JPH0675106B2 - Radar equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention aims to extend the detection range performance of a target by using pulse compression of a phase modulation method using a Barker code and to secure range resolution. The present invention relates to a medium PRF pulse Doppler radar that measures a distance to a target using a pulse repetition frequency (hereinafter referred to as PRF).

[Conventional technology]

FIG. 4 is a block diagram showing a conventional medium PRF pulse Doppler radar device, in which (1) is a transmitter,
(2) is an antenna, (3) is a receiver, (4) is a signal processor, (5) is a clutter removal circuit, (6) is a pulse compressor, (7) is a frequency analysis circuit, and (8) is amplitude. Detection circuit,
(9) is an integrator, (10) is a signal detection circuit, and (11) is a plurality.
The PRF distance measuring circuit, (12) is a timing circuit, and (14) is a display.

FIG. 5 is a diagram showing a waveform of the received pulse after the pulse compression, the width of which is narrowed due to the overlap with the transmitted pulse, (15)
Is a transmitted pulse, (16) is a received pulse, (17) is a pulse-compressed waveform of a received pulse with the same width, (18) is a narrowed received pulse, and (19) is a narrowed received pulse. Waveform after pulse compression of (20) is distance side lobe, (2
1) is the threshold level, and (22) is the quantized signal after signal detection processing.

FIG. 6 is a conceptual diagram showing a target undetectable area due to an overlap between a transmission pulse and a reception pulse of a conventional radar.

Next, the operation will be described. The transmission signal generated by the transmitter (1) is sent to the antenna (2) and the antenna (2)
Emitted from the target toward. This transmitted signal is reflected by the target and is received again by the antenna (2), and the receiver (3)
The signal is input to, and after being amplified, frequency converted, phase detected, and analog / digital converted, it is sent to the signal processor (4). In the signal processor (4), unnecessary clutter components are first removed by a double erasure delay line canceller type clutter removal circuit (5), and then pulse compression of the signal is performed by a pulse compressor (6). As a result, the signal-to-noise ratio is improved and the pulse width is narrowed. Then, in the frequency analysis circuit (7), a narrow band Doppler signal is obtained by the fast Fourier transform process, and in the amplitude detection circuit (8), the amplitude detection of each narrow band Doppler signal is performed, and then integrated by the integrator (9) After that, the signal is detected from the noise in the signal detection circuit (10), and the range in which the signal exists for each PRF.
Gate is required. The range-finding circuit (11) calculates the true target distance by the correlation process using the range gates of the plurality of PRFs from which the signals are detected. The result is sent as target data to the display (14) and displayed. The conventional radar that operates in this way is
When 5) and the received pulse (16) overlap to form a narrow received pulse, perfect pulse compression is not performed, the distance side lobe (20) rises, and the noise level during detection processing rises,
Detection performance may be degraded, or range side lobes (2
In some cases, 0) was erroneously detected as a signal, and the compression ratio decreased, the pulse width of the signal widened, and the range gate position was erroneous. For example, when the threshold level is the same as that in FIG. 6C, the distance side lobe (20) is detected as a signal, and the pulse width of the original signal is widened (f). As shown in), the center position is displaced. For this reason, the received signal in the range where pulse compression is not completely performed is not processed. Therefore, a non-detection area corresponding to the transmission pulse width occurs before and after the transmission pulse (15), and
It was causing Eclipse.

[Problems to be Solved by the Invention]

The conventional medium PRF pulse Doppler radar device is configured as described above, and since the target was detected by the above method, the target detection performance deteriorates because there are many periods when the transmitted pulse and the received pulse overlap. Or PRF capable of signal detection
There was a problem that the distance could not be measured due to the small number.

The present invention has been made in order to solve such a problem, and the conventional radar does not perform signal processing when the transmission pulse overlaps even a little, whereas it does not perform signal processing regardless of the overlap between the transmission pulse and the reception pulse. In addition to signal processing, the range side lobe rises and the noise level at the time of signal detection increases, which reduces detection performance and prevents side lobe detection. The purpose is to change the threshold level for signal detection from, to increase the signal detection distance range and the number of signal detection PRFs, and to improve the detection performance.

[Means for Solving the Problems]

The radar device according to the present invention is provided with a threshold control circuit which receives a transmission pulse timing from a timing circuit of a signal processor and performs a threshold level control according to a range gate. The control is performed.

[Action]

The threshold control circuit according to the present invention performs signal processing irrespective of the overlap between the transmission pulse and the reception pulse, and the transmission pulse and the reception pulse overlap to form a narrow reception pulse. When it rises, the side lobe itself is not detected as a signal, and the detection performance is not deteriorated by the rise of the noise level at the time of signal detection, or the compression rate is lowered and the pulse width of the signal is widened to increase the range. • The threshold level control according to the range gate is performed by receiving the transmission pulse timing from the timing circuit so that the gate position is not mistaken.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows the configuration of the radar device according to the present invention. In the figure, (1) to (12) and (14) are the same devices or parts as the above-mentioned conventional radar device. In the present invention, (13) is a threshold control circuit. FIG. 2 is a conceptual diagram showing the waveform of the narrowed received pulse after pulse compression and the threshold level control in the present invention. In the figure, (15) is 13-bit Barker code phase modulation. The transmitted pulse, (16) the received pulse, (17) the waveform of the normal received pulse after pulse compression, (18) the narrowed received pulse, and (19) the narrowed received pulse. The waveform after pulse compression, (20) is the distance side lobe, and (21) is the threshold level. FIG. 3 is a conceptual diagram showing a decrease in the target undetectable area or an increase in the target detectable PRF number due to the overlapping of the radar transmission pulse and the reception pulse in the present invention.

Next, the operation of the radar device according to the present invention will be described. The transmission signal generated by the transmitter (1) is sent to the antenna (2) and radiated from the antenna (2) toward the target. This transmission signal is reflected by the target, is received again by the antenna (2), is input to the receiver (3), and is subjected to amplification, frequency conversion, phase detection, analog / digital conversion, and then a signal processor ( 4). In the signal processor (4), in synchronism with the PRF signal from the timing circuit (12), unnecessary clutter components are first removed by a clutter removal circuit (5) such as a dual erase delay line canceller system, and then pulse The compressor (6) performs pulse compression of the signal, improving the signal-to-noise ratio and narrowing the pulse width. Then, in the frequency analysis circuit (7), a narrow band Doppler signal is obtained by the fast Fourier transform process, and in the amplitude detection circuit (8), the amplitude detection of each narrow band Doppler signal is performed, and then integrated by the integrator (9) The signal is sent to the rear signal detection circuit (10), but up to this point it is the same as the conventional radar device. When the received pulse (16) is not blanked before and after the transmitted pulse (15) as shown in FIG. The threshold level (21) is increased as the received pulse width decreases and the pulse width of the signal increases because the distance side lobe (20) is erroneously detected or the pulse compression rate decreases. It is possible to prevent the range from being expanded and the range gate position being mistaken. The figure (a) shows the transmission pulse (1
5), the received pulse (16) that does not overlap the transmitted pulse (15) has a low side lobe after pulse compression and is completely pulse-compressed as shown in FIG.
However, in the received pulse (18) having a narrow pulse width in FIGS. 7 (c) and 7 (d), the distance side lobe (20) of the compressed waveform (19) also rises and the pulse compression rate also decreases. The pulse width is widening. However, when the pulse width data synchronized with the transmission pulse timing from the timing circuit (12) shown in FIG. 7E is received, the threshold level is changed according to the range gate as shown in FIG. By doing so, it is possible to prevent the range side lobe from being erroneously detected and the range / gate position to be erroneously caused by the spread pulse width. The above operation is realized by the threshold control circuit (13) sending this threshold level to the signal detection circuit (10) with reference to the timing of the transmission pulse. The signal detectable range and the number of PRFs expanded by this invention are shown in FIG. Here, the case where the number of PRFs is 4 is shown, but it is clear that the PRF is improved as compared with the conventional radar. Then, the target range / gate position data for each PRF detected by the signal detection circuit (10) is sent to the distance measurement circuit (11),
Distance measurement using correlation processing by multiple PRFs is performed and sent as distance information to the display (14) for display.

〔The invention's effect〕

As described above, the conventional radar does not perform signal processing on the reception pulse when it overlaps with the transmission pulse even slightly, whereas the present invention performs signal processing regardless of the overlap between the transmission pulse and the reception pulse. In addition, a threshold control circuit is added between the timing circuit and the signal detection circuit of the signal processor, and the threshold level according to the range gate is sent to the signal detection circuit based on the timing of the transmission pulse. With such a configuration, it is possible to detect a signal even when the reception pulse width is narrow due to a wide transmission pulse, and to minimize the area where the distance cannot be detected to improve the detection performance.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a radar device according to an embodiment of the present invention, and FIG. 2 is a concept showing a waveform of a narrowed received pulse after pulse compression and threshold level control in the present invention. FIG. 3 is a conceptual diagram showing a decrease in the target undetectable area or an increase in the number of target detectable PRFs due to the overlapping of the transmission pulse and the reception pulse of the radar according to the present invention, and FIG. 4 is a conventional medium PRF. FIG. 5 is a block diagram showing a pulse Doppler radar device, FIG. 5 is a diagram showing a waveform after pulse compression of a received pulse whose width is narrowed due to overlapping with a transmitted pulse, and FIG. 6 is a conventional radar transmitted pulse. In the conceptual diagram showing the target undetectable area due to the overlap of received pulses, (1) is the transmitter, (2) is the antenna,
(3) is a receiver, (4) is a signal processor, (5) is a clutter removal circuit, (6) is a pulse compressor, (7) is a frequency analysis circuit, (8) is an amplitude detection circuit, and (9). Is the integrator, (1
0) is a signal detection circuit, (11) is a multiple PRF distance measurement circuit, (12)
Is a timing circuit, (13) is a threshold control circuit,
(14) is a display, PRF is a pulse repetition frequency, τo is a transmission pulse width, τr is a reception pulse width, Tk is a threshold level, and τB is a reception signal non-detection range. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A transmitter for generating a transmission wave of a constant frequency, pulse-modulating it with a predetermined pulse width and pulse repetition frequency, and further phase-modulating the inside of this pulse width with a Barker code. An antenna that radiates and receives the reflected wave from the target, and amplifies and frequency converts the received wave.
Receiver for phase detection / analog / digital conversion and clutter removal / pulse compression /
In a radar device equipped with a signal processor for calculating a target distance by performing frequency analysis / amplitude detection / integration / signal detection / multi-pulse repetition frequency ranging, and a display device for displaying target data, the signal processor is A timing circuit for generating a transmission / reception timing of a radar, a clutter removing circuit for removing unnecessary clutter, and a pulse compressor for pulse-compressing a received signal subjected to phase modulation by a Barker code included in an output signal of the clutter removing circuit. A frequency analyzer for obtaining a narrow band Doppler signal by performing a fast Fourier transform on the output of the pulse compressor; an amplitude detection circuit for performing amplitude detection of each narrow band Doppler signal output from the frequency analyzer; An integrator that integrates the output of the amplitude detection circuit for each narrow band Doppler signal, and a synchronization with the transmission pulse from the above timing circuit A threshold control circuit that generates a threshold level according to the range gate and sends it to the signal detection circuit, and an amplitude comparison level of the receiver noise and the signal that receives the output of the integrator is set to the range from the threshold control circuit.・ Determine based on the threshold level of each gate, detect only the signal, and
A transmission pulse composed of a signal detection circuit for calculating the gate position and a distance measurement circuit for performing distance measurement by correlation processing using the target range / gate position data for each of a plurality of pulse repetition frequencies detected by the signal detection circuit. A radar device comprising means for controlling a threshold level of signal detection for each range gate corresponding to a pulse width of a received signal blanked by a transmission pulse in synchronization with a timing.