JPS6026985B2 - Pulse Doppler radar signal processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing method for pulsed Doppler radar, in which pulse repetition frequency (hereinafter referred to as Ph) is determined.

) in a pulse Doppler radar having two different transmission signals Prf, a signal processing method is proposed in which the radar reception signals caused by the two transmission Ph' are processed by the same signal processing circuit. In addition, here, the high frequency pulse is Hprf (Hi heat P: 10 to 30
Mph (M
edium PM: 10 to 3 Hz), and a pulse Lprf (mountain wPrf:
It is explained as 0.3 ~ 50%).

In order to detect a moving target with a radar with LPH, the frequency shift due to the movement of the radar platform and the average clutter frequency shift are compensated for the zero Doppler frequency, and then the clutter frequency component is removed. filter circuit (for example, digital filter, Rec
usive Combnlter FIRnotchmt
er, etc.), and detecting a moving target is performed from the signal that has passed through this filter circuit.

For example, to be specific, in order to apply Doppler compensation to an intermediate frequency signal obtained by appropriately converting the frequency of a received signal, and then constructing a digital filter shown in FIG. 1 for signal 1, an A/D converter is required. 2, sampling is performed at time intervals shown by arrows in FIG.

In other words, the transmission pulse interval is divided into appropriate bins based on the transmission pulse time, and consecutive N
(for example, N=1024) range bins.
The data is sampled by applying a range gate at the time indicated by the arrow in the figure, and is sequentially held in the shift register of the delay circuit 3 as digital data after A/D conversion.

In this case, once N pieces of data are input to the shift register constituting the delay circuit 3, no data is input until the next transmission pulse.

That is, the data corresponding to the transmission pulse interval is taken into the shift register as one group.

Therefore, data is sequentially captured based on the transmitted pulse.

More specifically, N pieces of data from a transmission pulse to the next transmission pulse are sampled and input to a shift register constituting the delay circuit 3. Therefore, the delay time of the shift register is 1/rrf.

The output of this delay circuit 3 is temporally 1/PM, 2/Prf... as data corresponding to the same range bin.
The data is delayed by . . . and is input to the clutter removal filter 4 together with the current data. The signal 5 from which the clutter frequency component has been removed by the filter 4 is then input to a target detection circuit 6, which produces an output (information) 7 regarding the presence or absence of a moving target when the moving target frequency is detected.

In such a configuration, since data of N range bins as one group are continuously input, the movement purpose detection process can be continuously performed on N range bins.

However, now the range bin width is set to 0.5rs, for example.
When set to ec, high-speed processing performance exceeding the 2M ratio is required for continuous N data sampling, subsequent A/○ conversion, delay bag, filter circuit, etc.

For example, an A/D converter requires a high-speed, wide-band circuit with good conversion linearity.

This also applies to other circuits, which make them more expensive and require additional circuits to improve functionality, leading to larger sizes.

By the way, the above explanation describes an example of signal processing in a radar with LpM, but in order to detect a moving target using a signal processing means as shown in FIG. 1 in a radar with a higher pulse repetition frequency. It is necessary to divide the target speed region and provide filter circuits with different pass band widths in parallel to perform signal processing, which may also lead to an increase in the size of the signal processing circuit. This invention proposes a radar signal processing method that improves these conventional problems, and its feature is that the conversion speed is high in radars that can generate radio waves with pulse repetition frequencies that differ by more than one order of magnitude. , when transmitting Hprf using an A/D converter of about 100 to 20 Hz, Mprf
Even when transmitting data, data is collected at the same sampling rate, and the same signal processing circuit (FFT processor = radar processor, etc.) is used to detect a moving target.

In Fig. 3, 8 is a transmitter, 9 is a duplexer, and 10
Hasida antenna, 11 is a frequency conversion circuit connected to duplexer 9, 12 is a first switching switch, 13 is H
prf receiving circuit, 14 is Mprf receiving circuit, 15 is second
16 is a speed filter circuit, and 17 is a coder processor. In such a configuration, P from the radar processor 17 is set to 1/Ph by the setting signal 18, and the transmitting section 8
A high frequency pulse signal 19 is output at time intervals of , and is radiated into space via the duplexer 9 and the antenna 10.

The radio waves radiated in this way are reflected from the moving target, the ground, or the sea surface and are returned to the antenna 10 and the duplexer 9.
The received pulse 20 is input to the frequency conversion circuit 11 as the received pulse 20 via the converter circuit 11, and the received pulse 20 is converted into a high frequency (
Intermediate frequency (lnt) signal from Radiohe
It is converted into a signal 21 and sent to the selector switch 12.

In the frequency conversion circuit 11, frequency compensation such as a Doppler frequency shift due to movement of the radar platform is performed by a control signal 22 from the radar processor 17. The changeover switch 12 is switched in synchronization with the transmitting section 8 by a signal 18 from the recorder processor 17, and the intermediate frequency signal 21 is input to either the Hph receiving circuit 13 or the Mph receiving circuit 14. .

If the Hp[f signal is used, the receiver circuit 13 receives the range bin designation signal 2 from the coder processor 17.
3, a range gate is applied so that only the intermediate frequency signal 21 corresponding to the target distance section passes through, and the clutter frequency component of Hprf due to reflection from the ground or sea surface in the intermediate frequency signal 21 is removed by a filter circuit. Afterwards, the Doppler signal 24 from the moving target reaches the cut-off switch 15. On the other hand, when the Mprf signal is used, the Mprf receiving circuit 14 receives the range/bin designation signal 25 from the data processor 17.
After being range gated so that only the signal corresponding to the bin passes, and further removing the Mph clutter frequency component by a filter circuit, the Doppler signal 26 due to the moving target reaches the cut-off switch 15.

The changeover switch 15 is controlled by a signal 18 from the recorder processor 17, and the signal 24 or 26 that has passed through the changeover switch 15 is input to a speed filter circuit 16.

Here, the speed filter circuit 16 includes, for example, a fast Fourier transform processor (hereinafter referred to as FFT processor).

), the FFT processor samples the input signal at regular intervals, and performs the Fourier transform process at high speed when NI pieces of data are collected in the case of HpM and N2 pieces of data in the case of Mph. , the converted frequency axis data 27 is sent to the radar processor, and depth of eye velocity detection processing is performed. Figure 4 A, the mouth is two Ph,
That is, it shows an example of data sampling using HpM and Mprf, and FIG. 5 shows an example of the configuration of an FFT processor.

Figure 4 A shows the reception range when transmitting using Hprf.
There are 9 bottles. When the mouth in FIG. 4 is transmitting Mph, the receiving range bin is 8 pegs, and the pulse interval ratio in the mouth in FIG. 4 is A:mouth = 1:9.

In the case where the range bin designation signal 2 from the radar processor 17 shown in FIG. 3 is transmitted in FIG.
3, the range bin B is range gated and only the reflected signal from the target corresponding to this distance is input to the velocity filter circuit 16 as the Doppler signal 24,
It is sampled at the time interval (1/Hph) shown by the arrow in FIG. For example, 512 pieces), the fast Fourier transform basic circuit 30 is controlled by the Hprf control circuit 31 to obtain target frequency information for range bin B, and the information is sent to the radar processor 17 to detect the speed of the target. will be held.

Next, input the range bin designation signal 23 to the range bin B2.
, and repeat the above operations to perform target speed detection processing. Thereafter, similarly, the positions of the range pins are sequentially changed and target speed detection processing is performed for all range pins.

In addition, a speed filter generator 16 is provided corresponding to each range/bin.
If an FFT processor is provided, target speed information for each range bin can be obtained simultaneously.

Next, in the case of FIG. 4 where Mph is being transmitted, the range pin designation signal 25 from the radar processor 17 determines the range pin position within the pulse interval °C, ○, . ，
G-phantom: A range gate is applied by specifying the G-phantom in time, and only the reflected signals from the target corresponding to these distances are sent to the velocity filter circuit as the Doppler signal 26. 16.

In this case, as in the case of FIG. 4A, the sample is sampled at the time indicated by the arrow in the figure, and is stored in the memory 29 after passing through the A/D converter 28 shown in FIG.
When the needle circle) is reached, the Fourier transform basic circuit 30 is converted to M.
It is controlled by the ph control circuit 32 to obtain target frequency information for each coarse range bin (G,,G,.,○2r......G8,), and is sent to the radar processor 17 to obtain the target frequency information. Speed detection is done. Next, the range bin chicks are changed using the range pin designation signal 25 to detect the target speed of the range bins Q, G, 2, G, . . . G82.

Thereafter, processing is performed in the same manner by sequentially changing the range/pin position.

4A and 4B show the relationship between data sampling, while FIGS. 4C and 2 show an example of the Mprf group and show an example of target distance detection.

In the case of Fig. 4 C, each range bin (BJB2,...
、． skin. It is assumed that the radar processor 17 detects the target speed for range bin B2 after the landmark speed information for &) has been collected.

In this case, each transmission pulse (tBo, t8,,t82・”...
), a reflected pulse wave of the target having a detection speed with respect to range bin B2 is returned. The case of FIG. 4D is an example of M-pM in which the number of range bins is one less than that of FIG. 4C in the M-ph group. In Figure 4, each range bin (C,,C2,......
It is assumed that after the above target speed information for C8) is collected, the same target speed as the detected speed in FIG. 4C is detected in range bin C4. Each of the above M-
Information about which range bin the target was detected for the pM group is stored in the seeder processor 7.

Radar p. Setusa 17 tested Chinese against the range bottle silk detected for each M-pM group.
Calculate the target distance using the remainder theorem. For example, in the examples shown in Figure 4C and D, the time origin of the two pM transmission pulses is set to t.
8o and tco are drawn to match, but if the targets are the same, the transmission pulse (ph=A in FIG. 4C) is used.

) and the transmitted pulse (prf=B) in FIG. 4 2, the target reflected echo returns at the same target distance, that is, at the same time. In FIG. 4C, the reflected echo for the transmitted pulse t8o returns to the range bin B2 for the transmitted pulse tB2. Similarly, in FIG. 42, the reflected echo for the transmitted pulse tco is located at the range bin C4 of the transmitted pulse tc2. In other words, the target distance can be found from the combination of range pins by pR
Until the removal of F and the distance corresponding to Atsushi's greatest common divisor (the transmission pulse tB9 in Figure 4 C and the distance between the transmission pulses tc and o in Figure 4 2), the range bin that gives the true target position is This comes from the fact that there is only one combination that gives C4. In this way, the means of calculating the target distance from the range bin number or the time difference with the transmitted pulse in which the presence of the target is detected using slightly different PD groups is known as multiple PRF ranging. Radar
The processor 17 calculates the target distance for the pM group by calculating the above algorithm through program processing.

That is, target detection processing is performed based on the frequency information sent to the radar processor 17 regardless of which repetition frequency group is used for transmission.

33 and 34 are target speed information and target distance information generated from the radar processor 17, respectively.

Since the present invention is configured as described above, it is possible to unify the signal processing system of a pulse Doppler radar having a means for switching and transmitting Hprf and Mph based on a radar processor command, thereby achieving a reduction in size and weight. , the radar system can be simplified.

In addition, in the embodiment, the cut-off switch 12 and 15
Although shown as a contact type, it goes without saying that it can be made into a semiconductor, and other parts can be modified in various ways without departing from the gist of the invention. Brief explanation of the drawings Figure 1 is a block diagram showing a signal processing method in a secondary radar configured to transmit low-frequency pulses, and Figure 2 is for explaining the operation of the configuration shown in Figure 1. 3 is a block configuration diagram showing the signal processing method according to the present invention, FIG. 4 is a waveform diagram for explaining the operation in the configuration shown in FIG. 3, and FIG. 5 is a waveform diagram showing the speed shown in FIG. 3. It is a block diagram showing one example of a filter circuit, 8 is a transmitter, 9 is a duplexer, 10 is an antenna, 11 is a frequency conversion circuit, 12 is a first cut-off switch, and 13 is Hph.
A receiving circuit, 14 is an Mprf receiving circuit, 15 is a second changeover switch, 16 is a speed filter circuit, 17 is a coder processor, 28 is an A/D converter, 29 is a memory, 30 is a Fourier transform basic circuit, 31 and 32 are control circuits.

illustration ship figure N ball figure M ship figure size rudder Figure 5

Claims (1)

[Claims] 1 A means for switching and transmitting two groups of pulses whose pulse repetition frequencies differ by one order of magnitude from each other according to a command from a radar processor, a means for converting the frequency of a reflected received signal from the target, and a means for converting the frequency of the received signal reflected from the target. two receiving circuits which are provided corresponding to each of the transmitted pulses and which perform distance gate processing and filter processing based on the timing of the transmitted pulse by introducing the output of the frequency converting means; and the frequency converting means and the two receiving circuits. A first switch is provided between the first and second switches and switches the connection between the frequency conversion means and the receiving circuit according to the repetition frequency of the transmission pulse, and the output of the receiving circuit is introduced to perform signal processing related to the target speed. a speed filter circuit; a second switch that is provided between the receiving circuit and the speed filter circuit and switches the receiving circuit connected to the speed filter circuit in conjunction with the first switch; It consists of the above-mentioned radar processor that obtains speed information to the target and target speed information based on the output and the above-mentioned distance gate processing, and repeats based on commands from the above-mentioned radar processor. Two groups of transmission pulses whose frequencies differ by one order or more from each other are appropriately switched and transmitted to the target, and the first,
and a second switch is switched according to the repetition frequency of the transmission pulse, and in the transmission and reception of the above two groups, the ratio of the repetition frequency of the transmission pulse and the range within one period of the pulse are determined.
By setting the ratio of the number of bins in an integer relationship, the received signals of both groups can be processed at the sampling rate of one group to obtain information about the target, regardless of the difference in the repetition frequency of the transmitted pulses. A signal processing method for pulse Doppler radar that is characterized by: