JP3081987B2 - Active phased 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 an active phased array antenna, and more particularly to an active phased array antenna suitable for use in the millimeter wave band.

[0002]

2. Description of the Related Art In an active phased array antenna in which a plurality of radiating elements are arranged in a straight line or in a plane, the spacing between the radiating elements is reduced so that grating lobes do not appear in the visible region in order to widen the beam scanning range. There is a need. That is, if the beam scanning range is ± θ ° and the wavelength of the used frequency is λ, the required element interval d is expressed by the following equation.

[0003]

Here, k is a constant determined by the phased array scale.

Conventionally, as a radiating element of an active phased array antenna having a wide beam scanning range, "Ph
used Array Antenna with a
Multi Layer Substrate "(I
EEE, Proc. H, Vol. 141, no. 4, A
ug. As disclosed in (1994), MicrostripPatch Antenna (hereinafter, referred to as MSPA), in which mutual coupling between elements is small and in which the gain is low during beam scanning, has been widely used. MSPA
When using as a radiating element, the structure of the active phased array antenna is, as shown in FIG.
A method of separately configuring the 201 array and the transmitting / receiving module 202 and a method of mounting a multi-chip module IC (MMIC) such as a phase shifter and an amplifier on the back surface of the MSPA have been considered.

Although the above method has been put to practical use in an active phased array antenna used in a microwave band, the configuration in which the MSPA 201 and the transmitting / receiving module 202 shown in FIG. 8 are separated is used in a high frequency band such as a millimeter wave band. It is very difficult to apply the method to an active phased array antenna which is used in view of the limitation of machining accuracy and maintainability.

[0007] That is, the transmission / reception module 202 is used to replace / repair the MSPA2 when it fails.
01 must be removed from the array. Here, the connector interval of the coaxial connector 203 for connecting the transmitting / receiving module 202 and the MSPA 201 array is ± 45 to ± 45.
In the case of an active phased array antenna having a beam scanning range of 60 °, it is λ / 2 (λ: wavelength). For example, the connector spacing is about 4.3 mm, 9 mm for an active phased array antenna in the millimeter wave band of 35 GHz.
In the microwave band of GHz, it is 16 mm. Therefore, it is necessary to use a microminiature coaxial connector 203 in an active phased array antenna in the millimeter wave band.
However, the center conductor of this microminiature coaxial connector 203 is very thin, and it is very difficult to fit it by hand.

Further, regarding a structure in which the MMIC is mounted on the back surface of the MSPA, for example, considering an active phased array antenna usable in a 35 GHz band, FIG.
As shown in FIG.
Has an area of about 20 mm ² and a mounting area of MMIC of 4 to 8 mm.
Since mm ² / chip is required, there is a limit to the number of packages to be mounted. However, a chip used in the transmission / reception module generally requires six amplifiers, three switches, one phase shifter and one attenuator as shown in FIG. Since the mounting area is about 4 mm ^{2 and the} mounting area of the phase shifter and the attenuator is about 6 mm ² , the occupied area of the MMIC is 48 mm ² . Further, considering the connection between the MMICs and the connection with the external leads, the actual area becomes larger, and as a result, it is extremely difficult to mount the MMIC on the back surface of the MSPA. Further, in the structure in which the MMIC is mounted on the back surface of the MSPA, it is necessary to solve the problem of heat radiation. Thus, it has been extremely difficult to apply the above structure to an active phased array antenna in the millimeter wave band.

Therefore, in the active phased array antenna in the millimeter wave band, a slot line antenna or a dipole antenna is selected as the radiating element 205 as shown in FIG.
7, a configuration in which the transmission / reception module 206 is mounted has been applied.

[0010]

However, when a slot line antenna is used as the radiating element of the active phased array antenna and the configuration shown in FIG. 10 is adopted, if the beam width is widened, the array element pattern (radiating element Ripple and distortion of the element single pattern when the array is arranged are increased. Therefore, slot line antennas were not suitable as radiating elements for wide angle scanning active phased array antennas.

When a dipole antenna is used as the radiating element of the active phased array antenna and the configuration shown in FIG. 10 is employed, mutual coupling between the elements increases. Further, when the element intervals are densely arranged, the distortion of the array element pattern is large, and the gain change during beam scanning is large. FIG. 11 is a diagram showing an array element pattern when dipole antennas are arranged at element intervals necessary to achieve a beam scanning range of ± 45 ° and ± 60 °, and a solid line indicates ± 4 °.
5 ° and the dotted line correspond to a beam scanning range of ± 60 °. Referring to FIG. 11, when the beam is scanned at ± 60 °, 4.6 dB in the vertical plane (−60 °) and the horizontal plane (+ 6 °).
0 °), a gain decrease of 11.7 dB occurs. When such an active phased array antenna is applied to a radar device, the respective gain reductions are 9.2 dB and 23.4 dB due to a change in system gain, which has a serious adverse effect on system design.

[0012]

In order to solve the above problems, an active phased array antenna according to the present invention comprises:
A plurality of radiating elements and a plurality of transmitting / receiving modules provided corresponding to the respective radiating elements are mounted on the same plane, and the plurality of radiating elements are arranged on a circumference in a mounting plane.

In particular, in order to suppress the side lobe,
The transmitting and receiving module is operated by the phase weight and the amplitude weight obtained by the maximum S / N method.

In order to perform two-dimensional beam scanning, the active phased array antenna according to the present invention includes a plurality of radiating elements and a plurality of transmitting / receiving modules provided for the respective radiating elements mounted on the same plane. Along with
An active phased array antenna having a plurality of one-dimensional beam scanning active phased array antennas in which the plurality of radiating elements are arranged on the circumference in the plane, wherein the one-dimensional beam scanning active phased array antennas are arranged in parallel at equal intervals. And the center of the aperture of each one-dimensional beam scanning active phased array antenna is arranged on the circumference in a plane perpendicular to the mounting surface of each radiating element of the one-dimensional beam scanning active phased array antenna. Things.

[0015]

Next, an embodiment of the active phased array antenna of the present invention will be described in detail with reference to the drawings.

In the first embodiment of the present invention, the transmitting / receiving module and the radiating element are mounted on the same plane, and the radiating element groups are arranged so as to be arranged on the circumference in the mounting plane. With this configuration, the degree of coupling of the radiating elements is reduced, and as a result, a decrease in gain during beam scanning can be suppressed.

FIG. 1 is a perspective view showing the configuration of the present embodiment. A plurality of radiating elements 101 arranged on a circumference and a transmitting / receiving module connected to each of the radiating elements 101 via a feeder line 102 are shown. 103 are mounted on the same plane. The power distributor 104 distributes and supplies high-frequency power to each transmitting / receiving module 103. A control signal for controlling each transmitting / receiving module 103 is input from the signal input terminal 105.

FIG. 2 is a block diagram showing the configuration of this embodiment. The operation of this embodiment will be described with reference to FIG.

First, a description will be given of the transmission of a radar signal. The radar signal generated by the exciter 106 is uniformly distributed by the power distributor 104. The distributed radar signal is input to each transmitting / receiving module 103, and given a predetermined amplitude / phase weight. The amplitude / phase weight given to the radar signal in each transmission / reception module 103 is stored in the beam scanning controller 107 in advance for each beam directing direction. Then, based on the beam scanning control signal from the beam scanning controller 107, each transmission / reception module 103 gives a desired amplitude and phase weight to the radar signal. A radar signal to which a predetermined amplitude / phase weight is given is amplified and then radiated into space from a radiating element 101 arranged on the circumference.

Next, at the time of reception, a signal received by each radiating element 101 is guided to a corresponding transmitting / receiving module 103, and after being amplified, given a predetermined phase / amplitude weight for beam forming. Can be The phase / amplitude weight given to the received signal is also based on the beam scanning control signal from the beam scanning controller 107 as in the transmission. The output signal of each transmission / reception module 103 is synthesized by a power divider 104B prepared separately from the power divider for transmission, and transmitted to the receiver 109.

Next, the transmission / reception module according to the present embodiment will be described with reference to FIGS.

FIG. 3 is a block diagram showing the configuration of the transmission / reception module 103. In FIG. 3, the position of the switch indicates the state at the time of transmission. The radar signal from the power divider 104A is input from the input terminal 115, and is given a phase weight by the phase shifter 110. The radar signal to which the phase weight is given is amplified by the power amplifier 111, and then supplied to the variable attenuator 112, where the radar signal is given an amplitude weight. The radar signal to which the amplitude / phase weight is given is transmitted to the radiating element 101 via the input / output terminal 113.

On the other hand, at the time of reception, each switch in the figure comes into contact with the opposite side, and the reception signal from the radiating element 101 is given to the input / output terminal 113. The received signal is
Amplified by the low noise amplifier 114, the variable attenuator 11
5 gives the amplitude weight. The received signal is
Further, a phase weight is given by the phase shifter 110. The received signal to which the amplitude / phase weight is given is transmitted from output terminal 116 to power divider 104B.

Here, the control circuit 117 sends the beam scanning control signal from the beam scanning controller 107 to the variable attenuator 1
Decodes 12 and 115 are performed in accordance with the interface of the phase shifter 110, and the variable attenuators 112 and 115 and the phase shifter 110 are drive-controlled based on the control signal.

According to the experiment, the array element pattern when a plurality of radiating elements are arranged at equal intervals in a circumferential arrangement as in this embodiment can be approximated by cos θ.
A decrease in gain during the beam scanning can be suppressed. This is because the radiation pattern of a single element can be approximated by cos θ, and when a plurality of radiating elements are arranged in a circle, mutual coupling between the elements is small.

FIG. 4 shows the result of calculating the radiation pattern of the active phased array antenna of this embodiment under the following conditions.

Number of elements: 16 Element spacing: 0.5λ Frequency: 35 GHz (millimeter wave band) Array circumference radius: 50 mm Beam scanning direction: 60 ° Setting weight: Taylor distribution (side lobe level -30 dB, n = 4) Pattern: cos θ Next, an active phased array antenna according to a second embodiment of the present invention will be described with reference to FIGS. 2, 4, and 5. FIG.

Referring to FIG. 4, the first embodiment of the present invention is a conformal array in which radiating elements are arranged on a circumference, so that a tailor weight of side lobe level of -30 dB is applied. However, a side lobe of -18 dB is generated. Therefore, in the second embodiment of the present invention, unnecessary lobes generated in the circumferential array (see FIG. 4).
In this embodiment, the maximum S / N method is applied to the above-described first embodiment in order to suppress a relatively large level of side lobe occurring at 70 ° to 80 °.

The maximum S / N method is described in "Adaptive null formation in a curved array" (pp. 2-157, 1994 IEICE Spring Conference). It will be described with reference to FIG.

First, the shape of the antenna and the arrangement of the radiation elements are determined (S101). Further, the irradiation direction of the main beam in the beam search direction is determined (S102). A reference weight that maximizes the directivity gain in the determined main beam irradiation direction is calculated (S103). With respect to the side-rope characteristics formed by the calculated reference weights, an unnecessary signal is assumed in a direction in which a lower side-rope is desired to be achieved, and a power distribution is set (S104). An autocorrelation value and a crosscorrelation value between the respective radiating elements for the assumed unnecessary signal are calculated (S105). Calculate a covariance matrix having each calculated correlation value as an element (S
106). The inverse matrix of the calculated covariance matrix is calculated, and the above-described S1 is calculated using the calculated inverse matrix.
The adaptive weight is calculated by correcting the reference weight calculated in step S03 (S107). Where S
The covariance matrix calculated in 106 represents the power distribution in the search space of the unnecessary signal received by each radiating element. Therefore, in S107, the inverse matrix of the covariance matrix is calculated and multiplied by the reference weight. Correcting this means that the beam directivity determined by the reference weight is adapted to cancel the unnecessary signal.

In the beam scanning control device 107 shown in FIG. 2, a phase / amplitude weight obtained by applying the maximum S / N method is given to a radar signal input to each transmitting module 103, so that a beam directivity is obtained. The sidelobe level can be suppressed while maximizing the gain.
Here, FIG. 6 shows a calculation under the same conditions as described above in the present embodiment in which the maximum S / N method is applied to the above-mentioned first embodiment showing the radiation pattern as shown in FIG. FIG. Referring to FIG. 6, it can be seen that the side lobe level is improved by 7 dB to -23 dB as compared with the radiation pattern shown in FIG. Further, in this embodiment, the gain variation during beam scanning is
This is 2.6 dB, which is an improvement of 1.7 dB as compared with the case where the irradiation elements are linearly arranged.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

In the third embodiment of the present invention, two-dimensional beam scanning is performed, while the active phased array antenna of the first embodiment performs one-dimensional beam scanning.

FIG. 7 is a perspective view showing the configuration of the present embodiment. The two-dimensional active phased array antenna of the present embodiment uses a one-dimensional beam scanning active phased array shown in FIG. 1 to perform two-dimensional beam scanning. Array antenna 118
Are prepared, and they are arranged in parallel and at equal intervals. Here, in order to arrange the radiating elements 101 in a conformal array even in the XY plane in FIG.
The aperture center 120 of the one-dimensional active phased array antenna 118 is drawn in a plane (XY plane) perpendicular to the mounting surface (XZ plane in FIG. 7) of each radiating element 101 of the one-dimensional active phased array antenna 118. The one-dimensional active phased array antennas are arranged shifted back and forth so as to be arranged on the circumference 119. Here, the radiation pattern in the plane including the circumference 119 is also the same as the characteristic shown in FIG. In addition,
Also in this embodiment, it is possible to suppress the side lobe by applying the maximum S / N method described above.

[0035]

As described above, according to the active phased array antenna of the present invention, the radiating element group and the transmitting / receiving module provided corresponding thereto are mounted on the same plane, and the radiating elements are arranged on the circumference. As a result, gain fluctuation during beam scanning can be suppressed, and a wide beam scanning range can be realized.

Furthermore, since a precise connection structure is not required, maintenance and the like can be easily performed when applied to the millimeter wave band.

Further, by applying the maximum S / N method, unnecessary lobes (side lobes having a relatively large level) generated when radiating elements are arranged in a circle can be suppressed.

Further, in the present invention, a plurality of one-dimensional active phased array antennas are arranged in parallel, and the center of the opening of each one-dimensional active phased array antenna is positioned with respect to the mounting surface of each radiating element of the one-dimensional active phased array antenna. By arranging the one-dimensional active phased array antennas back and forth so that they are arranged on a circle drawn in a vertical plane, it is possible to easily realize expansion to two-dimensional beam scanning. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a first exemplary embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a transmission / reception module in FIG. 2;

FIG. 4 is a diagram illustrating an example of a radiation pattern calculated under predetermined conditions for the first embodiment of the present invention.

FIG. 5 shows the maximum S / N applied to the second embodiment of the present invention.
It is a flowchart which shows the processing procedure of a method.

FIG. 6 is a diagram illustrating an example of a radiation pattern calculated under predetermined conditions for the second embodiment of the present invention.

FIG. 7 is a perspective view showing a configuration of a third exemplary embodiment of the present invention.

FIG. 8 is a perspective view showing a configuration of a main part of a conventional active phased array antenna.

9A and 9B are diagrams illustrating a configuration of a conventional active phased array antenna, in which FIG. 9A is a diagram illustrating the area of the back surface of an MSPA on which an MMIC can be mounted, and FIG. FIG. 3 is a diagram illustrating a configuration.

FIG. 10 is a perspective view showing a configuration of a main part of a conventional millimeter wave band active phased array antenna.

FIG. 11 is a diagram showing an example of an array element pattern in the conventional active phased array antenna shown in FIG.

[Explanation of symbols]

 Reference Signs List 101 radiating element 102 feeder 103 transmitting / receiving module 104 power distributor 105 signal input terminal 106 exciter 107 beam scan controller 108 receiver 109 input terminal 110 phase shifter 111 power amplifier 112, 115 variable attenuator 113 input / output terminal 114 low Noise amplifier 116 Output terminal 117 Control circuit 118 One-dimensional active phased array antenna 119 Circumference 120 Center of aperture

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-107335 (JP, A) JP-A-1-254007 (JP, A) JP-A-1-311704 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01Q 3/26-3/42 H01Q 21/22 G01S 7/02 G01S 7/28

Claims (1)

(57) [Claims] 1. A plurality of radiating elements and a plurality of transmitting / receiving modules provided corresponding to each of the radiating elements are mounted on the same plane, and the plurality of radiating elements are arranged on the circumference in the plane. An active phased array antenna having a plurality of one-dimensional beam scanning active phased array antennas, wherein the one-dimensional beam scanning active phased array antennas are arranged in parallel at equal intervals, and each of the one-dimensional beam scanning active phased array antennas is provided. An active phased array antenna wherein the centers of the apertures are arranged on the circumference in a plane perpendicular to the mounting surface of each radiating element of the one-dimensional beam scanning active phased array antenna.