems, the present invention provides an antenna body comprising an radiating conductor and a feeding terminal, and an equivalent circuit connected in series, which comprises an inductance component, a resistance component and a capacitance component. The matching circuit to be connected is composed of an inductance element connected in series to the antenna body, and first and second capacitance elements connected in parallel to the antenna body. It is characterized by using a capacitance element.

Further, the second capacitance element is a capacitance element having a variable capacitance.

Further, a matching circuit is provided on the side of the power feeding terminal of the antenna body.

According to the matching circuit of the present invention and the antenna device using the matching circuit, the high-frequency circuit employed in the radio equipment for transmitting and receiving the input impedance of the antenna body and the wide frequency range by the inductance element and the second capacitance element. It becomes possible to adjust the resonance frequency by matching the characteristic impedance of (1) and the first capacitance element of which the capacitance is variable.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In each embodiment and each modification, the same or equivalent parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a circuit diagram of a first embodiment of a matching circuit according to the present invention. The matching circuit 10 includes the antenna body 1
An inductance element 12 made of, for example, a chip inductor connected in series with 1, and a trimmer capacitor connected in parallel with the antenna body 11, a first capacitance element 13 having a variable capacitance made of a varactor diode, and a chip capacitor, for example. The second capacitance element 14 has a fixed capacitance.

At this time, one end of the inductance element 12 is connected to the power supply terminal 15 of the antenna main body 11, and the other end is a power supply V for supplying a voltage to the antenna main body 11.
Connected to. In addition, the first capacitance element 13
Is connected between a connection point A of the power feeding terminal 15 of the antenna body 11 and the inductance element 12 and the ground,
The second capacitance element 14 is connected between the connection point B of the inductance element 12 and the power supply V and the ground.

FIG. 2 shows a matching circuit 10 of the first embodiment.
The perspective view of the antenna device 16 using is shown. This antenna device 16 has an antenna body 11, an inductance element 12, first and second capacitance elements 13 and 14 that form a matching circuit 10, and transmission lines 17a and 17b and a ground electrode 18 formed on the surface. Mounting board 19
It is configured by mounting on top of.

At this time, the power feeding terminal 1 of the antenna body 11
5 is connected to the transmission line 17a, and the inductance element 1
3 is connected to the transmission lines 17a and 17b, and the power supply V is connected to the transmission line 18b. That is, the inductance element 13 is connected to the antenna body 11 and the power supply V via the transmission lines 17a and 17b.

Further, the first capacitance element 13 is
It is connected between the transmission line 17 a and the ground electrode 18, and the second capacitance element 14 is connected between the transmission line 17 b and the ground electrode 18.

In general, the high-frequency circuit (not shown) mounted on the radio equipment for transmitting and receiving a wide range of frequencies together with the antenna device 16 is designed such that its characteristic impedance is unified to 50Ω.

Next, the antenna body 11 used in the antenna device 16 of FIG. 2 will be described. Antenna body 11
As shown in FIG. 3, the equivalent circuit of 1 is a circuit in which the inductance component 1, the resistance component 2, and the capacitance component 3 are connected in series between the power supply terminal 15 and the ground. And
The inductance component 1, the resistance component 2, and the capacitance component 3 constitute the radiation conductor 4.

Further, as shown in FIG. 4, the antenna body 11 is spirally wound in the longitudinal direction of the base body 5 inside a rectangular parallelepiped base body 5 containing barium oxide, aluminum oxide and silica as main components. On the surface of the radiating conductor 4 and the base body 5,
A power supply terminal 15 for applying a voltage to the radiation conductor 4 is provided. At this time, one end of the radiation conductor 4 forms the power feeding portion 6 connected to the power feeding terminal 15, and the other end forms the free end 7 inside the base body 5.

In the case of the above-mentioned antenna body, the use of a rectangular parallelepiped base containing barium oxide, aluminum oxide, and silica as a main component slows down the propagation speed and shortens the wavelength. Is ε, the effective line length is ε ^1/2 times, which is longer than the effective line length of the conventional linear antenna. Therefore, since the area of the current distribution increases, the amount of radio waves radiated increases, and the gain of the antenna device can be improved.

FIGS. 5 and 6 show the antenna body 11 of FIG.
The perspective view of the modification of FIG. Antenna body 11 of FIG.
The a includes a rectangular parallelepiped base 5a, a radiation conductor 4a spirally wound in the longitudinal direction of the base 5a along the surface of the base 5a, and a power supply terminal 15a on the surface of the base 5a. At this time, one end of the radiation conductor 4a is connected to the power supply terminal 15a for applying a voltage to the radiation conductor 4a on the surface of the base body 5a. The other end of the radiation conductor 4a is
The free end 7a is formed on the surface of the base 5a. In this case, the radiation conductor 4a can be easily formed in a spiral shape on the surface of the base body 1a by screen printing or the like.
The manufacturing process of 1a can be simplified.

The antenna main body 11b of FIG. 6 has a rectangular parallelepiped base 5b, a radiating conductor 4b formed in a meandering shape on the surface of the base 5b, and a power supply terminal 15 on the surface of the base 5b.
b. At this time, one end of the radiation conductor 4b is connected to the base 5
On the surface of b, it is connected to a power supply terminal 15b for applying a voltage to the radiation conductor 4b. Also, the radiation conductor 4b
The other end of forms a free end 7b on the surface of the substrate 5b. In this case, the meandering radiation conductor 4b is attached to the base 5
Since only the one main surface of b is formed, the height of the base body 5b can be reduced, and accordingly, the height of the antenna body 11b can be reduced. The meandering radiation conductor 4b may be formed inside the base body 5b.

Next, referring to FIG. 7, in the antenna device 16 shown in FIG. 2, the inductance element 12 has a chip inductor having an inductance value of 220 nH, and the first capacitance element 13 has a capacitance value of 0.1 pF to 0.75 pF. The pass characteristics when a variable capacitor and a chip capacitor having a capacitance value of 5 pF are used for the second capacitance element 14 are shown. In FIG. 7, the solid line shows the case where the capacitance value of the first capacitance element 13 is 0.75 pF, the broken line shows the case where the capacitance value of the first capacitance element 13 is 0.1 pF, and points A and B are respectively The resonance frequency in the case of is shown.

From this figure, the first capacitance element 1
By changing the capacitance value of 3 from 0.1 pF to 0.75 pF, the resonance frequency of the antenna device 16 is set to 350 M.
It has been demonstrated that it is possible to move from Hz (point B) to 240 MHz (point A).

According to the matching circuit 10 of the first embodiment described above, the input impedance of the antenna device 16 composed of the antenna body 11 and the matching circuit 10 is adjusted by the inductance element 12 and the second capacitance element 14 to the antenna. The resonance frequency of the antenna device 16 is matched with the device 16 by matching the characteristic impedance of 50 Ω, which is a characteristic impedance of a high-frequency circuit (not shown) mounted on a radio device that transmits and receives a wide range of frequencies, and by means of the variable capacitance first capacitance element 13. It can be adjusted to a desired frequency. Therefore, even if the bandwidth of the antenna device 16 is narrow, it is possible to handle a wide range of frequencies.

Further, according to the antenna device 16 using the matching circuit 10, since the antenna body 11 and the matching circuit 10 are integrated and miniaturized, the antenna device 16 can be attached to a portable radio device transmitting and receiving a wide range of frequencies. .

Furthermore, since the antenna device 16 can be housed inside the housing of a wireless device that transmits and receives a wide range of frequencies, the protruding part can be eliminated from the wireless device.

When a varactor diode whose capacitance can be changed by an applied voltage is used as the variable capacitance first capacitance element 13, it is easy to change the applied voltage to the varactor diode. Moreover, the resonance frequency can be adjusted to a desired frequency.

FIG. 8 shows a circuit diagram of a second embodiment of the matching circuit according to the present invention. Matching circuit 20 according to the second embodiment
Is the second compared to the matching circuit 10 of the first embodiment.
The difference is that the capacitance element 14 is composed of a variable capacitance element. At this time, the second capacitance element 14 having a variable capacitance is replaced by the first capacitance element 1
Similar to 3, it includes, for example, a trimmer capacitor and a varactor diode.

According to the matching circuit 20 of the second embodiment described above, the resonance frequency of the antenna device 21 composed of the antenna main body 11 and the matching circuit 20 is largely moved to bring it to a desired frequency. Even if the input impedance of the antenna device 21 greatly deviates from the characteristic impedance of 50Ω, which is a characteristic impedance of a high-frequency circuit (not shown) mounted on a radio device that transmits and receives a wide range of frequencies together with the antenna device 21, the second capacitance is made variable. By changing the capacitance of the capacitance element 14, the input impedance of the antenna device 21 can be matched with the characteristic impedance of the high frequency circuit.

9 (a) to 9 (h) are circuit diagrams of the first to eighth modified examples of the matching circuit 20 of the second embodiment.

The matching circuits 31 to 38 which are the first to eighth modified examples are compared with the matching circuit 20 which is the second embodiment, and the first and second capacitance elements 13 and 14 are provided.
And the third and fourth capacitance elements 39 and 40 are connected in series or in parallel.

Third and fourth capacitance elements 39,
40 designates the first and second capacitance elements 13, 14
When connected in series to (Fig. 9 (a), (c),
(E), (f), (g)) shows that even if the capacitances of the first and second capacitance elements 13 and 14 that are variable in capacitance are greatly adjusted, the first capacitance element 13 and the third capacitance element Since the combined capacitance of the element 39 and the combined capacitance of the second capacitance element 14 and the fourth capacitance element 40 change only a minute amount, the minute capacitance can be adjusted.

Further, the third and fourth capacitance elements 39 and 40 are the first and second capacitance elements 1 and 2.
3 and 14 are connected in parallel (Fig. 9 (b),
In (d), (f), (g) and (h), even if the capacitances of the first and second capacitance elements 13 and 14 having variable capacitance are adjusted to be small, Since the combined capacitance of the third capacitance element 39 and the combined capacitance of the second capacitance element 14 and the fourth capacitance element 40 change greatly, the capacitance can be changed greatly.

At this time, in the first and second modified examples described above, the second capacitance element 14 is a capacitance element having a fixed capacitance, which is a modified example of the matching circuit 10 of the first embodiment.

In the above embodiment, the antenna body has the radiation conductor spirally wound inside the base body made of a dielectric material containing barium oxide, aluminum oxide and silica as a main component. Although the case has been described, the equivalent circuit of the antenna main body may be a circuit as shown in FIG. 3, and the shape thereof is not an essential condition for implementing the present invention.

Further, the case where the base body of the antenna body is made of a dielectric material containing barium oxide, aluminum oxide or silica as a main component has been described, but the base body is not limited to this dielectric material and the base material is not limited to this. A dielectric material containing titanium or neodymium oxide as a main component, a magnetic material containing nickel, cobalt, or iron as a main component, or a combination of a dielectric material and a magnetic material may be used.

Further, although the case where the antenna body has one radiation conductor has been described, the antenna body may have a plurality of radiation conductors arranged in parallel. In this case,
It is possible to have a plurality of resonance frequencies according to the number of radiating conductors, and one antenna can support multiple bands.

Also, as the variable capacitance element, a variable capacitor having a capacitance value of 0.1 pF to 0.75 pF has been described, but it is sufficient if the capacitance value is variable, and the variable range of the capacitance value is It is not an essential condition for carrying out the present invention.

Further, although the case where the resonance frequency is made variable has been described, it can be naturally used even when the resonance frequency is not made variable.

[0041]

According to the first aspect of the matching circuit, the inductance element and the second capacitance element allow the input impedance of the antenna device including the antenna body and the matching circuit to be transmitted and received with the antenna device over a wide range of frequencies. It is possible to adjust the resonance frequency of the antenna device to a desired frequency by matching the characteristic impedance of the high frequency circuit mounted on the wireless device, and using the first capacitance element having a variable capacitance. Therefore, even if the bandwidth of the antenna device is narrow, it is possible to support a wide range of frequencies,
It can be used for a wireless device that transmits and receives a wide range of frequencies.

According to the second aspect of the matching circuit, the input impedance of the antenna device is increased by largely moving the resonance frequency of the antenna device formed of the antenna body and the matching circuit to obtain a desired frequency. The input impedance of the antenna device is changed by changing the capacitance of the second capacitance element whose capacitance is variable, even if the characteristic impedance of the high-frequency circuit mounted on the radio device that transmits and receives a wide range of frequencies with the device greatly deviates. It is possible to match the characteristic impedance of the high frequency circuit.

According to the antenna device of the third aspect, since the antenna body and the matching circuit are integrated and miniaturized, the antenna device can be attached to a portable radio device that transmits and receives a wide range of frequencies.

Further, since the antenna device can be housed inside the housing of the portable wireless device which transmits and receives a wide range of frequencies, the protruding part can be eliminated from the wireless device.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment according to a matching circuit of the present invention.

FIG. 2 is a perspective view of an antenna device using the matching circuit of FIG.

FIG. 3 is an equivalent circuit diagram of an antenna body forming the antenna device of FIG.

FIG. 4 is a perspective view of an antenna body forming the antenna device of FIG.

FIG. 5 is a perspective view showing a modified example of the antenna body of FIG.

FIG. 6 is a perspective view showing another modification of the antenna body of FIG.

7 is a diagram showing pass characteristics of the antenna device of FIG.

FIG. 8 is a circuit diagram of a second embodiment according to the matching circuit of the present invention.

9 is a circuit diagram showing (a) first to (h) eighth modified examples of the matching circuit of FIG.

FIG. 10 is a perspective view of a conventional antenna device.

11 is a perspective side view of an antenna main body that constitutes the antenna device of FIG.

[Explanation of symbols]

 1 Inductance component 2 Resistance component 3 Capacitance component 4 Radiating conductor 10, 20, 31-38 Matching circuit 11 Antenna body 12 Inductance element 13, 14 Capacitance element 15 Feeding terminal 16, 21 Antenna device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoichiro Suga 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Inside Murata Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. A matching circuit, which comprises a radiation conductor and a feeding terminal, and which is connected to an antenna body composed of an inductance component, a resistance component, and a capacitance component, in which an equivalent circuit is connected in series, wherein the matching circuit is connected in series to the antenna body. A matching circuit comprising an inductance element and first and second capacitance elements connected in parallel to the antenna body, wherein the first capacitance element is a capacitance element having a variable capacitance. 2. The matching circuit according to claim 1, wherein the second capacitance element is a capacitance element having a variable capacitance. 3. An antenna device, wherein the matching circuit according to claim 1 or 2 is provided on a side of a power feeding terminal of the antenna body.