JPS628076A - Radar equipment - Google Patents

Abstract

PURPOSE:To accurately correctly detect a target even when a clutter and the target are present in the same range gate by performing a receiving strength comparison between main and subs systems by a comparator only for a reflected wave in a Doppler frequency range wherein no clutter is expected to be present to thereby remove the effect of the clutter. CONSTITUTION:Received signals which have passed the same range gates, for example, 5a and 5b of main and sub systems are divided into (m) signals corresponding to the Doppler frequencies of the received signals by (2m) BPF's 8all...8 a1m and 8b11...8b1m and outputted to detectors 611...61m and comparators 711...71m, respectively, for every Doppler frequency. On the other hand, the upper limit Doppler frequency of a clutter is calculated by a Doppler frequency calculator 9 to output signals to comparators corresponding to frequencies not larger than the upper limit Doppler frequency, stopping the generation of a detection stop signal. Therefore, since a interference-wave removing operation by the comparison between the received waves of the main and sub systems is performed only for reflected waves from a target in a Doppler frequency range wherein no clutter is present, a target detection stop by the clutter is checked and therefore the target is accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to radar equipment, and particularly relates to interference wave removal thereof.

[Conventional technology] FIG. 3 is a block diagram showing a conventional radar device.

Figure 4 is a diagram showing the directivity pattern of the antenna.

In the figure, (1a) is the main antenna with directivity as shown in pattern A, (lb) is the omnidirectional sub-antenna as shown in pattern B, and (2) is the transmitting/receiving antenna connected to the main antenna (1a). switch, (3) generates a transmit pulse;
A transmitter (4a) transmits the reflected wave from the target of the transmitted wave through the transmitter/receiver switch (2) and the main antenna (1a) as a transmitter. a main receiver for receiving and amplifying to the required level, (4b)
is a sub-receiver which receives the reflected wave through a sub-antenna (1b) and amplifies it to a required level, and (5a) and (5b) divide the reflected wave reception signal according to its pulse phase.

n range gates (5al)...(5an) each connected to a main receiver (4a) and a sub receiver (4b) in a range gate group that obtains n signals corresponding to the target distance.
) and (5bl)...(5bn), (
6) is a detector group consisting of a plurality of detectors (61)...(6n) that determine the presence or absence of a target according to the strength of the signal from each range gate (5al)...(5an); 7)
is a comparator group consisting of a plurality of comparators (7a)...(7n) that compare signals from the range gates corresponding to the same distance among the range gate groups (5a) and (5b). Only those comparators whose received signal strength from the main antenna (1a) is higher than the received signal strength from the main antenna (1a) output their detection stop signals to the corresponding detectors.

Next, we will explain its operation. The transmission pulse signal generated by the transmitter (3) passes through the transmitter/receiver switch (2) and is radiated into the air from the main antenna (1a), and the reflected wave from 14 m is transmitted as a reception signal to the main antenna (1a), The signal passes through the transmitter/receiver switch (2) and is input to the receiver (4a).

The output of the receiver (4a) is input to a plurality of range gates (5al)...(5an) corresponding to the target distance, and their output signals are sent to the detectors (61)...(6n). entered.

The operation of the main system for detecting a target is 0 or more, in which the presence or absence of a target is determined.

Next, the interference wave removal operation by the subsystem will be explained. The reflected wave from the target is transmitted by an omnidirectional antenna (1b) similar to the main system.
), passes through the receiver (4b), and is input to a plurality of range gates (5bl)...(5bn) corresponding to the target distance. Range gates (5al)...(5an) and (sbt)...corresponding to the same distance between the main and sub-systems
The output of (5bn) is the comparator (71)...(7
n). The comparators (71)...(7n) compare the receiver signal strengths of both systems, and the comparator (71)...(7n) detects the signal strength of the sub-system where the signal strength is greater. A detection stop signal is sent to the detectors (61)...(6n), and from the detectors (61)...(6n),
Even if the signal strength from the main system is above a predetermined value, the output of the target detection signal is stopped. When the signal strength from the main system is greater, there is no output from the comparators (71)...(7n).

The corresponding detectors (61)...(6n) detect the target as is. In other words, the directivity patterns of the main antenna (la) and the sub antenna (1b) are as shown in Figure 4 A and H, so when there is a target in the directivity direction of pattern A of the main antenna (1a), the main system reception If the intensity is greater than the subsystem reception intensity and the target is in the sidelobe or backlobe direction of pattern A, or if only reflected waves (clutter) or interference waves from the ground surface are present, the subsystem reception intensity is The system reception strength is greater than the main system reception strength. Therefore, when the subsystem reception strength increases due to the above operation, the outputs of the detectors (61)...(6n) are changed to the comparators (71)...
...The detection is stopped by the detection stop signal from (7n), and target detection due to clutter, interference waves, side lobes, and reflected waves from the backlobe direction are all removed, and only the target in the directional direction of the main antenna (1a) is detected. Detected.

[Problems to be solved by the invention] Since the conventional radar device is configured as described above,
When only the target exists in the desired direction, or when only clutter or interference waves exist, the required operation will be performed reliably, but if the target and clutter or interference waves exist at the same time, the main system and subsystem The magnitude of the received output from the subsystem depends on the signal strength of the clutter, interference waves, and the reflected wave from the target.1 Since the signal strength of the reflected wave from the target is usually smaller, the received output of the subsystem depends on the signal strength of the reflected wave from the target. becomes larger, and the target is not detected correctly. That is, in a range gate where the clutter or interference wave is larger than the reflected wave from the target, there is a problem that the target cannot be detected.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a radar device that can correctly detect a target even if the clutter and the target exist in the same range gate.

[Means for solving interlayer points] The radar device according to the present invention divides each received signal corresponding to the distance of the target, that is, each range gate output, into a plurality of signals corresponding to the Doppler frequency of the target, A detector and a comparator are provided for each of these divided signals, and the upper limit Doppler frequency of clutter is calculated from the speed of the mother aircraft equipped with this radar device, and comparison is made corresponding to the Doppler frequency range that has a predetermined relationship with the Doppler frequency. This device is equipped with a Doppler frequency calculator that outputs a signal only to the comparator and stops generation of the detection stop signal from the comparator.

[Function] In the present invention, the Doppler frequency calculator calculates the Doppler frequency range in which clutter is predicted to exist, and the comparator corresponding to this Doppler frequency range then stops the detection of the detector. Outputs a signal that stops signal generation. In this way, the influence of clutter is removed by having the comparator compare the reception intensities of the main and subsurface systems only for the reflected waves in the Doppler frequency range where it is predicted that no clutter exists.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which (la) (lb) (2) (3) (4a
) (4b) (5a), (5al)...(5an)
(5b), (5b1), . . . (5bn) are the same as those in FIG. 3, so their explanation will be omitted. (8a) and (8b) represent each range gate (5) of the range gate group (5a) (5b).
al)...(5an).

(5bl)... (5bn) are connected to m bandpass filters (8all
)”・(8al+s)”(8anm), (8bll)
Consisting of "(8b1m)" and (8bnm), (6
) is the same detector group as in Fig. 3, but each bandpass filter (8all) of the bandpass filter group (8a)...
・n connected to (8aln)” (8anm) respectively
m detectors (611)...(61m)...(6a
m), and these detectors (611) are equipped with CF A R (Constant False Ala) which does not detect clutter with continuous Doppler frequencies.
rm Rate) detector is used. (7) is also a comparator group similar to Fig. 3, but m comparators for each range gate, a total of nm comparators (711)-(71m)"・(7n+s
).

Each bandpass filter (8all) (8bll) of both bandpass filter groups (8a) (8b) ... (8a
lt) (8b1m)=・(8anm) (8bnm). (9) calculates the upper limit Doppler frequency f dcmax of clutter from the ground speed of the mother aircraft on which this radar device is mounted, and uses the comparator (
A comparator (711) that compares Doppler frequency signals in a frequency range below the upper limit Doppler frequency f dcmax of this clutter with a Doppler frequency calculator that controls 711)...(71m)...(7am)... The comparator outputs a signal to stop the generation of the detection stop signal from the comparator.

Next, the operation will be explained using a second operation explanatory diagram. In Figure 2a, (10) is the mother aircraft which is the aircraft on which the radar device is mounted, A is the antenna pattern of the main antenna (LA), B is the antenna pattern of the auxiliary antenna (2b), and (11) is the ground. Yes, the figure shows the main antenna (1a
) is the Doppler frequency spectrum of the main system reception signal, and C in the same figure is the Doppler frequency spectrum of the sub system reception signal due to the sub antenna (1b). Now, the mother machine (lO)
flies horizontally in the direction of the arrow at a speed vb, the target approaches the mother aircraft (10) from behind at a relative speed vt, and the main antenna (
It is assumed that 1) has the maximum sensitivity at the rear. The upper limit Doppler frequency f dcmax of the clutter and the Doppler frequency fdt of the reflected wave from the target are expressed by the following equation.

f dcmax= 2 vb/λ...(
1) fdc = 2vt/λ (2)
Here, λ is the wavelength of the transmitted wave. In other words, from the goal.

The reflected wave has a positive Doppler frequency +fdt because the target is approaching the mother aircraft (10) at a relative velocity vt.

On the other hand, clutter reflected from the ground surface in front has a positive Doppler frequency, and clutter reflected from the ground surface behind has a negative Doppler frequency, so the clutter spectrum is
Upper and lower Doppler frequencies determined by formula (1) ±f dct
It has a spread between max.

In the configuration shown in FIG. 1 above, the received signals that have passed through the same range gates of both the main and subsystems, for example (5al) (5bl), are each passed through m bandpass filters (8all)...
8a1m), (8bll)=(8b1m), and is divided into m signals corresponding to the Doppler frequency of the received signal.

They are a detector (611) for each Doppler frequency...(
61m) Output to comparator (711)...(71m). On the other hand, the Doppler frequency calculator (9) calculates the upper limit Doppler frequency f dcmax of clutter, and outputs a signal to the comparator corresponding to the frequency below that frequency to stop generation of the detection stop signal.

Now, if the relative speed of the target is greater than the mother aircraft speed, + f
dt>+f dcmax, and the target and clutter spectra are separated as shown in FIG. Therefore, at the Doppler frequency of the reflected wave from the target.

Since the output of the detection stop signal from the comparator (711) is not stopped, the detection due to the interference wave existing in this Doppler frequency range is stopped, that is, the operation of removing the false detection of the interference wave is performed. However, since clutter does not exist in this Doppler frequency band, detection is not stopped due to clutter. On the other hand, if the relative speed of the target is smaller than the mother aircraft speed, +f d
c< + f dcmax.

The Doppler frequency of the reflected wave from the target falls into the clutter Doppler frequency region, but in this Doppler frequency region, as mentioned above, the output of the detection stop signal from the comparator (711) is stopped, so there is no clutter in the same range. Even if the target exists, the detector (611)... detects the presence of the target.

However, since a CFAR detector is used as the detector (611), clutter is not detected.

As described above, since the interference wave removal operation by comparing the received waves by both the main and subsystems is performed only on the reflected waves from the target in the Doppler frequency range where clutter does not exist, target detection stoppage due to clutter is prevented, and The target is correctly detected even if there is clutter.

The rest of the operation of the radar device is the same as the conventional one shown in FIG. 3, so a detailed explanation will be omitted.

[Effects of the Invention] As described above, according to the present invention, a received signal of the same range is divided into a plurality of signals corresponding to the target Doppler frequency,
Among the divided signals, the interference wave removal operation can be performed only on signals corresponding to a frequency range that has a predetermined relationship with the upper limit Doppler frequency of the reflected wave from the ground surface calculated from the speed of the aircraft. This has the effect of providing a radar device that can detect the target even if the clutter and the target are present in the same range gate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
3 is a block diagram showing a conventional radar device, and FIG. 4 is a diagram showing directivity patterns of the main and sub-tube antennas. In the figure, (1a) is the main antenna, (lb) is the sub-antenna, (3) is the transmitter, (4a) and (4b) are the receivers,
(5a) (5b) is the range group 8 group, (6) is the detector group, (7) is the comparator group, (8a) (8b) is the bandpass filter group, and (9) is the Doppler frequency calculator. be. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] (1) The reflected wave from the target received by the directional main antenna is divided by the range gate according to the distance of the target, and the strength of the received signal is divided by the received signal strength by the omnidirectional sub antenna. In a radar device that removes interference waves from a received signal by comparing the reflected waves from the target with the strength of the received signal divided according to the distance of the target, the interference waves from the main antenna and the sub antenna are Each received signal corresponding to the distance of the target is divided into a plurality of signals corresponding to the Doppler frequency of the target, and the presence or absence of the target is determined according to each of these divided received signals from the main antenna. The intensity of the divided signals from the detector and the main and auxiliary antennas are compared for the same distance and the same Toplar frequency, and depending on the comparison result, A plurality of comparators each output a detection stop signal to the detector, calculate the upper limit Doppler frequency of the reflected wave from the ground surface from the speed of the aircraft, calculate a Doppler frequency that has a predetermined relationship with this Doppler frequency, and calculate the Doppler frequency. A radar device comprising: a Doppler frequency calculator that outputs a signal only to the comparator corresponding to a Doppler frequency range having a predetermined relationship with the comparator, and stops generation of a detection stop signal from the comparator. (2) The above detector does not detect reflected waves from the ground surfaceC
The claim is that the comparator, which is a FAR detector and whose detection stop signal output is stopped by the signal from the Doppler frequency calculator, corresponds to a frequency range below the upper limit Doppler frequency of waves reflected from the ground surface. Radar device of Item 1.