JPH0310080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a radar signal processing device that performs interference signal detection and interference signal data extraction processing in a pencil beam scanning three-dimensional radar device.

(Prior art) In general, radar received signals include unnecessary received signals in addition to the target signal, so these unnecessary received signals may make it impossible to detect the target signal or cause signals other than the target signal to be detected. There may be cases where the received signal is erroneously detected. In particular, when strong electromagnetic waves within the radar reception band (hereinafter referred to as jamming signals) are artificially mixed in from the outside, it becomes difficult to detect targets in the direction of arrival of the jamming signals, and it becomes difficult to automatically track targets. When processing is performed by a computer, a large number of interference signals are erroneously detected, so that automatic target tracking processing may become impossible even in areas other than the direction in which the interference signals arrive.

Radar equipment that is likely to receive such interference signals must have a method for suppressing the interference signal from the received signal, the position data of the interference source, and the range in which the interference signal affects the target detection performance of the radar (hereinafter referred to as run length). The present invention has a means for accurately detecting the interference signal, inhibiting target detection processing for the received signal affected by the interference signal, and preventing signal detection exceeding the processing capacity of the computer. The following two-dimensional radar devices having such interference prevention means are available.

This radar logarithmically amplifies the radar received signal to create a logarithmic video, integrates this logarithmic video for each radar sweep, and when this integrated value exceeds a preset threshold, that radar sweep is used as a disturbance signal. It determines that the radar sweep has been affected by the radar sweep, outputs a pulse (hereinafter referred to as a strobe response) as a result of the determination, and prohibits the received signal of the radar sweep from being input to the circuit that performs target detection processing. ing. On the other hand, the strobe response that is continuously detected in the azimuth direction is processed,
The radar sweep that is determined to be affected by a jamming signal for the first time (hereinafter referred to as the leading edge of the strobe) and the radar sweep that is determined to be free from the influence of a jamming signal for the first time after the leading edge of this strobe is detected (hereinafter referred to as the "after strobe") The center azimuth and run length of the interference signal are calculated from the azimuth data (midway between the leading edge and the trailing edge) of these radar sweeps and output to the outside. In this way, the two-dimensional radar receives the jamming signal from one location over a number of radar sweeps related to the antenna azimuth beam width, so it is possible to detect the center azimuth and run length of the jamming signal.

On the other hand, 3D radar uses a pencil beam scanning method in which a sharp aerial pencil beam is scanned in the azimuth and elevation directions, and the number of transmissions and receptions per scan is usually one. Even if a signal is received, the next signal is received only after the antenna beam scan in the elevation direction (hereinafter referred to as elevation scan) or the antenna beam scan in the azimuth direction has been performed once. Now, in this three-dimensional radar system, if we consider the case where the antenna that electronically scans the pencil beam in the elevation direction is mechanically rotated, if the rotational speed of the antenna is approximately the same as that of the two-dimensional radar (i.e., the data rate is are almost the same), the antenna rotation angle within the elevation scan time is larger than the antenna rotation angle within the pulse repetition time in the two-dimensional radar, and the number of radar sweeps that receive the jamming signal with sufficient strength is This will be less than in the case of radar. Therefore, it is difficult to detect the center direction and run length of the jamming signal using the jamming prevention means used in the two-dimensional radar.

The same reason also applies when an antenna that performs electronic pencil beam scanning in the azimuth direction is mechanically scanned in the elevation direction, or when all pencil beam scanning in the elevation and azimuth directions is performed electronically. This makes it difficult to detect the central azimuth or central elevation angle and run length of the jamming signal using the anti-jamming means.

(Object of the invention) The object of the invention is to solve such problems,
An object of the present invention is to provide a radar signal processing device having a function of detecting the central azimuth, central elevation angle, and run length of a disturbance signal in a three-dimensional radar.

(Structure of the Invention) A radar signal processing device according to the present invention includes a receiving means for receiving a received signal including a disturbance signal by an antenna pencil beam scanned in the azimuth direction and the elevation direction of a search space; clutter removal means for removing the clutter region and extracting the disturbance signal; average amplitude extraction means for extracting an average disturbance intensity for each scanning beam from among the plurality of disturbance signals extracted by the clutter removal means;
maximum signal detection means for detecting a first average disturbance signal in the first scanning beam having the maximum intensity among the average disturbance intensities obtained for each scanning beam unit; signal extraction means for extracting second and third average disturbance signals of adjacent scanning beams in the direction of elevation and fourth and fifth average disturbance signals of scanning beams adjacent in the elevation direction; azimuth detection means for detecting the center direction from which the interfering signal arrives from the scanning beam direction giving the average interfering signal intensity and each average interfering signal intensity; and the first, fourth and fifth average interfering signal intensities and each average. elevation angle detection means for detecting the elevation angle of the center of arrival of the interfering signal from the elevation angle of the scanning beam giving the interfering signal strength; azimuth range detection means for detecting the azimuth range of the interference signal from a predetermined reference level to be determined; and elevation angle range detection means for detecting an elevation angle range.

Although the configuration of the present invention detects the position data and run length of the interference signal source in both the azimuth direction and the elevation direction, it is possible to detect the position data and run length of the interference signal source only in the azimuth direction or the elevation direction. It is clear that the configuration for detection can be easily made.

(Embodiments of the Invention) Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a radar signal processing device according to an embodiment of the present invention, and FIG. 3 is an operational waveform diagram of FIG. shall be scanned by the rotation of the antenna. In this embodiment, a radar reception signal 101 is input from the input terminal 1, and a logarithmic video signal 101 is input.
Logarithmic amplifier 2 outputs 2 and this logarithmic video 1
An A/D converter 3 that converts 02 into A/D, and an A/D converter 3 for A/D converting the 02, and an A/D converter 3 for correcting the received signal strength that has been attenuated by STC (Sensitivity Time Control) in the receiving system.
An STC amplitude correction circuit 4, a clutter area setting circuit 6 that generates a clutter area gate 103 indicating that it is a ground clutter area, and an STC amplitude correction circuit that receives this clutter area gate 103 while the clutter area gate is on. a clutter removal circuit 5 for inhibiting the output video 105 of 4;
A receiver noise removal circuit 7 removes receiver noise from the output 106 of the clutter removal circuit 5, and the output 107 of this noise removal circuit 7 is integrated over one radar sweep, and the integrated value is calculated in the clutter area and An average amplitude extraction circuit 8 extracts and outputs an average interference signal amplitude value by dividing the time corresponding to the area of receiver noise only by the time subtracted, and the output of this average amplitude extraction circuit 8 is divided into one radar sweep. Sweep memory 13 outputs after delaying for 2 radar sweeps and 2 radar sweeps, and the average amplitude value output corresponding to three antenna beams adjacent in the elevation direction is obtained from the output of this sweep memory 13 and the output of the average amplitude extraction circuit 8. From these, the local maximum value and the next largest average amplitude value of the local maximum value (corresponding to the antenna beam adjacent to the antenna beam giving the local maximum value) are extracted and output along with information specifying the antenna scanning beam. Signal extraction circuit 9
and an elevation scan memory 10 that stores the output of the elevation signal extraction circuit 9 for two consecutive elevation scans, and from the outputs of the elevation signal extraction circuit 9 and the elevation scan memory 10, it stores the output of the elevation signal extraction circuit 9 for three consecutive elevation scans. The maximum value in the azimuth direction of the average amplitude of the elevation angle output and the azimuth signal received from the antenna 20 at the input terminal 15 and the next largest average value of this maximum value (corresponding to the antenna beam adjacent to the antenna beam giving the maximum value) An azimuth signal extraction circuit 11 extracts amplitude values and azimuth data corresponding to each antenna beam, and outputs them together with elevation direction data. It receives a reference signal from input terminal 16 to be set, selects the output of azimuth signal extraction circuit 11 according to this reference signal, calculates the azimuth, elevation angle, and run length of the interference signal source, and outputs it from output terminal 14. It is configured to include an arithmetic circuit 12.

FIG. 2 is a schematic diagram of an example of an antenna beam pattern in this embodiment. The antenna 20 rotates in a clockwise direction 30 as shown in the figure, and one antenna beam is formed in the elevation direction in one transmission or reception, and by scanning this antenna beam in the elevation direction 32, this embodiment It is assumed that the radar device has a three-dimensional coverage area. Antenna beam 41 in this figure
49 schematically represents an antenna beam continuously formed in the elevation direction over three consecutive elevation angle scans, and it is assumed that the interference signal is radiated from the arrow direction 31.

FIG. 3 is a waveform diagram illustrating the operation of FIG. 1. In FIG.
After the amplitude is converted into a digital code by the A/D converter 3, the amplitude is converted into a digital code. This logarithmic video 102 includes ground clutter in addition to interference signals, and the STC adds attenuation to signals received from a short distance.
The A/D converted logarithmic video is then subjected to amplitude correction of the STC inverse characteristic by the STC amplitude correction circuit 4, and this amplitude correction output 105 (FIG. 3) is sent to the clutter removal circuit 5.

This clutter removal circuit 5 receives a logarithmic video 105 that has undergone amplitude correction and a clutter area gate 103 (see FIG. ), the logarithmic video from the STC amplitude correction circuit 4 is cut off for a period specified by the clutter area gate 103, and then the logarithmic video 106 (FIG. 3) is sent to the receiver noise removal circuit 7. This receiver noise removal circuit 7 compares the logarithmic video sent from the clutter removal circuit 5 with a preset threshold value corresponding to the receiver noise level, and outputs 1 of the clutter removal circuit 5.
Of the 06 outputs, only the logarithmic video amplitude signal that exceeds this threshold is output to the average amplitude extraction circuit 8 (signal 107 [Figure 3]), and at the same time the number of data per radar sweep output to this circuit 8 (hereinafter (referred to as the number of samples). This average amplitude extraction circuit 8 integrates its output for one radar sweep,
By dividing this integral value by the number of samples 104 per radar sweep sent from the noise removal circuit 7, the average amplitude value 108 (the third
) is extracted and sent to the elevation angle signal extraction circuit 9 and sweep memory 13.

This sweep memory 13 uses a signal obtained by delaying the average amplitude value 108 from the flattened amplitude extraction circuit 8 by one radar trigger interval and a signal for extracting the local maximum value in the elevation direction of the average amplitude value, and the like by two radar trigger intervals. The delayed signal and the elevation angle signal extraction circuit 9
Output to. This elevation angle signal extraction circuit 9 determines whether one of the three types of average amplitude values sent from the average amplitude extraction circuit 8 and the sweep memory 13 is a local maximum value, and if it is a local maximum value,
Among the information specifying the amplitude value and the antenna beam, and the average amplitude value corresponding to the antenna beam adjacent to the antenna beam that gives this local maximum value, the value that gives the next largest value after the local maximum value, and the antenna beam. Specified information is extracted and sent to the elevation scan memory 10 and the azimuth signal extraction circuit 11.

This situation will be explained with reference to FIG. In this figure, assuming that the currently formed antenna beam is beam 43, the average amplitude value corresponding to the antenna beams 41 and 42 is obtained from the sleep memory 13, and the average amplitude value corresponding to the antenna beam 43 is obtained from the average amplitude extraction circuit 8.
The average amplitude value corresponding to is output. First, in the elevation signal extraction circuit 9, the antenna beams 41, 4
2 and 43, and the antenna beam 42
Determine whether or not is the maximum value. That is, as a result of comparing the antenna beam 42 with the antenna beams 41 and 43, if the average amplitude value is larger than both, it is determined that the antenna beam 42 has the maximum value. When it is determined that this antenna beam 42 has the maximum value, its average amplitude value and information specifying the antenna beam 42 (eg, beam number) are extracted.
At the same time, the antenna beams 41 and 43 are compared,
The larger of these values and the corresponding antenna beam designation information are also extracted.

On the other hand, the elevation scan memory 10 stores the output of the elevation signal extraction circuit 9 over two consecutive elevation scans, and compared to the output of this circuit 9, the outputs before the elevation scan and before the elevation scan are sent to the azimuth signal extraction circuit 11. send out. This direction signal extraction circuit 1
1 is the same as the operation of the elevation signal extraction circuit 9, and the elevation signal extraction circuit 9 and the elevation scan memory 10.
, and extract the maximum value of the average amplitude in the azimuth direction, the next largest average amplitude value after the maximum value corresponding to the antenna beam adjacent to the antenna beam giving the maximum value, and the azimuth data corresponding thereto.

Now, in the model of Fig. 2, each antenna beam 4
Assuming that the received power of the interference signals No. 2, 45, and 48 is maximum at each elevation angle scan, the interference signal reception level at each antenna beam is shown as shown in FIG. In this figure, 42A, 45A,
48A shows the pattern in the azimuth direction of the antenna beams 42, 45, 48, and the antenna gain of each antenna beam with respect to the interference signal arriving from the direction 31 is the reception level 51, 52, 53 of the interference arrival direction 31, respectively. The antenna gain corresponds to In this model, antenna gain 52 of antenna pattern 45A is maximum, and below antenna pattern 4
The antenna gain 53 of 8A is followed by the antenna gain H of the antenna pattern 42A. Therefore, the local maximum value output of the average amplitude value from the elevation angle signal extraction circuit 9 in FIG. and extracted as the average amplitude value next to the local maximum value,
Furthermore, the azimuth angles θ ₂ and θ ₃ of the noses of the antenna beams 42 and 45 are extracted as azimuth data corresponding to the outputs 55 and 56.

In this way, the two-dimensional maximum value and the value next to the maximum value of the average amplitude value of the interference signal obtained by the elevation data extraction circuit 9 and the azimuth data extraction circuit 11, the antenna beam elevation angle information corresponding thereto, and The azimuth angle information is sent to the arithmetic circuit 12, and the arithmetic circuit 12 calculates the center azimuth, center elevation angle azimuth direction run length, and elevation direction run length of the interfering signal source from each data and the reference signal. Since the processing algorithm is the same for both the elevation angle direction, calculation of the run lengths for the center azimuth and azimuth directions will be described here.

Now, in FIG. 4, the antenna beams 42, 4
The azimuth angle of the beam nose direction of 5,48 is θ ₁ , θ ₂ ,
If θ ₃ , the outputs 54, 55, 56 are as shown in Fig. 5a.
As shown in , the value is proportional to the antenna pattern characteristics. Here, if the maximum value of the average amplitude is A ₂ and the next largest value after the maximum value is A ₃ , then the center azimuth of the interference signal θ _I
is calculated using the following formula.

θ _I = θ ₂ + θ ₃ /2 + △θ (1) Here, the correction angle △θ is the amount of correction related to the maximum value A ₂ and the next largest value A ₃ after the maximum value, and the antenna beam pattern characteristics are Gaussian. When approximated by a function, it becomes a linear function with the value of A ₂ −A ₃ as shown in FIG. 5b.

Next, this function will be explained using a formula.

Aerial pattern 45A, 48A in Fig. 4
The characteristics f(θ) and g(θ) are shown by the following equations (assuming the beam nose direction of pattern 45A is 0 degrees).

f(θ)=A・exp{−a(θ _I −θ ₂ ) ² } …(2) g(θ)=A・exp{−a(θ _I −θ ₃ ) ² } …(3) Here, A is the maximum amplitude constant, a is the constant, θ _I is the direction of the jamming wave, θ ₂ and θ ₃ are the patterns 45A, 48
The orientation of each beam nose in A is shown.

Further, the characteristics of the logarithmic amplifier are expressed by the following equation, where k and b are constants.

h(x)=k·lnbx (4) Therefore, the pattern characteristics at the output of the logarithmic amplifier are as follows.

h(f(θ)) = k・lnA・exp{−a(θ _I −θ ₂ ) ² } = k[lnA−a(θ _I −θ ₂ ) ² ] …(5) h(g(θ ))=k・lnA・exp{−a(θ _I −θ ₃ ) ² } =k[lnA−a(θ _I −θ ₃ ) ² ] …(6) These equations (5) and (6) are A ₂ at angle θ, respectively,
This corresponds to A ₃ , and taking the difference between them gives the following.

A ₂ −A ₃ =h(f(θ))−h(g(θ)) =k[lnA−a(θ _I −θ ₂ ) ² ] −k[lnA−a(θ _I −θ ₃ ) ² ] = ka [(θ _I − θ ₃ ) ² − (θ _I − θ ₂ ) ² ] = 2 ka (θ ₂ − θ ₃ ) θ _I − ka (θ ³ ₂ − θ ² ₃ Find θ _I from this formula And it becomes like this.

θ _I = 1/2ka (θ ₂ - θ ₃ ) (A ₂ - A ₃ ) + θ ₂ + θ ₃ /2...
...(7) In this equation, θ ₂ +θ ₃ /2 is a constant, but since θ _I is shown by equation (1), Δθ is the following equation.

△θ=1/2ka (θ ₂ - θ ₃ ) (A ₂ - A ₃ )...(8) Here, 2ka (θ ₂ - θ ₃ ) is a constant, so △θ and
A ₂ − _{A 3} is in a linear relationship.

Thus, the slope of the straight line in FIG. 5b is determined by the antenna pattern. Therefore,
The interference direction θ _I can be determined by determining Δθ from the actually measured A ₂ and A ₃ .

On the other hand, for the run length θ _R , the antenna beam pattern characteristics of the received interference signal strength are determined by the maximum value A ₂ ,
A ₃ is estimated, and the estimated pattern characteristics are determined from the angle range in which the estimated pattern characteristics exceed the reference signal value set externally. That is, assuming that 57 is the pattern characteristic estimated from the outputs 55 and 56 and 58 is the reference signal level, the angular range θ _R exceeding the reference signal level 58 is the run length.

Regarding the center elevation angle and the run length in the elevation direction, it is necessary to calculate the elevation angle of the antenna beam from the information specifying the antenna beam instead of the angle data, but the subsequent processing is based on the run length in the center azimuth and azimuth direction. The process is the same as that obtained.

Note that in this example, the maximum value in the elevation direction was first extracted, and then the maximum value in the azimuth direction was detected.
This order can be reversed, and it is also easily possible to perform processing in the azimuth direction and the elevation direction at the same time. Furthermore, multiple antenna beams can be formed in one transmission.

(Effects of the Invention) As explained above, according to the present invention, the azimuth, elevation angle and This has the effect that run length can be detected reliably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a schematic diagram showing an example of the antenna beam pattern in this embodiment, FIG. 3 is a signal waveform diagram of the block in FIG. 1, and FIG. Schematic diagram shown, 5th
Figures a and b are explanatory diagrams of a method for calculating the direction of the interference signal source from the average amplitude values obtained from adjacent antenna beams. In the figure: 1... Radar reception signal input terminal, 2... Logarithmic amplifier, 3... A/D converter, 4... STC amplitude correction circuit, 5... clutter removal circuit, 6... clutter area setting circuit, 7 ...Receiver noise removal circuit, 8
... Average amplitude extraction circuit, 9 ... Elevation angle signal extraction circuit, 10 ... Elevation angle scan memory, 11 ... Direction signal extraction circuit, 12 ... Arithmetic circuit, 13 ... Sweep memory, 14 ... Interference signal output terminal, 15...
...Azimuth input terminal, 16...Reference signal input terminal,
20... Antenna, 30... Antenna rotation direction, 31
... Interfering signal arrival direction, 32 ... Elevation angle scanning direction,
41-49...Aerial pencil beam, 42A,
45A, 48A...Aerial beam 42, 45, 4
8 azimuth patterns, 51, 52, 53... Reception level of interference signal, 54, 55, 56... Amplitude output of each antenna beam 42, 45, 48, 57...
Specified pattern characteristics, 58... Reference signal level, 101... Radar reception signal, 102... Logarithmic video, 103... Clutter area gate, 104
...Sample number signal, 105...STC amplitude correction circuit output, 106...Clutter removal circuit output, 1
07... Receiver noise removal circuit output, 108... Average amplitude value, 109... Interfering signal.

Claims (1)

[Claims] 1. Receiving means for receiving a received signal including a disturbance signal by an antenna pencil beam scanned in the azimuth and elevation directions of a search space, and a clutter for removing a clutter region from the received signal and extracting the disturbance signal. an average amplitude extraction means for extracting an average disturbance intensity for each scanning beam unit from among the plurality of interference signals extracted by the clutter removal means; maximum signal detection means for detecting a first average disturbance signal in a first scanning beam having a maximum intensity from , and second and third average disturbance signals in scanning beams adjacent in the azimuthal direction to the first scanning beam; signal extraction means for extracting the signal and fourth and fifth average jamming signals of elevationally adjacent scanning beams; and scanning for providing said first, second and third average jamming signal strengths and respective average jamming signal strengths. azimuth detecting means for detecting the center azimuth from which the jamming signal arrives from the beam azimuth; and the arrival of the jamming signal from the elevation angle of the scanning beam giving the first, fourth and fifth average jamming signal intensities and each average jamming signal strength. elevation angle detection means for detecting a center elevation angle;
and an azimuth range detection means for detecting an azimuth range of the interfering signal from a third average interfering signal strength, an arrival center azimuth of the interfering signal, and a predetermined reference level for determining the interfering signal; A radar signal processing device comprising an elevation angle range detecting means for detecting an elevation angle range of the interfering signal from an average interfering signal strength, an elevation angle of the arrival center of the interfering signal, and the reference level.