JP2817733B2 - Radar equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device, and more particularly to a radar device for an anti-aircraft radar for detecting a moving long-distance target.

[0002]

2. Description of the Related Art As shown in FIG.
A plurality of transmissions were performed to suppress clutter, and the Doppler frequency was calculated from the phase change of the received signal. For example, in the example of FIG. 6, transmission and reception are performed four times, during which the transmission frequency, the transmission pulse width, the transmission interval, and the beam direction are fixed.

As a technique for detecting a target at a long distance, there is a method called pulse compression. FIG. 5 shows an example of a configuration of a radar using conventional pulse compression. The transmitter 1 generates a transmission signal. The transmission modulation signal generator 2 outputs a modulation signal required for pulse compression. The transmission / reception switch 3 performs switching to output a transmission signal from the transmitter to the antenna and a reception signal from the antenna to the receiver. The antenna 4 has directivity and enables transmission and reception in a required direction. The receiver 5 uses the synchronization signal output from the coherent signal generator 6 to perform phase detection into an I component and a Q component. A / D converters 7 and 8 convert an analog video signal into a digital signal. Received signal storages 11 and 12 store received signals.

The received data compressor 9 performs pulse compression using the phase change determined by the Doppler coefficient generator 16 and the transmission modulation signal generator 2. The maximum signal detector 10 selects the maximum value of the pulse-compressed received signal. The estimated reception signal generator 13 calculates the reception signal before pulse compression from the reception signal after maximum pulse compression. The unnecessary signal eliminator (I) 14 and the unnecessary signal eliminator (Q) 15 calculate the maximum value calculated by the estimated received signal generator 13 from the received signals before pulse compression stored in the received signal storages 11 and 12. The signal component is removed by subtraction.

[0005]

A first problem is that, in the prior art, there is a limit to a transmission / reception time for detecting a target. The reason is that a plurality of transmissions and receptions are performed to secure transmission energy required for clutter suppression and target detection. The second problem is that E
I had to make several fearful transmissions detected by a CM machine (radio wave jammer). The reason is that transmission of the same radar data (frequency, pulse width, pulse interval, beam direction) is repeatedly performed in order to secure transmission energy required for clutter suppression and target detection.

According to the present invention, a target is detected by one transmission / reception, and the frequency, pulse width, pulse interval, and beam direction, which are radar specifications, can be changed for each transmission. It is another object of the present invention to provide a radar device capable of preventing radar detection by an ECM machine.

[0007]

The radar apparatus according to the present invention comprises:
A Doppler frequency component is extracted from one received signal so that a target can be detected by one transmission / reception. More specifically, a filter coefficient generator (9 in FIG. 1) that outputs an appropriate filter coefficient based on the transmission frequency and pulse interval, and a signal other than clutter is determined based on the Doppler frequency and position of the signal. Clutter suppressor (1 in FIG. 1)
4).

Another feature is that the frequency, pulse width, pulse interval, and beam direction are changed for each transmission. Specifically, it includes a radar specification generator (1 in FIG. 1) that outputs information of each specification to each processor.

[0009]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of a radar apparatus according to the present invention. FIG. 1 shows the configuration of the conventional radar apparatus having a pulse compression function shown in FIG. 5 with the function according to the present invention added thereto, except for a radar specification generator 1, a filter coefficient generator 9 and a clutter suppressor 14. The configuration is the same as or similar to that of the conventional radar device of FIG.

The radar specification generator 1 arbitrarily outputs information under the condition that the frequency, pulse width, pulse interval, and beam direction of a transmission pulse can be targeted by one transmission pulse. The antenna 2 forms a beam under the conditions of the frequency, the beam direction, and the pulse interval output from the radar specification generator 1. The transmission / reception switch 3 sends the signal output from the transmitter 5 to the antenna 2,
The signal received by the antenna 2 is output to the receiver 6.
The transmission modulation signal generator 4 outputs a modulation signal so that pulse compression can be performed after receiving a long transmission pulse determined by the frequency and pulse width output from the radar specification generator 1. The transmitter 5 outputs transmission energy based on the modulation signal output from the transmission modulation signal generator 4 and the frequency, pulse width, and pulse interval output from the radar specification generator 1.

The receiver 6 amplifies the power received from the antenna 2 and performs phase detection. The A / D converter 7 includes a receiver 6
Is A / D converted. The reception data storage 8
The received data for one transmission is stored. The filter coefficient generator 9 outputs a filter coefficient in consideration of the target Doppler frequency from the frequency and pulse interval output from the radar specification generator 1. The pulse compressor 10 performs pulse compression for each Doppler frequency based on the modulation signal information of the transmission pulse output from the transmission modulation signal generator 4 and the filter coefficient output from the filter signal generator 9.

The maximum signal detector 11 includes a pulse compressor 10
The maximum signal is selected from the output signals, and the signal, the distance, and the Doppler frequency are output. The estimated received signal generator 12 estimates the received signal before pulse compression based on the pulse-compressed maximum signal output from the maximum signal detector 11, its Doppler frequency, and the modulation signal information output from the transmission modulation signal generator 4. . The unnecessary signal remover 13 removes the received signal stored in the received data storage 8 by subtracting the received signal calculated by the estimated received signal generator 12, and outputs the signal to the received data storage 8. The clutter suppressor 14 determines whether or not the signal is a clutter based on the Doppler frequency and distance of the signal output from the maximum signal detector 11 and the beam direction output from the radar specification generator 1, and outputs a signal other than the clutter.

[0013] The received signal of one transmission is converted to a pulse compressor 10,
The signal is detected by iterative processing in the maximum signal detector 11, the estimated received signal generator 12, the unnecessary signal remover 13 and the received data storage 8, and clutter suppression is performed based on the Doppler frequency and position. As a result, it is possible to suppress the time side lobe generated in the pulse compression of the long transmission pulse necessary for performing the target detection in one transmission. Also, clutter suppression using the Doppler frequency component of one received signal becomes possible.

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIGS. The radar specification generator 1 outputs radar specification information in which the transmission pulse width, transmission pulse interval, beam direction, and frequency, which are radar specifications, change for each transmission, as in the timing example shown in FIG. The antenna 2 receiving this information calculates parameters for beamforming from the beam direction and frequency in advance, performs beamforming immediately before transmission determined by the transmission pulse interval, and continues until the end of the reception section. .
The transmission modulation signal generator 4 receiving the radar specification information prepares a modulation signal corresponding to the transmission frequency and the pulse width in advance, and immediately after the transmission determined by the transmission pulse interval,
The prepared modulation signal is output to the transmitter 5 and is output to the pulse compressor 10 and the estimated reception signal generator 12 as modulation signal information. Transmitter 5 receiving radar specification information
Prepares parameters such as an internal trigger signal and filter settings necessary for transmission from the transmission frequency and pulse width in advance, and outputs the modulated transmission signal output from the transmission modulation signal generator 4 at the timing determined by the pulse interval. Outputs energy. The receiver 6 receiving the radar specification information prepares parameters such as an internal trigger signal and filter setting necessary for reception from the transmission frequency in advance, and sets the frequency setting specified at the timing determined by the pulse interval. .

A filter coefficient generator 9 receiving radar specification information calculates a filter coefficient necessary for pulse compression in consideration of Doppler from a frequency, a pulse interval, and a previously specified Doppler speed, and generates a pulse compressor. Output to 10 The pulse compressor 10 receiving the modulated signal information and the filter coefficients required for pulse compression calculates pulse compression parameters from the modulated signal and the filter coefficients, and performs pulse compression on the received data. The clutter suppressor 14 that receives the radar specification information determines whether the signal is clutter based on the beam direction, the distance between the signals output by the maximum signal detector 11, and the Doppler frequency, and outputs a signal other than the clutter.

The specific effects obtained in the embodiment of the present invention will be described with reference to FIGS. According to the present invention, the target can be detected by one transmission. FIG.
An example of the detection time of the conventional and the present invention is shown. FIG. 4 (a)
The figure shows the transmission / reception timing in a conventional radar that performs target detection by four transmissions at a transmission / reception ratio of 25% defined as a ratio between the maximum detection distance and the transmission time. FIG. 4 (b)
The transmission / reception timing of the present invention when four transmission times of the related art are received with one transmission pulse is shown. Than this,
It can be seen that the target can be detected in 40% of the conventional time.

FIG. 4C shows the reduction rate of the time required for transmission and reception between the conventional radar having four hits and the radar system of the present invention, using the transmission / reception ratio of the conventional radar as a parameter. According to this, the transmission / reception time is 30 to 40%
It can be seen that it is shortened. Since the target can be detected by one transmission in this way, it is possible to change each radar specification for each transmission as shown in FIG.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a configuration diagram showing the second embodiment. The radar specification generator 1, the pulse compressor 10, and the estimated received signal generator 12 are different from the first embodiment shown in FIG. I have.

The radar specification generator 1 predicts a target position such as a tracking process in a device other than the present invention, and uses the target prediction position, which is the information, as an input source, the frequency as the radar specification, and the transmission pulse. The width, the transmission interval, and the beam direction can be set more efficiently, and the beam scanning time can be reduced. In other words, since it is not necessary to detect a target farther than the predicted position of the target, the reason is that the transmission pulse width and transmission interval can be shortened, restrictions on usable frequencies can be relaxed, and the beam direction can be limited.

When the modulation signal to be used is designated in advance by the pulse width and frequency, the pulse compressor 10 and the estimated reception signal generator 12 modulate the signal based on the radar specification information output from the radar specification generator 1. A demodulated signal corresponding to the signal can be prepared. In the second embodiment, input and output of information assuming that is performed.

As described above, the coefficient of the filter for separating the Doppler frequency, which varies depending on the transmission frequency and pulse interval, is changed, and the clutter suppression is performed by the received signal for one transmission. Therefore, it is possible to detect the target by one transmission signal. Then, radar data including the transmission frequency, pulse width, pulse interval, and beam direction can be output to each processing unit from one place. For this reason,
It is possible to change radar specifications every transmission and prevent radar detection from the ECM machine.

[0022]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. Radar specification generator 1 in FIG.
Is composed of a processor, a sequencer, or a gate array having a plurality of output interfaces and outputting radar specification information under predetermined conditions. The antenna 2 has a plurality of phase shifters and the like that can perform beam scanning in all directions in an arbitrary order, and is configured by a phased array radar that forms an equal phase plane for beam forming. However, the effect of the present invention is provided, except that the beam cannot be arbitrarily scanned even with a reflector type antenna. Receiving data storage 8,
Filter coefficient generator 9, pulse compressor 10, maximum signal detector 11, estimated received signal generator 12, unnecessary signal remover 1
The 3 and the clutter suppressor 14 are composed of a processor, a sequencer or a gate array, a memory, and a digital IC in order to execute arithmetic processing and determination processing of a large amount of data at high speed.

Next, the operation of this embodiment will be described in detail with reference to FIGS. Radar specification generator 1
Determines the frequency from the usable frequency and the predicted target distance. Since the detection distance, the clutter suppression performance, and the like change depending on the frequency, a usable frequency is determined in advance according to a target distance to be predicted, and a frequency to be used arbitrarily is determined from the frequencies. The transmission pulse width to be used is determined by the target distance to be predicted. From the maximum detection distance R _max calculated in advance for each frequency, its pulse width τ _max, and the predicted target distance R, the minimum pulse width τ that can be used can be determined by equation (1).

[0024]

(Equation 1)

The pulse interval to be used is determined by the target distance to be predicted. Pulse interval is the sum of the reception time and the transmission pulse width, minimum t _r of the reception time obtained by (2), this minimum value of the pulse interval is determined from.

[0026]

(Equation 2) Where R: predicted target distance c: speed of light

The beam direction to be used is determined based on the target direction to be predicted. If the target distance is unknown, the processing is performed using the required maximum distance. The example of FIG. 1 shows a case where the maximum distance required for each direction is specified in advance.

The filter coefficient generator 9 outputs a filter coefficient necessary for pulse compression based on the transmission frequency and the pulse interval contained in the radar specification information. Here, the coefficients of the filter are the phase change speed ω corresponding to the Doppler frequency and the number n of samples of the pulse interval, and are determined by the equations (3) and (4).

[0029]

(Equation 3)

[0030]

(Equation 4)

Where f_c : Transmission frequency v: Doppler velocity c: Light velocity t: Pulse interval t_s : A / D sampling interval When pulse compression is performed by FFT processing, n
Is output as a power of 2 exceeding the value calculated by equation (4).
You. Ω is the assumed Doppler velocity v₁ , V _Two ,
…, V_m Substituting for v in equation (3)
ω₁ , Ω_Two ,…, Ω _m Is output.

The pulse compressor 10 calculates a demodulated signal using the modulated signal information and the phase change speed ω, and performs pulse compression. For example, a case where pulse compression is performed using FFT will be described below. The modulated signal f (i) (i = 1,..., L) is exchanged as follows to calculate the demodulated signal g (i) (i = 1,.

[0033]

(Equation 5)

Next, the received signal r (i) (i = 1,..., L)
Then, the following data extension is performed to prepare r ′ (i) (i = 1,..., N).

R ′ (i) = 0 (i = 1,..., K) r ′ (i) = r (i−k) (i = k + 1,..., K + 1) r ′ (i) = 0 (i = k + l + 1,..., n) Here, k indicates a sampling number corresponding to a pulse width.

G (i) and r (i) ′ (i =
1,..., N) are subjected to FFT processing, and the same frequency is calculated for each of them, and IFFT is performed, whereby pulse compression can be performed. If a plurality of phase change speeds ω are specified, the demodulated signal g of each ω
Pulse compression is performed to obtain (i). Therefore, when there are m sets of ω, m sets of data after pulse compression up to the maximum distance are output.

The clutter suppressor 14 includes the maximum signal detector 1
In step 1, it is determined whether or not there is clutter by a method which is determined in advance from the distance of the signal output, the Doppler frequency, and the beam direction output from the radar specification generator 1. For example, a signal having a Doppler frequency near 0 at a low elevation angle and a signal having a predetermined position and Doppler frequency are determined to be clutter, and this signal is not output. Also,
When the transmission pulse width is short, the Doppler frequency may not be able to be separated finely. As a countermeasure, there is a method of controlling the range of the Doppler frequency determined as clutter by the transmission pulse width.

[0038]

The first effect is that the transmission / reception time for detecting a target can be greatly reduced, thereby enabling high-speed target tracking, beam scanning, and expansion of a scanning range. The reason is that the target is detected by receiving one long transmission pulse necessary for the target detection, and the clutter can be suppressed.

The second effect is that it is possible to prevent radar detection by the ECM machine by changing the frequency, pulse width, pulse interval, and beam direction, which are radar specifications, every transmission. . The reason is ECM
This is because the machine detects radar based on the same radar data that is repeated, and the present invention does not repeat the same radar data.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of a radar apparatus according to the present invention.

FIG. 2 is a time chart showing the operation of the embodiment of the present invention.

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the effect of the present invention.

FIG. 5 is a configuration diagram of a conventional radar device.

FIG. 6 is a time chart showing the operation of a conventional radar device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 radar specification generator 2 antenna 3 transmission / reception switch 4 transmission modulation signal generator 5 transmitter 6 receiver 7 A / D converter 8 reception data storage 9 filter coefficient generator 10 pulse compressor 11 maximum signal detector 12 Estimated received signal generator 13 Unwanted signal remover 14 Clutter suppressor

Continuation of front page (56) References JP-A-5-281342 (JP, A) JP-A-6-294864 (JP, A) JP-A-61-54478 (JP, A) JP-A-51-137395 (JP, A) , A) JP 50-15555 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/00-7/64 G01S 13/00-13/95

Claims (2)

(57) [Claims] 1. The frequency of a transmission pulse as radar data,
A radar specification generator (1) that arbitrarily outputs a pulse width, a pulse interval, and a beam direction under a condition that a target can be detected by one transmission pulse; a frequency, a beam direction, and a frequency that the radar specification generator (1) outputs. An antenna (2) that forms a beam with a pulse interval as a condition, a transmission / reception switch (3) that outputs a signal output by a transmitter to the antenna, and a signal received by the antenna to a receiver, and the radar specification generation. A transmission modulation signal generator (4) that outputs a modulation signal for performing pulse compression after receiving a long transmission pulse, which is determined from a frequency and a pulse width output by the transmitter (1); and the transmission modulation signal generator ( 4) a modulated signal output by
A transmitter (5) that outputs transmission energy from the frequency, pulse width, and pulse interval output by the radar specification generator (1); and a receiver that amplifies power received from the antenna (2) and performs phase detection. (6), an A / D converter (7) for A / D converting an output signal of the receiver (6), a reception data storage (8) for storing reception data for one transmission, and the radar A filter coefficient generator (9) for outputting a coefficient for producing a filter that takes into account a target Doppler frequency from a frequency and a pulse interval output from the specification generator (1); and the transmission modulation signal generator (4) A pulse compressor (10) that performs pulse compression for each Doppler frequency based on modulation signal information of a transmission pulse to be output and a filter coefficient output by the filter coefficient generator (9), and an output of the pulse compressor (10). A maximum signal detector (11) for selecting a maximum signal from the signals and outputting the signal, a distance and a Doppler frequency; a maximum signal after pulse compression output from the maximum signal detector (11); An estimated received signal generator (12) for estimating a received signal before pulse compression based on a frequency and modulated signal information output from the transmission modulated signal generator (4); and an estimated received signal generator (8) stored in the received data storage (8). The unnecessary signal remover (13) that removes the largest signal component by subtracting the received signal calculated by the estimated received signal generator (12) from the received signal, and outputs the signal component to the received data storage (8). It is determined whether or not clutter is present based on the Doppler frequency and distance of the signal output from the maximum signal detector (11) and the beam direction output from the radar specification generator (1). Radar apparatus characterized by having a clutter suppression for outputting a signal other than (14). 2. A radar specification generator (1) outputs a frequency, a pulse width, a pulse interval, and a beam direction of a transmission pulse based on target predicted position information from an external device under a condition that a target can be detected by one transmission pulse. The radar according to claim 1, wherein the pulse compressor (10) and the estimated received signal generator (12) prepare a demodulated signal corresponding to the modulation signal based on the radar specification information output from the radar specification generator (1). apparatus.