JPS62233781A - Measuring instrument for arrival direction - Google Patents

Abstract

PURPOSE:To easily correct deviations of phases and amplitude of plural input signals at respective analog circuit parts with high accuracy and to uniform them by providing plural complex multiplying circuits between plural A/D converters and a Fourier transform processing circuit. CONSTITUTION:The plural complex multiplying circuits 39-42 corresponding to plural wave receiving elements 1-4 are provided which are interposed between the plural A/D converters 22-29 and the Fourier transform processing circuit 30 and supplied with correcting multiplying values. The correcting multiplying values corresponding to the deviations of the phases and amplitudes of signals of respective channels at the analog circuit parts are supplied to the plural complex multiplying circuits 39-42 to correct the deviations. Consequently, the constitution is simplified and the cost is reduced to easily correct the deviations of the phases and amplitudes of the plural input signals at the respective analog circuit part with high accuracy, thereby uniforming them.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a direction of arrival measuring device suitable for application to radio telescopes, radars, sonar, etc.

[Essentials of invention]

The present invention separately digitizes the O-shift phase and 90-degree phase shift signals of a plurality of human input signals, performs Fourier transform on the plurality of digital signals, and uses the plurality of conversion outputs to generate a plurality of input signals. In a direction-of-arrival measuring device configured to measure direction, a plurality of complex multiplication circuits each corresponding to a plurality of input signals are provided between a plurality of A/D converters and a Fourier transform circuit to which a correction multiplication value is given. As a result, deviations in phase and amplitude due to each analog circuit section of each of a plurality of input signals can be easily and highly accurately corrected and made equal to each other with a simple structure and low cost.

[Conventional technology]

A conventional wide-field radio telescope will be described below with reference to FIG. (1) to (4) are the reception of 4 pieces (generally, there is a plurality of pieces, but for ease of explanation, for example, 4 pieces (referred to as [lil)) arranged in a straight line at equal intervals. An antenna (horn antenna) that receives radio waves from celestial bodies.

In this case, if the received signal is a narrow band, the received voltage of each of the antennas (1) to (4) at each instant has a sinusoidal distribution with a spatial frequency that differs depending on the radio wave arrival direction. Therefore, by Fourier transforming the received voltages of each of the antennas (1) to (4), it is possible to measure the directions and intensities of radio waves arriving from multiple directions at the same time.

Therefore, the S HF band from antennas (1) to (4) (
The delivery signals of θ to 3 channels of 10Gllz band) are supplied to the first mixing circuits (5) to (8), respectively, and frequency-converted into intermediate frequency signals of 0 to 3 channels of IGIIz band. Note that the channels here represent numbers corresponding to antennas (1) to (4) as wave receiving elements. (98) is a first local oscillator that supplies local oscillation signals to these mixing circuits (5) to (8). Each mixing circuit (5) to (
8), the frequency-converted signals of channels 00 to 3, together with the signals shifted by 90 degrees by the 90 degree phase shifters (10) to (13), are sent to the second mixing circuit ( 14), (15); (16)
, (17); (18).

(19) ; (20) and (21) are supplied with orthogonal two-phase baseband signals in the 2.0 MIIz band of channels 0 to 3, that is, the respective mixing circuits (14);
, (16), (18).

Real signal and mixing circuit (15) from (20),
(17).

(19), 0~ consisting of imaginary signals from (21)
It is converted into a 3-channel complex signal. (9B) is a second local oscillator that supplies local oscillation signals to these mixing circuits (14) to (21). This two-stage frequency conversion is performed to lower the frequency of the received signal to facilitate digital conversion.

Each signal from the mixing circuits (14) to (21) is supplied to the A/D converters (22) to (29) to provide a digital signal (the sampling frequency at the time of digitization is as high as possible in the case of a radio telescope). After converting the signal into a high-speed Fourier transform circuit (preferably, wideband processing is performed), the signal is supplied to a fast Fourier transform circuit (30). Furthermore, as mentioned above, even after frequency converting the received signals from antennas (1) to (4), phase gradient information remains.
Spatial Fourier transform allows decomposition of the direction of arrival of radio waves.

In this case, since the number of antennas is four, the Fourier transform circuit (30) performs fourth-order Fourier exchange.

Fourier strange 11! Outputs (complex signals) in four directions are obtained from the circuit (30). Such a fast Fourier transform circuit (3
Regarding 0), Special Training No. 60-5449 is a good reference.

The complex outputs in four directions from the fast Fourier transform circuit (30) are supplied to the square integration circuits (31) to (34), where the power is determined and integrated, and the outputs in the four directions are sent to the output terminal (
35) to (38), and are supplied to a display device via a data processing computer (not shown). Such square integration circuits (31) to (34) and this type of radio telescope are described in Japanese Patent Application Laid-Open No. 30-165.
No. 079 can be used as a reference.

Note that if the number of antennas is increased or the antennas are arranged in a two-dimensional array, the number of direction resolutions increases and the antenna becomes two-dimensional. In an optical telescope, the incoming light is Fourier transformed using a lens, and the resulting real image is formed on a photographic plate, but when two-dimensionalization is performed with a radio telescope, a fast Fourier transform circuit takes the place of the lens.

[Problem that the invention seeks to solve]

The radio telescope described above consists of an analog circuit section and a digital circuit section. The digital circuit section operates accurately and stably, but the analog circuit section has unstable elements.
The performance of a radio telescope is determined by the performance of the analog circuit. The most important thing in this radio telescope is how to minimize the phase difference and gain difference between the analog circuit sections of each channel, since the direction is resolved from the slight time difference between the received signals of each antenna.

The conventional method for solving this problem is to find out how much phase difference and gain difference there is for each channel from the antenna to the input side of the A/D converter for a suitable test signal, and calculate the amount by After the mixing circuit, each channel's signal was phase-corrected and gain-corrected.

However, in this method, the measurement is complicated, the components that can finely adjust the phase of the intermediate frequency signal are expensive, and there are problems in terms of frequency characteristics and variable range. Moreover, analog circuits have problems such as changes over time and temperature characteristics, and it is almost impossible to always align the phase characteristics and amplitude characteristics of the analog circuit sections of each channel to be the same.

In addition, phase correction and amplitude correction between the circuit sections of each channel are as follows.
Since it would be difficult to perform such correction in the intermediate frequency stage, it may be possible to perform such correction in an analog manner at the baseband, but unlike the intermediate frequency stage, the ratio of the center frequency to the bandwidth to be handled, that is, the ratio bandwidth to be handled is large, so it is more practical. Have difficulty.

In view of these points, the present invention separately digitizes the O-shift phase and 90-degree phase shift of a plurality of input signals, subjects the plurality of digital received signals to Fourier transform, and uses the plurality of converted outputs to perform a Fourier transform. , a direction-of-arrival measurement device that measures the direction of arrival of an incoming wave to a plurality of receiving elements, has a simple configuration, a low cost, and a method for measuring the phase and amplitude of each of the plurality of input signals by each analog circuit section. The purpose is to propose something that can easily and accurately correct and even out deviations.

[Means for solving problems]

The present invention provides a plurality of nine
0 degree phase shifters (10) to (13), and a plurality of A/D conversions to which the plurality of input signals and each output signal from the plurality of 90 degree phase shifters (10) to (13) are separately supplied. Vessel (22) ~ (
29) and a Fourier transform circuit (30) to which digital signals from the plurality of A/D converters (22) to (29) are supplied.
In a direction-of-arrival measuring device that measures the directions of arrival of a plurality of input signals using a plurality of conversion outputs from a Fourier transform circuit (30), the direction-of-arrival measurement device includes a plurality of A/D converters (22) to ( 29) and the Fourier transform circuit (30), and a plurality of receiving elements (
1) to (4), a plurality of complex multiplication circuits (3
9) to (42) are provided.

[Effect]

According to the present invention, a plurality of complex multiplication circuits (39) to
(42) is corrected by giving a correction multiplication value corresponding to the deviation in phase and amplitude of the signal of each channel due to the analog circuit section, thereby correcting the deviation.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2, but parts in FIG. 1 that correspond to those in FIG. do. That is, in the present invention, A/D converters (22), (23)
; (24) , (25) ; (26)
.

(27); (2B), (2'l) and the fast Fourier transform circuit (30) are provided with O to 3 channels of complex multiplication circuits (39) to (42), and the analog part of each channel is Correct the deviation of the resulting complex signal.

Next, referring to FIG. 2, the complex multiplication circuit (3
The circuit configurations (same configuration) of 9) to (42) will be explained. For example, when using the O channel complex signal as a reference, 1 to
Let the necessary amounts of amplitude correction for the complex signals of three channels be R1, R2, and R3, respectively, and the necessary amounts of phase correction for the complex signals of channels 1 to 3 when using the O channel complex signal as a reference, respectively, φt + Φ2 +! 3, the complex multiplication circuits (40) to (40) of channels 1 to 3 (
42), the complex multiplication correction value Rk exp (iΦk) = (Rk-cos (Φk)) + i (Rk-sin ((1'k)) ( However, it should be multiplied by k=1.2.3).

Therefore, (51) is an A/D converter (22).

The input terminal (52) to which the real signal from (24), (26) or (28) is supplied is the A/D converter (2).
3).

This is an input terminal to which an imaginary number signal from (25), (27) or (29) is supplied. Real number input from the input terminal (5()) is supplied to multipliers (53) and (54).

The imaginary number input from the input terminal (52) is sent to the multiplier (55).
.

(56).

Next, how to create a complex multiplication correction value in this complex multiplication circuit will be explained. The necessary phase correction amount Φk (k=1.2.3) from the input terminal (65) is stored in the ROM (
63) and (64) as addresses to obtain the respective outputs cos (Φk) sin (Φk), and supply these to the calculators (66) and (67), and input terminals (70). Rk-cos(Φk) and Rk-5in(Φk) are obtained by multiplying by the amplitude correction required 1qRk supplied by Rk-cos(Φk) and stored in registers (68) and (69), respectively.

Then, Rk - cos(Φk) from the register (68) is supplied to multipliers (53) and (55) to be multiplied by the real number input and the imaginary number input, respectively. Also, register (69)
, Rk −5in(Φk) is supplied to multipliers (54) and (56) to be multiplied by the real number input and the imaginary number input, respectively.

The output of the multiplier (53) and the output of the multiplier (56) are fed to a subtracter (58) to subtract the latter from the former to obtain a real output at the output terminal (60). Both outputs of the multiplier (54) and the multiplier (55) are fed to an adder (59) and summed to obtain an imaginary output at the output terminal (61).

In addition, in the 0 channel complex multiplier (39), Φ = O Rk=1 It's fine.

Since digital operations are performed in such a complex multiplication circuit,
There are no problems with frequency characteristics.

Since such a digital compound multiplication circuit has a digital circuit configuration, automatic correction control using a microcomputer is possible, and it becomes easy to cope with changes over time.

The above amplitude correction amount is determined by the Fourier transform circuit (30
) can be provided with a bypass function. In other words, by directly connecting the input terminal and output terminal of the Fourier transform circuit (30), the square integration circuits (31) to (3
4) does not integrate the power for each direction identified by the Fourier transform circuit (30), but integrates the power for each channel. Therefore, each antenna (1) ~
For example, if each antenna (1) to (4) receives radio waves from a radio wave radiation source such as a point source on a celestial body so that equal received signals can be obtained by (4), each channel Gain differences and striking amplitude deviations of analog circuits can be obtained. In addition, in order to obtain the necessary amount of amplitude correction from the power integration results of the signals of each channel, a processing circuit such as a data processing computer to which the outputs of the square integration circuits (31) to (34) in FIG. 1 are supplied is required. Alternatively, the computer that controls the large-scale recording device that records the observation results can do this.

In addition, the necessary amount of phase correction is determined by converting the signal that has been amplitude corrected and passed through the Fourier transform circuit (30) into square integration circuits (31) to (
34) and its output is given to the computer mentioned above for analysis. The radio wave radiation source used when determining the required amount of phase correction may be the same as that used when determining the required amount of amplitude correction.

The above-mentioned complex multiplication circuits (39) to (42) are required for the number of channels, that is, N in the case of N channels, but the circuit amount is equivalent to two stages of the fast Fourier transform circuit (30), so the fast Fourier transform circuit Since a part of the circuit can be reused, there is no need to increase the circuit design.

That is, the complex multiplication circuit is a fast Fourier transform circuit (30).
The reason why two stages of can be used instead is that one stage of the N-order fast Fourier transform circuit (30) consists of an N/21[1i1 butterfly operation circuit, and each butterfly circuit always has one complex multiplication circuit. be. However, since the butterfly circuit has two separate complex addition circuits in addition to the complex multiplication circuit, it becomes redundant.

Note that the number of wave receiving elements is arbitrary. Further, the present invention can also be applied to sonar (its phaser), radar, etc.

〔Effect of the invention〕

According to the present invention described above, the O-shift phase and 90-degree shift phase of a plurality of input signals are digitized separately, the plurality of digital signals are Fourier transformed, and the plurality of input signals are processed by the plurality of transform outputs. A direction-of-arrival measuring device for measuring the direction of arrival of a signal has a simple configuration, l1l
It is possible to easily and accurately correct deviations in phase and amplitude of each of a plurality of input signals due to each analog circuit section at a low cost.

In addition, by using a microcomputer, such correction can be automatically performed with arbitrary precision according to the number of bits.
You can do it as many times as you like.

Furthermore, the complex multiplication circuit can utilize the butterfly circuit of the fast Fourier transform circuit, and when integrated into an LSI, the circuit design can be shared. Since the complex multiplication circuit has a digital circuit configuration, it is less expensive than analog circuits. If the backfly circuit of the fast Fourier transform circuit is used as the complex multiplication circuit, the amount of hardware required will only need to be increased by two stages.

Furthermore, the complex multiplier circuit is a conventional digital phase shifter (for example, one that digitally switches an analog delay line with several bits, or one that controls the current flowing through a coil wrapped in ferrite in a waveguide with several bits). It is much cheaper and has much less error.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a complex multiplication circuit thereof, and FIG. 3 is a block diagram showing a conventional example. (1) to (4) are antennas as receiving elements; (10)
- (13) are 90 degree phase shifters, (22) - (29) are A/
D converter, (30) is Fourier transform circuit, (39) to (
42) is a complex multiplier, and (31) to (34) are square integration circuits.

Claims (1)

[Claims] A plurality of 90-degree phase shifters to which a plurality of input signals are separately supplied, and each of the plurality of input signals and each output signal from the plurality of 90-degree phase shifters is separately supplied. It has a plurality of A/D converters and a Fourier transform circuit to which digital signals from the plurality of A/D converters are supplied, and the plurality of input signals are converted by the plurality of conversion outputs from the Fourier transform circuit. In the direction-of-arrival measurement device configured to measure the direction of arrival, a plurality of input signals corresponding to the plurality of input signals, respectively, are inserted between the plurality of A/D converters and the Fourier transform circuit, and are given correction multiplier values. A direction-of-arrival measuring device characterized by comprising a complex multiplication circuit.