JPH04143688A - Radar signal processor - Google Patents

Abstract

PURPOSE:To contrive the error detection prevention at the time of target automatic detection by exactly finding average value got by subtracting its range bin number from reference cell number when a blanked range bin enters a reference cell. CONSTITUTION:A ranges bin in which a disturbance electric wave such as jamming exists or the range bin in the neighborhood thereof is blanked with the use of a jamming remover 5 to output. Constant false alarm rate (CFAR) processing is performed by jamming removal auxiliary CFAR 6 on the output. In other words, blanked range bin number information is input to count its number when the range bin blanked in the reference cell is put in to subtract from the reference range bin number so as to exactly calculate average value. And a threshold coefficient 9 predetermined in this average value is multiplied 10 to compare 11 CFAR threshold indicating the output of a multiplication device 9 with the data of the notice cell ranges bin so as to output as a target when the data of the notice cell range bin are large.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radar signal processing device that automatically detects targets such as aircraft.

[Prior Art] FIG. 3 is a block diagram of a conventional radar signal processing device. In the figure, (1) is a radar antenna whose elevation angle can be continuously changed during rotation.

(2) is an auxiliary antenna that receives interference waves such as jamming coming from side lobes, and (3) is a receiver that converts microro signals from the radar antenna (1) and auxiliary antenna (2) into electrical signals.

(4) is an MTI for suppressing unnecessary signals 1, such as g-clutter, included in the electrical signal from the receiver (3).
, a pre-stage signal processing device that performs pulse compression, etc., and detects and compares the amplitude of the radar antenna (1) and auxiliary antenna (2) signals from the pre-stage signal processing device (4), and detects jamming and other interference. A jamming removal device that determines the presence or absence of jamming radio waves, and blanks the data of that range bin or that range bin and neighboring range bins if there is a jamming radio wave (121 is a CFAR or the like for the signal from the jamming removal device (5)). (7) is a downstream signal processing device (1) that performs automatic target detection processing.
This is a display device that displays the processing results from 2) on a PPI scope or the like.

FIG. 4 is a diagram illustrating the operation of the jamming removal device (5) of the conventional radar signal processing device configured as described above. Radar antenna (from the front stage signal processing device (4)
The signal from 1) has three channels: a sum signal (hereinafter referred to as Σ channel), and an azimuth difference signal (hereinafter referred to as Bearing).
(B) It is called a channel. ) and a height difference signal (hereinafter referred to as the Elevation (E) channel). Further, the signal from the auxiliary antenna (2) from the ffJ stage signal processing device (4) is S L B (Side
Lobe Blanker) signal (hereinafter referred to as SLB channel). (13) is the Σ channel and SLB
An amplitude detector detects the amplitude of each signal of the channel, (14) a threshold coefficient that controls the amplitude value of the SLB channel, (10) a multiplier that multiplies the signal of the SLB channel by the threshold coefficient, (15)
) is the noise level, which is the minimum amplitude of the radar signal processing device, and (11) is the Σ channel signal and the multiplier (lO
) and also compare the output of .

This is a comparator that compares the SLB channel signal and noise level (15) and outputs 1 (or true) when the following conditions are satisfied.

Σ<k -5LB SLB>m Here, Σ: Σ channel amplitude k: Threshold coefficient SLB: SLB channel amplitude m: Noise level (L6) is an AND circuit that performs AND of the output of the comparator (II) , (17) is a blanking control that blanks the data of the range bin or the range bins nearby when the output of the AND circuit (16) is 1, and outputs 0 to the B channel, E channel, and Σ channel. (181 is an interlocking switch that switches the connection to the blanking controller (17) side when the output of the AND circuit (16) is 1.

FIG. 5 is a diagram illustrating antenna patterns of the radar antenna (1) and the auxiliary antenna (2) of the radar signal processing device configured as described above. Radar antenna (1)
The antenna pattern is a pattern that concentrates and radiates energy in a specific direction, and also consists of a main lobe and several side lobes. On the other hand, the antenna pattern of the auxiliary antenna (2) is the radar antenna (
The sidelobe level of the radar antenna (1) is composed of which beams have a radiation intensity of a constant wide width over the entire area radiated by the radar antenna (1).

FIG. 6 is a diagram illustrating the operating principle of the jamming removal device (5) of the radar signal processing device configured as described above. For example, when jamming comes from the target and side lobes, in the Σ channel, the target received by the main lobe and the jamming received by the side lobes have amplitude characteristics as shown in FIG. 6(a). Similarly, in the SLB channel, the auxiliary antenna with constant radiation intensity (
The target and jamming received in 2) are shown in Figure 6(b).
) The amplitude characteristics are as shown below. These Σ channels,
The presence or absence of jamming is determined based on the amplitude value of the SLB channel, and if there is jamming, the data in that range bin or the range bins in the vicinity of that range bin is set to 0, thereby producing an output as shown in Figure 6(c). It's something you get.

FIG. 7 is a diagram illustrating the operation of the downstream signal processing device (12) of the conventional radar signal processing device configured as described above. For the signal from the jamming removal device (5),
The average value of the data of the reference cell range bins before and after the cell range bin of interest is calculated. (9) is a preset threshold coefficient, (10) is a multiplier that multiplies the average value by the threshold coefficient (9), and (11) is the threshold value that is the output of the cell range bin of interest and the multiplier (lO). Compare.

If the data in the cell range bin of interest is larger than the threshold value, the comparator regards it as a target and outputs l. The above operations are performed for all range bins, and the processing results are output to the display device (7).

[Problems to be Solved by the Invention] In the radar signal processing device described above, when interference waves such as jamming come in from side lobes, all the data in the mixed range bin or in the range bin and neighboring range bins are blanked and zeroed out. Therefore, blanked data, that is, 0, is entered in the reference cell range bin of the CFAR that is processed by the subsequent signal processing device (12).

CFAR threshold level becomes lower.

P f a (Probability of fal)
There is a problem in that this leads to an increase in se alara+ (false alarm probability).

This invention was made to solve the above problem, and includes a blanking counter (8) that counts the number of blanked range bins when the blanked range bins enter the reference cell of the CFAR, By subtracting the value of the blanking counter (8) from the total number of reference cells,
This is a radar signal processing device whose purpose is to accurately calculate the average value and prevent false detection during automatic target detection.

[Means for Solving the Problems] A radar signal processing device according to the present invention includes a radar antenna, a receiver, a signal obtained through a pre-stage signal processing device, and
There is a jamming removal device that determines the presence or absence of jamming or other interference from the signals obtained through the auxiliary antenna, receiver, and front-stage signal processing device, and blanks the data in the range bin where the interference is present. It has a jamming removal compensation CFAR that counts the number of range bins when it enters the CFAR reference cell, accurately calculates the average value, and automatically detects the target, and a display device that displays the results. be.

[Operation] In this invention, interference radio waves such as jamming coming in from side lobes are compared with signals from a radar antenna and a judgment is made, and data of the range bin where the interference radio waves are present or the range bins in the vicinity of that range bin is blanked. However, by calculating the average value taking into account the number of range bins when the range bin falls within the reference cell of the CFAR, it is possible to prevent false detection during automatic target detection.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of this invention (1)
- (5) and (7) are the same as the conventional device described above. (6) is the signal from the jamming removal device (5), counts the number of blanked range bins, and
This is a jamming removal compensation CFAR that accurately calculates the moving average in FAR and performs automatic target detection processing.

FIG. 2 is a diagram showing the internal structure of the jamming removal compensation CF A R (6). CFAR processing is performed on a signal received by a radar antenna [1] and an auxiliary antenna (2), passed through a receiver (3), a pre-stage signal processing device (4), and output from a jamming removal device (5). At this time, the blanked range bin number information from the jamming removal device (5) is input.

A blanking counter (8) is provided which outputs the number of range bins when a blanked range bin enters a reference cell, and this number of range bins is subtracted from the number of reference cell range bins to accurately calculate an average value. (9) is a threshold coefficient set in advance, (10) is a multiplier that multiplies the average value of the data of the reference cell range bin and the threshold coefficient (9), (11) is the data of the target cell range bin and the multiplier (lO) CFAR which is the output of
This is a comparator that compares thresholds and outputs 1 when the data in the cell range bin of interest is large.

In the radar signal processing device configured as described above, by blanking the range bin where interference radio waves such as jamming coming from the side lobe are present,
Missing data in CFAR reference cell range bins can be avoided by counting the number of missing range bins and subtracting that number from the number of reference cell range bins.
Accurate average values can be obtained, making it possible to prevent false detection during automatic target detection.

[Effects of the Invention] As explained above, in this invention, when a range bin in which interference radio waves such as jamming coming from side lobes are present is blanked, and the range bin enters the reference cell of the CFAR, Calculating a moving average that takes the range bins into consideration has the effect of making it possible to prevent false detections.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, and Fig. 2 is a diagram showing an embodiment of the invention.
The figure which shows the detailed block diagram of AR. FIGS. 3, 4, and 7 are diagrams showing conventional radar signal processing devices, and FIGS. 5 and 6 (a) to (c) are diagrams explaining the operation of conventional radar signal processing devices. be. In the figure, (1) is a radar antenna, (2) is an auxiliary antenna, (3) is a receiver, C4) is a front-stage signal processing device,
(5) is a jamming removal device, (6) is a jamming removal compensation CFAR, (7) is a display device, (8) is a blanking counter, (9) is a threshold coefficient, (10)
is a multiplier, [11] is a comparator, (12) is a post-stage signal processing device, (13) is an amplitude detector, (14) is a threshold coefficient, (15) is a noise level, (
16) is an AND circuit, (17) is a blanking controller, and (18) is an interlocking switch. In addition, in FIG. 9, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A radar antenna that can change the angle of elevation while rotating, an auxiliary antenna that receives interference waves such as jamming coming from side lobes, a receiver that receives signals from this radar antenna and the auxiliary antenna, and this receiver. MTI (MovingTar)
A pre-stage signal processing device that performs clutter suppression processing such as getIndicator (moving target indicating device), detects the amplitude of the radar antenna and auxiliary antenna signals from this pre-stage signal processing device, and compares them to determine the presence or absence of jamming radio waves. , a jamming removal device that blanks the data in that range bin or the range bins in the vicinity of that range bin when there is a jamming signal; and a CFAR ( ConstantFalseAla
rmRate: Jamming removal compensation CFAR that performs automatic target detection processing by accurately deriving the average value in the process (constant false alarm probability), and this jamming removal compensation CFAR
Processing results from PPI (PlanPositionI
1. A radar signal processing device characterized by comprising a display device for displaying on a scope or the like.