JP5152302B2 - Array antenna apparatus and impedance matching method thereof - Google Patents

Description

  The present invention relates to an array antenna device and an impedance matching method thereof, and more particularly to an impedance matching method of a phased array antenna in which a plurality of antenna elements on which phase shifters and the like are mounted are arranged.

  In a radar antenna related to the present invention, a phased array antenna in which a plurality of antenna elements on which phase shifters and the like are mounted is often used. FIG. 8 is a configuration diagram of an example of a phased array antenna related to the present invention.

  Referring to the figure, an example of a phased array antenna related to the present invention includes an antenna element 10 and a phase shifter 30 provided in each system of # 1 to #n (n is an integer of 2 or more), It includes a combination distributor 40A and 40B for combining and distributing the output of the phase shifter 30.

  In this phased array antenna, it is necessary to perform impedance matching in order to efficiently transmit electric power between a plurality of antenna elements 10 arranged in parallel and a feeding circuit (combining / distributing devices 40A and 40B in the configuration shown in the figure). In the phased array antenna, mutual coupling with adjacent elements occurs. Since this mutual coupling is in a different coupling state for each beam scanning angle, there is a problem that impedance mismatch occurs depending on the scanning angle and the gain is lowered.

  The following methods are generally known as methods for impedance matching for each scanning angle. One is a method of installing a matching circuit between the antenna element and the feeding circuit (see Patent Documents 1 and 2).

  Patent Document 1 discloses a wireless device in which a matching circuit having a variable capacitance element is provided between each antenna and a changeover switch. In this wireless device, the variable capacitance elements of the respective matching circuits are adjusted so that the voltages received and detected by the respective antennas are maximized.

  Patent Document 2 discloses an array antenna in which a matching circuit is provided for each antenna and impedance matching is performed with each antenna.

  The other one is a method of matching impedance between the antenna element and the feeding circuit by setting a reactance element arranged around the antenna element to a desired element value for each scanning angle (see Patent Document 3). A method of controlling impedance by combining the techniques described in Patent Documents 1 to 3 is also known.

JP 2006-324984 A JP 09-321526 A JP 2007-135186 A

  However, in an array antenna in which a large number of antenna elements described in Patent Documents 1 to 3 are arranged, in order to optimally match the impedances of the antenna element and the feeder circuit in the entire scanning range, all scanning angles in the beam scanning range are used. Therefore, it is necessary to obtain the element impedances of all the antenna elements according to the measurement or simulation, thereby increasing the device scale.

  Further, in the array antennas described in Patent Documents 1 to 3, it is necessary to apply a bias voltage to the variable capacitance element used in the matching circuit in order to adjust the impedance. In order to obtain the optimum condition of the matching circuit for each antenna element. Therefore, it is necessary to apply a different bias voltage for each matching circuit, which causes an increase in hardware scale.

  Therefore, an object of the present invention is to provide an array antenna apparatus and an impedance matching method thereof that do not require measurement of element impedance for each antenna and do not require adjustment to a different bias voltage for each matching circuit.

  In order to solve the above problems, an array antenna apparatus according to the present invention includes a plurality of antenna elements, a feeding circuit that feeds power to the plurality of antenna elements, the plurality of antenna elements, A plurality of matching circuits that are respectively provided between the power supply circuit and perform impedance matching; and a control unit that controls the plurality of matching circuits, wherein the control unit includes an element impedance of a central antenna element in a beam scanning range. And a matching condition between the antenna element and the feeding circuit is determined based on the calculated element impedance, and the determined matching condition is applied to the matching circuits of all the antenna elements.

  The impedance matching method according to the present invention includes a plurality of antenna elements, a power feeding circuit that feeds power to the plurality of antenna elements, and a plurality of antenna elements that are arranged and the power feeding circuit. An impedance matching method for an array antenna apparatus including a plurality of matching circuits each provided for impedance matching and a control unit for controlling the plurality of matching circuits. The method is performed by the control unit, and is performed at the center in the beam scanning range. Including an impedance matching step of calculating an element impedance of the antenna element, determining a matching condition between the antenna element and the feeding circuit based on the calculated element impedance, and applying the determined matching condition to the matching circuit of all the antenna elements It is characterized by that.

  Further, a program according to the present invention is provided in each of a plurality of antenna elements, a power feeding circuit that feeds power to the plurality of antenna elements, and a plurality of antenna elements that are arranged and the power feeding circuit. A program of an impedance matching method for an array antenna apparatus including a plurality of matching circuits for performing impedance matching and a control unit for controlling the plurality of matching circuits, wherein the control unit includes a central antenna element in a beam scanning range. In order to execute an impedance matching step of calculating an element impedance of the antenna element, determining a matching condition between the antenna element and the feeder circuit based on the calculated element impedance, and applying the determined matching condition to the matching circuits of all antenna elements It is characterized by that.

  According to the present invention, it is possible to obtain an array antenna device and an impedance matching method thereof that do not require the element impedance to be measured for each antenna and do not need to be adjusted to a different bias voltage for each matching circuit.

It is a block diagram of an example of the array antenna apparatus which concerns on this invention. It is an antenna equivalent circuit diagram of an example of the array antenna apparatus which concerns on this invention. It is a VSWR versus beam scanning angle characteristic diagram before applying the present invention. It is an amplitude versus beam scanning angle characteristic diagram before applying the present invention. It is a VSWR vs. beam scanning angle characteristic diagram after applying the present invention. It is an amplitude vs. beam scanning angle characteristic diagram after applying the present invention. It is a flowchart which shows an example of the impedance matching method which concerns on this invention. It is a block diagram of an example of the phased array antenna relevant to this invention.

  First, the operation principle of the present invention will be described before the description of the embodiment. In the present invention, by utilizing the fact that the antenna elements of the array antenna are periodically arranged, the matching condition obtained from the element impedance of the central antenna element in the beam scanning range is applied to all matching circuits, An optimum matching state is realized for each beam scanning while setting the bias voltage controlled by the control unit to the same value in all the matching circuits.

  In the present invention, a matching circuit for adjusting impedance is provided between a plurality of arranged antenna elements and a power feeding circuit. The matching circuit is provided with a variable capacitance element (for example, a varactor diode, MEMS (Micro Electro Mechanical Systems), liquid crystal, etc.), and the impedance condition acquired from the central antenna element in the beam scanning range is set for all the antenna elements. Assuming the optimum condition, the bias voltage applied from the control unit to the variable capacitance element of the matching circuit is controlled, and the optimum matching condition obtained at the center in the beam scanning range is given to all the matching circuits. Impedance matching is performed between the power feeding circuits to suppress reflection loss within the beam scanning range.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an example of an array antenna apparatus according to the present invention. In the figure, the same components as those in FIG. 8 described above are denoted by the same reference numerals and description thereof is omitted.

  Referring to FIG. 1, an example of an array antenna apparatus according to the present invention includes an antenna element 10 provided in each system of # 1 to #n (n is an integer of 2 or more), a matching circuit 20, and a phase shifter. 30, combining distributors 40 </ b> A and 40 </ b> B that combine and distribute the outputs of the respective phase shifters 30, a control unit 50, and a program storage unit 60.

  The matching circuit 20 is composed of a variable capacitance element. The control unit 50 controls the variable capacitance element. The combiner / distributor 40 </ b> A and 40 </ b> B distributes power to the respective antenna elements 10. The program storage unit 60 stores an impedance matching method program described later.

  FIG. 2 is an antenna equivalent circuit diagram of an example of the array antenna apparatus according to the present invention. Referring to the figure, the antenna equivalent circuit includes a feeder circuit 1, an antenna element 2, and a matching circuit 3.

  The power feeding circuit 1 can be expressed by a power supply impedance 1a (impedance value is Zg) and a power supply voltage 1b (voltage value is Vg). The antenna element 2 can be expressed by an element impedance 2a (impedance value is Za). The matching circuit 3 can be expressed by a matching circuit impedance 3 a (impedance value is Zm), and has a function of adjusting impedance on the power source side as viewed from the antenna element 2.

  The antenna element 10 and the matching circuit 20 in FIG. 1 are equivalent to the antenna element 2 and the matching circuit 3 in the equivalent circuit in FIG. When the phased array antenna performs beam scanning while changing the feeding phase for feeding power to each element, the element impedance 2a changes due to the influence of mutual coupling with adjacent elements. However, since the power supply impedance 1a of the power supply circuit 1 does not change at this time, impedance mismatch occurs between the power supply circuit 1 and the antenna element 2, and the reflection loss changes depending on the scanning angle.

  In order to suppress the reflection loss caused by this mismatch, a varactor diode, MEMS, liquid crystal, or the like is used as a variable capacitance element constituting the matching circuit 20 (see FIG. 1), and a bias voltage applied to the matching circuit 20 by the control unit 50. Is controlled to change the element value (capacitance) of the variable capacitance element constituting the matching circuit 20 and adjust the impedance viewed from the antenna element 10, and the antenna element 10 and the feeder circuit (in this embodiment, the combiner / distributor 40A). , 40B).

  In the control unit 50, the element impedance of the central antenna element in the beam scanning range is obtained in advance by actual measurement or simulation, and the power supply side impedance viewed from the antenna element and the optimum impedance are obtained from the obtained element impedance for each beam scanning. Stores control data for impedance matching. Thereby, the variable capacitance element of the matching circuit 20 can be controlled according to the beam scanning angle.

  In the present invention, the matching circuit 3 (see FIG. 2) of the entire phased array antenna is adjusted and viewed from the antenna element 2 using the optimum condition obtained from the element impedance of only the central antenna element in the beam scanning range. By varying the impedance, the impedance matching state with the element impedance 2a is adjusted according to the scanning angle.

  Next, the operation of this embodiment will be described with reference to the drawings. Referring to FIG. 2, the antenna is generally impedance-matched so that the element impedance Za and the power source impedance Zg are Zg = Za * (* means conjugate).

  However, in a phased array antenna, when the elements are arranged in an array or the feeding phase to the antenna element is changed by a phase shifter for beam scanning, the element impedance Za is caused by the influence of mutual coupling between adjacent elements. Change. For this reason, the element impedance Za mismatches with the element impedance Zg, and the reflection loss increases. For this reason, in the phased array antenna, the reflection loss changes depending on the scanning angle, and the antenna gain decreases.

  3 and 4 show an antenna element as an example, in a square arrangement, 9 elements in the vertical direction × 9 elements in the horizontal direction, and the element matching before arranging the elements in the array with the vertical and horizontal element intervals of 0.5λ. VSWR (Voltage Standing Wave Ratio) obtained by simulation and antenna pattern results.

  FIG. 3 is a VSWR obtained by simulation, and it can be seen that when antenna elements matched by a single element are arranged in an array, the VSWR deteriorates due to mutual coupling, and the VSWR changes depending on the scanning angle.

  Also, FIG. 4 shows an antenna pattern obtained by simulation, and the VSWR deteriorates due to mutual coupling as shown in FIG. 3. Therefore, the antenna gain is compared with the gain curve when the VSWR indicated by the broken line is sufficiently suppressed. It can be seen that the decrease in

  However, in the array antenna, it is necessary to obtain all the element impedances of all the antenna elements within the scanning range, and it takes a lot of time and cost to create control data, and each antenna element matching circuit has a separate bias. Since it is necessary to apply a voltage, there has been a drawback that the scale of the apparatus is increased.

  In view of this situation, the present invention focuses on the periodicity of the array antenna and considers that the element impedance of the central element is equivalent to the element impedance of the entire array antenna. Impedance matching is possible.

  5 and 6 show the VSWR (FIG. 5) and the antenna pattern result (FIG. 6) when the present invention is applied under the same conditions as the simulations of FIGS. FIG. 5 shows a calculation result of VSWR when the element value (capacitance) of the variable capacitance element of the matching circuit 20 (see FIG. 1) is determined so as to obtain an optimum matching state according to the beam scanning angle. It can be seen from FIG. 5 that VSWR is suppressed at any scanning angle.

  Next, FIG. 6 shows an antenna pattern when calculated under the matching conditions of FIG. The waveform shown by the solid line in FIG. 6 is the antenna pattern when the present invention is applied, and the waveform shown by the broken line is the antenna pattern when the matching circuit of FIG. 4 is not installed. From the results shown in FIGS. 5 and 6, even when only the matching condition obtained from the element impedance of the central element is used, an increase in reflection loss due to mutual coupling of the array antennas can be suppressed.

  As a supplementary explanation of the present invention, in the above description, the antenna element used for the matching condition has been described as the antenna element at the center of the antenna opening. However, in an array antenna having a sufficiently large opening, the antenna element need not necessarily be at the center. However, the effect of the present invention can be sufficiently obtained if the antenna element is in a position where the periodicity near the center is well maintained.

  Next, the impedance matching method according to the present invention will be described. FIG. 7 is a flowchart showing an example of the impedance matching method according to the present invention. As described in the description of FIG. 1, an example of the array antenna device according to the present invention includes the control unit 50, and the control unit 50 controls the matching circuit 20 including variable capacitance elements. That is, the control unit 50 controls the matching circuit 20 to perform impedance matching between the antenna element 10 and the feeding circuit (in the present invention, the combiner / distributor 40A and 40B as an example). Therefore, the main body of the step (processing) shown in FIG.

  Referring to FIG. 7, the control unit 50 calculates the element impedance of the central antenna element 10 in the beam scanning range (step S1). The calculated element impedance value is stored in a memory (not shown).

  Next, the control unit 50 determines matching conditions between the antenna element 10 and the feeder circuit (in the present invention, the combiner / distributor 40A and 40B as an example) based on the calculated element impedance (step S2).

  Next, the control unit 50 gives the determined matching condition to the matching circuits 20 of all the antenna elements 10 (step S3).

  Next, a program for the impedance matching method according to the present invention will be described. As described in the description of FIG. 1, an example of the array antenna apparatus according to the present invention includes the program storage unit 60. The program storage unit 60 stores a program for the impedance matching method shown in the flowchart of FIG. The control unit 50 reads the program from the program storage unit 60 and controls the matching circuit 20 based on the program. Since the contents of the control have already been described, the description here is omitted.

  As described above, according to the embodiment of the present invention, the following effects can be obtained. The first effect is that reflection loss due to impedance mismatch between the antenna element and the feeding circuit caused by mutual coupling can be reduced as compared with the related art.

  The second effect is that optimum impedance matching can be performed for each beam scanning, and a decrease in antenna gain at the time of beam scanning can be reduced as compared with the related art.

  The third effect is that since the matching condition of the matching circuit of the entire antenna aperture is obtained only by the element impedance of the central antenna element in the beam scanning range, the matching circuit can be controlled more easily than the related art.

  The fourth effect is that all the bias voltages applied to the matching circuit for the entire antenna aperture can be set to the same value, so that the number of bias power supplies can be reduced as compared with the related art, thereby preventing an increase in device scale. It is.

  As another embodiment, the present invention can be applied to a case where a reactance element is used instead of the matching circuit, or a case where the matching circuit and the reactance element are used in combination.

DESCRIPTION OF SYMBOLS 1 Feeding circuit 2 Antenna element 3 Matching circuit 10 Antenna element 20 Matching circuit 30 Phase shifter 40A Combining distributor 40B Combining distributor 50 Control unit 60 Program storage unit

Claims (9)

A plurality of antenna elements arranged;
A power feeding circuit for feeding power to the plurality of antenna elements arranged;
A plurality of matching circuits provided between the plurality of antenna elements and the feeding circuit, respectively, for impedance matching;
A control unit for controlling the plurality of matching circuits,
The control unit calculates an element impedance of the central antenna element in the beam scanning range, determines a matching condition between the antenna element and the feeder circuit based on the calculated element impedance, and uses the determined matching condition for all antennas. An array antenna apparatus, characterized by being applied to an element matching circuit.   2. The array antenna according to claim 1, wherein the matching circuit is configured by a variable capacitance element, and the matching condition in the control unit is a capacitance of the variable capacitance element for matching the antenna element and a feeding circuit. apparatus.   3. The array antenna apparatus according to claim 1, wherein the feeding circuit is a combiner / distributor, and a phase shifter is further provided between the matching circuit and the feeding circuit. A plurality of antenna elements arranged, a plurality of power feeding circuits feeding power to the plurality of arranged antenna elements, and a plurality of matching circuits provided between the plurality of arranged antenna elements and the power feeding circuit, respectively, for impedance matching An impedance matching method for an array antenna apparatus including a circuit and a control unit for controlling the plurality of matching circuits,
This is executed by the control unit, calculates the element impedance of the central antenna element in the beam scanning range, determines the matching condition between the antenna element and the feeder circuit based on the calculated element impedance, and determines all the determined matching conditions. An impedance matching method including an impedance matching step applied to a matching circuit of the antenna element of the present invention.   5. The impedance matching according to claim 4, wherein the matching circuit is configured by a variable capacitance element, and the matching condition in the control unit is a capacitance of the variable capacitance element for matching the antenna element and the feeding circuit. Method.   6. The impedance matching method according to claim 4, wherein the power feeding circuit is a combiner / distributor, and a phase shifter is further provided between the matching circuit and the power feeding circuit. A plurality of antenna elements arranged, a plurality of power feeding circuits feeding power to the plurality of arranged antenna elements, and a plurality of matching circuits provided between the plurality of arranged antenna elements and the power feeding circuit, respectively, for impedance matching A program for an impedance matching method of an array antenna apparatus, including a circuit and a control unit that controls the plurality of matching circuits,
The control unit calculates the element impedance of the central antenna element in the beam scanning range, determines the matching condition between the antenna element and the feeder circuit based on the calculated element impedance, and applies the determined matching condition to all antennas. A program for executing an impedance matching step applied to the element matching circuit.   8. The program according to claim 7, wherein the matching circuit includes a variable capacitance element, and the matching condition in the control unit is a capacitance of the variable capacitance element for matching the antenna element and the feeding circuit.   9. The program according to claim 7, wherein the power feeding circuit is a combiner / distributor, and a phase shifter is further provided between the matching circuit and the power feeding circuit.

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