JP3784807B2 - Microstrip antenna - Google Patents

Description

  The present invention relates to a transmission / reception separation type microstrip antenna used for a mobile communication base station, for example.

  With the rapid spread of mobile phones and wireless LANs in recent years, the wireless communication field has been dramatically developed. In these wireless communications, an antenna is indispensable, and among them, a microstrip antenna (MSA) is often used because of its small size and light weight and simple structure.

  Conventionally, as shown in FIG. 18, a transmission / reception separation type microstrip antenna used in a mobile communication base station includes a reception microstrip antenna 11, a transmission microstrip antenna 12, and a dielectric that supports them. A substrate 13, a ground plate 14 attached to the entire back surface of the dielectric substrate 13, a transmission microstrip antenna feeding point 15, and a receiving microstrip antenna feeding point 16 are provided.

The transmission microstrip antenna feeding point 15 and the reception microstrip antenna feeding point 16 are insulated from the ground plate 14 and penetrate the dielectric substrate 13, and are electrically connected to the transmission microstrip antenna 12 and the reception microstrip antenna 11. Connected. In this antenna configuration, when the wavelength of the center frequency of the resonance frequency between the receiving microstrip antenna 11 and the transmitting microstrip antenna 12 is λ ₀ , the receiving microstrip antenna 11 and the transmitting microstrip antenna 12 are used. substantially and the distance of a line connecting the center point and λ _0/2, mutual coupling between the receiving microstrip antenna 11 and the transmitting microstrip antenna 12 (isolation) is about -30dB with.

On the other hand, a technique for securing an isolation characteristic between transmission and reception antennas of about −32 dB by changing a power feeding method for transmission and reception by using an antenna element for both transmission and reception is disclosed (for example, see Patent Document 1). .
JP-A-5-41608

  As described above, the mutual coupling amount between the transmission / reception antenna elements of the transmission / reception separation type microstrip antenna shown in FIG. 18 and the microstrip antenna disclosed in Patent Document 1 is about −30 to −32 dB. For this reason, in practice, it is necessary to compensate for the mutual coupling amount to about −90 dB by inserting a filter with a steep attenuation characteristic, that is, a filter with good separation.

  However, such a steep filter having a steep attenuation characteristic is expensive. Inserting this filter increases the cost of the antenna system. In addition, the insertion of the filter increases the shape and weight, which hinders downsizing and weight reduction of the antenna system.

  Therefore, in view of the above-described problems, the present invention has an object to provide a microstrip antenna that reduces the amount of mutual coupling between transmitting and receiving antenna elements without using a steep filter, and achieves downsizing and cost reduction. To do.

  In order to achieve the above object, a feature of the present invention is a microstrip antenna including a transmitting microstrip antenna and a receiving microstrip antenna that are disposed apart from each other in a horizontal direction with respect to a plane on a dielectric substrate. And a rectangular slot formed between the receiving microstrip antenna feeding point and the transmitting microstrip antenna feeding point on the ground plate attached to the back surface of the dielectric substrate, and a metal covering the slot. The gist is that the microstrip antenna includes a shield.

  The distance between the transmitting microstrip antenna and the receiving microstrip antenna is the distance between the center points of the receiving microstrip antenna 1 and the transmitting microstrip antenna 2.

  According to the microstrip antenna according to the feature of the present invention, the amount of mutual coupling between transmitting and receiving antenna elements can be reduced without using a steep filter, and the size and cost can be reduced. In addition, by covering the slot with a shield, there is no influence of a conductor such as a filter or amplifier existing behind the ground plate, and the amount of mutual coupling between the transmitting and receiving antenna elements does not deteriorate.

In the microstrip antenna according to the feature of the present invention, if the length of the long side of the slot is L and the length of the short side is W, 0.7λ ₀ <L <1.0λ ₀ , W <0.5λ ₀ is preferred. When the slot designed in this way is formed, in particular, the amount of sneak current from the transmitting microstrip antenna to the receiving microstrip antenna can be reduced, and the amount of mutual coupling between the transmitting and receiving antenna elements is greatly reduced.

In the microstrip antenna according to the feature of the present invention, the shield has a rectangular parallelepiped shape. When the width is S_W and the height is S_H, S_W <0.5λ ₀ , 0.05λ ₀ <S_H <0.2λ _0. It is preferable that By covering the slot with the shield designed in this way, practicality is improved without being affected by conductors such as filters and amplifiers existing behind the ground plate.

  In addition, the microstrip antenna according to the feature of the present invention may have a plurality of slots and the shield may cover the plurality of slots. Even if a plurality of slots are formed, the amount of mutual coupling between the transmitting and receiving antenna elements can be reduced, and the size and cost can be reduced.

  In the microstrip antenna according to the feature of the present invention, a plurality of pairs of transmitting and receiving microstrip antennas having different excitation frequency bands may be arranged on the dielectric substrate. According to this microstrip antenna, it can be used as a transmission / reception separation type microstrip antenna for multi-frequency sharing.

  According to the present invention, it is possible to provide a microstrip antenna capable of reducing the amount of mutual coupling between transmitting and receiving antenna elements without using a steep filter, and reducing the size and price.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(First embodiment)
The microstrip antenna according to the first embodiment of the present invention is a transmission / reception separation type microstrip antenna for IMT-2000 used for a mobile communication base station.

  The microstrip antenna according to the first embodiment includes a reception frequency band microstrip antenna (hereinafter referred to as “reception microstrip antenna”) 1 and a transmission frequency band as shown in FIGS. A microstrip antenna (hereinafter referred to as “transmitting microstrip antenna”) 2, a dielectric substrate 3 supporting these, a ground plate 4 attached to the entire back surface of the dielectric substrate 3, and a transmission frequency band Microstrip antenna feeding point (hereinafter referred to as “transmitting microstrip antenna feeding point”) 5 and reception frequency band microstrip antenna (hereinafter referred to as “receiving microstrip antenna feeding point”) 6. , One slot 7 and one shield 8.

  FIG. 3 is a diagram in which a shield 8 is installed on the ground plate 4 shown in FIG. 2 as shown in FIG. In the following drawings, for convenience of explanation, the surface of the dielectric substrate 3 on which the reception microstrip antenna 1 and the transmission microstrip antenna 2 are installed is the surface, the transmission microstrip antenna feeding point 5 and the reception microstrip antenna feeding point. The ground plate 4 side on which 6 is installed is defined as the back surface.

  The transmitting microstrip antenna feeding point 5 and the receiving microstrip antenna feeding point 6 are insulated from the ground plate 4 and penetrate the dielectric substrate 3, and are electrically connected to the transmitting microstrip antenna 2 and the receiving microstrip antenna 1. Connected.

In this antenna configuration, when the center frequency of the resonance frequency of the reception microstrip antenna 1 and the transmission microstrip antenna 2 is λ ₀ , the reception microstrip antenna 1 and the transmission microstrip antenna 2 are It is placed approximate lambda _0/2 apart in a horizontal direction with respect to the plane of the dielectric substrate 3.

Further, in the first embodiment, when the wavelength of the resonance frequency of the receiving microstrip antenna 1 and lambda _r, receiving microstrip antenna 1 is a positive quadrilateral side is lambda _r / 2. Similarly, when the wavelength of the resonance frequency of the transmitting microstrip antenna 2 and lambda _t, transmitting microstrip antenna 2 is a positive quadrilateral side is lambda _t / 2.

The slot 7 is a rectangular gap formed between the receiving microstrip antenna feeding point 6 and the transmitting microstrip antenna feeding point 5 on the ground plate 4 attached to the back surface of the dielectric substrate 3. . Specifically, the slot 7 has a long side in a direction orthogonal to a line connecting the receiving microstrip antenna feeding point 6 and the transmitting microstrip antenna feeding point 5, and a short side in a direction parallel to the connecting line. It has a rectangular shape. Further, when the length of the long side of the slot L, and the length of the short side is is W, a _{0.7λ 0 <L <1.0λ 0,} W <0.5λ 0.

  The shield 8 covers the slot 7 and is made of metal. Here, for example, iron, copper, nickel, or an alloy thereof is preferably used as a metal that is a raw material of the shield.

The shield 8 has a rectangular parallelepiped shape. When the width is S_W and the height is S_H, S_W <0.5λ ₀ and 0.05λ ₀ <S_H <0.2λ ₀ . Here, the width S_W and the height S_H of the shield 8 are the dimensions inside the shield, as shown in FIG.

  FIG. 4 is a cross-sectional view taken along the line A-A ′ in FIG. 3A, and FIG. 5 is a cross-sectional view taken along the line B-B ′ in FIG. Thus, the slot 7 is covered with the shield 8.

  Next, the measurement result of the mutual coupling amount when the microstrip antenna according to the first embodiment is used will be described.

The antenna element in the reception band (1940-1960 MHz) when the resonance frequency of the reception microstrip antenna 1 is 1950 MHz, the resonance frequency of the transmission microstrip antenna 2 is 2140 MHz, and the lengths L and W of the slot 7 are changed. FIG. 6 shows the calculation result of the maximum value of the inter-total coupling amount. In this case, the width S_W of the shield 8 and 0.3λ _0, the height S_H of the shield 8 was set to 0.07λ _0.

As apparent from FIG. 6, the mutual coupling amount of the reception band varies greatly depending on L and W, and it is necessary to select an appropriate slot size (combination of L and W) in order to reduce the mutual coupling amount. In FIG. 6, the frequency characteristics of the mutual coupling amount between the antenna elements when L and W that minimize the mutual coupling amount between the antenna elements in the reception band, that is, L = 0.97λ ₀ and W = 0.013λ ₀ are selected. Is shown in FIG. 7 in comparison with a conventional microstrip antenna without a slot shown in FIG.

  When the embodiment according to the present invention is compared with the conventional example, the amount of mutual coupling between the antenna elements is greatly reduced in the band of IMT-2000, for example, the frequency of 1.90-1.98 GHz, and the transmission microstrip It can be seen that the amount of electricity flowing from the antenna 2 to the receiving microstrip antenna 1 can be reduced.

  According to the microstrip antenna according to the first embodiment, particularly in the IMT-2000 band, the amount of mutual coupling between the transmitting and receiving antenna elements can be reduced, and the size and the price can be reduced. Further, when a conductor such as a filter or an amplifier is present behind the ground plate 4, there is a problem in that the amount of mutual coupling between the transmitting and receiving antenna elements is deteriorated. The practicality is improved without being affected by.

(Second Embodiment)
The microstrip antenna according to the first embodiment includes one slot 7, but the microstrip antenna according to the second embodiment includes a plurality of slots 7.

  As shown in FIGS. 8 to 11, the microstrip antenna according to the second embodiment includes a reception microstrip antenna 1, a transmission microstrip antenna 2, a dielectric substrate 3 that supports them, and a dielectric. A ground plate 4 attached to the entire back surface of the substrate 3, a transmission microstrip antenna feeding point 5, a receiving microstrip antenna feeding point 6, two slots 7 a and 7 b, and one shield 8 are provided. .

The slots 7 a and 7 b are rectangular gaps formed between the receiving microstrip antenna feeding point 6 and the transmitting microstrip antenna feeding point 5 on the ground plate 4 attached to the back surface of the dielectric substrate 3. It is. Specifically, the slots 7a and 7b have long sides in a direction orthogonal to a line connecting the receiving microstrip antenna feeding point 6 and the transmitting microstrip antenna feeding point 5, and are short in a direction parallel to the connecting line. It has a rectangular shape with sides. The slot 7a, L the length of the long side of 7b, and the length of the short side is is W, both slot 0.7Ramuda ₀ a _{<L <1.0λ 0, W <} 0.5λ 0 condition Fulfill.

  Since the arrangement and size of the reception microstrip antenna 1 and the transmission microstrip antenna 2, the shield 8, and the like are the same as those of the microstrip antenna according to the first embodiment, the description thereof is omitted here.

  9 is a cross-sectional view along AA ′ in FIG. 8A, FIG. 10 is a cross-sectional view along BB ′ in FIG. 8A, and FIG. 11 is a cross-sectional view along C-- in FIG. It is C 'sectional drawing. In this way, two slots 7 having different lengths are covered by one shield 8. Even if two slots 7 are provided, as in the first embodiment, the amount of mutual coupling between the antenna elements is greatly reduced in the reception band, and the transmission microstrip antenna 2 to the reception microstrip antenna 1 can be reduced. The sneak current can be reduced.

  According to the microstrip antenna according to the second embodiment, by forming the plurality of slots 7, the amount of mutual coupling between the transmitting and receiving antenna elements can be reduced, and the size and the price can be reduced.

(Third embodiment)
The microstrip antenna according to the first embodiment includes one pair of transmission and reception microstrip antennas 1 and 2, but the microstrip antenna according to the third embodiment has different transmission frequency bands. A plurality of trust and reception microstrip antenna pairs are provided on a dielectric substrate.

  As shown in FIGS. 12 to 16, the microstrip antenna according to the third embodiment supports the receiving microstrip antennas 1a, 1b, and 1c and the transmitting microstrip antennas 2a, 2b, and 2c. A dielectric substrate 3, a ground plate 4 attached to the entire back surface of the dielectric substrate 3, a transmission microstrip antenna feeding point 5, a receiving microstrip antenna feeding point 6, and three slots 7a, 7b, 7c and one shield 8 are provided. In the microstrip antenna according to the third embodiment, the transmitting and receiving microstrip antenna pairs 1a and 2a, 1b and 2b, 1c and 2c have different excitation frequency bands, respectively, and transmission / reception separation for three frequencies is shared. Type microstrip antenna.

In this antenna configuration, when the center frequency of the resonance frequency of the reception microstrip antenna 1a and the transmission microstrip antenna 2a is λ _0a , the reception microstrip antenna 1a and the transmission microstrip antenna 2a are: In the horizontal direction with respect to the plane of the dielectric substrate 3, the dielectric substrate 3 is placed approximately λ _0a / 2. Similarly, when the wavelength of the center frequency of the resonance frequency of the reception microstrip antenna 1b and the transmission microstrip antenna 2b is λ _0b , the reception microstrip antenna 1b and the transmission microstrip antenna 2b are dielectrics. They are placed approximately λ _0b / 2 apart in the direction horizontal to the plane of the substrate 3. When the wavelength of the center frequency of the resonance frequency of the reception microstrip antenna 1c and the transmission microstrip antenna 2c is λ _0c , the reception microstrip antenna 1c and the transmission microstrip antenna 2c are dielectric substrates. is placed approximate lambda _0c / 2 apart in the direction parallel to the third plane.

Further, in the third embodiment, when the wavelength of the resonance frequency of the receiving microstrip antenna 1a and lambda _ra, receiving microstrip antenna 1a is a positive quadrilateral side is lambda _ra / 2, for transmission When the wavelength of the resonance frequency of the microstrip antenna 2a is λ _ta , the transmission microstrip antenna 2a is a regular quadrangle whose one side is λ _ta / 2. Similarly, when the wavelength of the resonance frequency of the receiving microstrip antenna 1b and lambda _rb, receiving microstrip antenna 1b are side is a positive quadrilateral lambda _rb / 2, the resonance frequency of the transmitting microstrip antenna 2b Λ _tb , the transmitting microstrip antenna 2b is a regular quadrangle having one side of λ _tb / 2. Further, _assuming that the wavelength of the resonance frequency of the reception microstrip antenna 1c is λ _rc , the reception microstrip antenna 1c is a regular quadrangle having one side of λ _rc / 2, and has the resonance frequency of the transmission microstrip antenna 2c. If the wavelength is λ _tc , the transmitting microstrip antenna 2c is a regular quadrangle having one side of λ _tc / 2.

The slots 7a, 7b, and 7c include receiving microstrip antenna feeding points 6a, 6b, and 5c and transmitting microstrip antenna feeding points 5a, 5b, and 5c on the ground plate 4 attached to the back surface of the dielectric substrate 3. These are rectangular gaps formed between the two. Specifically, the slots 7a, 7b, 7c have long sides in a direction orthogonal to a line connecting the receiving microstrip antenna feeding points 6a, 6b, 6c and the transmitting microstrip antenna feeding points 5a, 5b, 5c. And a rectangular shape having a short side in a direction parallel to the connecting line. The slot 7a, 7b, respectively L _a length of the long side of _{7c, L b, L c,} W a length of the short side, respectively, W _b, When W _c, the slot 7a is 0.7Ramuda _0a <L _a <1.0λ _0a, satisfies the condition of W _a <0.5λ _0a, slot 7b satisfies _{0.7λ 0b <L b <1.0λ 0b} , W b <0.5λ 0b conditions, slot 7c is _{0.7λ 0c <L c <1.0λ 0c} , W c <0.5λ 0c satisfy the.

  In addition, since the configuration of the shield 8 and the like is the same as that of the microstrip antenna according to the first embodiment, the description thereof is omitted here.

  13 is a cross-sectional view along AA ′ in FIG. 12A, FIG. 14 is a cross-sectional view along BB ′ in FIG. 12A, and FIG. 15 is a cross-sectional view along C— in FIG. It is C 'sectional drawing, FIG. 16 is DD' sectional drawing in Fig.12 (a). In this way, slots 7a, 7b, 7c are formed between the feeding points 5a and 6a, 5b and 6b, 5c and 6c of the respective transmitting and receiving microstrip antenna pairs, and three slots 7a having different lengths are formed. , 7b, 7c are covered by a single shield 8.

  Even if a plurality of transmission and reception microstrip antenna pairs having different excitation frequency bands are provided on the dielectric substrate, the mutual coupling amount between the antenna elements is greatly reduced in the reception band as in the first embodiment. The amount of electricity flowing from the transmitting microstrip antennas 2a, 2b, 2c to the receiving microstrip antennas 1a, 1b, 1c can be reduced.

  According to the microstrip antenna according to the third embodiment, by providing a plurality of transmission and reception microstrip antenna pairs, the amount of mutual coupling between the transmitting and receiving antenna elements is reduced, and the size and price are reduced. Can do. The microstrip antenna according to the third embodiment can be used as a multi-frequency shared transmission / reception separation type microstrip antenna.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the first to third embodiments, the center of the slot 7 is near the center of the dielectric substrate 7 or a line connecting the receiving microstrip antenna feeding point 6 and the transmitting microstrip antenna feeding point 5. However, the position of the slot 7 is not necessarily the center of the dielectric substrate 7 or the center between the feeding points.

  For example, as shown in FIG. 17, the slot 7 may be displaced from the center of the dielectric substrate 3 by a distance of Δx in the X direction (lateral direction in the drawing) and Δy in the Y direction (vertical direction in the drawing). Good.

  Thus, even if the position of the slot 7 moves (Δy) from the center position of the two feeding points toward one of the feeding points, it moves in the direction perpendicular to the direction connecting the two feeding points (Δx). Even so, in the reception band, the amount of mutual coupling between the transmitting and receiving antenna elements can be greatly reduced, and the amount of sneak current from the transmitting microstrip antenna to the receiving microstrip antenna can be reduced. Therefore, even if a manufacturing error occurs at the position of the slot 7, the amount of mutual coupling between the transmitting and receiving antenna elements can be reduced.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a composition perspective view of the microstrip antenna concerning a 1st embodiment. It is a block diagram of the microstrip antenna according to the first embodiment, (a) is a front view, (b) is a back view, and (c) is a side view (part 1). It is a block diagram of the microstrip antenna according to the first embodiment, where (a) is a front view, (b) is a back view, and (c) is a side view (part 2). It is A-A 'sectional drawing of Fig.3 (a). It is B-B 'sectional drawing of Fig.3 (a). It is a graph which shows the maximum value of the mutual coupling amount of the microstrip antenna which concerns on 1st Embodiment. It is a graph which shows the amount of mutual coupling of the microstrip antenna concerning a 1st embodiment. It is a block diagram of the microstrip antenna according to the second embodiment, where (a) is a front view, (b) is a back view, and (c) is a side view. It is A-A 'sectional drawing of Fig.8 (a). It is B-B 'sectional drawing of Fig.8 (a). It is C-C 'sectional drawing of Fig.8 (a). It is a block diagram of the configuration of a microstrip antenna according to a third embodiment, (a) is a front view, (b) is a back view, and (c) is a side view. It is A-A 'sectional drawing of Fig.12 (a). It is B-B 'sectional drawing of Fig.12 (a). It is C-C 'sectional drawing of Fig.12 (a). It is D-D 'sectional drawing of Fig.12 (a). It is a block diagram of the configuration of a microstrip antenna according to another embodiment, (a) is a front view, (b) is a back view. It is a block diagram of a conventional microstrip antenna, where (a) is a front view, (b) is a back view, and (c) is a side view.

Explanation of symbols

1, 1a, 1b, 1c, 11 Microstrip antenna for reception frequency band 2, 2a, 2b, 2c, 12 Microstrip antenna for transmission frequency band 3, 13 Dielectric substrate 4, 14 Ground plate 5, 5a, 5b, 5c , 15 Microstrip antenna feed point for transmission frequency band 6, 6a, 6b, 6c, 16 Microstrip antenna feed point for reception frequency band 7, 7a, 7b, 7c Slot 8 Shield

Claims (5)

A microstrip antenna comprising a transmitting microstrip antenna and a receiving microstrip antenna that are installed in a horizontal direction with respect to a plane on a dielectric substrate,
A rectangular slot formed between a receiving microstrip antenna feeding point and a transmitting microstrip antenna feeding point on a ground plate attached to the back surface of the dielectric substrate;
A microstrip antenna, comprising: a shield made of metal covering the slot. The length of the long side of the slot is L, and the length of the short side is is W, to claim 1, characterized in that the _{0.7λ 0 <L <1.0λ 0,} W <0.5λ 0 The described microstrip antenna. 3. The shield according to claim 1, wherein the shield has a rectangular parallelepiped shape, and S_W <0.5λ ₀ and 0.05λ ₀ <S_H <0.2λ ₀ when the width is S_W and the height is S_H. The microstrip antenna described in 1.   The microstrip antenna according to claim 1, wherein a plurality of the slots are formed, and the shield covers the plurality of slots. The microstrip antenna according to any one of claims 1 to 4, wherein a plurality of pairs of transmitting and receiving microstrip antennas having different excitation frequency bands are disposed on the dielectric substrate.

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