JP4689493B2 - Array antenna - Google Patents

Description

  The present invention relates to an array antenna composed of a plurality of subarrays having a feed waveguide as a feed circuit.

  In the conventional waveguide array antenna, the feeding circuit is constituted only by the waveguide. FIG. 4 is a structural diagram of a conventional subarray including a waveguide feeding circuit (see, for example, Non-Patent Document 1). In FIG. 4, a patch antenna 101 serving as an element antenna and a microstrip line 102 that feeds the patch antenna are configured on the upper surface of a dielectric substrate 103. In addition, a feed waveguide 106 is formed inside the metal housing 105, and the feed waveguide 106 and the patch antenna 101 are electrically connected by a feed pin 104.

  The received power of each element antenna is combined by the feed waveguide 106 and output to the output terminal at the lower end of FIG. Then, the antenna shown in FIG. 4 is used as a unit subarray, and an array antenna can be configured by arranging a plurality of unit subarrays.

“Low-Cost, High-Efficiency Quasi-Planar Array of Waveguide-Fed Circularly Polarized Microwave Antennas” IEEE Trans. on Antennas and Propagation, Vol. 53, no. 6. June 2005

  However, the prior art has the following problems. The shape of the aperture of the array antenna is generally rectangular, but sometimes it is elliptical. FIG. 5 is an illustration of an array antenna having an elliptical aperture shape. When an elliptical aperture array antenna is configured using the antenna shown in FIG. 4 as a unit sub-array, for example, as shown in FIG. 5, a feed waveguide of the sub-array at the center portion and the peripheral portion in the array plane. The total lengths of are different from each other.

  Therefore, it is necessary to compensate the total length of the feed waveguide during power combining. FIG. 6 is an exemplary diagram of a configuration for compensating the total length of the feeding waveguide. As shown in FIG. 6, in order to combine the received power of each sub-array in the same phase over a certain frequency band, the waveguide 110 is added, and the length of the feed waveguide is made the same between the sub-arrays. Thus, it is necessary to perform power synthesis after compensating for the phase difference during synthesis.

  However, although the waveguide has an advantage of its low loss property, it has a drawback that the weight and size are increased as compared with a coaxial line, a microstrip line, and the like. Therefore, there is a problem that adding such a waveguide 110 causes an increase in the weight and size of the entire power feeding circuit.

  On the other hand, FIG. 7 is an exemplary diagram of a configuration of a power feeding circuit that is lightweight and downsized. As shown in FIG. 7, it is conceivable to perform phase difference compensation using a lighter and smaller transmission line such as a coaxial cable 111 or a microstrip line instead of the waveguide 110.

  However, the waveguide 110 is a frequency dispersive line in which the partial differential with respect to the frequency of the phase constant does not become a constant, whereas the transmission line using the coaxial cable 111 has no frequency dispersive TEM (Transverse Electro Magnetic). It becomes a line or a quasi-TEM line whose frequency dispersibility is almost negligible.

  FIG. 8 is a diagram showing the phase characteristics of the power feeding circuit having the configuration of FIG. With the configuration of FIG. 7, when phase difference compensation is performed on the transmission line using the coaxial cable 111, as shown in FIG. 8, the phase difference is correctly compensated at a specific frequency and in-phase synthesis is possible. There is a problem that the phase difference is unavoidable at frequencies other than, and the combined power between the subarrays is deteriorated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain an array antenna that realizes phase difference compensation between sub-arrays over a certain frequency bandwidth in a lightweight and small size.

The array antenna according to the present invention includes one or more first subarrays having a longest feed waveguide as a feed circuit and a feed having a length shorter than the longest feed waveguide of the first subarray as a feed circuit. One or more second sub-arrays having waveguides and the output terminals of the respective feed waveguides of the first sub-array and the second sub-array are connected, and the received power of the first sub-array and the second sub-array is In an array antenna including a power combiner to be combined, an inductor is loaded on a TEM line or a quasi-TEM line at a constant period so as to have a frequency dispersion equivalent to that of the feed waveguide of the second sub- array. And a delay line inserted between the output terminal of the power supply waveguide of the second sub-array and the power combiner.

  According to the present invention, an inductor is loaded on a light-weight, small-diameter TEM or quasi-TEM line at a constant period, thereby intentionally configuring a line having frequency dispersion, and inserting the line into a feeding circuit in the subarray. Thus, it is possible to obtain an array antenna that realizes phase difference compensation between the sub-arrays in a light weight and a small size over the entire fixed frequency bandwidth.

Hereinafter, preferred embodiments of the array antenna of the present invention will be described with reference to the drawings.
The array antenna of the present invention compensates for the phase difference caused by the difference in the length of the feed waveguide by inserting a delay line configured by loading a short-circuited short-stub stub, and performs in-phase power synthesis in a certain frequency band. It can be performed over the entire area, and as a result, the device can be reduced in weight and size.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of an array antenna according to Embodiment 1 of the present invention. The element antenna 1 is mounted on a dielectric substrate 2. Also, rectangular feed waveguides 4a and 4b are formed in the metal housings 3a and 3b as feed circuits. Each of the feed waveguides 4a and 4b and the element antenna 1 are electromagnetically coupled via feed pins 11 inserted in the wall surfaces of the feed waveguides 4a and 4b.

  These components constitute subarrays 5a and 5b, respectively. Here, the length of the feed waveguide 4b included in the subarray 5b (corresponding to the first subarray) is shorter than the length of the feed waveguide 4a included in the subarray 5a (corresponding to the second subarray). Therefore, the feed waveguide 4b corresponds to the longest feed waveguide.

  Furthermore, the power supply waveguide 4a in the subarray 5a passes through the waveguide-microstrip line converter 6, the microstrip line substrate 7a, the microstrip line-coaxial line converter 14, the coaxial cable 12a, and the power combiner 13 Connected to. Similarly, the feed waveguide 4b in the sub-array 5b is also connected to the power combiner via the waveguide-microstrip line converter 6, the microstrip line substrate 7b, the microstrip line-coaxial line converter 14, and the coaxial cable 12b. 13 is connected.

  A low noise amplifier 10 is connected to the output end of the waveguide-microstrip line converter 6 (see the partially enlarged view in the lower part of FIG. 1). These components constitute one array antenna.

  Here, as described above, the length of the feed waveguide 4a is shorter than that of the feed waveguide 4b which is the longest feed waveguide. Therefore, in order to compensate for the phase difference caused by this difference in length, the microstrip line substrate 7a connected to the feeding waveguide 4a having a short length is short-circuited at the tip thereof whose ground is grounded through the through hole 8. Stubs 9 are periodically loaded. Here, the through hole 8 and the tip short-circuit stub 9 correspond to a delay line.

  Next, the operation of the array antenna in the first embodiment of the present invention will be described. When the lengths of the feed waveguides 4a and 4b are different between the sub-arrays 5a and 5b, in order to maximize the antenna gain by synthesizing the received power between the sub-arrays by the power combiner 13, It is necessary to compensate for the phase difference caused by the difference in length between the waveguides 4a and 4b over the entire antenna operating frequency band.

  However, when the phase difference compensation is to be realized by making the lengths of the microstrip line substrates 7a and 7b different from each other, the above-described problem occurs. In other words, the feed waveguide is a line having frequency dispersion, whereas the microstrip line is a line having almost no frequency dispersion, so that even if a specific frequency is used, phase difference compensation can be performed. However, the phase difference compensation error becomes large at other frequencies.

  On the other hand, the array antenna according to the first embodiment is inserted over the entire desired frequency band by inserting a delay line having a frequency dispersion equivalent to that of the feed waveguide into the microstrip line substrate 7a. Sufficient phase difference compensation can be performed. In the first embodiment, by using a delay line constituted by periodically loading the short-circuited short stub 9 operating as an inductor on the microstrip line substrate 7a, the frequency dispersibility equivalent to that of the feed waveguide is obtained. It has gained.

FIG. 2 is an equivalent circuit diagram per unit length of the TEM line in which the inductor is periodically loaded in the first embodiment of the present invention. In FIG. 2, L ₀ and C ₀ indicate the inductance and capacitance per unit length that each TEM line originally has. L _s indicates an equivalent inductance per unit length generated by the periodically loaded inductor. Here, the phase constant β (ω) of the TEM line is given by the following equation (1).

On the other hand, the phase constant β _WG (ω) of the feed waveguide is given by the following equation (2). In the following equation (2), c ₀ is the speed of light, and a is the transverse dimension of the waveguide.

In a normal TEM or quasi-TEM line, since L _s → ∞, the frequency dispersibility given by the partial differentiation with respect to ω of β is 0 from the above equation (1). However, it can be seen that by giving a certain finite amount of L _s , a dispersion characteristic equivalent to that of the feed waveguide given by the above equation (2) can be obtained.

  Therefore, the microstrip line substrate 7a on which the short-circuited stubs 9 are periodically loaded operates as a delay line having a frequency dispersion equivalent to that of the feed waveguide, and the subarray 5a, The phase difference caused by the difference in the length of the feed waveguides 4a and 4b in 5b can be compensated well over a certain frequency band. As a result, deterioration of the array antenna gain can be suppressed.

  Further, by loading the low noise amplifier in the preceding stage of the delay line, it is possible to suppress the deterioration of the G / T ratio (reception antenna gain / reception noise ratio) of the reception antenna due to the loss of the delay line.

  As described above, according to the first embodiment, the in-phase power synthesis of each subarray received power is performed by connecting the delay line configured by loading the short-circuited short-circuit stub on the microstrip line to the subarray feed circuit. Can be realized in a small size and light weight over the entire frequency band.

Embodiment 2. FIG.
In the first embodiment, as an example of the delay line, the case where the tip of the tip short-circuit stub is grounded through the through hole has been described. In the second embodiment, as an example of another delay line, a case where the tip of the tip short-circuited stub is grounded using a coplanar line will be described.

  FIG. 3 is a configuration diagram of the array antenna according to the second embodiment of the present invention. The element antenna 1 is mounted on a dielectric substrate 2. Also, rectangular feed waveguides 4a and 4b are formed in the metal housings 3a and 3b as feed circuits. Each of the feed waveguides 4a and 4b and the element antenna 1 are electromagnetically coupled via feed pins 11 inserted in the wall surfaces of the feed waveguides 4a and 4b.

  These components constitute subarrays 5a and 5b, respectively. Here, the length of the feed waveguide 4b included in the subarray 5b (corresponding to the first subarray) is shorter than the length of the feed waveguide 4a included in the subarray 5a (corresponding to the second subarray). Therefore, the feed waveguide 4b corresponds to the longest feed waveguide.

  Furthermore, the power supply waveguide 4a in the subarray 5a passes through the waveguide-microstrip line converter 6, the microstrip line substrate 7a, the microstrip line-coaxial line converter 14, the coaxial cable 12a, and the power combiner 13 Connected to. Similarly, the feed waveguide 4b in the sub-array 5b is also connected to the power combiner via the waveguide-microstrip line converter 6, the microstrip line substrate 7b, the microstrip line-coaxial line converter 14, and the coaxial cable 12b. 13 is connected.

  A low noise amplifier 10 is connected to the output end of the waveguide-microstrip line converter 6 (see the partially enlarged view in the lower part of FIG. 3). These components constitute one array antenna.

  Here, as described above, the length of the feed waveguide 4a is shorter than that of the feed waveguide 4b which is the longest feed waveguide. Therefore, in order to compensate for the phase difference caused by the difference in length, a coplanar line 20 is formed on a part of the microstrip line substrate 7a connected to the feeding waveguide 4a having a short length. Further, the coplanar track 20 is periodically loaded with a short-circuited short-circuit stub 21 whose tip is connected to the ground plane surface of the coplanar track 20. Here, the coplanar line 20 and the tip short-circuit stub 21 correspond to a delay line.

  Next, the operation of the array antenna according to Embodiment 2 of the present invention will be described. The second embodiment is different from the first embodiment only in that the delay line is configured by the coplanar line 20 instead of the microstrip line substrate 7a. Therefore, the operation equivalent to that of the first embodiment is exhibited.

  In the delay line, an inductor element such as a tip short-circuited stub is required. In the second embodiment, this inductor element is realized by the tip short-circuited stub 21 of the coplanar line 20. As a result, the through hole 8 required in the first embodiment is not necessary, and the manufacturing cost can be reduced.

  As described above, according to the second embodiment, the in-phase power synthesis of the received power of each subarray is performed by connecting the delay line configured by loading the short-circuited stub at a fixed period to the coplanar line to the subarray feed circuit. It can be realized in a small size and light weight over the entire fixed frequency band. Furthermore, since the through hole is not used, the manufacturing cost of the delay line can be reduced.

  In the above description, phase compensation for two types of feed waveguides having different lengths has been described. However, the array antenna in the present invention is not limited to this. Even in an array antenna including a subarray having three or more types of feed waveguides having different lengths, a similar effect can be obtained by providing a delay line corresponding to each length.

It is a block diagram of the array antenna in Embodiment 1 of this invention. FIG. 3 is an equivalent circuit diagram per unit length of a TEM line in which inductors are periodically loaded in the first embodiment of the present invention. It is a block diagram of the array antenna by Embodiment 2 of this invention. FIG. 6 is a structural diagram of a conventional subarray including a waveguide feeding circuit. It is an illustration figure of the array antenna which made the opening surface shape elliptical. It is an illustration figure of the structure which compensates the total length of a feed waveguide. It is an illustration figure of the structure of the electric power feeding circuit which aimed at weight reduction and size reduction. It is the figure which showed the phase characteristic of the electric power feeding circuit which has the structure of FIG.

Explanation of symbols

  1 element antenna, 2 dielectric substrate, 3a, 3b metal casing, 4a feed waveguide, 4b feed waveguide (longest feed waveguide), 5a subarray (second subarray), 5a subarray (first Sub-array), 6 waveguide-microstrip line converter, 7a, 7b microstrip line substrate, 8 through-hole, 9 short-circuited stub (delay line), 10 low noise amplifier, 11 feed pin, 12a, 12b coaxial cable , 13 Power combiner, 14 Microstrip line-coaxial line converter, 20 Coplanar line, 21 Short-circuited stub (delay line).

Claims (6)

One or more first sub-arrays having the longest feed waveguide as a feed circuit;
One or more second subarrays having a feed waveguide with a length shorter than the longest feed waveguide of the first subarray as a feed circuit;
An array comprising: a power combiner that is connected to output terminals of the respective feed waveguides of the first subarray and the second subarray, and combines the received power of the first subarray and the second subarray. In the antenna,
A TEM line or a quasi-TEM line is loaded with an inductor at a constant period so as to have a frequency dispersion equivalent to that of the second sub-array feed waveguide, and the second sub-array feed waveguide An array antenna, further comprising a delay line inserted between an output terminal and the power combiner. The array antenna according to claim 1, wherein
An array antenna, further comprising a low noise amplifier in front of the delay line. The array antenna according to claim 2,
The delay line is configured as a microstrip line on a dielectric substrate as a quasi-TEM line, and a tip short-circuited stub provided on the dielectric substrate at a constant period is loaded as an inductor. The array antenna according to claim 3,
The tip antenna short-circuited stub is grounded through a through hole. The array antenna according to claim 2,
2. The array antenna according to claim 1, wherein the delay line is configured as a coplanar line on a dielectric substrate as a quasi-TEM line, and a short-circuited short stub provided on the dielectric substrate at a constant period is loaded as an inductor. The array antenna according to claim 5, wherein
The array antenna according to claim 1, wherein the tip short-circuited stub is grounded by a ground plane surface of the coplanar line.

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