JPH0356431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a target detection device, and more particularly to a target detection device that selects and detects a target pulse signal from among received signals in a pulse radar.

In pulse radar, which receives reflected pulse signals from targets such as aircraft, ships, and vehicles, and searches for and detects the presence and location of these targets,
In addition to the desired target pulse signal, the received signal contains unnecessary interference signals such as thermal noise from the radar receiver, clutter caused by reflections from the ground or sea surface, and interference signals from external transmission sources. Significantly impedes detection ability.

Conventionally, as a measure to improve the unnecessary interference signals, particularly the clutter and interference signals, a target detection apparatus 1 shown in the block diagram of FIG. 1 has been used. In the figure, the pulse signal received and demodulated by the radar receiver is
(MOVING TARGET INDICATOR) circuit or logarithmic CFAR (CONSTANT FALSE ALARM
By passing through the clutter suppressing means 51 including a RATE) circuit, the clutter present therein is suppressed to a specific level and is input to the target detection device 1 as the first pulse signal. For example, if an MTI circuit is used in the clutter suppression means 51, a received signal reflected from a moving target such as an aircraft is detected, and a fixed object such as the earth or a mountain is detected.
That is, the received signal reflected from the fixed clutter is removed and input to the signal detection device.

The MTI circuit detects moving targets and removes fixed clutter based on the following principles. When a radio wave is reflected from a moving target, the frequency of the reflected wave is subject to a frequency shift related to the speed of the moving target due to the Doppler effect, and the reflectance from a fixed clutter is affected by the frequency shift. I don't accept it. By detecting the frequency shift due to the Doppler effect or the phase shift corresponding thereto, only the moving target can be detected. The standard MTI circuit of a pulse radar is a circuit that detects the phase of the reflected wave, delays it by one period, and adds it to the detection output of the next period with the opposite polarity.As a result, the reflected signal from the fixed clutter is removed, leaving only the signal reflected from the moving target (for more information on MTI, see Chapter 3 of "Radar Technology" published by the Institute of Electronics, Information and Communication Engineers). An example of the waveform of the input signal to this target detection device is conceptually shown in FIG. Figure 3 shows the signal received as the radar antenna rotates in the horizontal plane, with the amplitude on the vertical axis and the rotational azimuth of the antenna on the horizontal axis. It corresponds to the azimuth angle and also to the time axis related to the antenna rotation speed. In the figure, _A1 is a target pulse signal generated by a reflected wave from a relatively large target object, and its amplitude envelope is expressed as a time-series signal with a symmetrical shape weighted by the transmission and reception radiation pattern of the radar antenna. . Needless to say, the time interval of this signal pulse train is the repetition period (T) of the radar transmission pulse.
It corresponds to Further, A ₂ is a target pulse signal from a relatively small target object, B is thermal noise of the radar receiver, C is a clutter remaining signal suppressed and removed by the clutter suppressing means 51, and D is interference from an external transmission source. It's a signal. Generally, the state of the received signal at the output of the clutter suppressing means 51 is as follows:
Regardless of the magnitude of their levels, the target pulse signal expected as a received signal is as shown in Figure 3 A ₁ or
As shown in A ₂ , it is a time series signal with a large number of pulses (called the number of hits) that are continuously weighted by the transmission and reception radiation pattern of the radar antenna, and the individual pulses are normally arranged at intervals of the radar's pulse repetition period. Although the number of hits varies depending on the pulse repetition period T, radiation beam width of the antenna, rotational angular velocity of the antenna, received signal level, etc.
Usually it is about 10 to several dozen hits. On the other hand, the clutter remaining signal or interference signal is the third
As shown in Figures C or D, the level may be relatively large, but the number of hits is only about one or several hits. This is because at the input stage of the clutter suppressing means 51,
The reflected signal from the clutter has a number of hits equal to or greater than the number of hits of the target pulse signal _A1 or _A2 , but most of the reflected signal from the clutter is removed by the clutter suppressing means 51. This is because the signal is suppressed below the level of the thermal noise B of the receiver, and only a part of the signal becomes the clutter remaining signal C and is output from the clutter suppressing means 51. For example, if the clutter suppression means 51 has MTI
When a circuit is used, the signal reflected from the ground or mountains will not be an ideal fixed clutter signal with zero Doppler frequency deviation due to fluctuations within the fixed clutter and fluctuations due to antenna scanning. , the fixed clutter signal is a fixed clutter signal with some Doppler frequency shift, so the MTI circuit does not remove all of the fixed clutter signal; most of it is removed, but a part remains, and the fixed clutter signal is A small number of clutter remaining signals C are output (for fluctuations within fixed clutter, fluctuations due to antenna scanning, etc., see sections 3 and 4 of "Radar Technology" published by the Institute of Electronics, Information and Communication Engineers).

The conventional target detection device 1 shown in FIG. 1 is equipped with a video integration means 2 and a peak value detection means 3, and the video integration means 2 usually uses a feedback addition type integration circuit to eliminate the receiver thermal noise and noise-like clutter. It suppresses residual signals, interference signals, etc., and improves the ability to detect the desired target pulse signal. FIG. 5 shows block diagrams of three types of video integration means. Figure 5a shows a single feedback addition type integrator circuit, which includes an adder 30, a multiplier circuit 31 (multiplier K<1), and a delay circuit (delay time T) 3.
2. The transmission characteristic of this video integration means is expressed as the Laplace-transformed transfer function F(p)
When expressed in the form, F(p)=1/1−Ke ^−PT . When the target pulse signal _A1 or _A2 in FIG. , the amplitude envelope is distorted from a symmetrical shape corresponding to the antenna radiation pattern to an asymmetrical shape, resulting in an error in the radar's direction measurement of the target object. As a method to improve this drawback, the double feedback summing type integrator circuit shown in Fig. 5b and the weighted summing type integrator circuit shown in Fig. 5c are used, in which the amplitude envelope of the target pulse signal approximates the radar antenna radiation beam. has been adjusted to do so. An example of the waveform of the output signal of these video integration means is conceptually shown in FIG. 4a. The output of the video integrating means 2 is passed to the peak value detecting means 3, with a predetermined threshold level as a reference, only the peak values of the signal input above this level are outputted, and those below that level are cut off. In this case, if the level of the target signal pulse is relatively large with respect to the level of unnecessary signals such as clutter remaining signals or interference signals, the threshold level of the peak value detection means 3 is appropriately set. It is possible to completely prevent unnecessary signals from being detected as erroneous target signals by cutting them out. However, on the other hand, if the target pulse signal level is low and the unnecessary signal level is very high, even if the target pulse signal is emphasized by the video integration means 2, the unnecessary signal level may still be at a higher level. many. If so,
When the threshold level is set in the peak value detection means 3 so that the peak value of the low-level target pulse signal can be detected, unnecessary signals are naturally also output from the peak value detection means 3, and as a result, they are detected as false target signals. resulting in failure. This effect will be explained with reference to an example of the waveform of the output signal of the video integrating means in _FIG . The level of signal C′ and
Since it is large compared to D', if a level (L ₁ ) with the constant low potential shown by the one-dot chain line 301 in the figure as the threshold level is set as a reference level, only the peak value of the target pulse signal can be set. is detected
All unnecessary signals on C' or D' are cut out. On the other hand, when the target pulse signal level is relatively low, as is clear from the comparison of A' ₂ , C' and D' in Fig. 4a, the peak value of the target pulse signal A' ₂ is detected. When a level (L ₂ ) is set based on the constant low potential shown by the dashed line 302 in the figure, the clutter remaining signal C' and the interference signal D' are detected along with the peak value of the target pulse signal. This can cause false target signals.

To solve this drawback, video integration means 2
A method in which an amplitude limiting means is provided at the front stage of the signal to suppress the amplitude level of the high-level clutter remaining signal or interference signal, making it an unnecessary signal at a level corresponding to the relatively low-level target pulse signal, and then performing video integration. is sometimes used, but in this case, the high-level target pulse signal is also suppressed, making it impossible to correctly extract the signal strength information and degrading the accuracy of the extracted target orientation information. There are drawbacks.

That is, in conventional target detection devices, when the target pulse signal level is low and the level of unnecessary signals such as clutter or interference signals from external transmission sources is very high, the unnecessary signals are output in the same way as the target pulse signal. This has the disadvantage that it is detected as an erroneous target signal.

An object of the present invention is to solve the above-mentioned drawbacks, and even when the level of unnecessary signals such as clutter or interference signals is high compared to the target pulse signal, the high-level unnecessary signals are removed and the desired signal is removed. An object of the present invention is to provide a target detection device capable of detecting only a target pulse signal.

The target detection device of the present invention is a pulse radar having a clutter suppression function, and includes a video integrating means for integrating a first pulse signal that has been received and demodulated and subjected to clutter suppression processing; A second signal which is in a phase relationship and is formed as a time-series signal in response to this pulse signal.
a third pulse signal having a predetermined amplitude and phase relationship with the first pulse signal and formed as a time series signal in response to the first pulse signal; a reference level calculating means for outputting a reference signal corresponding to a level of 1/n (n>1) of the amplitude level of either the pulse signal or the peak pulse; and the first pulse signal and a predetermined amplitude. and the amplitude level of a fourth pulse signal which is in a phase relationship and is formed as a parallel signal corresponding to this pulse signal is compared with the level of the reference signal to determine a predetermined reference level in this parallel pulse signal. Level comparing means outputs a pulse counting signal for pulse signals exceeding the predetermined reference level, and the pulse counting signal is inputted to count the number of pulses exceeding the predetermined reference level, and the counted value is within a predetermined number of pulses. a hit number counting means for outputting a gate signal corresponding to whether or not the number of hits is included in the number of hits; and an unnecessary signal removing means that selects and outputs only the pulses to be detected.

The present invention will be described in detail below with reference to the drawings.

FIG. 2a is a block diagram showing a first embodiment of the target detection device of the present invention. The target detecting device 4 of this embodiment includes a video integrating means 5, a level comparing means 6, a peak value detecting means 7, a reference level calculating means 8, a hit number counting means 9, and an unnecessary signal removing means 10.

The pulse signal received and demodulated by the radar receiver is input to the target detection device 4 as the first pulse signal via the clutter suppressing means 51 as required. An example of the waveform of this input signal is conceptually shown in Figure 3. As mentioned above, the signal received as the radar antenna rotates in the horizontal plane is represented by the amplitude on the vertical axis.
It is displayed with the rotational azimuth angle of the antenna on the horizontal axis. In the figure, A ₁ is a target pulse signal generated by a reflected wave from a relatively large target object, A ₂ is a target pulse signal generated by a reflected wave from a relatively small target object, B is the thermal noise of the radar receiver, and C is the clutter suppression described above. The clutter remaining signal from the means 51 and D is the interference signal from an external transmission source. As mentioned above, the number of hits of these pulse time series signals is usually around ten or several dozen hits in the case of the target pulse signals _A1 and _A2 , and the number of hits in the unnecessary signal C.
In the case of and D, it is usually only one or a few hits. This input signal is input to the video integration means 5 included in the target detection device 4, and is input to the receiver thermal noise B and the noise-like clutter remaining signal C.
and the interference signal D, etc., and the desired target pulse signals _A1 , _A2, etc. are emphasized and output. As already explained, the video integration means 5 can be roughly divided into the three types of circuits shown in FIG. . An example of the waveform of the output signal of this video integration circuit 5 is shown in FIG. Second
In Figure a, the output signal of the video integrating means 5 is input to the level comparing means 6, which includes the level comparing means 6, the hit value detecting means 7, the reference level calculating means 8, the hit number counting means 9 and the unnecessary signal removing means. A more detailed block diagram of this embodiment including 10 is shown in FIG. In the figure, the first pulse signal inputted from the input terminal 101 is integrated by the video integration means 5, and then is integrated by the level comparison means 6.
is input. The level comparison means 6 includes a composite delay circuit in which a predetermined number of delay circuits (delay time T) 18 are connected in cascade, and a predetermined number of comparison circuits 19 corresponding to the delay circuits 18. Specific reference points 201, 202 and 203 are selected from among the connection points of the delay circuit 18,
It is configured such that pulse signals from these reference points are output to the peak value detection means 7. The pulse signal from the reference point 202 is the second pulse signal. Further, the parallel pulse signals from each connection point of the delay circuit 18 in the composite delay circuit are connected to the fourth
It is configured to be input to the comparison circuit 19 as a pulse signal. In this embodiment, eight delay circuits 18 and eight comparison circuits 19 are used in combination, but the number is not limited to eight.
It is generally selected in relation to the desired number of hits at the output of the video integration means 5 of the expected target pulse signal. The integrated pulse signal input to the composite delay circuit is transmitted via the delay circuit 18, but the pulse signals extracted from the reference points 201, 202 and 203 are transmitted through the peak value detection means 7 included in the peak value detection means 7. The reference points 201 and 2 are used as amplitude level standards of the second pulse signal inputted to the comparison circuit 20 and taken out from the reference point 202 selected as the midpoint of the composite delay circuit.
It is compared with the amplitude level of the pulse signal taken out from 03. Looking at the temporal transition of the second pulse signal at reference point 202, at the leading edge of the pulse train, (pulse amplitude level at reference point 201)>(pulse amplitude level at reference point 202)> (pulse amplitude level at reference point 203), and at the trailing edge always (pulse amplitude level at reference point 201).
)<(pulse amplitude level of reference point 202)<(pulse amplitude level of reference point 203)
It is. At the point in time when the peak pulse of the target pulse signal passes through the reference point 202 (reference point 20
1)<(pulse amplitude pulse at reference point 202)>(pulse amplitude level at reference point 203). The peak value detection comparison circuit 20 compares the pulse amplitude levels of these three reference points, and
The gate circuit 21 is operated at the time when the peak pulse passes through the reference point 202, and only the peak pulse is selected from a series of pulse signals inputted to the gate circuit 21 from the reference point 202, and the reference level calculation means 8 and unnecessary The signal is sent to the signal removing means 10. In the reference level calculating means 8, the amplitude level of the input peak pulse is 1/n (n>1).
A reference level signal corresponding to 1 is generated and outputted to each of a predetermined number of comparison circuits 19 constituting the level comparison means 6. At this point, the amplitude level of each of the parallel pulses constituting the fourth pulse signal output from each connection point of the delay circuit 18 is compared with the reference level in this comparison circuit 19, and the reference level is For pulse signals exceeding the reference signal level, the pulse counting signal is input to the hit number counting means 9, and the number of hits exceeding the reference signal level is counted. Number of hits counting means 9
In addition, it is determined whether this number of hits is within a predetermined range of the number of hits set in advance in relation to the standard number of hits of the target pulse signal, and if it is within the predetermined range, the signal is allowed to pass. The gate signal is sent to unnecessary signal removing means 10. At this point, the peak pulse from the peak value detection means 7 is input to the unnecessary signal removal means 10, and only this peak pulse is selected and output from the output terminal 102 by the passable gate signal. . Needless to say, peak pulses that do not match the passable gate signal are cut and not output. The operation of selecting and outputting this peak pulse signal, including the target pulse signal and unnecessary signals, will be explained in detail with reference to _FIG . The peak value detection means 7 selects and outputs only one peak pulse of _A'1 . One of these outputs is sent to the reference level calculating means 8, which uses the amplitude level value of the peak pulse as a reference potential, and sets a reference level that is a level corresponding to 1/n (n>1) of the pulse amplitude value. do. This level setting is performed using the peak level value _L3 of _A'1 as a reference potential, as shown in FIG. This is an extremely effective means for removing unnecessary signals, and is one of the requirements of the present invention. In the figure,
Only those pulses exceeding a dashed-dotted line 304 indicating a predetermined reference level L ₃ /n with respect to the peak level value L ₃ indicated by a dashed-dotted line 303 are counted as valid pulses by the hit number counting means 9. Similarly, the above A' ₂ , C' and
In the case of D', the respective peak pulses are output from the peak value detection means 7, and the reference levels L ₄ /n, L ₅ /n and L ₆ /n are respectively set.
n is set and only pulses exceeding a predetermined reference level are counted by the hit number counting means 9. Therefore, assuming an input signal as shown in FIG. _4b , the peak value detection means 7 in _FIG . Then, each peak pulse is output. At the same time, the hit number counting means 9 counts the number of pulse hits each exceeding the reference level, and determines whether the counted value is within a predetermined range of hits. Normally, the number of hits of unnecessary signals such as clutter remaining signals and interference signals is about one or several hits at the output stage of the clutter suppressing means, and the number of hits increases by passing through the video integrating means 5. However, the reference level setting means 8 used in the present invention allows
Even when the unnecessary signal level is high, the reference level is set to follow the high level, so the number of hits counted by the hit number counting means 9 is smaller than the standard number of hits of the target pulse signal. This is a fairly low number. Furthermore, even in the case of a relatively low level target pulse signal, the reference level calculation means 8 sets the reference level in accordance with the low level, so that the number of hits is equal to the standard number of hits of the target pulse signal. The numbers will be close. Therefore, the gate signal sent from the hit number counting means 9 to the unnecessary signal removing means 10 indicates whether the signal can pass or not for A' ₁ and A' ₂ in FIG. 4b, and for C' and D'. As a result, the peak value detection means 7 outputs the unnecessary signal from the unnecessary signal removal means 1.
Among a series of peak pulses such as A' ₁ , D', C', and A' ₂ inputted to 0, the peak pulses corresponding to unnecessary signals C' and D' are removed and the target pulse signals A' ₁ and A' Only the peak pulse corresponding to ₂ is output.
In other words, the output terminal 102 outputs only the target peak pulse signal from which unnecessary signals such as clutter remaining signals and interference signals, which cause false target signals, are almost completely removed due to the action of the target detection device 4 of this embodiment. , the position of the desired target object is confirmed via commonly used threshold control means 52 and target signal information extraction means 53 shown in FIG. 2a. Most of the unnecessary signals are removed by the target detection device 4, but not all unnecessary signals are removed ideally. There is also a clutter remaining signal with a large number of hits similar to the pulse signal A', and such unnecessary signals pass through the unnecessary signal removing means 10 and are sent to the target detection device 4.
is output from. In order to further remove unnecessary signals from the output of the target detection device 4, the output signal of the target detection device 4 is subjected to threshold control processing by the threshold control means 52. Threshold control processing divides the entire two-dimensional search range of the pulse radar's distance search range and azimuth search range into subareas formed by small predetermined distance sections and small predetermined azimuth sections, and separates each subarea. This is a process of automatically raising/lowering a threshold (target detection reference level) independently of each other to detect a target.

The signal of a moving target such as an aircraft outputted from the target detection device 4 does not stay in one small area for a long time, but moves to adjacent areas over time that is related to the speed and movement path of the moving target and the range of the small area. Move to another sub-area. On the other hand, the clutter remaining signals that do not move remain in one small area. The threshold, which is set independently for each sub-area, is automatically set high for sub-areas where the signal remains for a long time, and is controlled to be high for sub-areas where the signal does not remain for a long time. In contrast, the setting is automatically controlled to be low. Unnecessary signals are further removed by such threshold control processing. For the target signal that has passed through the threshold control means 52, the target signal information extraction means 53 extracts not only the amplitude value of the target signal but also the position information of the target, that is, the target distance information and the target direction information. The position of the intended target object is confirmed.

Further, FIG. 2b shows the second target detection device of the present invention.
FIG. 2 is a block diagram showing an embodiment of the invention. The target detecting device 11 of this embodiment includes a video integrating means 12, a level comparing means 13, a peak value detecting means 14, a reference level calculating means 15, a hit number counting means 16, and an unnecessary signal removing means 17.

The pulse signal received and demodulated by the radar receiver is input to the target detection device 11 of this embodiment via the clutter suppressing means 51 as required. This input signal is input to the video integration means 12 included in the target detection device 11, and the weight addition type integration circuit shown in FIG. 5c is applied as this integration means. FIG. 7 is a block diagram showing this embodiment in more detail than the block diagram of FIG. 2b. The first pulse signal is input to the input terminal 103.
is inputted to the video integration means 12 from. The video integration means 12 includes a predetermined number of delay circuits (delay time T).
23 are connected in cascade, a predetermined number of load circuits 22 corresponding to the delay circuits 23, and pulse outputs from these load circuits are added, and the addition result is attenuated by a predetermined attenuation ratio. A circuit 24 is provided. This predetermined attenuation ratio is a predetermined value corresponding to the so-called target signal integral gain, which increases the level of the target signal as it is integrated by the integrating means. From the connection point of each delay circuit 23 in the composite delay circuit, a predetermined number of parallel pulses are supplied, on the one hand, as a pulse signal for video integration to the weighting circuit 22, and on the other hand, as the fourth pulse to the level comparison means 13. A specific reference point 204 in the composite delay circuit (when the number of delay circuits is p,
The third pulse signal is output from the connection point between the p+1/2th and p+3/2nd delay circuits.

The video integral output of the input first pulse signal is input as the second pulse signal to the peak value detection means 14, and a peak pulse is detected from among the series of integral pulse signals. Peak value detection means 14
is equipped with two delay circuits 25, a peak value detection comparison circuit 26, and a gate circuit 27, and its function is similar to that of the intermediate connection of the cascaded delay circuits 18 in FIG. 6 in the first embodiment. This is almost the same as when peak pulses are detected by extracting reference pulses from points 201, 202, and 203. Further, the third pulse signal taken out from the reference point 204 is input to the reference level calculation means 15, and the operation of generating the reference level signal is the same as in the first embodiment.
A reference level signal corresponding to 1/n (n>1) of the amplitude level of the input third pulse signal is generated and sent to a predetermined number of comparison circuits 28 constituting the level comparison means 13. Note that when the third pulse signal is input to the reference level calculation means 15,
In addition to generating a reference level signal corresponding to the third pulse signal at the time when the peak pulse is present, a reference level signal corresponding to the third pulse signal at the time when the peak pulse is not present is also generated. generated and output. Therefore, even when a peak pulse does not exist, the passable gate signal may be inputted from the hit number counting means 16 to the unnecessary signal removing means 17, but at this point, the peak value Since neither the peak pulse nor any other signal is input to the unnecessary signal removing means 17 from the detection means 14, the unnecessary signal removing means 17
No signal is output from the output terminal 104 to the output terminal 104. Reference level setting method in this case, hit number counting means 16 and unnecessary signal removing means 17
The functions and the like are exactly the same as in the first embodiment. In this embodiment shown in FIG. 7,
Although nine delay circuits 23 and nine load circuits 22 are used, and eight comparison circuits 28 are used, these numbers are not limited to the above values, and can be any number of standard hits of the expected target pulse signal. is selected in relation to the number of video integration additions in the video integration means 12 that are related to the video integration means 12. For example, if the number of video additions is N, the numbers of delay circuits, load circuits, and comparison circuits are N, N, and N-1, respectively. Further, the explanation of the operation of this embodiment related to FIG. 4b is almost the same as that of the first embodiment.

As described above in detail, the target detection device of the present invention is characterized by the presence of unnecessary signals that cause false target signals such as clutter and interference signals that are at a higher level than the level of the intended target pulse signal. Even in such cases, there is an effect that most of these unnecessary signals can be removed and the target detection ability of the radar can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an example of a conventional target detection device, FIG. 2 a and b are block diagrams of first and second embodiments of the target detection device of the present invention, and FIG. FIG. 4 is a conceptual diagram of the waveform of the received signal corresponding to the antenna rotation azimuth. FIG. 4 is a conceptual diagram of the waveform of the received signal similar to the above at the output of the video integrating means. FIG. 5 is a block diagram of three types of video integrating means. 7 are detailed block diagrams of first and second embodiments of the target detection apparatus of the present invention, respectively. In the figure, 1, 4, 11...Target detection device, 2, 5, 12
...Video integration means, 3,7,14...Peak value detection means, 6,13...Level comparison means, 8,1
5... Reference level calculation means, 9, 16... Hit number counting means, 10, 17... Unnecessary signal removal means,
18, 23, 25, 32, 35, 37... Delay circuit, 19, 28... Comparison circuit, 20, 26... Comparison circuit for peak value detection, 21, 27... Gate circuit, 22, 38... Load circuit, 24, 30, 3
3, 39...addition circuit, 31, 34, 36...multiplication circuit, 51...clutter suppression means, 52...threshold control means, 53...target signal information extraction means, 101, 103...input terminal ,102,
104...Output terminal, 201, 202, 203,
204...Reference point.

Claims (1)

[Scope of Claims] 1. In a pulse radar having a clutter suppression function, video integrating means integrates a first pulse signal that has been received and demodulated and has been subjected to clutter suppression processing, and a video integration unit that integrates a first pulse signal that has been received and demodulated and has been subjected to clutter suppression processing; peak value detection means for detecting a peak pulse from a second pulse signal formed as a time-series signal in response to the pulse signal; 1/1/1 of the amplitude level of either the third pulse signal or the peak pulse, which is formed as a time series signal in response to this pulse signal.
a reference level calculation means for outputting a reference signal corresponding to a level of n (n>1); and a reference level calculation means having a predetermined amplitude and phase relationship with the first pulse signal and forming a parallel signal corresponding to the pulse signal. level comparison means for comparing the amplitude level of the fourth pulse signal to be outputted with the level of the reference signal and outputting a pulse counting signal for pulse signals exceeding a predetermined reference level among the parallel pulse signals; A hit count that inputs a pulse counting signal, counts the number of pulses exceeding the predetermined reference level, and outputs a gate signal corresponding to whether or not the counted value is within a predetermined number of pulses. and an unnecessary signal removing means that receives the gate signal and selects and outputs only the pulse corresponding to the gate signal from a series of peak pulse signals output from the peak value detection means. Characteristic target detection device. 2. In the device according to claim 1,
The integrated pulse signal output from the video integration means is input to the level comparison means, and the time series pulse signal output from a predetermined connection point of the cascaded delay circuits provided in the level comparison means is used to A target detection device that forms a second pulse signal and forms the fourth pulse signal using parallel pulse signals output from each connection point including both terminals of the cascaded delay circuits. 3. In the device according to claim 1,
The second pulse signal is formed by the integral pulse signal output from the video integrating means, and the time series pulse is output from a specific connection point of a cascaded delay circuit provided in the video integrating means. A target detection device for forming the third pulse signal by a signal, and forming the fourth pulse signal by a parallel pulse signal output from a predetermined connection point of the cascaded delay circuits.