JPH0229994B2 - DEISHITARU * BIIMUKEISEISOCHI - Google Patents

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a device for forming reception antenna beams by digital signal processing, and for forming a plurality of antenna beams simultaneously for signals received by a number of antenna elements. Discrete Fourier transform is performed using the phase difference correction value between the antenna elements necessary for This method attempts to detect the direction of arrival of the signal.

[Prior art]

A conventional direction detection device detects the direction of arrival of a signal using a configuration as shown in FIG.

In the figure, 1 is an antenna part, 2 is a receiver, 3 is a control computer, 4 is a power supply circuit, 5 is a multilayer board, 6 ₁
~ _6o is an antenna element, 7 is a radiator, 8 is a microwave amplifier, and 9 is a phase shifter.

A conventional direction detection device is configured as described above,
The signal that has propagated through space reaches the aperture of the antenna section 1, is received by the radiators 7 of the antenna elements ₆₁ to _6o , is amplified by the microwave amplifier 8, and is then input to the phase shifter 9. If the arrival direction of the signal is in the front direction of the aperture of the antenna section 1, the phases of the signals received by each of the antenna elements 6 ₁ to 6 _o are all the same, and the input terminal of the phase shifter 9 is also in the same phase. Here, if the control computer 3 sets the phase shift amount of the phase shifter 9 via the multilayer substrate 5 so that the direction of the receiving beam is in the front direction of the aperture surface of the antenna section 1, the phase shift of each phase shifter 9 can be set. Since all the quantities are uniform, for example zero degrees, a uniform phase distribution is obtained at the output end of each phase shifter 9, that is, at the input end of the feeder circuit 4. Since the power supply circuit 4 is configured to have a uniform distribution ratio and equal phase, the power supply circuit 4
The output signal level of is maximum. The output signal of the feeder circuit 4 is mixed by the receiver 2, converted to an intermediate frequency, amplified and detected, and detected as a signal. Signal detection information is sent from the receiver 2 to the control computer 3, and the control computer 3 determines the signal arrival direction depending on the presence or absence of signal detection information from the receiver 2 in the receive beam direction instructed to the antenna section 1. can be known. By the way, control computer 3
For the antenna section 1, each phase shifter 9 of the antenna elements ₆₁ to _6o is installed at each scanning angle so that the receiving beam scans a certain angular range in the front left and right or up and down directions in fine angular steps. The amount of phase shift to be applied to is calculated and the data is transferred through the multilayer substrate 5, and the presence or absence of signal detection information from the receiver 2 is confirmed. Therefore, there is a drawback that it usually takes several hundred milliseconds to several seconds to direct the reception beam at each small angle within the necessary angular range and to receive the reception signal each time.

[Summary of the invention]

This invention was made with the aim of improving these drawbacks, and is intended to improve the radiator, microwave amplifier, mixer, intermediate frequency amplifier, phase detector, video amplifier, sample/hold circuit, and analog/digital converter. A large number of built-in antenna elements are arranged, and the digitized received signal at the output terminal is processed using the phase difference correction value between the antenna elements necessary to simultaneously form multiple antenna beams. By performing Fourier transform and Fourier transforming the time-series received signals for each of the many antenna beams obtained by discrete Fourier transform, many receive beams are simultaneously formed, and the signal arrival direction is This paper proposes a digital beam forming device that can significantly shorten the time for detecting.

[Embodiments of the invention]

FIG. 2 is a schematic diagram showing an embodiment of the present invention, and numerals 1, 4 to 8 are almost the same as the conventional device described above. 10 is an antenna element 6 ₁ to 6 _o
A mixer that de-ampers the incoming radio wave received by the built-in radiator 7 with a microwave amplifier 8 and converts it into an intermediate frequency using a local oscillation signal; 11 is an intermediate frequency amplifier that amplifies the intermediate frequency signal to a sufficiently high level; 12 13 is a video amplifier that amplifies the phase-detected video signal; 14 is a sample/hold circuit that samples the video signal and holds its voltage; 15 is an analog An analog/digital conversion circuit that converts a signal into a digital signal; 16 an oscillator unit that generates a local oscillator signal and a reference signal for phase detection; and 17 a signal processor that detects the arrival direction of the signal received by the antenna unit 1. , 18 is the antenna element 6
Buffer memory 19 receives and stores phase data from ₁ to _6o , and 19 is a frequency analyzer that forms a large number of antenna beams and gives maximum output in the antenna beam direction corresponding to the input phase of the incoming radio wave to each antenna element. , 20 is a detection circuit for detecting signals from multiple antenna beam outputs, and 21 is a sample/detection circuit.
a timing control circuit that controls the timing of a hold circuit and an analog/digital conversion circuit; 2;
2 is a frequency control circuit that controls the oscillation frequency of the oscillator section.

In the digital beam forming device configured as described above, the arrival direction of the signal is directed to the antenna section 1.
If the antenna is in the front direction (normal direction) of the aperture surface, the phase data of each antenna element 6 ₁ to 6 _o will all be in phase. In addition, when the antenna is deviated from the front direction by θ, the phase difference between two antenna elements adjacent to each other is φ _r
is expressed by the following equation.

φ _r =2π/λd sinθ (1) where d is the array interval of the antenna elements, and λ is the free space wavelength.

As shown in equation (1), the phase difference φ _r between the antenna elements 6 ₁ to 6 _o changes depending on the direction of arrival of the signal, so this phase difference φ _r is corrected to zero, and the output of all elements is Adding them will give you the maximum output. Therefore, the phase difference φ _r for a predetermined angle θ is (1)
Since it is obtained from the formula, each antenna element 6 ₁ to 6 _o
If the phase difference φ _r for a large number of angles is corrected and added to the output phase data of , the output at the angle where the corrected phase difference becomes zero becomes the maximum output and becomes the arrival direction of the signal. In short, it is sufficient to perform the Fourier transform shown in the following equation.

E(0)= _o 〓 ^k=1 e ^j(k-1) 〓 ^r ………(2) Here, k is a positive integer and is the number of the antenna element. n is the number of antenna elements. θ ₁ ,
θ _k and θ _o-1 are preset signal arrival directions.

If φ=2π/λd sinθ _k , equation (4) becomes E(θ _k )=n, and the maximum output is obtained. Also, θ ₁
If θ _B is the beam width of the antenna, then sin θ ₁ = sin θ _B = λ/nd (6), so equations (2) to (5) become as follows.

However, p=sinθ/ _sinθB , and p is a positive integer.

Equation (7) indicates discrete Fourier transform, and if the actual calculation is performed using the fast Fourier transform method, the processing time can be significantly reduced to several milliseconds.

The angle θ can be in the horizontal or vertical direction with respect to the front direction, but in equation (7), the Fourier transform is only for the angular region on one side, so the phase of antenna elements 6 ₁ to 6 _o in equation (7) In other words, it is sufficient to reverse the order of the data, that is, from antenna element 6 ₁ to antenna element 6 _o sequentially, to sequentially from antenna element 6 _o to antenna element 6 ₁ , and in order to process these data simultaneously, fast Fourier transform is performed. This is possible by using two channels.

The above explanation based on FIG. 2 is an example in which the opening surface of the antenna section 1 is a flat surface. Even if the opening surface is cylindrical or any other arbitrary shape, the principle of the present invention still applies. Applicable. The phase difference φ _r between the antenna elements shown in equation (1) is when the antenna elements are arranged linearly or in a plane at a constant interval d, so the three-dimensional position of the antenna elements is is given, the phase difference between each antenna element can be calculated and determined in advance. Then, by performing discrete Fourier transform using equation (8) using these phase differences, an antenna beam can be formed for any aperture shape.

In equation (8), Dk is the phase difference of the k-th antenna element with respect to the preset signal arrival direction Op. φ _k is the phase difference between the actual received signals input to the k-th antenna element. Furthermore, Ak is a coefficient that weights the output signal of each antenna element and controls the pattern characteristics of the receiving antenna beam.

Next, the received signal for each receiving antenna beam is subjected to integration processing in the order of sampling time corresponding to the range gate. As the integration process, both non-coherent integration in which amplitude information of received signals is added and coherent integration in which fast Fourier transform processing is performed using phase information can be used. The detection circuit 20 detects the signal with the maximum amplitude from among a large number of range gates.

This invention using such a principle transmits phase data from each antenna element 6 ₁ to 6 _o to a signal processor 1.
7, and a fast Fourier transformer 19 performs fast Fourier transform on beam directions twice as many as the number n of antenna elements. A detection circuit 20 detects the maximum output value of the frequency analyzer 19 and outputs a preset angle of the receiving antenna beam direction. Furthermore, a transmitting device (not shown in the present invention) that radiates a pulse-modulated transmission signal into space with a wide antenna beam is connected, and the pulse modulation timing of the transmission signal is synchronized with the timing control circuit 21, and the transmission signal and the oscillator section are synchronized. The fact that the distance and speed to the target can be obtained by synchronizing the 16 frequencies and processing the received signal for each range gate according to the present invention can be easily inferred from the principles of conventional radar equipment. The timing control circuit 21 simultaneously controls the sample/hold circuits 14 and analog/digital conversion circuits 15 of all the elements in order to obtain phase data of the antenna elements 6 ₁ to 6 _o . The frequency control circuit 22 uses the oscillator section 16 to match the incoming signal frequency and the reference signal frequency.
control the frequency of

〔Effect of the invention〕

As explained above, the present invention is capable of digitally forming a plurality of receiving antenna beams at the same time using phase data of antenna elements.
Moreover, by performing fast Fourier transform processing, there is an effect that the direction of arrival of a signal can be detected in a short time.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional digital beam forming device, and Fig. 2 is a schematic block diagram showing an embodiment of the present invention.
is a receiver, 3 is a control computer, 4 is a feeding circuit, 5 is a multilayer board, 6 ₁ to 6 _o are antenna elements, 7 is a radiator, 8 is a microwave amplifier, 9 is a phase shifter, 10 is a mixer, 11 is an intermediate frequency amplifier, 12 is a phase detector, 13 is a video amplifier, 14 is a sample/hold circuit, 15 is an analog/digital conversion circuit, 16 is an oscillator section, 17 is a signal processing section, 18 is a buffer memory, and 19 is a frequency 20 is a detection circuit, 21 is a timing control circuit, and 22 is a frequency control circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Radio waves arriving from the target are received by a radiator, amplified by microwave amplification, an intermediate frequency signal is obtained by a local oscillation signal in a mixer, and after being amplified to a sufficiently high level by an intermediate frequency amplifier, it is combined with a reference signal by a phase detector. An antenna element that transmits the received signal data by performing quadrature phase detection, amplification by a video amplifier, conversion to a digital signal by a sample/hold circuit and an analog/digital converter, and a large number of the above antenna elements at a predetermined element interval. an antenna section configured with a feeding circuit that distributes a local oscillator signal and a reference signal to each of the antenna elements, and a multilayer board that distributes power and various control signals necessary for the active circuit of the antenna element; an oscillator section that generates a local oscillator signal and a reference signal; and a buffer memory that chronologically stores received signal data digitized by the plurality of antenna elements in the order in which it was sampled for each of the antenna elements in accordance with the range gate number. , reads the received signal data of a large number of the antenna elements of the same range gate with the same sampling order stored in the buffer memory, and calculates each phase difference correction value between the antenna elements that changes depending on the direction of forming the receiving antenna beam. Discrete Fourier transform processing in which received signal data for each antenna element is multiplied and then added is applied to each of a large number of receiving antenna beams and stored, and then discrete Fourier transform processing is performed repeatedly in the same sampling order for reception. a frequency analyzer that stores processing results in time series corresponding to range gates for each antenna beam and then performs integral processing on the time series processing results corresponding to each range gate for each receiving antenna beam; A detection circuit detects the maximum amplitude signal from a large number of range gates obtained for each receiving antenna beam, and a sampling timing signal at fixed time intervals is supplied to the sample/hold circuit and analog/digital converter in the antenna element. A signal consisting of a timing control circuit to supply, and a frequency control circuit that changes and controls the frequencies of the local oscillator signal and the reference signal of the oscillator section, and also changes and controls the frequency of the sampling timing signal generated by the timing control circuit. A digital beam forming device characterized by comprising a processing section.