JPH0271185A - Radar device - Google Patents

Abstract

PURPOSE:To eliminate disturbance signals with object signals maintained constantly within an equal distance gate by a method wherein a transmission/ receiving interval is varied per pulse or every several pulses and received data is arranged to process signals synchronizingly. CONSTITUTION:A range gate number increase/decrease generator 11 and an adder 12 are provided between a PRF (pulse repetition frequency) identifier 17 and a timing control circuit 14, so that a data arranging circuit 6 and a range gate control circuit 13 for controlling said circuit 6 are added to output of a buffer memory 5. In order to vary a transmitting/receiving pulse interval per pulse or every several pulses with hardly changing a signal detection range, the PRF from a data processor 15 is synthesized by the range gate increase/ decrease generator 11 and the adder 12 and sent to a timing control circuit 14 while it is sent to the range gate control circuit 13. This permits data to be re-arranged in synchronism with change in transmitted PRF to prevent tracking of a disturbing device which follows at high speed and to track only object signals.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a method for controlling multiple pulse repetition frequencies (hereinafter referred to as PRF).
Say. ) to track a target by always selecting the optimal PRF to avoid the target from entering an undetectable area.

[Conventional technology]

Fig. 5 is a configuration diagram showing a conventional medium PRF pulse Doppler type radar device. In Fig. 2, (1) is a transmitter;
(2) is the antenna, (3) is the receiver, (4) is the signal processor, (5) is the buffer memo +7. (7) is a frequency analysis circuit, (8) is a target distance detection circuit, (9) is a target frequency detection circuit, (10) is an angular error detection circuit, (14) is a timing control circuit, and (15) is a data processor. , (16
) is the target tracking filter, (17) is the PRF determiner,
(18) is a PRF selector, and (19) is a display.

FIG. 6 is a conceptual diagram showing the change in PRF for each signal processing cycle of a conventional radar and the change in tracking of the jamming PRF of a jamming device.
In the figure, (20) is the transmitted pulse, (21) is the received pulse, and (22) is the interference pulse.

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 being subjected to amplification, frequency conversion, phase detection, and analog/digital conversion, the signal is sent to a signal processor (4). In the signal processor (4), the timing control circuit (
Data sampled based on the PRF signal from 14) is manually input to the buffer memory (5). After fast Fourier transform and amplitude detection are performed in the frequency analysis circuit (7), the target distance detection circuit (8) uses the output.
, maximum amplitude distance gate detection, distance discriminator formation, and distance error detection, target frequency detection circuit (9), maximum amplitude frequency bin, frequency discriminator formation, and frequency error detection, and angle error detection circuit (10), monopulse angle detection. Performs signal processing such as error detection, calculates the distance gate number, distance error, frequency bin number, frequency error, and angle error regarding the target for each PRF, and sends them to the data processor (15) at each signal processing cycle. . Signal processor (
The target data from step 4) is manually estimated or predicted by the target tracking filter (16), and the distance and speed of the target are determined. This distance and speed data is passed to the PRF determiner (17
) and is also input to the display (1) as target data.
9) and displayed. A PRF determiner (17) ranks and selects a PRF capable of detecting a target from among PRFs within a range that can be used as a radar device, and sends the selected PRF to a PRF selector (18). The PRF selector (18) sequentially selects 1) RF from the selectable ranked PRFs according to the priority order, and connects the timing control circuit (14) of the signal processor (4) and the target tracking filter (16). ) to operate with that PRF.

Based on the PRF selected in this way.

Even if the transmission pulse is changed as shown in Fig. 6(a), the most advanced jamming device is P as shown in Fig. 6(b).
A few pulses after the moment the RF changes, the new PRF starts jamming. Therefore, there is a need for a radar device that can switch PRFs more quickly and does not allow tracking by jammers.

[Problem to be solved by the invention]

The conventional medium-PRF pulsed Doppler type radar device is configured as described above, and selects a PRF based on the speed and distance of the target being tracked to avoid areas where the signal cannot be detected. In order to keep the calculation load of the target tracking filter constant on average, a plurality of selectable PRFs with no signal undetectable regions are set every signal processing cycle. It was switched randomly or at regular intervals.

However, in radars with wide antenna beam widths and radars whose beam width changes depending on the scanning angle, such as phased array antennas, the width of the clutter frequency becomes wider and the range overlapping with the signal frequency increases, making further pulse compression necessary. In the radar used, there is a large overlap between the transmitted pulse and the received signal pulse, so the range of the optimal PRF that can be selected in order to avoid areas where the signal cannot be detected is limited. Therefore, it is difficult to arbitrarily switch the PRF at random or at regular intervals in order to keep the load on the tracking filter constant, as in conventional radars. Similarly, it is difficult to switch the PRF randomly or at regular intervals in order to counter a jamming device that performs pulse jamming or range gate stealer by following the radar's transmitted PRF. Even if the switching is done randomly, the same P
The period of RF transmission and reception was long, and jamming devices could easily follow and jam the transmitted pulses.

By the way, fluctuations in the load of the tracking filter can be solved by improving the processing speed of the signal processor that executes it, but PRF
There was a problem in that it was not possible to select arbitrarily.

This invention was made in order to solve such problems, and it is possible to detect that the pulse interference that follows the radar transmission PRF and the followability of the distance gate/stealer are delayed by several pulses from the moment the PRF is changed. The transmission pulse time interval is always changed every pulse or every few pulses within a range where the PRF does not change significantly, and the distance gate position of the received signal is also changed in synchronization with this, so that the target signal is always within the distance gate. It is an object of the present invention to provide a radar device that continues tracking in such a way that it is taken in by the transmitted pulse, and conversely eliminates the interference signal that has become difficult to follow the transmitted pulse.

[Means to solve the problem]

The radar device according to the present invention increases or decreases the number of range gates in the basic PRF from the data processor in the signal processor, changes the transmission/reception interval every pulse or every few pulses, and synchronizes with this. By rearranging the received data and processing the signals, the target signal is always kept within the same distance gate, and the interference signal is made asynchronous with the target, reducing its effect and making it possible to eliminate it. .

[Effect]

In this invention, the PRF from the data processor is combined with the output of a range gate increase/decrease generator for changing the transmission pulse interval every pulse or every few pulses within a range where the signal detection range hardly changes. In addition to sending data to the timing control circuit, it is also sent to the range gate control circuit so that the data can be rearranged in synchronization with changes in the transmission PRF, allowing high-speed tracking. It also makes it difficult to track incoming jamming devices, and tracks only the target signal.

〔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 (5), (7) to (10), (14
) to (19) are the same devices or parts as the conventional radar device described above. In this invention, (6) is a data rearrangement circuit, (11) is a range gate number increase/decrease generator, and (12) is a range gate number increase/decrease generator.
) is an adder, and (13) is a range gate control circuit.

FIG. 2 is a conceptual diagram showing how to change the transmission pulse interval for each transmission pulse of the radar and change the interference PRF tracking of the jamming device according to the present invention. In FIG. 1, (20) is the transmission pulse, (21)
) is the received pulse, and (22) is the interference pulse. FIG. 3 is a diagram showing the transmission pulse, reception pulse, and interference pulse shown in FIG. 2 for each transmission interval. FIG. 4 shows the rearrangement processing of received data in the signal processor according to the present invention.

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 radiated from the antenna (2) to the target. This transmitted signal is reflected by the target and returned to the antenna (
2), input to the receiver (3), amplified and
After frequency conversion, phase detection, and analog/digital conversion, the signal is sent to a signal processor (4). Signal processor (
4), the data sampled based on the PRF signal from the timing control circuit (14) is stored in the buffer memory (
5) +, -manpower. Also, a data processor (15)
is estimated or predicted by the target tracking filter (16) using target data from the signal processor (4), and this distance and speed data is used to determine the distance and speed of the target.
7) and is also displayed on the display as target data (
19), and the PRF determiner (17) ranks and selects a PRF that can detect a target from among the PRFs within the range that can be used as a radar device, (18).

The PRF selector (18) sequentially selects PRFs according to priority from the selectable ranked PRFs, and instructs the signal processor (4) and target tracking filter (16) to operate on that PRF. do. The process up to this point is the same as the conventional radar device. The signal processor (4) uses the pulse repetition time interval PRIO corresponding to the optimum PRF sent from the data processor (15) and the pulse repetition time interval PRIO at random or constant intervals to change the transmission/reception interval every pulse or every few pulses. The output n of the range gate number increase/decrease generator 3 (11) that changes the frequency for each transmission pulse is added to the adder (12).
and sends the output to the timing control circuit (14) and range gate control circuit (13). A timing control circuit (14) generates a transmission/reception signal in synchronization with the transmission timing of the output of the adder (12), and transmits and receives signals from the transmitter (1) and the receiver (3).
), the data from the receiver (3) is sampled and stored in the buffer 7 memory (5). The range gate control circuit (13) includes an adder (12
) from the transmission/reception interval data PRr and the PRF determiner (17
) and the transmission/reception interval increase/decrease data n from the range gate increase/decrease generator (11). Sort the data so that it is retained.

By the way, if we are currently tracking a target at a distance of RO, the time delay T from the transmission pulse to the target signal pulse is
O is T O = 2RQ/C (C is the speed of light). How many times the time delay TO of the target signal is the transmission pulse interval, that is, the quotient is the optimum P that allows the signal to be detected by the PRF determiner (17).
Since this value is obtained when performing the RF selection process, the range gate control circuit (13) uses this value as a range ambiguity coefficient. Furthermore, since the time delay TO of the target signal is also sent from the PRF determiner (17) at the same time, this is also used. In Figure 2(a), PRI
(1) is the sum of the output data n (1) of the range gate number increase/decrease generator (11) and the pulse repetition time interval PRIG corresponding to the optimum PRF, and PRI (2) is the sum of n (2) and PR
The sum of IO is sequentially added by the adder (12),
Sent.

By the way, the delay λ(3) of the received signal (21) with respect to the transmitted pulse (20) at PRI(3) is calculated by dividing the previous two transmitted pulse intervals P RI (1) and P RT (2) by
This is the value subtracted from the delay TO of the true target signal. This is shown in the following equation.

λ(3)=TO-1PR1(1)+PR+(2)1=
no− to −p+nol −i n (t) + n (
2) l-(+) In the case of Figure 2, the range ambiguity coefficient is 2, and in the case of other PRIs, this time delay will differ for each transmitted pulse, as in equation (1). Therefore, as shown in Figure (b), the interference signal (22) is delayed by several pulses from when it detects that the PRF has changed until it is sent out in synchronization with it, so it cannot be synchronized with the radar pulse. It becomes difficult to do so. At this time, each received PRI
Figure 3 shows the received signal and interference signal for each time. In the figure, the 1mth pulse time interval PRI (m) is the output data n (m) of the range gate number increase/decrease generator (11) and the optimum P
It is the sum of the pulse repetition time interval PRIG equivalent to RF, and the output data n(
m) is sequentially 0. -2.
+2. The transmission pulse I in the same figure (a) is changed within the range where the PRF does not change significantly as +I, O, -1...
(20) is received as the received signal 1° (21) in Figure 2(c), so the time delay λ(3) is as shown in equation (1) compared to the case where PRI does not change. (n
Changes by (1) + (2)l. Similarly, other
The signal is received at the third PRI with respect to the transmitted pulse,
The time delay λ(m) is (n(m −2)+n(m
-1)) changes. The interference signal (22) is different from the target signal and is received at a shifted position. This signal is arranged in a two-dimensional memory of range gate and time axis.
It is figure (a). The range gate control circuit (13) is PR
Using the range ambiguity coefficient from the F determiner (17) and the target signal time delay TO, the time delay λ(K+1) of the (K+1)th target signal from the first transmission pulse is calculated.
is calculated and determined by the formula shown below, and based on the result, the data rearrangement circuit (6) rearranges the data stored in the buffer memory (5) with reference to the target signal time delay.

λ(k+1)=TO−IPRI(k)+PRI(k−1
)+...+PRL(ki-i)+...)=(TO-
1rPRIO) -(n(k)+n(k-1) +-1
--(2) However, K-i≧1 In FIG. 3(C), the time delay λ(3) of the received signal when the PRF is not changed is as shown in equation (1) (
To-2PRIO+, and the range gate at this time is N
becomes. On the other hand, the range gate number increase/decrease generator (1
When PRF is changed using the output data n (m) of 1), the time delay λ(
3) changes. n(1)=0. n(2)=
-2, the range gate of λ(3) is 2 range gates more than N (therefore, when rearranging data, -2 should be added to the range gate number.Next, in the same figure (d) ), n(2) = -2, n(3) = 2, and 1n(2) + n(3)l = o, so when rearranging data, just add O to the range gate number. In this way, only the signals can be arranged at the true range gate position N.As described above, Fig. 4(b)
A data array based on the target signal is completed.

For each range gate, a fast Fourier transform is performed in a frequency analysis circuit (7). As is clear from this figure,
Although the signal always exists within a certain range gate, the jamming signal is dispersed, so its jamming effect becomes ineffective.

And, like conventional radar, two frequency analysis circuits (7)
Amplitude detection is performed after fast Fourier transform, and the target distance detection circuit (8) uses the output to detect the maximum amplitude distance gate, form a distance discriminator, and detect distance error, and the target frequency detection circuit (9) uses the output to detect the maximum amplitude distance. Amplitude frequency bin detection/
Frequency Discriminator Formation and Frequency Error Detection The angular error detection circuit (10) performs signal processing such as monopulse angular error detection, and calculates the target distance gate number, distance error, and frequency bin number at the specified PRF. The frequency error and further the angular error are calculated and sent to the data processor (15) every signal processing cycle. These target data from the signal processor (4) are input to a tracking filter (16) and estimated or predicted to determine the distance and velocity of the target. This distance, speed, and angle data are sent to the display (19) and displayed as target data. in this way.

Interfering signals can be removed while tracking the target signal.

〔Effect of the invention〕

As described above, the present invention ζ is applicable to the conventional radar device during tracking. Using the PRF selection method that allows target detection, a range gate number increase/decrease generator and an adder are added between the PRF determiner and the timing control circuit, and a data rearrangement circuit and a control circuit are added to the output of the buffer memory. With a simple configuration that just adds a range gate control circuit to the basic PRF, the number of range gates can be increased or decreased, the transmission/reception interval can be changed every pulse or every few pulses, and in synchronization with this, the reception data can be changed. By rearranging and processing the signals, the target signal is always kept within the same distance gate, and the interference signal becomes asynchronous with the target, dramatically reducing its effect and making it possible to eliminate it.

[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 conceptual diagram showing changing the transmission pulse interval for each transmission pulse of the radar and changing the jamming PRF tracking of the jamming device according to the present invention. , FIG. 3 is a diagram showing the transmission pulse, reception pulse, and interference pulse shown in FIG. 2 for each transmission interval, and FIG. The figure shown in FIG. 5 is a configuration diagram showing a conventional medium PRF pulse Doppler type radar device. FIG. 6 is a conceptual diagram showing a change in PRF for each signal processing cycle of a conventional radar and a change in tracking of the jamming PRF by a jamming device. In the figure, (1) is the transmitter, (2) is the antenna, and (3) is the transmitter.
) is the receiver, (4) is the signal processor, (5) is the buffer memory, (6) is the data sorting circuit, (7) is the frequency analysis circuit, (8) is the target distance detection circuit, and (9) is the Target frequency detection circuit, (10) is angle error detection circuit, (11)
is the range gate number increase/decrease generator, (12) is the adder, (
13) is a range gate control circuit, and (14) is a timing control circuit. (15) is a data processor, (16) is a tracking filter,
(17) is the PRF judger, (18) is the PRF selector, (19) is the display, is the range ambiguity coefficient, Σ is the monopulse sum channel, Δ is the monopulse difference channel, and To is the time equivalent to the target distance. delay, PRIO is the pulse repetition time interval corresponding to the optimal PRF, n(m) is the number of range gate increases/decrements, λ(k) is the target signal time delay for each PRI, and B(k) is the time from the transmitted pulse of the interfering signal. The delay, PRI(k), is the transmission pulse interval, T(k) is the signal processing period, and TX is the transient time at PRF switching. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A transmitter that generates a signal of a constant frequency and pulse-modulates it with a predetermined pulse width and pulse repetition frequency, an antenna that radiates the transmitted wave into space and receives the reflected wave from the target, and amplifies and frequency converts the received wave.・A receiver that performs phase detection and analog/digital conversion and signal processing such as frequency analysis, amplitude detection, maximum value detection, discriminator formation, and error detection are performed on the digital signal to obtain data regarding the distance and speed of the target. Estimate or predict the target position with a tracking filter using the signal processor to calculate and the target data from the signal processor, and calculate the distance and speed of the target,
In a radar device equipped with a data processor that selects a pulse repetition frequency at which a target can be detected based on this distance and speed data, and a display that displays target data, the signal processor is configured to select an optimal pulse repetition frequency that is selected by the data processor. The pulse repetition frequency is used as a reference, and the transmission pulse interval is constantly changed every pulse or every few pulses with respect to the pulse repetition frequency to the extent that the speed and distance detectable area do not change. A radar device characterized by having means for rearranging data in synchronization with a transmission pulse.