JP3469834B2 - Broadband array antenna - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband array antenna, and more particularly to means for combining an inverted F antenna with a parasitic element to broaden the characteristic band.

[0002]

2. Description of the Related Art Conventionally, an enemy / friend identification (IFF) system for identifying an enemy or an ally by receiving a response signal from an opponent to a transmitted inquiry radio signal has been known. When applying the enemy-friend identification (IFF) system that uses a radio frequency signal with a wavelength of about 300 mm to the aircraft, the antenna mounted on each aircraft is mainly attached to the nose part, from the viewpoint of reducing air resistance. A low height antenna is required. In particular, if there is no choice but to place it at the nose in front of the cockpit due to various reasons, it is important to reduce the posture from the viewpoint of securing the field of view of the pilot. Further in this case,
In terms of electrical characteristics, the front-rear ratio (Front
1030MHz (transmission) and 1090MHz as frequency with high directional radiation pattern of to back ratio (hereinafter referred to as FBR)
Since it is necessary to cover (reception) with one antenna, it is required to guarantee a specific bandwidth of 5.7% or more.

Conventionally, as a device that satisfies the above requirements, a forced excitation antenna as described below is disclosed in Japanese Patent Laid-Open No. 3-213005.
It is proposed in Japanese Patent Publication No.

FIG. 8 is a functional block diagram showing a configuration example of a conventional forced excitation antenna. The forced excitation antenna shown in this example includes a first excitation circuit 100 and first and second monopole antennas 101 and 102 connected to each other via the first excitation circuit 100 and the first excitation circuit 100.
A double tuning circuit 103, a second excitation circuit 105 connected to the input / output connector 104 via the double tuning circuit 103, and a second
Double tuning circuit 106 and the second exciting circuit 10
And a third monopole antenna 107 connected to the 5. The forced excitation antenna configured as described above uses, for example, a top-load type monopole antenna in which a loading element is loaded on the top of a monopole as an antenna element in order to realize the low-profile shape required for the reason described above. The element length is reduced to less than half that of a normal monopole antenna.

The operation of the forced excitation antenna shown in this example is described in detail in the above-mentioned publication, so its explanation is omitted. However, there are the following problems due to the reduction of the antenna size. That is, since the input impedance of this forced excitation antenna exhibits a low resistance characteristic of several ohms, it is difficult to achieve impedance matching with a transceiver whose interface is designed in a 50 ohm system. Therefore, the impedance matching is achieved by adopting the first and second double tuning circuits 103 and 106. Furthermore, in order to realize a high FBR directional pattern, the first excitation circuit 100 and the second excitation circuit 100
The excitation circuit 105 is used to operate the antenna as a binomial coefficient endfire array with a predetermined excitation distribution. Therefore, the conventional forced excitation antenna requires a complicated excitation circuit and a tuning circuit (matching circuit) in order to achieve a desired low-profile shape and electrical performance, and as a result, the manufacturing cost becomes high. There was a point.

In order to solve the above problems, the inventors of the present application have proposed an array antenna which can obtain a high FBR directional radiation pattern even in a low profile without using the above-mentioned complicated excitation circuit and tuning circuit. (See Japanese Patent Laid-Open No. 9-55621). Since the details are described in the publication, only the essential points will be briefly described below.

FIG. 9 is a diagram for explaining a configuration example of the array antenna disclosed in the above-mentioned Japanese Patent Laid-Open No. 9-55621. The array antenna shown in this example has an inverted antenna as a feeding element.
The F antenna 200 and the inverted L antennas 210 and 220 as parasitic elements, which are arranged in front of and behind the F antenna 200, are spaced apart by the intervals AS1 and AS2, respectively. The horizontal plane 230 with diagonal lines in the figure means the body of the aircraft or the ground plate. The inverted F antenna 200 is composed of a feed pin portion H, a short-circuit pin portion Hs, and top horizontal portions WL and WR.
Power is supplied from the lower portion of H, and the lower portion of the short-circuit pin portion Hs is grounded to the body or the ground plate 230. The two inverted L antennas 210 and 220 are composed of vertical parts HR and HD and horizontal parts WRR and WRD, respectively, and each vertical part H and HD.
The lower portions of R and HD are grounded to the body or the ground plate 230.

The array antenna shown in this example operates as follows. That is, this array antenna basically uses the principle of the Yagi-Uda antenna, and is a parasitic element with an element length of λ / 4 or more or λ / 4 or less at a predetermined distance from the feeding element. By arranging appropriately,
This is operated as a reflector or a director. An example of specific shape parameters is shown in Table 1
Show as. The shape shown as this type 1 is disclosed in
-55621 and the same as that disclosed in FIG.
It has a bandwidth of R ≤ 2 of about 10% and an FBR of about 18 dB. Therefore, by adopting such a configuration, the desired electrical performance that satisfies the system requirements described above while maintaining the low-profile shape (0.08λ = 22.6mm) without requiring any complicated excitation circuit and matching circuit Can be obtained.

[0009]

However, the conventional array antenna as described above has the following problems. In other words, in general, antennas for aircraft are required to operate under severe environmental conditions such as temperature change of -85 ° C to + 71 ° C. It is necessary to design the resonance frequency bandwidth sufficiently wider than the system required value and with a margin. From this point of view, the above ty
Although conventional array antennas such as pe1 satisfy the system requirement value, as shown in Fig. 3 to be described later, the reception frequency (1.
On the 09 GHz side, there was not enough margin for fluctuations in frequency characteristics, and there was a problem in putting it to practical use. The present invention was made in order to solve the above-mentioned problems relating to the conventional array antenna, and it is possible to secure a sufficient margin while maintaining a high FBR directional pattern even in a low-profile shape, with respect to the frequency characteristic fluctuations. It is an object of the present invention to provide a wideband array antenna capable of guaranteeing the performance of the antenna.

[0010]

In order to solve the above-mentioned object, the invention of claim 1 of the wideband array antenna according to the present invention is a first parasitic element having a predetermined element length.
And an inverted F antenna as a feeding element and a predetermined element length
The second parasitic element which it has is erected in order on the ground plate.
In the array antenna, a part of the first parasitic element is arranged so as to be located above the part of the feeding element with a required distance from the feeding element, and the first parasitic element is disposed .
The parasitic element, the second parasitic element, and the feeder element are set so that their respective element lengths are different from each other. The invention of claim 2 wherein the wideband array antenna according to the present invention, where
A first parasitic element having a constant element length and a feeding element
All inverted F antennas and a second unpaid antenna with a predetermined element length
Array antenna in which the electric element and the electric element are sequentially erected on the ground plate
In the above, the second parasitic element is arranged so that a part of the second parasitic element is located below the part of the feeding element with a required distance from the feeding element, and the first parasitic element and the front
The element lengths of the second parasitic element and the feeding element are set to be different from each other. According to the invention of claim 3 of the wideband array antenna of the present invention, a first parasitic element having a predetermined element length, an inverted F antenna as a feeding element, and a second parasitic element having a predetermined element length. An array antenna in which an element and a standing element are sequentially erected on a ground plate, and a part of the first parasitic element is arranged above the part of the feeding element with a required distance from the feeding element. In addition, a part of the second parasitic element is disposed below the part of the power feeding element with a required space from the power feeding element, and the length of each element is To be different from each other. A wideband array antenna according to a fourth aspect of the present invention is the wideband array antenna according to the third aspect, wherein the first parasitic element operates as a director by setting the element length to λ / 4 or less. At the same time, the element length of the second parasitic element is set to λ / 4 or more to operate as a reflector. A wideband array antenna according to a fifth aspect of the present invention is the wideband array antenna according to the first, second, third or fourth aspect, wherein each of the parasitic elements has an inverted L shape. . The invention according to claim 6 of the wideband array antenna according to the present invention is the wideband array antenna according to claim 1, claim 2, claim 3, claim 4 or claim 5, wherein the feed element and each parasitic element are not fed. The element is configured using a conductive pattern formed on the surface of the dielectric substrate.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on the illustrated embodiments. The wideband array antenna according to the present invention is shown in FIG. 3 of the above-mentioned JP-A-9-55621.
It is also possible to operate as a two-element array antenna composed of an inverted F antenna and one parasitic element as disclosed in
Furthermore, it is possible to operate a combination of many parasitic elements, but as an example, when operating as a three-element array antenna composed of the most common inverted F antenna and two parasitic elements. Will be described.

FIG. 1 is a block diagram showing an embodiment of a wideband array antenna according to the present invention. The wideband array antenna shown in this example is an inverted F antenna 10 as a feeding element that is erected on a ground plate, and has a predetermined element length, and a part of the element is arranged above the feeding element 10. As described above, the inverse L antenna 20 as the first parasitic element arranged in front of the inverse F antenna 10 at the required distance A1, and the required distance A2 behind the inverse F antenna 10 having a predetermined element length. An inverted L antenna 30 as a second parasitic element arranged is provided, and the lengths of the respective elements are different from each other.

The inverted F antenna 10 is a feed pin whose height is Hf = Hs.
11 and the short-circuit pin 12 and the top horizontal part 13 having a length of WL + WR, and power is supplied from the lower part of the power supply pin 11. In addition, the height of the two parasitic elements 20 and 30 and the length of the horizontal part are set to H
1, W1 and H2, W2, in this embodiment the total length of the linear conductor Ld = H1 + W1 the first parasitic element 20 (first inverted L antenna) is a waveguide, Lr = H2 + W2 second parasitic element 30 (second reverse L
The antennas) are each made to function as a reflector. In the conventional array antenna, the height H1 of the director is
And the height Hf (Hs) of the inverted F antenna are equal, the characteristic configuration of the wideband array antenna according to the present invention is
The reason is that the waveguide and the inverted F antenna are made closer to each other while making> Hf.

It is also possible to operate the first parasitic element 20 as a reflector and the second parasitic element 30 as a director by adjusting the element to a predetermined length as described later. .

The wideband array antenna shown in this example operates as follows. That is, the wideband array antenna according to the present invention basically uses the principle of the Yagi-Uda antenna similar to that described in Japanese Patent Laid-Open No. 9-55621, and each parasitic element 20, 30 is When the length is λ / 4 or less, it operates as a waveguide, and when it is λ / 4 or more, it operates as a reflector. That is, the total length Ld of the first parasitic element 20 is set to approximately λ / 4 or less, and the total length Lr of the second parasitic element 30 is set to
Is set to λ / 4 or more, and they operate as a director and a reflector, respectively.

At this time, the inventors of the present application have arranged the director 20 (first parasitic element) and the feeder element 10 closer to each other by using the above-mentioned structure than in the conventional array antenna. It was newly found that the stronger the coupling of, the wider band characteristics with high FBR directional pattern can be obtained. Below, as an example, the design frequency f0 = 1.06 GHz (λ0 = 283 mm), which is the center frequency of the IFF system, and the linear conductor radius ra = 2.1 m.
Using m, the element length of the inverted F antenna 10 is Hf + WL + WR≈0.25λ0
The result of simulating the characteristics of the wideband array antenna according to the present invention in the case of is described in detail below.

FIG. 2 shows the bandwidth characteristics of the voltage standing wave ratio VSWR ≦ 2 with respect to the array spacing A1 with the height H1 of the waveguide as a parameter, and the FBR performance at the practically important transmission frequency 1.03 GHz (-x FIG. 7 is a diagram showing gain ratio Gd / Gr characteristics in the axial direction) and in the rear (+ x axis direction). However, the length W1 of the horizontal portion of the waveguide is set to the optimum W1 = 0.104λ0 for the reason described later, and the parameters relating to the reflector 30 are set to the same values as those of the conventional array antenna type1.

Feeding the waveguide 20 with a narrow array spacing A1 Inverse F
When the antenna 10 is moved closer to the antenna 10, the horizontal portion of the director is arranged above the inverted F antenna element, and the bandwidth is sharply improved at A1 <0.1λ0. There is A1 that has the optimum bandwidth for. At this time, for each H1, A1 for which Gd / Gr is the optimum value and A1 for which the VSWR bandwidth is the optimum value are almost the same.

Therefore, when the shape with the maximum bandwidth is obtained under the condition that Gd / Gr ≧ 30 dB is obtained from FIG. 2, H1 = 0.102λ0 and A1 = 0.055λ0 shown by black circle dots in FIG. 2 are obtained. The wideband array antenna of is called type2), the bandwidth is 18.8%, and Gd / Gr can be 32.9 dB. Also, Gd
When the shape is selected under the condition that / Gr is optimum, H1 = 0.098λ0 and A1 = 0.055λ0 shown by white triangles in Fig. 2 are obtained (hereinafter,
This type of wideband array antenna is called type3), Gd / G
It is possible to obtain 45.9 dB as r and 16.4% as bandwidth.

As described above, in the wideband array antenna according to the present invention, the arrangement intervals of the directors 20 are A1 <0.1λ0.
By doing so, the performance (bandwidth ≈ 10%, Gd / Gr ≈ 18 dB) of the conventional array antenna (type 1) can be significantly improved without being limited to the type 2 or type 3 shape.
Although the effect of the reflector 30 will be described later, the reflector is set as H2 <Hf (Hs) instead of the proximity arrangement of the director 20 described above.
Similar wide band characteristics can be obtained even if 30 is arranged close to the power feeding element 10.

Table 1 shows the shape parameters of type 2 and type 3 antennas together with the case of type 1.

[Table 1] As is clear from this table, in the wideband array antenna according to the present invention, the total length L is shortened to about 78% as compared with the conventional one (type 1) by setting the array spacing A1 to be narrow, and as a result, It is also effective in downsizing the antenna.

FIG. 3 is a diagram showing a simulation result of frequency characteristics of return loss of type 2 and type 3 which are optimum shapes of the wide band array antenna according to the present invention. The VSWR value corresponding to the return loss is also shown on the right axis for reference, and the conventional array antenna is also shown for comparison.
The characteristics of (type 1) are also shown. When evaluated with VSWR ≤ 2 (equivalent to -9.54 dB or less in terms of return loss), the wideband array antenna according to the present invention is widened to a higher frequency side than the bandwidth of the conventional type 1, and particularly in the type 2, The bandwidth will be doubled. Therefore, if the wideband array antenna according to the present invention is used, the conventional array antenna (t
It is possible to solve the shortage of margin for the frequency fluctuation to the low frequency side of the reception frequency (1.09 GHz), which was a problem in ype1).

FIG. 4 is a diagram showing the directional gain and the frequency characteristics of Gd / Gr of the wideband array antennas (type 2, type 3) according to the present invention. The bandwidth where Gd / Gr is almost 10 dB or more is t
With ype2, the band is widened to the high frequency side about twice as much as the conventional type1, and the band and the band of VSWR ≤ 2 are almost the same frequency band, so the wide band array antenna according to the present invention is It can be seen that it operates as a Yagi-Uda antenna with unidirectionality within the VSWR ≤ 2 band. Also, Gd / Gr has a maximum value at a practically important transmission frequency of 1.03 GHz, which is a significant improvement over the conventional type 1.

The directional gain Gd is not so different from the conventional array antenna (type 1) at the transmission frequency of 1.03 GHz, but Gd
Comparing the bandwidths defined by ≧ 7 dBi, the bandwidth of type 2 is approximately 45 MHz, and that of type 3 is approximately 13 MHz.

Here, the influence of the length W1 of the horizontal portion of the waveguide on the characteristics will be considered. FIG. 5 is a diagram showing a bandwidth defined by VSWR ≦ 2 and Gd / Gr at a transmission frequency of 1.03 GHz when W1 is changed in the above-described type2. W1
Is changed from 0.104λ0 of type2, the characteristic of type2 shown by the black dot is that Gd /
Gr has also decreased, so the length of the horizontal part of the waveguide is W1 =
It can be seen that 0.104λ0 is optimal.

Next, the effect of the reflector 30 will be considered.
In the conventional array antenna (type 1), the center of the conductor in the vertical part of the reflector of height H2 and the horizontal part of the top of the inverted F antenna 10 are fed.
The distance from the end of R is 0.01λ0. Therefore, if the reflector 30 is further placed close to the feeding inverted-F antenna 10, the height H
2 must be lower than Hf (= 0.08λ0).

Therefore, in the type 2 shape, the height H2 of the reflector is set as a parameter in the range of 0.061λ0 to 0.098λ0.
The effect on the antenna characteristics was investigated by changing the array spacing A2 from 0.16λ0 to 0.28λ0. For H2 <0.08λ0, the reflector is placed below the inverted F antenna A2 = 0.13
It was changed from λ0 to 0.28 λ0. Figure 6 shows that H2 <Hf (= 0.08λ
It is a figure which shows the structural example which arrange | positions the reflector 30 closely as (0).

As a result, although not shown in the drawing, the bandwidth of VSWR ≦ 2 and Gd / Gr deteriorated sharply from the characteristics of type 2. However, if the length W2 of the horizontal part of the reflector is adjusted to a predetermined length, VS
Bandwidth of WR ≤ 2 has the same performance as type2, but Gd / G
Since the directivity pattern characteristic deteriorates a little such that r becomes 10.3 dB at the transmission frequency of 1.03 GHz, the array antenna of this shape parameter is applicable mainly to the application where only wide band VSWR characteristics are required.

Next, another embodiment of the present invention will be described. In the above-described embodiment, the antenna is formed by using the linear conductor having the radius ra, but the dielectric substrate having the relative permittivity εr is erected vertically on the ground plate, and the above-mentioned ty is formed on one surface of the substrate.
The conductor pattern forming the wide band array antenna shape according to the present invention such as pe2 or type3 may be formed by copper foil by etching or the like. This will be described below.

FIG. 7 is a diagram showing an example in which a wideband array antenna similar to that of the basic embodiment (FIG. 1) is formed on a dielectric substrate. The wideband array antenna shown in this example is a ground plate.
A feeding reverse F element 73 and parasitic elements 74 and 75 are formed on one surface of a dielectric substrate 72 erected on 71. There is no conductor pattern on the surface opposite to the surface on which each element is formed. The shape parameter in this case is that the wavelength is approximately λ / √εr to 0.95λ.
Since it is shortened to, the distance between the feeding element and each parasitic element,
It is necessary to shorten the feeding element length and each parasitic element length to approximately 1 / √εr to 0.95 as compared with the case of the above-described basic embodiment. Further, a plate-shaped conductor may be held on one surface of a dielectric material such as a foam material with an adhesive or the like, and the plate-shaped conductor may form the conductor pattern. In this case, since εr≈1, it is not necessary to reduce the distance between the feeding element and each parasitic element, the length of the feeding element, and the length of each parasitic element.

In the above embodiments, the case where the inverted L-shaped conductor is used as the parasitic element has been described.
The wideband array antenna according to the present invention is not limited to this. That is, it is obvious that the element length of the parasitic element is an important parameter as an operating condition of the Yagi-Uda antenna, and its shape may be arbitrary. When using parasitic elements of any shape, set the element length to about λ / 4 or less as a waveguide and about λ / 4 or more as a reflector, and describe these parasitic elements as described above. As described above, a wide band characteristic can be obtained by arranging the power feeding elements close to each other at a required interval to strengthen the coupling between the elements.

[0032]

As described above, the present invention uses the structure in which the parasitic element is arranged close to the inverted F antenna, and operates the parasitic element as a director or a reflector to reduce the total length of the array antenna. Since it is compact and has a wide profile while maintaining a high FBR directional pattern with a low profile, it is a wideband array that can guarantee sufficient performance even when the frequency characteristics fluctuate as an IFF antenna for an aircraft. It is extremely effective in realizing an antenna.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a wideband array antenna according to the present invention.

FIG. 2 is a diagram showing the bandwidth and Gd / Gr (FBR) characteristics of the wideband array antenna according to the present invention.

FIG. 3 is a diagram showing frequency characteristics of return loss of the wideband array antenna according to the present invention.

FIG. 4 is a diagram showing directional gain and frequency characteristics of Gd / Gr (FBR) of a wideband array antenna according to the present invention.

FIG. 5 is a diagram showing the bandwidth and Gd / Gr (FBR) characteristics with respect to changes in the horizontal length W1 of the director of the wideband array antenna according to the present invention.

FIG. 6 shows a wideband array antenna according to the present invention.
Diagram showing a configuration example where H2 <Hf

FIG. 7 is a diagram showing an example in which a wideband array antenna according to the present invention is configured using a dielectric substrate.

FIG. 8 is a functional block diagram showing a configuration example of an array antenna using a conventional top load type monopole element.

FIG. 9 is a diagram illustrating a configuration example of an array antenna including a conventional inverted F antenna and a parasitic element.

[Explanation of symbols]

..Inverted F antenna (feeding element) 11 ... Inverted-F antenna feed pin (length Hf) 12- ・ Inverted F antenna short-circuit pin (length Hs) ..Horizontal top of inverted F antenna (length WL + WR) 20..Director (parasitic element) 30..Reflector (parasitic element)

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chen Qiang 1-3-3-3, Mikamimine, Taihaku-ku, Sendai City, Miyagi Prefecture (72) Inventor Kunio Sawaya 4-2-1-3, Hachiman, Aoba-ku, Sendai City, Miyagi Prefecture ( 56) References JP-A-6-232625 (JP, A) JP-A-61-2232704 (JP, A) JP-A-6-69715 (JP, A) JP-A-5-90828 (JP, A) JP Flat 10-322124 (JP, A) Actual flat 3-14813 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 13/08 H01Q 9/36 H01Q 19/28

Claims (6)

(57) [Claims] 1. A first parasitic element having a predetermined element length.
And an inverted F antenna as a feeding element and a predetermined element length
The second parasitic element which it has is erected in order on the ground plate.
In the array antenna, a part of the first parasitic element is arranged so as to be located above the part of the feeding element with a required distance from the feeding element, and the first parasitic element is disposed .
A wideband array antenna , wherein the parasitic element, the second parasitic element, and the feed element are set so that their respective element lengths are different from each other. 2. A first parasitic element having a predetermined element length.
And an inverted F antenna as a feeding element and a predetermined element length
The second parasitic element which it has is erected in order on the ground plate.
In the array antenna, a part of the second parasitic element is arranged below the part of the feeding element with a required distance from the feeding element, and the first parasitic element is arranged .
A wideband array antenna , wherein the parasitic element, the second parasitic element, and the feed element are set so that their respective element lengths are different from each other. 3. A first parasitic element having a predetermined element length, an inverted F antenna as a feeding element, and a second parasitic element having a predetermined element length are erected in order on a ground plate. In the array antenna, a part of the first parasitic element is arranged so as to be located above the part of the feeding element with a required distance from the feeding element, and the second parasitic element is provided.
A part of the parasitic element is located below the part of the feeding element with a required distance from the feeding element, and the lengths of the respective elements are different from each other. Wideband array antenna characterized by setting. 4. The element length of the first parasitic element is set to λ / 4 or less to operate as a director, and the element length of the second parasitic element is set to λ / 4 or more. 4. The wideband array antenna according to claim 3, wherein the wideband array antenna is operated as a reflector. 5. The wideband array antenna according to claim 1, 2, 3, or 4, wherein each parasitic element has an inverted L shape. 6. A conductive pattern formed on the surface of a dielectric substrate for each of the feeding element and each parasitic element, wherein the feeding element and the parasitic element are formed by using a conductor pattern. The wideband array antenna according to claim 5.