JPH1164487A - Monitoring system for phased array antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring system for phased array antenna in which highly accurate beam control and monitoring can be carried out in the near field. SOLUTION: A phased array antenna radiates high frequency variable phase signals from a plurality of radiation elements 3. The output phase of each radiation element 3 is controlled by a phase shifter 1 under control of a phase controller 2. A near field monitor 4 arranged in the near field of the phased array antenna receives a high frequency signal from each radiation element 3. That signal is detected by an amplification antenna 5 and converted digitally through an ADC(A/D converter) 6 before being inputted to a monitor 7A. The monitor 7A calculates a phase value, an amplitude value and a beam pattern simulating a far field accurately from the receiving signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring a phased array antenna in which a digital phase shifter is electronically scanned to form a radio wave of a high frequency signal, and more particularly to a method for monitoring a high frequency signal received in the near field. The present invention relates to a phased array antenna monitoring method that simulates a far-field beam pattern (radiation pattern) and can be used for beam control and fault monitoring.

[0002]

2. Description of the Related Art A conventional monitoring system for a phased array antenna of this type will be described with reference to a structural diagram shown in FIG.

In the phased array antenna shown in FIG. 1, first, a high frequency signal S1 supplied from a power supply line is distributed by a power distributor 8 to each of a plurality of phase shifters 1 (1 to n) at a predetermined distribution ratio. Distribute. Each of the phase shifters 1 is connected to N radiating elements 3 (1, 2,..., N-1, n = N) having substantially the same performance. The aperture plane of each radiating element 1 is generally on the same plane perpendicular to the radiation center axis (central axis) of this array antenna. The phased array antenna forms a sharp beam by controlling the phase of the phase shifter 1 corresponding to each of the radiating elements 3 (1 to n) by the phase controller 2, and scans this beam temporally. It is an antenna based on what you do. Such an aerial is used for guidance landing of an aircraft.

One of the above-mentioned phased array antenna monitoring methods is a near-field monitoring method. In this monitoring method, a near-field monitor (receiving antenna) 4 is installed in front of and near each radiating element. The monitor 4 receives a pulsed high frequency signal as the scanned beam of the array antenna passes. The received high frequency signal is amplified and detected by the amplification detector 5. Monitoring device 7B
Monitors the beam width, side lobe level, beam accuracy (deviation from the ideal value of beam directivity), and the like using this detection signal. When monitoring the high-frequency signal beam emitted into the space in this way, it is common to monitor the beam pattern near the array antenna because it is necessary to avoid restrictions on airport premises and the effects of obstacles. is there.

Another one of the phased array antenna monitoring methods is an integral monitoring method. In this monitoring method, pickups (antennas) are arranged close to the respective radiating elements 3 (the pickup array 9 is an aggregate of these), and a part of the radiated power radiated by each of the radiating elements 3 is picked up. , And a detector (DET) 1
After detection at 0, a radiation beam is formed by synthesis, and the beam angle, beam width, side lobe, and the like are monitored from the waveform. In this monitoring method, it is possible to form a beam substantially equivalent to a high-frequency signal received in the far field.

Further, as an application of the integral monitor method, the phase and amplitude of the radiation vector of the radiating element 3 are measured while controlling the phase of the phase shifter 1 corresponding to the radiating element 3 on a one-to-one basis. Is possible. Conventionally, when the measurement is performed in this manner, the integral monitor (9 and 1) is used.
The phased array antenna was kept in a normal state by correcting the error due to the temperature characteristic of 0). However, although the high-frequency signal picked up near the radiating element 3 simulates an ideal far-field signal, the signal used for operation is not a signal including multipath in an actual environment and alignment of an array antenna, and the like. I couldn't say I was watching.

[0007]

Among the conventional phased array antenna monitoring methods, the integral monitoring method measures a phase value and an amplitude value radiated by each radiating element from a high frequency signal picked up near the radiating element. However, since feedback is performed so as to set an ideal phase value from this value, it is not possible to consider the effect of multipath that actually occurs, and the ideal radiation pattern and the actual radiation fed back from the integral monitor There was a difference from the pattern.

Although the integral monitor is useful as a monitor for the array antenna itself, it is not affected by the outside world because it picks up a high frequency signal near the radiating element of the array antenna. There is a disadvantage that a real signal equivalent to being affected by the outside world is not monitored.

On the other hand, the actually radiated high frequency signal is
In the near-field monitor method of monitoring with antenna monitors, in order to monitor the beam pattern in the near field,
Correlation with the far-field pattern received by an aircraft or the like becomes low.
This is because the phase (distance) difference between each radiating element and the near-field receiving point cannot be ignored, and the phase planes of the high-frequency signals from each radiating element are not aligned in the receiving direction.

Accordingly, the present invention eliminates both the disadvantages of the integral monitor system and the near-field monitor system, combines the advantages of both, and allows the radiated high-frequency signal to be received in the near field while the high-frequency signal in the far field is received. By simulating the beam pattern of the signal and controlling the phase so that the signal phase at the aperture surface of the antenna monitor becomes the same phase, the high frequency signal (beam pattern etc.) actually received on an aircraft or the like can be obtained. The purpose is to monitor and control.

[0011]

SUMMARY OF THE INVENTION A phased array antenna monitoring system according to the present invention emits a variable phase high frequency signal from a plurality of radiating elements to generate a predetermined radio beam in a far field of a phased array antenna. A phased array antenna monitoring method for monitoring a radiation vector, wherein the antenna is arranged in a near field of the phased array antenna,
A near-field monitor that receives a high-frequency signal from each of the radiating elements; the near-field monitor measures the phase and amplitude values of the high-frequency signal received from each of the radiating elements; A monitoring circuit that corrects each of the above to a phase value in the far field based on the distance difference between the corresponding radiating element and the near-field monitor.

One of the phased array antenna monitoring methods is that the near-field monitor receives the phase value and the amplitude value of the high frequency signal received from each of the radiating elements by using the radiating phase of each of the radiating elements. Can be measured by rotating once by a predetermined phase unit, and the measured amounts can be obtained by Fourier transform.

According to another one of the phased array antenna monitoring methods, the monitoring circuit uses an average value of the corrected phase values as a reference value, and the corrected phase value determines a predetermined amount from the reference value. The radiating element exceeding the radiating element may be configured to cause a phase controller to perform a phase correction so that the corrected phase value falls within the predetermined amount.

In one of the phased array antenna monitoring methods, the phase controller controls the radiating element with a digital signal, and the predetermined amount is １ ／ of the digital signal.
A configuration having a phase amount corresponding to a bit can be adopted.

In another one of the phased array antenna monitoring methods, the monitoring circuit determines that the phased array antenna is faulty when the radiating element having a phase value exceeding the predetermined amount remains. Configuration can be taken.

In still another phased array antenna monitoring method, the monitoring circuit sets an average value of the amplitude values of the high frequency signal as a reference value and indicates an amplitude value exceeding a predetermined amount from the reference value. When it is recognized that the radiating element is present, a configuration may be adopted in which the phased array antenna is determined to be an obstacle.

Still another one of the phased array antenna monitoring methods is that the monitoring circuit obtains the high-frequency signal received by the near-field monitor and radiates far-field radiation from the phase value and the amplitude value. It is possible to adopt a configuration further including a beam combining unit that simulates a pattern.

The phased array antenna monitoring method may be configured so that when the monitoring circuit recognizes a deviation of the radiation pattern simulated by the beam combining means from a desired value, a beam failure alarm is generated.

In the phased array antenna monitoring method according to the present invention, the output (radiation) phase of the high-frequency signal is sequentially rotated in a desired step for each radiating element, and the high-frequency signal received by the near-field monitor each time is rotated. Measure the phase and amplitude of. The method of obtaining the phase and amplitude of each radiating element by rotating the vector in this manner is generally well known. At this time, a phase value and an amplitude value for each radiating element are obtained (see FIGS. 3 and 4 described later). The measured phase value includes a close phase error due to reception in the vicinity. This phase measurement value is corrected by a phase shift angle obtained from a path (distance) difference from each radiating element to a receiving point (near field monitor), and this is used as a reference phase shift value.

This reference phase is based on a high-frequency signal radiated into space from each phase shifter actually used and affected by the outside world. Can be artificially synthesized. Using the phase-corrected signal, the beam width, the side lobe level, and the beam accuracy (also referred to as a radiation vector) can be monitored in real time in the monitoring device.

According to the present invention, a radiation vector from each radiating element that reflects the effect of multipath can be obtained using a near-field monitor. The acquired phase value becomes equal to the phase value of the high-frequency signal (radiation element vector) measured in the far field by correcting the close phase error. Therefore, if the received high-frequency signal has a phase deviation exceeding the reference value set in advance by the parameter,
By controlling the output phase of the radiating element in a direction to cancel it, high-precision phase control that is not affected by aging, temperature change, or the like can be performed.

By combining these vectors, that is, the phase value and the amplitude value, it is possible to simulate a radiation pattern in the far field. With these functions, it is possible to integrate a monitoring device that has been conventionally complemented by both the near-field monitor and the integral monitor.

[0023]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a phased array antenna monitoring system according to an embodiment of the present invention.

Also in this phased array antenna monitoring method, N phase shifters 1 (1-n), phase controllers 2 and N having the same characteristics as those shown in FIG. Radiating elements 3 (1, 2,..., N−1, n =
N) and the power distributor 8 constitute a phased array antenna. The connection between the components is the same. Each of the radiating elements 3 is connected to a corresponding phase shifter 1, and each phase shifter 1 controls an output phase to each of the radiating elements 3 by a phase controller 2.

The near field monitor 4 and the amplification detector 5 are the same as those in FIG. The amplification detector 5 amplifies the high-frequency signal received by the near-field monitor 4 and detects it to generate a signal having a DC component. This signal is digitally converted by an A / D converter (ADC) 6 and supplied to a monitoring device 7A. The monitoring circuit 7A performs various operations including a microprocessor and a storage circuit,
As described later in detail, the phase value and the amplitude value of the high-frequency signal received by the near-field monitor 4 are measured from the digital signal received from the A / D converter 6, and the measured phase value is used as the radiation element 3 Each and near field monitor 4
Is corrected based on the path (distance) difference between The monitoring device 7A sends the corrected phase value to the phase controller 2, and the phase controller 2 controls the output phase of each radiating element 3 using the corrected phase value. The monitoring device 7A also has a failure detection function for the phased array antenna.

FIG. 2 is an explanatory diagram of the phase correction in the embodiment of FIG. Hereinafter, a method for measuring the phase value of a high-frequency signal using the near-field monitor 4 will be described with reference to FIGS.

First, a method of measuring the phase value of a high-frequency signal received by the near-field monitor 4 from the radiating element 3 will be described. As shown in FIG. 1, when the near-field monitor 4 is disposed in the direction of the angle θ with respect to the radiation center axis (center axis) of the phased array antenna, the phase controller 2 transmits the high-frequency signal in the direction of the angle θ. Phase control is performed on each phase shifter 1 so as to form a phase plane.

First, the phase controller 2 is an optional phase shifter 1
(1 to n) is selected, and the selected phase shifter 1 is controlled in phase until it makes one rotation in the minimum bit unit. At this time, the combined vector obtained by the near-field monitor 4 is detected by the amplification detector 5. The detection signal digitally converted by the A / D converter 6 is subjected to amplitude level measurement by the monitoring device 7A. Then, the measured values for each phase shifter 1 are set to X0, X1, X2,..., _Xn−1 , respectively, and the Fourier transform F (K) of the sample value Xn is obtained with n being the total number of samples. Here, K indicates the K-th radiating element 1. F
(1) is the amplitude value of the radiation element 3-1. By calculating tan ^-1 (imaginary part / real part) using the real part and the imaginary part of F (1), the output phase value of the radiating element 3-1 can be obtained.

Next, the monitoring device 7A corrects the phase value measured by the method described above. As for the physical distance L from each radiating element 3 (1-n) to the near-field monitor 4, the angle θ of the near-field monitor 4 with respect to the center axis of the phased array antenna differs depending on each radiating element 3 (1-n). Therefore, it is slightly different. Referring to FIG. 2, when a vertical line is drawn from the center axis of the phased array antenna to the near-field monitor 4, the intersection between the center axis and the vertical line and the aperture plane aligned with the radiating element 3 are aligned. The distance is set to 1.

Now, the radiator is N, the radiating element number to be measured is n, the element spacing of the radiating element 3 is d (mm), and the distance between one of the near arms (3-n) and the near field monitor 4 is L. ,
Number of elements of the radiating element 3 The distance from the point where the field monitor 4 and the opening plane of the radiating element 3 intersect the three points of the center axis of the phased array antenna to the radiating element (3-n) is Dn, and each radiating element 3 (1 to Assuming that a difference between L and the distance between n) and the near-field monitor 4 is Δdn, the following equations (1) to (3) are established.

L = 1 / cos θ (1) Dn = ((N−1) / 2−n)) × d (2)

The monitoring device 7A stores Δdn as a phase correction parameter in advance. This parameter corresponds to one-to-one with the close phase error of the radiation beam. The monitoring device 7A corrects the phase measurement value for each radiating element 3 and calculates a phase value obtained when monitoring is performed in a pseudo remote manner.

FIG. 3 is a diagram showing an example of phase correction of a high-frequency signal received from each of the radiating elements 3 by the near-field monitor 4 of FIG. This phased array antenna is
In this figure, 62 radiating elements 3 are arranged in a straight line.

The phase value of the signal received by the near-field monitor 4 and detected by the amplification detector 5 is indicated by a broken line A. This actually measured phase value distribution shows a mountain-shaped characteristic in which the phase value is delayed toward the periphery of the radiating element 3. In this phase value distribution,
Since the nearby phase error cannot be ignored, it is necessary to correct the phase value so that the phase values of the high frequency signals from all the radiating elements 3 are aligned on the receiving surface of the near-field monitor 4. Distance (d1, d2,..., D) between each radiating element 3 and a near-field receiving point (near-field monitor) 4
Since (n-1, dn) is stored in the monitoring device 7A and known in advance, the monitoring device 7A corrects the phase value by converting the path difference Δdn of Expression (3) into a phase angle in a predetermined frequency band to be used. I do. Thus, each radiating element 3 as shown by the broken line B in FIG.
Phase value of the high frequency signal from the near field monitor 4
Is corrected so as to be substantially flat at the receiving point (correction step 1). The phase value correction using the Fourier transform or the like is performed by the monitoring device 7A.

The corrected phase value obtained by the above operation may be regarded as pseudo far phase data of each phase shifter 1. Here, if the correction phase value deviates from the reference value by a predetermined amount or more, the monitoring device 7A further performs phase correction. First, the average value of the corrected phase values after the pass difference correction obtained in the correction step 1 is set as the reference value. The predetermined amount is, for example, ± 1/2 LSB of the phase control bit of the phase shifter 1 (1/2: 1/1/2 of the least significant bit of the phase shifter 1).
2 bits). Note that the reference value and the predetermined amount may be appropriately changed according to system requirements.

If the corrected phase value is shifted by 1/2 or more of the least significant bit, the output phase of the phase shifter 1 is corrected in the reverse direction by the phase controller 2 (correction step 2), and the monitoring device 7A Corrects a high-frequency signal received by the near-field monitor 4 into a beam equivalent to that received in the far field. When the radiating element 3 having a phase value exceeding 1/2 LSB remains, the monitoring circuit 7A determines that the phased array antenna is faulty and outputs fault information to the antenna system.

As described above, in the phased array antenna monitoring method according to the embodiment of FIG. 1, first, the phase value and the amplitude value of the actually radiated high-frequency signal can be simulated at the near field point. The feature is that the operation state of the antenna can be easily monitored. That is, the simulated phase value uses the radiation vector obtained from the near-field monitor 4 as the phase value and the amplitude value of the far-field radiation vector. Is included.

This monitor system is used in the correction step 1
± 1 / 2LS with respect to the average phase value after phase value correction by
B and each correction phase value are compared. For example, when at least one of the correction phase values exceeds the threshold of ± 1/2 LSB, the monitoring device 7A performs the second-stage correction as shown in correction step 2. The correction value of the second stage is sent to the phase controller 2 as correction control data indicated by a broken line B in FIG.
This is fed back to the phase control of the phase shifter 1.

In this case, as in the first case, the monitor system uses the effect of using the actually radiated signal to monitor the far-field beam of the phased array antenna and to perform highly accurate phase control based on this. Can be performed.

FIG. 4 is a diagram showing an example of the amplitude value of the high frequency signal received from each of the radiating elements 3 by the near field monitor 4 of FIG. FIG. 5 is a pattern simulation diagram of a fezed array antenna created using the phase values of FIG. 3 and the amplitude values of FIG.

The amplitude value distribution shown in FIG. 4 is obtained by Fourier transform when correcting the phase value at the receiving point of the near-field monitor 4 described above. The measured phased array antenna supplies a large amount of high-frequency signals to the central radiating element 3. The near field monitor 4
Are located near the radiating elements 3, but there is no propagation loss difference due to a path difference that requires correction of the amplitude value for each radiating element 3.

Here, even if the amplitude value obtained by the near-field monitor 4 is abnormal, the monitoring device 7A outputs failure information of the phased array antenna in the same manner as in the case of a large deviation of the phase value. For example, the monitoring device 7A provides an amplitude value considered as an ideal value from the measured values in FIG. 4 as an amplitude reference value for each radiating element 3, and the amplitude value received from each of the radiating elements 3 (1 to n) is If it is determined that the amplitude is deviated from the amplitude reference value by ± 1 dB or more, fault information is output.

The monitoring apparatus 7A uses the corrected phase value after the correction in (correction step 2) in FIG. 3 and the amplitude value shown in FIG. 4 to radiate a radiation pattern (radiation vector) simulating the far field from the equation (4). Is beam synthesized in real time.

In equation (4), i (t) is the amplitude intensity at the angle θn (t) with respect to the central axis, An is the amplitude value of element number n of radiating element 3, and θn is the amplitude value of radiating element 3 of element number n. This is the beam scanning angle.

The pattern simulation diagram of FIG. 5 shows the result of the above-mentioned beam combining. In this figure, the beam direction is 3 °, the beam width is 1.5 °, and the side lobe is -25 dB.
It has the following radiation pattern. The monitoring device 7A analyzes this radiation pattern by a known method, monitors the characteristics of the phased array antenna, and when it detects a fault, generates fault information of the array antenna and reports this fault information to the host device.

As described above, in the phased array antenna monitoring method, since the beam combining of the array antenna is performed in real time by the monitoring device 7A, the radiation received by the aircraft in a far space close to the environment where the high frequency signal is actually received is obtained. There is a feature that a signal equivalent to a pattern can be monitored in the near field. That is, in this monitoring method, the radiation pattern in the far field can be simulated and monitored using the amplitude value obtained from the near-field monitor 4 and the phase value in consideration of the path difference.

[0048]

As described above, the present invention is directed to a near-field monitor which is disposed in the near field of a phased array antenna and receives high frequency signals from each of the radiating elements of the phased array antenna, and a near-field monitor. Measures the phase value and the amplitude value of the high frequency signal received from each of the radiating elements, and further measures each of the phase values based on the difference in distance between the corresponding radiating element and the near-field monitor. Since it has a monitoring circuit that corrects to the phase value in the field, the phase value and the amplitude value of the far field in the near field can be simulated under conditions close to the environment in which an aircraft or the like actually receives a high-frequency signal. This has the effect of facilitating highly accurate beam monitoring and control of the array antenna.

[Brief description of the drawings]

FIG. 1 is a configuration system diagram showing an embodiment of a monitoring system for a phased array antenna according to the present invention.

FIG. 2 is an explanatory diagram of phase correction in the embodiment of FIG.

FIG. 3 is a diagram showing an example of phase correction of a high-frequency signal received from each of the radiating elements 3 by the near-field monitor 4 of FIG. 1;

FIG. 4 is a diagram showing an example of an amplitude value of a high-frequency signal received from each of the radiating elements 3 by the near-field monitor 4 of FIG. 1;

FIG. 5 is a pattern simulation diagram of a fezed array antenna created using the phase values of FIG. 3 and the amplitude values of FIG. 4;

FIG. 6 is a configuration system diagram showing a conventional phased array antenna monitoring method.

[Explanation of symbols]

 Reference Signs List 1 (1-1 to 1-n) phase shifter 2 phase controller 3 (3-1 to 3-n) radiating element 4 near-field monitor 5 amplification detector 6 A / D converter (ADC) 7A, 7B monitoring Device 8 Power divider

Claims (8)

[Claims] 1. A phased array antenna monitoring method for monitoring a radiation vector in a far field of a phased array antenna for generating a predetermined radio wave beam by radiating a variable phase high frequency signal from a plurality of radiating elements, A near-field monitor arranged in the near field of the phased array antenna and receiving a high-frequency signal from each of the radiating elements; and a phase value of the high-frequency signal received by the near-field monitor from each of the radiating elements. And a monitoring circuit that measures an amplitude value and corrects each of the phase values to a phase value in the far field based on a distance difference between the corresponding radiating element and the near-field monitor. A phased array antenna monitoring method. 2. The phase and amplitude values of the high frequency signal received by the near-field monitor from each of the radiating elements are obtained by rotating the respective radiating phases of the radiating elements by a predetermined phase unit. 2. A phased array antenna monitoring method according to claim 1, wherein the measured values are obtained by performing a Fourier transform on the measured values. 3. The radiating element, wherein the monitoring circuit uses the average value of the corrected phase values as a reference value, and applies the corrected phase value to the radiating element whose corrected phase value exceeds a predetermined amount from the reference value. 2. The monitoring system for a phased array antenna according to claim 1, wherein the phase controller performs a phase correction so that the value falls within the predetermined amount. 4. The device according to claim 3, wherein the phase controller controls the radiating element with a digital signal, and the predetermined amount is a phase amount corresponding to ビ ッ ト bit of the digital signal. A phased array antenna monitoring method. 5. The phased array antenna according to claim 3, wherein the monitoring circuit determines that the phased array antenna is faulty when the radiating element having a phase value exceeding the predetermined amount remains. A phased array antenna monitoring method. 6. If the monitoring circuit determines that there is the radiating element having an amplitude value exceeding a predetermined amount from the average value of the amplitude values of the high frequency signal as a reference value, the monitoring circuit determines the phased value. 3. The monitoring system for a phased array antenna according to claim 2, wherein it is determined that the array antenna is faulty. 7. The monitoring circuit further includes a beam combining unit that obtains the high-frequency signal received by the near-field monitor, and simulates a far-field radiation pattern from the phase value and the amplitude value. 2. A method for monitoring a phased array antenna according to claim 1, wherein: 8. The phased array antenna according to claim 7, wherein the monitoring circuit generates a beam failure alarm when the deviation of the radiation pattern simulated by the beam combining means from a desired value is detected. Monitor method