JP5710882B2 - Radar signal processing device - Google Patents

Description

  The present invention relates to a radar signal processing apparatus for synthesizing different received signals for short distance and for long distance in a pulse compression radar and subjecting it to predetermined signal processing.

  Pulse compression radar uses a frequency modulation signal with a pulse width longer than pulse radar (several microseconds to several tens of microseconds), and applies pulse compression technology to provide a large detection capability even when the peak power of transmission is low. Can be realized.

  In such a pulse compression radar, a short-range target detection based on a pulse radar system is realized prior to a transmission wave (hereinafter referred to as “long pulse”) generated based on the frequency modulation signal. By transmitting a modulation pulse (hereinafter referred to as “short pulse”), it is possible to detect a target at a short distance even though the pulse width of the long pulse is long.

  In the pulse compression radar, a short-distance video (hereinafter referred to as “short-distance video”) obtained from a received wave arriving in response to a short pulse (hereinafter referred to as “short-pulse received wave”) and a long A long-distance video (hereinafter referred to as a “far-distance video”) obtained from a received wave (hereinafter referred to as a “long pulse received wave”) that arrives in response to a pulse is simply combined with a predetermined distance as a boundary. In such a case, an unnatural step occurs in the luminance and gradation value at the boundary. Such a step is caused by the difference in sensitivity of processing performed in the course of radar signal processing between the short pulse reception wave and the long pulse reception wave.

  Conventionally, as a technique for solving such a problem, for example, as disclosed in Patent Document 1 to be described later, “by applying special sensitivity time control (STC) to a short-distance video, There was a radar device that smoothly connects the level of a target signal at the boundary with a distance image and its STC processing method.

JP 2008-175582 A

  By the way, in the above-described conventional example, the target that is a reflector is able to smoothly connect a short-distance image and a long-distance image, but depends on the specifications (pulse width, frequency shift width, etc.) of the transmission signal. Since the characteristics differ for each of the following three signals included in the short pulse reception wave and the long pulse reception wave, the amplitude is simply discontinuous when the images are connected, and the above-mentioned steps are not enough for clutter and noise. Was not resolved.

(1) Reflected wave coming from reflector
(2) System noise
(3) Clutter such as sea surface reflection and rain / snow reflection

  An object of the present invention is to provide a radar signal processing apparatus that can flexibly adapt to various performances, specifications, and target distributions of a pulse compression radar, and can stably detect a target over a wide range.

In the first aspect of the present invention, the signal conversion means can correspond to the first received wave adapted to the pulse radar system on the range, and the second received wave adapted to the pulse compression radar system is The first reception wave is multiplied by a compression ratio c for the first reception wave and a mixing ratio w (≦ 1) given as a monotonic non-decreasing function of the level of the first reception wave, and the first reception wave is obtained. Get the converted wave. The noise conversion means multiplies the first received wave by the ratio of the occupied band between the second received wave and the first received wave and the complement (= 1-w) of the mixing ratio w, A converted wave of noise superimposed on the first received wave is obtained. The synthesizing means includes a mixing ratio W (≦ 1) given as a monotonous non-increasing function of the sum of the converted wave of the first received wave and the converted wave of the noise superimposed on the first received wave and the distance indicating the range. ) And the product of the product of the complement of the mixing ratio W (= (1−W)) and the signal obtained by the compression processing of the second received wave, To do.

According to a second aspect of the present invention, in the radar signal processing device according to the first aspect, the mixing ratio w is the first reception when the target detected by the pulse radar system is a standard target. The value of the monotonic non-decreasing function with respect to the wave level.

As described above, according to the present invention, it is difficult for the instantaneous value of a signal to be subjected to signal processing to be accompanied by an unnatural jump that may occur in the conventional example.
In the present invention, the instantaneous value of the signal to be subjected to subsequent signal processing is less likely to be accompanied by an unnatural jump compared to the first aspect of the invention.

In the present invention, the instantaneous value of noise superimposed on either the first received wave or the second received wave described above is less likely to cause the unnatural jump described above.
The pulse compression radar to which the present invention is applied flexibly adapts to the configuration and specifications of the pulse compression radar, and can achieve positioning and ranging with high accuracy without causing unnecessary confusion to the user.

  Therefore, the radar apparatus to which the present invention is applied can be flexibly adapted to various needs regarding the configuration and specifications, and desired performance can be maintained with high accuracy.

It is a figure which shows one Embodiment of this invention. It is a figure explaining operation | movement of this embodiment. It is a figure which shows the mixing ratio applied according to an amplitude in this embodiment. It is a figure which shows the mixing ratio applied according to a range in this embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of the present invention.
In the figure, the transmission unit 11 includes a specification (hereinafter simply referred to as “specification”) related to transmission of the short pulse and the long pulse described above by a control unit (not shown) (for example, provided in an instruction device described later). .) And the triggers for these short and long pulses to be transmitted. The receiving unit 12S is provided corresponding to the short pulse received wave described above, and the output of the receiving unit 12S is connected to the first input of the radar signal processing device 20 according to the present embodiment via the signal processing unit 13S. Is done. The receiving unit 12L is provided corresponding to the long pulse reception wave described above, and the output of the receiving unit 12L is connected to the second input of the radar signal processing device 20 via the signal processing unit 13L. The above specifications are given to the third input of the signal processing unit 20, and a video signal delivered to a pointing device (not shown) is obtained at the output of the signal processing unit 20.

The radar signal processing unit 20 includes the following elements.
(1) Amplitude adjustment unit 30 connected in series to the output of signal processing unit 13S described above
(2) In addition to the first and second inputs connected to the output of the amplitude adjustment unit 30 and the output of the signal processing unit 13L, the starting point r and width R of a “composite section” described later are A synthesis processing unit 40 having a third input and outputting the video signal described above.

The amplitude adjustment unit 30 includes the following elements.
(1) A signal amplitude adjusting unit 31 in which the radar signal VS output from the signal processing unit 13S is input to the first input and the above-described specifications are given to the second input.
(2) A noise amplitude adjustment unit 32 in which a similar radar signal VS is input to the first input and the above-described specifications are given to the second input.

(3) The mixture ratio calculation unit 33 in which the radar signal VS is input to the first input and threshold values TH and th (≦ TH) to be described later are given to the second input.
(4) Multiplier 34 in which the outputs of signal amplitude adjusting unit 31 and mixing ratio calculating unit 33 are connected to the first and second inputs, respectively.
(5) A complement setting unit (CV) 35 cascaded to the output of the mixture ratio calculation unit 33

(6) Multiplier 36 in which the output of noise amplitude adjusting unit 32 and the output of complement setting unit 35 are connected to the first and second inputs, respectively.
(7) An adder 37 in which the outputs of the multipliers 34 and 36 are connected to the first and second inputs, respectively, and the output is connected to the first input of the synthesis processing unit 40.

The composition processing unit 40 includes the following elements.
(1) A range number Nr that is synchronized with the sweep performed by the pulse compression radar apparatus according to the present embodiment and discretely indicates the range in each sweep in the order of time series is given to the first input, and the radar signal processing apparatus 20 is a mixture ratio calculation unit 41 in which the start point r and the width R of the “range section” to be subjected to video composition processing are given to the second input.
(2) A multiplier 42 in which the radar signal VS ′ output from the amplitude adjustment unit 30 (adder 37) is connected to the first input, and the second input is connected to the output of the mixing ratio calculation unit 41.

(3) A complement setting unit (CV) 43 cascaded to the output of the mixture ratio calculation unit 41
(4) A multiplier 44 in which the radar signal VL output by the signal processing unit 13L is connected to the first input, and the output of the complement setting unit 43 is connected to the second input.
(5) An adder 45 having outputs of the multipliers 42 and 44 connected to the first and second inputs, respectively, and outputting the above-described video signal to the output.

The feature of the present invention resides in the procedure of processing performed by the amplitude adjustment unit 30 and the synthesis processing unit 40 in the present embodiment.
Therefore, hereinafter, the linkage and operation performed in the previous stage of the radar signal processing device 20 in order to generate a signal to be processed will be described.

  The transmission unit 11 sequentially cyclically transmits short pulses and long pulses at intervals, periods, (peak) power, and the like defined as the above-described specifications.

  The receiving unit 12S detects the short pulse received wave that arrives in response to the short pulse transmitted in this manner, and the signal processing unit 13S performs predetermined signal processing (time axis) on the radar signal obtained as a result of the detection. The radar signal VS ′ (FIG. 2 (a), broken line portion) is generated by performing a long pulse delay compression process with respect to the short pulse above.

Similarly, the receiving unit 12L detects a long-pulse received wave that arrives according to the long pulse transmitted, and the signal processing unit 13L performs pulse compression processing on the result, thereby providing a radar signal VL (FIG. 2). (a) Solid line part) is generated.
In the following description, it is assumed that these radar signals VS and VL are obtained in a manner corresponding to the range direction.

  Hereinafter, the operation of each unit in the radar signal processing apparatus 20 will be described with reference to FIGS. 1 and 2.

The signal amplitude adjustment unit 31 acquires in advance the following items determined by the above-described specifications.
(1) Short pulse width T1
(2) Long pulse width T2
(3) Long pulse frequency deviation width B2

Further, the signal amplitude adjustment unit 31 multiplies the radar signal VS by a coefficient Ca (= (T2 · B2)) determined by these items, thereby generating a radar signal Va (a broken line part in FIG. 2B). Such a coefficient Ca is equal to the compression ratio (= Ca) of the long pulse to the short pulse, as shown in the following equation including the short pulse bandwidth (≈1 / T1).
Ca = (T2 · B2) / (T1 · (1 / T1)) = T2 · B2

Therefore, the radar signal Va is obtained as a product of “a radar signal VS obtained by detecting a short pulse received wave that arrives in response to a short pulse” and the compression ratio.
The mixture ratio calculator 33 is given in advance two threshold values TH and th set in advance as follows, and monitors the magnitude relationship between the threshold values TH and th and the instantaneous value vs of the radar signal VS.

(1) Threshold th set in advance to a value equal to or higher than the noise floor determined based on the overall noise figure and characteristics of the receiving unit 12S and the signal processing unit 13S
(2) Threshold TH (≧ th) calculated in advance based on the level of the short pulse received wave coming from the standard target to be detected in response to the short pulse

Moreover, the mixture ratio calculation part 33 identifies the following three periods based on such a magnitude relationship.
(1) Small amplitude period in which the instantaneous value vs of the radar signal VS is less than the threshold th
(2) Medium amplitude period in which the instantaneous value vs of the radar signal VS is less than the threshold value TH and greater than or equal to the threshold value th
(3) Large amplitude period in which the instantaneous value vs of the radar signal VS is greater than or equal to the threshold value TH

Further, as shown in FIG. 3, the mixture ratio calculation unit 33 outputs the following mixture ratio w during the above three periods determined according to the instantaneous value vs of the radar signal VS.
(1) Small amplitude period w = 0
(2) Large amplitude period w = 1
(3) Medium amplitude period w = (vs-th) / (TH-th) (a)

  The multiplier 34 generates a radar signal Va ′ by multiplying the radar signal Va by such a mixing ratio w.

In other words, during the small amplitude period, the amplitude of the short pulse received wave is small because the level is so small that the instantaneous value vs of the radar signal VS is less than the threshold th, and most components are only noise components. The component of the radar signal Va input to the unit 31 is suppressed and is not included in the radar signal Va ′.
On the other hand, during the large amplitude period, the short pulse received wave is likely to be a component of the reflected wave that has arrived with a large amount of power from some target, and therefore the radar signal Va input to the amplitude adjusting unit 31. Are included in the radar signal Va ′ without being suppressed.

  Further, in the medium amplitude period, the received component of the received wave that has arrived from the target in accordance with the short pulse is included in the short pulse received wave as the amplitude (level) increases. Therefore, the radar signal Va ′ includes the components of the radar signal Va weighted by the mixing ratio w (≦ 1) represented by the above equation (a) indicating such a ratio.

On the other hand, the noise amplitude adjuster 3 2, a coefficient determined by the above-described item Cn (= (T1 · B2) ) by multiplying with the radar signal VS, generates a radar noise signal Vn. Such a coefficient Cn is a proportionality coefficient that enables conversion of “the level of noise superimposed on a short pulse” to “the level of noise superimposed on a long pulse” as shown in the following equation, It is given as the ratio of the occupied bandwidth between the long pulse and the short pulse (the ratio of the reception bands of the receiving units 12L and 12S).
Cn = (T1 · B2) = B2 / (1 / T1) (b)
In the above equation (b), even if the level of noise superimposed on the radar signal VS increases as the reception band is wider, the noise has no correlation with the long pulse or the short pulse, and the pulse Since it does not increase or decrease during the compression process, terms related to the pulse compression process are not included.

  Therefore, the radar noise signal Vn is obtained as a product of “a radar signal VS obtained by detecting a short pulse received wave that arrives in response to a short pulse” and the ratio (= Cn).

The complement setting unit 35 calculates a complement w ′ (= 1−w) for “1” of the mixing ratio w.
The multiplier 36 multiplies the radar noise signal Vn by such a mixing ratio w ′ to generate a radar noise signal Vn ′.

  That is, in any of the small amplitude period, the large amplitude period, and the medium amplitude period, the radar noise signal Vn ′ includes “1” of the mixing ratio w corresponding to the ratio of the radar signal Va included in the radar signal Va ′. The radar noise signal Vn is included at a ratio equal to the complement w '.

The adder 37 adds the radar noise signal Vn ′ to the radar signal Va ′, thereby generating the above-described radar signal VS ′.
That is, the level of the signal component and the noise component included in the radar signal VS received in response to the short pulse is a value in which the level difference with the radar signal VL received in response to the long pulse is adapted to the SN ratio. It is corrected.

  Therefore, the radar signal VS is delivered to the synthesis processing unit 40 as the radar signal VS ′ while keeping the SN good without excessive deterioration.

Among the signal components described above, the clutter signal component indicating the clutter and other distribution targets to be detected by the radar apparatus according to the present invention is weighted with a greater weight than the noise as the level increases.
Therefore, the clutter signal component is included in the radar signal VS ′ without accompanying an unnatural jump of instantaneous values (FIG. 2 (c)) caused by weighting in the same manner as other signal components and noise components having different properties. (FIG. 2 (d)).

Further, in the synthesis processing unit 40, the units are linked as follows.
The mixing ratio calculation unit 41 has the above-described range in the range indicated by the above-described start point r and width R (indicating the “width of the range section” on which the video synthesis processing should be performed by the radar video synthesizer 20). It is determined whether or not the range Rc indicated by the number Nr is applicable, and the following three sections are identified as a result of the determination.

(1) Near range section where range Rc is less than start point r (Fig. 4 (1))
(2) Middle range section where range Rc is greater than or equal to start point r and less than (r + R) (FIG. 4 (2))
(3) Far range section where range Rc is (r + R) or more ((3) in Fig. 4)

Furthermore, as shown in FIG. 4, the mixture ratio calculation unit 41 outputs the following mixture ratio W determined according to such three sections.
(1) Near range section W = 1
(2) Far range section W = 0
(3) Middle range section W =-(Rc-r-R) / R (b)
The multiplier 42 multiplies the radar signal VS ′ by such a mixing ratio W to thereby obtain the radar signal VSW.
Is generated.

That is, in the near range section, the radar signal VS ′ generated according to the short pulse received wave is not suppressed, and the radar signal VSW is not suppressed.
It is reflected in. On the contrary, in the far range section, the radar signal VS ′ is suppressed and the radar signal VSW is suppressed.
Is not reflected.

Further, in the middle range section, the range signal VS ′ is weighted smaller as the range Rc is larger, as shown in the above equation (b), and the radar signal VSW.
It is reflected in.
The complement setting unit 43 calculates a complement W ′ (= 1−W) for “1” of the mixing ratio W.

The multiplier 44 multiplies the above-described radar signal VL by such a mixing ratio W ′ to thereby obtain the radar signal VL (1-W).
Is generated.
That is, the radar signal VL (1-W) is used in any of the near range section, the far range section, and the middle range section.
The radar signal VL includes a larger ratio (= W ′ = (1−W)) as the range Rc is smaller.

The adder 45 is connected to the radar signal VSW described above.
By adding such a radar signal VL (1-W), a video signal to be displayed as an image is generated based on a desired instruction method.

  That is, the radar signal VS obtained based on the pulse radar system is connected to the radar signal VL obtained based on the pulse compression radar system when the instantaneous value exceeds the threshold th, but these radar signals VS are connected. , The instantaneous values at the boundary of VL are smoothly connected without an unnatural jump regardless of the presence or absence of the target in the range corresponding to the boundary.

  Further, the connection of these radar signals VS and VL is realized not only by the above boundary but also by converting the instantaneous value into the instantaneous value of the received wave of the pulse compression radar system for the range other than the boundary.

  Therefore, according to the present embodiment, the target detection is stably realized by flexibly adapting to any of a wide range and a variety of environments that can be accompanied by switching of the range, precipitation, snowfall, etc. The target can be detected accurately and smoothly by silent viewing of the screen.

  In addition, according to the present embodiment, in particular, clutter caused by rain and snow is received with a power that is proportional to the peak power or pulse width of a short pulse or a long pulse, and is generated in the range. However, it is displayed on the screen of the indicator without an unnatural jump in luminance and gradation values at the boundary between the short range and the far range.

In the present embodiment, the above-described calculation is realized by aligning the range of the instantaneous value (amplitude) of the short pulse received wave with the range of the instantaneous value (amplitude) of the long pulse received wave.
However, in such a calculation, if accuracy and responsiveness are sufficiently ensured and detection of a desired target (including a distribution target) is not impaired, for example, instead of the compression ratio Ca described above, The reciprocal is applied and the reciprocal is applied instead of the ratio Cn of the occupied bandwidth of the long pulse and the short pulse, so that the instantaneous value of the long pulse received wave is within the range of the instantaneous value (amplitude) of the short pulse received wave. You may implement | achieve by aligning the value range of a value (amplitude).

  In the present embodiment, the mixing ratio w does not have to correspond to the small amplitude period, the large amplitude period, and the medium amplitude period described above, and the instantaneous value vs for all or a combination of these periods. May be obtained by an arithmetic operation appropriately performed based on the above.

  Furthermore, in the present embodiment, the mixing ratio W may not be a value corresponding to each of the above-described near range section, far range section, and middle range section, and the range Rc may be set for all or a combination of these sections. It may be obtained by an arithmetic operation appropriately performed based on the above.

In the present embodiment, the present invention is applied to a marine radar apparatus.
However, the present invention can be applied to any type of radar apparatus as long as target detection in the short range and the far range is performed based on the pulse radar system and the pulse compression radar system, respectively.

  Furthermore, the present invention is not limited to a radar apparatus that performs a sweep. For example, a measurement that measures a relative distance from a target that is located in a specific direction without performing a sweep, such as a berthing distance meter or a range finder. The same applies to the distance device.

In the present embodiment, an unnatural jump of an instantaneous value of noise in which only the noise is included in each of the radar signals VS and VL is avoided at the boundary between the small amplitude period and the medium amplitude period.
However, such processing may not be performed when, for example, a signal having an amplitude equal to or lower than the noise floor is removed in advance by processing such as clipping or can be ignored.

Furthermore, in the present embodiment, the coefficient Ca multiplied by the radar signal VS to generate the radar signal Va described above is set to “ratio of compression ratio of long pulse to short pulse”.
However, such a coefficient Ca is not limited to the above-described ratio, and, for example, a radar signal VS indicating a common target (not necessarily a target located at the boundary between the near range section and the far range section). , The instantaneous value of VL may be obtained as a matching value, or may be corrected.

  In the present embodiment, the threshold values th and TH are set to different values. However, as long as desired accuracy regarding positioning and distance measurement can be obtained, both may be the same or three or more different. It may be set to a value. When these threshold values are three or more (= N) different values, the aforementioned small amplitude period, medium amplitude period, and large amplitude period may be extended to four or more periods.

  Further, the peak power of the short pulse and the long pulse may be not equal if the ratio between the two is known and the calculation target and calculation procedure of the processing described above can be optimized. Good.

  In the present embodiment, the complement w ′ does not have to be a complement to “1” of the mixing ratio w. For example, the complement w ′ is appropriately set or changed to a value indicating the degree to which the target or clutter should be emphasized. Also good.

  Further, in the present embodiment, the weight W ′ may not be a complement to “1” of the weight W, and may be, for example, a value that enables compression of the difference in peak power between a short pulse and a long pulse, or positioning. Or a desired value in accordance with the needs of distance measurement or may be changed as appropriate.

In the present embodiment, the calculation in which the signal amplitude adjusting unit 31 multiplies the radar signal VS by the coefficient Ca (= (T2 · B2)) is, for example, that the radar signal VS is received power P, a predetermined coefficient α, and a constant. When logarithmic transformation is performed with respect to β as indicated by y in the following expression, αlog (T2 · B2) may be added to y. Since such multiplier αlog (T2 · B2) or log (T2 · B2) is uniquely determined based on the specifications relating to the long pulse and the short pulse, the values calculated in advance are stored in a table. It may be referred to as appropriate, or may be calculated step by step.
y = αlogP + β

Furthermore, in the present embodiment, the calculation of multiplying the radar signal VS by the coefficient Cn (= (T1 · B2)) by the noise amplitude adjusting unit 32 is performed by, for example, converting the noise component included in the radar signal VS to the coefficient α described above. When logarithm conversion is performed on the constant β as indicated by yn in the following expression, αlog (T1 · B2) may be added to the yn. Since such multiplier αlog (T1 · B2) or log (T1 · B2) is uniquely determined based on the specifications relating to the long pulse and the short pulse, the values calculated in advance are stored in a table. It may be referred to as appropriate, or may be calculated step by step.
yn = αlog (kTp / T1) + β

  Here, the true number (kTp / T1) included in the above equation is the power of noise included in the radar signal VS, and is the Boltzmann coefficient k (= 1.38 × 10 −23 J / K) and the absolute temperature Tp ( The unit is “Kelvin”) and the value (= k · Tp · B) generally given to the reception bandwidth B [Hz], and the reception bandwidth B is the occupied bandwidth of the short pulse (≈1 / T1). Calculated by substitution.

  The above-described thresholds th and TH may be set as constants in advance, or may be set or updated as appropriate (automatically) according to specifications relating to the short pulse and the long pulse. A person who operates the radar apparatus may be able to set or update as appropriate.

  Further, in the present embodiment, the start point r and the width (= R) of the middle range section are not specifically shown. For example, the start point r is set to the blind distance (= c · T2 / 2) of a long pulse. The width R may be set to “1 nautical mile” suitable for the needs of positioning and ranging performed using the radar according to the present embodiment. Here, c represents the propagation speed of a long pulse (short pulse).

  Also, the starting point r and the width R may be set as constants in advance, or may be set or updated as appropriate (automatically) according to specifications relating to the short pulse and the long pulse. A person who operates the radar apparatus may be able to set or update as appropriate.

  Furthermore, in the present embodiment, both the short pulse and the long pulse are wireless signals, but these short pulse and long pulse achieve the target positioning and ranging within a desired range. As long as it is a wave signal, it may be an optical signal (including a laser beam), a sound wave (including an ultrasonic wave), or any other signal.

  In the present invention, the indication method employed for the above-described positioning and distance measurement is not limited to PPI (Plan Position Indicator), and any indication method may be used.

  Further, the present invention is not limited to the above-described embodiments, and various configurations of the embodiments are possible within the scope of the present invention, and any improvements may be made to all or some of the components.

11 Transmitter 12L, 12S Receiver 13L, 13S Signal processor 20 Radar signal processor 30 Amplitude adjuster 31 Signal amplitude adjuster 32 Noise amplitude adjuster 33, 41 Mixing ratio calculator 34, 36, 42, 44 Multiplier 35 , 43 Correction setting unit (CV)
37, 45 Adder 40 Composition processing section

Claims (2)

Correspondence between the first received wave adapted to the pulse radar system is achieved on the range, and the compression ratio c for the second received waves the first received wave adapted for pulse compression radar system, the first Signal conversion means for multiplying the first received wave by a mixing ratio w (≦ 1) given as a monotonic non-decreasing function of the received wave level to obtain a converted wave of the first received wave;
Multiplying the first received wave by the ratio of the occupied band of the second received wave and the first received wave and the complement (= 1-w) of the mixing ratio w , the first received wave Noise conversion means for obtaining a converted wave of noise superimposed on
The product of the sum of the converted wave of the first received wave and the converted wave of noise superimposed on the first received wave and the mixing ratio W (≦ 1) given as a monotonically non-increasing function of the distance indicating the range And a synthesizing means for subjecting the radar signal processing to the sum of the product of the complement of the mixing ratio W (= (1-W)) and the signal obtained by the compression processing of the second received wave; A radar signal processing apparatus comprising: The radar signal processing apparatus according to claim 1, wherein
The mixing ratio w is
The radar signal processing apparatus, wherein the target detected by the pulse radar system is a value of the monotonous non-decreasing function with respect to the level of the first received wave when the target is a standard target.