JPH0271186A - Radar device - Google Patents

Abstract

PURPOSE:To minimize an undetectable region of a distance and improve detection performance by a method wherein transmission pulse timing from a timing circuit of a signal processor is received and threshold level control is performed according to a range gate. CONSTITUTION:A threshold control circuit 13 which receives transmission pulse timing from a timing circuit 12 of a signal processor 4 and controls the threshold level according to a range gate is provided, and a signal detection circuit 10 is controlled with output of said circuit. The circuit 13 processes signals irrespective of overlap of transmitted pulses and received pulses, and the transmitted pulses and the received pulses are overlaid to be narrow received pulses. This prevents a side robe itself from being detected as a signal if the distance side robe is raised due to incompletion of pulse compression. While deterioration in detection ability due to rise in noise level at the time of signal detection is prevented, mislocation of a range gate due to widening of signal pulse width according to reduction in compression rate is prevented.

Description

[Detailed Description of the Invention] [Industrial Applications] This invention aims to extend target detection range performance and ensure range resolution by using phase modulation pulse compression using Parker code. The present invention relates to a medium-PRF pulsed Doppler type radar that measures the distance to a target using a pulse repetition frequency (hereinafter referred to as PRF) of .

[Conventional technology]

FIG. 4 is a configuration diagram showing a conventional medium PRF pulsed Doppler type radar device, and is similar to FIG.

(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 an amplitude detection circuit.

(9) is an integrator, α [is a signal detection circuit, (11) is a multiple PRF ranging circuit, (12) is a timing circuit, (
14) is a display.

Figure 5 is a diagram showing the waveform of the received pulse after pulse compression, the width of which has become narrower due to overlap with the transmitted pulse, (1
5) is the transmitted pulse, (16) is the received pulse.

(17) is the waveform of received pulses with the same width after pulse compression.

(18) is the received pulse with a narrower width, (19) is the waveform of the received pulse with a narrower width after pulse compression, (2
0) is the distance sidelobe, (21) is the threshold level, and (22) is the quantized signal after signal detection processing.

FIG. 6 is a conceptual diagram showing an area where a target cannot be detected due to the overlap between a transmitted pulse and a received pulse of a conventional radar.

Next, the operation will be explained. The transmission signal generated by the transmitter (1) is sent to the antenna (2) and
is emitted from the target towards the target. This transmitted signal is reflected by the target and received again by the antenna (2), and then sent to the receiver (3).
After amplification, frequency conversion, phase detection, and analog/digital conversion, the signal is processed @! 1 (41
sent to. A signal processor (4) removes clutter using a double erasure delay line canceller (1), etc. (51 first removes unnecessary rutter components, and then a pulse compressor (6) removes clutter from the signal. Compression is performed to improve the signal-to-noise ratio and narrow the pulse width. Then, the two-frequency analysis circuit (7) processes the fast Fourier transform to produce a narrow-band Doppler signal, and the amplitude detection circuit (8) produces a narrow-band Doppler signal. After amplitude detection of the band Doppler signal is performed and then integrated by the integral N(9), the signal is detected from the noise by the signal detection circuit 0ω, and the range gate where the signal exists is determined for each PRF. .Multiple PRFs where signals were detected
Using the range gate, the distance measuring circuit (11) calculates the true target distance by correlation processing. This result is sent to the display W (14) and displayed as target data. In a conventional radar that operates in this way, as shown in Figure 5, when the transmitted pulse (15) and the received pulse (16) overlap to form a narrow received pulse, complete pulse compression is not performed and a distance sidelobe ( 20) increases, which increases the noise level during the detection process and reduces detection performance, or the distance sidelobe (20) is mistakenly detected as a signal, and the compression ratio decreases, causing the signal pulse It was so wide that I sometimes misplaced the range gate. For example, if the threshold level in Figure (e) is the same as in Figure (C), the distance will detect the side lobe (20) as a signal, and the pulse width of the original signal will expand. f)
As shown in the figure, the center position will shift. For this reason, received signals in a range where pulse compression is not completely performed are not processed.

Therefore, a non-detection region corresponding to the width of the transmission pulse occurs before and after the transmission pulse (15), causing a considerable range eclipse.

[Problem to be solved by the invention]

Conventional medium-PRF pulsed Doppler radar equipment is configured as described above, and because it detects targets using the above method, there are many periods in which the transmitted pulse and received pulse overlap, resulting in deterioration of target detection performance. , signal detectable P
There were problems such as the inability to measure distance due to the small number of RFs.

This invention was made to solve this problem.In contrast to conventional radars, which do not process signals if they overlap even slightly with the transmitted pulse, In addition to signal processing, detection performance is reduced due to increase in distance sidelobes and increase in noise level during signal detection.
In order to prevent the detection of the sidelobe itself, the threshold level for detecting the signal from the noise is changed in the overlapping range of the transmitted and received pulses, and the signal detection distance range and the number of signal detection PRFs are increased. The purpose is to improve performance.

[Means to solve the problem]

The radar device according to the present invention includes a threshold control circuit that receives the transmission pulse timing from the timing circuit of the signal processor and performs threshold level control according to the range gate, and uses this output to control the signal detection circuit. It is designed to perform control.

[For production]

The threshold control circuit in this invention is as follows.

Signal processing is performed regardless of the overlap between the transmitted and received pulses, and when the transmitted and received pulses overlap and become a narrow received pulse, and the distance sidelobe rises without complete pulse compression, the sidelobe itself is processed as a signal. In order to prevent the detection performance from deteriorating due to an increase in the noise level when detecting the signal, or to prevent the range gate position from being incorrectly determined due to the reduction in the compression ratio and the widening of the signal pulse width. As in, receiving the transmit pulse timing from the timing circuit.

Performs threshold level control according to range gate.

〔Example〕

An embodiment of the present invention will be described below based on the drawings. 1st
The figure shows the configuration of a radar device according to the present invention. In the figure, (1) to (12) and (14) are the same 81 units or parts as the conventional radar device described above. In this invention,
(13) is a threshold control circuit.

FIG. 2 is related to this invention. This is a conceptual diagram showing the waveform of a narrowed received pulse after pulse compression and threshold level control. In Figure 2, (15) is a 13-bit Parker code phase modulated transmitted pulse, and [1B] is a received pulse. , (17) is the waveform of the normal received pulse after pulse compression, (18) is the received pulse with narrowed width,
(19) is the waveform of the received pulse whose width has been narrowed after pulse compression, (20) is the distance sidelobe, and (211 is the threshold level). Reducing target undetectable area due to overlapping pulses, or.

FIG. 3 is a conceptual diagram showing an increase in the number of target detectable PRFs.

Next, the operation of the radar device according to the present invention will be explained. The transmission signal generated by the transmitter (1) is sent to the antenna (2).
) and radiate it from the antenna (2) towards the target. This transmitted signal is reflected by the target and returned to the antenna (
2), is input to the receiver (3), and after being subjected to amplification, frequency conversion, phase detection, and analog/digital conversion, is sent to the signal processor (4). Signal processor (4
), in synchronization with the PRF signal from the timing circuit (12), a clutter removal circuit (5) such as a double-erasing delay line canceller (one-way type) first removes unnecessary and rutter components, and then a pulse compressor (12) removes unnecessary rutter components. In step 6), pulse compression of the signal is performed to improve the signal-to-noise ratio and narrow the pulse width.

Then, in the two-frequency analysis circuit (7), a narrowband Doppler signal is generated through fast Fourier transform processing, and the amplitude detection circuit (
In step 8), each narrowband Doppler signal is subjected to amplitude detection, integrated by the stage integrator (9), and then sent to the signal detection circuit 00), but up to this point it is the same as in the conventional radar device. As shown in Figure 2, when the received pulse (16) is not blanked at all before and after the transmitted pulse (I5), the signal detection threshold level (21
), and as the blanking rate increases and the received pulse width narrows, the threshold
By increasing the level (21)e, it is possible to prevent the range side lobe (20) from being erroneously detected and the range gate position from being erroneously determined due to a decrease in the pulse compression ratio and widening of the pulse width of the signal. In the same figure (a), the transmission pulse (1
5), and as shown in FIG. 5(b), the received pulse (16) that does not overlap with the transmitted pulse (15) has a low sidelobe after pulse compression, and is completely pulse compressed. However, in Figures (e) and (d), the received pulse (18) with a narrower pulse width has a compressed waveform (
The distance side lobe (20) of 19) also rises, the pulse compression ratio also decreases, and the pulse width widens.

However, upon receiving pulse width data synchronized with the transmission pulse timing from the timing circuit (12) shown in (e) of the same figure, the threshold level is adjusted according to the received pulse width τr as shown in (f) of the same figure. By changing the range, it is possible to avoid erroneously detecting distance side lobes and erroneously determining the range gate position due to the widened pulse width. This threshold level is controlled by the threshold control circuit (13
) sends the signal to the signal detection circuit αα based on the timing of the transmission pulse, thereby realizing the above operation.

and.

Signal detectable range and PRF expanded by this invention
The numbers are shown in Figure 3. Although a case in which there are four PRFs is shown here, it is clear that this is improved compared to the conventional radar described above. And the signal detection circuit QOI
The target range/gate position data for each PRF detected in is sent to the ranging circuit [11], where distance measurement is performed using correlation processing using multiple PRFs, and the distance information is displayed on the display (11).
4) Sent to.

Is displayed.

〔Effect of the invention〕

As described above, while conventional radars do not perform signal processing on received pulses if they overlap even slightly with transmitted pulses, this invention allows signal processing to be performed regardless of the overlap between transmitted pulses and received pulses. (Also, a threshold control circuit is added between the signal processor's timing circuit and the signal detection circuit, with the timing of the transmitted pulse as a reference.

With a simple configuration that simply sends the threshold level to the signal detection circuit, the signal can be detected even when the received pulse width is narrow due to the wide transmitted pulse, minimizing the area where distance cannot be detected and improving detection performance. It has the effect of saying that you can do something.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a radar device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing the configuration of a radar device according to an embodiment of the present invention.
FIG. 3 is a conceptual diagram showing level control, in which the radar's transmitting pulse and receiving pulse overlap in the present invention; this reduces the area where targets cannot be detected. Alternatively, a conceptual diagram showing an increase in the number of target detectable PRFs, Fig. 4 is a configuration diagram showing a conventional medium PRF pulse Doppler radar device, and Fig. 5 shows a received pulse whose width is narrowed due to overlap with a transmitted pulse. Figure 6 is a conceptual diagram showing the area where a target cannot be detected due to the overlap between the transmitted pulse and the received pulse of a conventional radar. In Figure 2, (1) is the transmitter and (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, (9
+i yo integral #QOl hat M detection circuit, (11)+!
Multiple fiP RFiff12 circuits, (12) is a timing circuit, (13) is a threshold control circuit, (1
4) is a display, PRF is a pulse repetition frequency, τ0 is a transmission pulse width, τr is a reception pulse width, Tkl:t threshold level, and τB is a reception signal non-detection range. Note 2. In each figure, the same reference numerals (same or equivalent parts are indicated).

Claims (1)

[Claims] A transmitter that generates a transmission wave of a constant frequency, pulse-modulates it with a predetermined pulse width and pulse repetition frequency, and further modulates the phase within this pulse width using a Parker code, and radiates the transmission wave into space and sends it away from the target. an antenna that receives the reflected waves, a receiver that amplifies the received waves, performs frequency conversion, phase detection, and analog/digital conversion;
In a radar device equipped with a signal processor that calculates the target distance by performing amplitude detection, integration, signal detection, and multi-pulse repetition frequency ranging, and a display that displays target data, in response to the transmission pulse timing, A radar device characterized by having means for controlling a signal detection threshold level according to the received pulse width.