JP2009068941A - Pulse radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively remove a background signal component included in an analog reception signal, and an error component superimposed on a signal by a processing in a system. <P>SOLUTION: A D/A converter 22 converts a digital reference background signal read from a storage part 21 into an analog signal, and outputs an analog reference background signal. An analog subtracter 13 performs subtraction between the analog reception signal and the analog reference background signal, and outputs an analog subtraction signal acquired by removing the background signal component from the analog reception signal. An A/D converter digitizes the analog subtraction signal, and outputs a digital subtraction signal. A correction part 24 corrects the digital subtraction signal, based on a digital correction signal read from the storage part 21, and outputs a digital response signal to be used for ranging of a target. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pulse radar device that receives a pulse signal received by a receiving antenna as an analog reception signal among pulse signals radiated into a radiation space where a target to be distance-measured exists, and performs distance measurement of the target. In particular, the present invention relates to removal of unnecessary signal components included in an analog reception signal.

  In the pulse radar apparatus, the analog received signal received by the receiving antenna includes an unnecessary background signal (I) in addition to the response signal (S) reflected and scattered by the target to be measured. ing. Examples of background signals include clutter signals and diffracted waves. The clutter signal is a reflection component depending on the surrounding environment other than the target, such as the ground (road surface). The diffracted wave is a noise component that diffracts a pulse transmitted from the transmitting antenna and directly enters the receiving antenna. Background signals that cause noise in distance measurement include non-reproducible signals (stochastic signals) and reproducible signals. The former can be removed to some extent by statistical processing such as calculating the average of the signal values. However, if statistical processing is applied to the latter, the signal will be emphasized and the S / I ratio will deteriorate.

  Patent Document 1 discloses an FM-CW radar that improves the S / N ratio by subtracting a digitized received signal from a reproducible background signal stored in advance. Patent Document 2 discloses a method for detecting a near object in which a digitally stored and reproducible background signal is converted to analog again, and a background signal component included in the received signal is removed by subtracting this from the received signal. A radar system is disclosed.

JP 2001-318143 A JP-T-2001-526767

  By the way, in general analog-digital conversion (hereinafter referred to as “A / D conversion”), a rounding error (hereinafter referred to as “quantization error”) is superimposed. In digital-analog conversion (hereinafter referred to as “D / A conversion”), aperture errors are also superimposed in addition to quantization errors. In Patent Documents 1 and 2 described above, these error components are not taken into consideration. Therefore, in Patent Document 1, when the intensity of the response signal is lower than the quantization error, a situation may occur in which the response signal itself is rounded by quantization due to A / D conversion and is eventually erased. On the other hand, in Patent Document 2, the response signal is not erased, but the strength of the response signal is smaller than the quantization error and the aperture error, and the S / I ratio cannot be sufficiently improved. In either case of Patent Documents 1 and 2, since the response signal intensity needs to be larger than the quantization error, an A / D converter or D / A conversion is performed as the S / I ratio decreases. In addition to increasing the number of output bits of the device, it is also necessary to use a memory with a larger capacity.

  The present invention has been made in view of such circumstances, and an object thereof is to effectively remove a background signal component included in an analog reception signal and an error component superimposed on the signal by processing in the system.

  In order to solve this problem, the present invention includes a storage unit, a D / A converter, an analog subtractor, an A / D converter, and a correction unit, and there is a target to be a distance measurement target. Provided is a pulse radar apparatus that receives a pulse signal received by a receiving antenna as an analog reception signal among pulse signals radiated to a radiating space to measure a target. The storage unit stores a digital reference background signal and a digital correction signal. The digital reference background signal is a digital signal for removing a background signal component caused by a background other than the target included in the analog reception signal. The digital correction signal is a digital signal for removing an error component superimposed on the signal by processing in the system including digitization and analogization of the signal. The D / A converter outputs an analog reference background signal by converting the digital reference background signal read from the storage unit into an analog signal. The analog subtracter outputs an analog subtraction signal obtained by removing the background signal component from the analog reception signal by performing subtraction between the analog reception signal and the analog reference background signal output from the D / A converter. The A / D converter outputs a digital subtraction signal by digitizing the analog subtraction signal. The correction unit corrects the digital subtraction signal output from the A / D converter based on the digital correction signal read from the storage unit, thereby outputting a digital response signal used for distance measurement of the target.

  Here, in the present invention, the digital reference background signal may be a signal obtained by digitizing an analog reception signal received without a target in the radiation space by an A / D converter. Further, the digital correction signal may be a signal obtained by digitizing an analog subtraction signal output from the analog subtractor by an A / D converter. This analog subtraction signal is obtained by subtracting an analog reception signal received without a target in the radiation space and an analog reference background signal output from the D / A converter by an analog subtractor.

  In the present invention, at least one of a first attenuator, a delay adjustment unit, and a second attenuator may be further provided. The first attenuator is provided between the D / A converter and the analog subtracter, and attenuates the gain of the analog reference background signal. The delay adjustment unit is provided between the storage unit and the D / A converter, and adjusts the delay amount of the analog reference background signal output from the D / A converter. The second attenuator is provided between the storage unit and the D / A converter, and adjusts the gain of the analog reference background signal output from the D / A converter. In addition, an evaluation unit that adjusts the delay of the delay adjustment unit or the gain of the second attenuation unit based on the digital reference background signal and the analog reception signal received in a state where the target is not present in the radiation space is further provided. May be.

  In the present invention, the D / A converter interpolates between the sample points of the input digital reference background signal using the previous and subsequent sample values, thereby providing an analog reference having higher resolution than the digital reference background signal. It is preferable to output a background signal.

  Furthermore, in the present invention, the D / A converter preferably sets the gain of the analog reference background signal variably according to the duty ratio. In this case, a low-pass filter that is provided between the D / A converter and the analog subtractor and that equalizes the analog reference background signal output from the D / A converter in terms of time may be further provided.

  According to the present invention, the background signal component included in the analog reception signal received by the receiving antenna is removed on an analog signal basis, and the error component included in the digital subtraction signal obtained by digitizing the processing result is digitally corrected. This is done on a digital signal basis using signals. This digital correction signal is a signal for removing an error component superimposed on the signal by processing in the system including digitization and analogization of the signal, and is stored in advance in the storage unit. Through such two-stage processing, the background signal component can be effectively removed, and both the quantization error superimposed on the signal by A / D conversion and the aperture error superimposed on the signal by D / A conversion are also effectively removed. can do.

(Background signal removal model)
First, prior to description of a specific configuration of the pulse radar device according to the present embodiment, an outline of background signal removal will be described. FIG. 1 is an explanatory diagram of background signal removal. FIG. 4A shows the waveform of an analog reception signal received in a situation where there is no target for distance measurement in the radiation space (hereinafter referred to as “reference environment”). The analog received signal in the reference environment is the background signal itself. As shown in FIG. 5B, the analog reception signal is digitized to generate a digital reference background signal. This digital reference background signal includes a quantization error to be superimposed by A / D conversion. Even if the target exists, if the S / I ratio of the analog reception signal is low, the analog reception signal can be regarded as a background signal. In this case, this is treated as an analog reception signal in the reference environment. . This is effective when detecting an object that exists constantly, such as a side groove on the road surface, as a target.

  FIG. 6C is an ideal form of a signal (analog subtraction signal) obtained by converting the digital reference background signal of FIG. Since a quantization error is superimposed on the digital reference background signal at the time of A / D conversion, the analog subtraction signal should be a signal of only the quantization error. However, in actuality, quantization error and aperture error are further superimposed on the analog reference background signal during D / A conversion. Therefore, the actual analog subtraction signal is a composite signal of the quantization error and the aperture error as shown in FIG. In this embodiment, in order to remove these error components, an analog subtraction signal is prepared as shown in FIG. 5E, and a digital correction signal obtained by digitizing the analog subtraction signal is stored in the system. The digital correction signal is used to remove an error component superimposed on the signal by processing in the system including digitization and analogization of the signal.

  When a digital subtraction signal obtained by digitizing the analog subtraction signal in FIG. 5D and the digital correction signal in FIG. 5E are subtracted, a flat signal is obtained as shown in FIG. Also, in the situation where the target exists in the radiation space (hereinafter referred to as “ranging environment”), even if the target fluctuates, the effects of quantization error and aperture error are removed as shown in FIG. An ideal digital response signal can be obtained. The present invention pays attention to this point, and the distance measurement accuracy is improved by performing the distance measurement of the target using such a digital response signal. On the other hand, as shown in FIG. 11H, it is difficult to ensure sufficient distance measurement accuracy with the digital response signal in which the error component is still superimposed.

(Pulse radar device)
FIG. 2 is a configuration diagram of the pulse radar device according to the present embodiment, which implements the above-described concept in hardware. This pulse radar apparatus is roughly classified into an analog processing unit 1 that performs processing based on an analog signal and a digital processing unit 2 that performs processing based on a digital signal. The analog processing unit 1 mainly includes a reception antenna 11, a radar circuit 12, and an analog subtractor 13, and receives a transmission pulse reflected mainly by the target T or the like. The receiving antenna 11 is used in a transmission system (in a ranging environment) in a state where a target T to be measured exists in a pulse radiation space (a ranging environment) or in a state in which a target T to be measured does not exist (reference environment). A transmission pulse transmitted by a transmission antenna (not shown) is received. The radar circuit 12 samples the reception pulse received by the reception antenna 11 and outputs an analog reception signal. The analog subtractor 13 subtracts the analog reception signal output from the radar circuit 12 and the analog reference background signal output from the D / A converter 22 in the digital processing unit 2, and analog subtracts the subtraction result. Output as a signal.

  The analog processing unit 1 includes an amplifier 14, a low-pass filter 15, and an attenuator 16 in addition to the circuit elements described above. The amplifier 14 is provided between the analog subtractor 13 and the digital processing unit 2 (more precisely, the A / D converter 23), and both when acquiring a digital correction signal and when acquiring a digital response signal. The analog subtraction signal output by the analog subtractor 13 is amplified. The low pass filter 15 and the attenuator 16 are provided between the D / A converter 22 in the digital processing unit 2 and the analog subtractor 13. The attenuator 16 attenuates the gain of the analog reference background signal output from the D / A converter 22 by the amount of gain amplification of the signal in the processing system from the analog subtractor 13 to the A / D converter 23. As the attenuator 16, for example, an attenuator can be used, and the digital reference background signal output by the D / A converter 22 is attenuated to the same gain as the analog reception signal.

  The digital processing unit 2 mainly includes a storage unit 21, a D / A converter 22, an A / D converter 23, and a correction unit 24, and an analog reception mainly received by the analog processing unit 1. A digital response signal is extracted from the signal. A signal necessary for performing this digital processing or a signal generated by this digital processing is stored / stored in the storage unit 21 and read out as necessary. There are three types of signals stored in the storage unit 21: a digital reference background signal, a digital correction signal, and a digital response signal. The digital reference background signal is the signal shown in FIG. 1B, and is used to remove the background signal component caused by the background other than the target T included in the analog reception signal received in the reference environment. This signal is obtained by digitizing the analog received signal in the reference environment by the A / D converter 23. The digital correction signal is the signal shown in FIG. 5E, and is used to correct an error component generated in processing inside the system. This signal is obtained by digitizing the subtraction value between the analog received signal in the standard environment and the analog reference background signal output by the D / A converter 22 by the A / D converter 23. The digital response signal is the signal shown in FIG. 5H and is used for ranging of the target T. This signal is obtained by correcting the digital subtraction signal output from the A / D converter 23 based on the digital correction signal read from the storage unit 21 in the ranging environment.

  The correction unit 24 is used in the ranging environment, and is a digitized digital subtraction signal input from the analog subtractor 13 in the analog processing unit 1 via the A / D converter 23 in order to extract a digital response signal. And the digital correction signal read from the storage unit 21 is subtracted to output a digital response signal. The digital response signal is treated as distance measurement target data, and thereby the distance to the target T, which is the distance measurement target, is calculated.

  The digital processing unit 2 includes an evaluation unit 25, a background signal adjustment unit 26, a noise signal adjustment unit 27, and a D / A converter 28 in addition to the circuit elements described above. The evaluation unit 25 is provided on the output side of the A / D converter 23 in the digital processing unit 2. The background signal adjustment unit 26 is provided between the storage unit 21 and the D / A converter 22, reads the digital reference background signal stored in the storage unit 21, and adjusts its gain (amplitude) and Adjust the delay amount (phase). The background signal adjustment unit 26 includes a delay adjustment unit 26a and a gain adjustment unit 26b. The noise signal adjustment unit 27 reads the digital correction signal stored in the storage unit 21 and performs gain control on the amplifier 14 via the D / A converter 28.

  In the present embodiment, the reason why the low pass filter 15 is provided is to generate an analog reference background signal with higher accuracy than the resolution of the amplitude (gain) of the D / A converter 22. The D / A converter 22 outputs a voltage value corresponding to the output value with a duty ratio. The low-pass filter 15 equalizes this duty ratio in time and outputs it as an analog reference background signal. As a result, the voltage of the analog reference background signal can be set at a level higher than the original resolution of the A / D converter 22, and a reference signal with higher accuracy can be obtained.

  FIG. 3 is a flowchart of the background signal removal process. From the initial state where no signal is stored in the storage unit 21, (1) a procedure until obtaining a digital reference background signal, and (2) until obtaining a digital correction signal. And (3) a procedure until obtaining a digital response signal which is distance measurement target data is shown in an integrated manner. Both the acquisition of the digital reference background signal and the digital correction signal is performed based on the analog reception signal received in the reference environment. On the other hand, the acquisition of the digital response signal is performed based on the analog reception signal received in the ranging environment. The analog reception signal is acquired via the reception antenna 11 and the radar circuit 12 every time it is necessary. At this time, if analog reception signals in each environment are stored, it is not necessary to acquire these signals a plurality of times.

  First, in step 1, a digital reference background signal is acquired. Specifically, an analog reception signal is acquired by the reception antenna 11 and the radar circuit 12 in a reference environment, that is, in a state where the target T does not exist in the radiation space. Theoretically, the analog received signal includes only the background signal component caused by the background other than the target T. The acquired analog reception signal is digitized by the A / D converter 23 and then stored in the storage unit 21 as a digital reference background signal. Note that the processing here is performed via the analog subtractor 13, the amplifier 14, and the correction unit 24, but in this state, the digital reference background signal and the digital correction signal are not yet stored in the storage unit 21. Therefore, it should be noted that these units 13, 14, and 24 do not perform processing as will be described later, and the input is directly output. If it is determined that the signal acquisition by the receiving antenna 11 or the like is not normal and the digital reference background signal is not appropriate, the acquisition of the digital reference background signal is repeated until it is acquired normally.

  In step 2, the digital reference background signal is read from the storage unit 21 and the analog reference background signal analogized by the D / A converter 22 is input to the analog subtractor 13. In the subsequent step 3, the analog subtractor 13 subtracts the analog reference background signal and the received signal, and outputs an analog subtracted signal. The output analog subtraction signal is digitized by the A / D converter 23 and output as a digital subtraction signal.

  In Step 4, the delay amount (phase difference) of the digital subtraction signal input to the digital processing unit 2 is evaluated by the evaluation unit 25, and the delay amount of the digital reference background signal input to the A / D converter 23 is appropriate. It is determined whether or not there is. When the delay amount of the digital subtraction signal is not the minimum (min), it is determined that the digital reference background signal input to the A / D converter 23 is not appropriate. In this case, the process proceeds to Step 5. In Step 5, based on the delay amount evaluated in Step 4, the delay amount of the digital reference background signal, that is, the output timing is adjusted with respect to the delay adjustment unit 26a in the background signal adjustment unit 26. Then, it returns to step 2. On the other hand, if the delay amount of the digital subtraction signal is the smallest in step 4, it is determined that the digital reference background signal input to the A / D converter 23 is appropriate, and the process proceeds to step 6.

  In step 6, as in step 2, the reference background signal is read from the storage unit 21, and the analog reference background signal is input to the analog subtractor 13 by the D / A converter 22. In subsequent step 7, as in step 3, the analog subtractor 13 subtracts the analog reference background signal and the analog reception signal, and outputs an analog subtraction signal. The output analog subtraction signal is digitized by the A / D converter 23 and output as a digital subtraction signal.

  In step 8, the gain of the digital subtraction signal input to the digital processing unit 2 in step 7 is evaluated by the evaluation unit 25, and whether or not the gain of the digital reference background signal input to the A / D converter 23 is appropriate. Is judged. When the gain of the digital subtraction signal is not the minimum (min), it is determined that the digital reference background signal input to the A / D converter 23 is not appropriate. In this case, the process proceeds to step 9, and the gain of the digital reference background signal is adjusted with respect to the gain adjustment unit 26 b in the background signal adjustment unit 26 based on the gain evaluated in step 8. Then, it returns to step 6. On the other hand, if the gain of the digital subtraction signal is minimum in step 8, it is determined that the digital reference background signal input to the A / D converter 23 is appropriate, and the process proceeds to step 10.

  In step 10, gain control for the amplifier 14 is performed. The digital subtraction signal when determined to be appropriate in step 8 is provisionally stored in the storage unit 21 as a digital correction signal. Then, gain control for the amplifier 14 is performed based on the digital correction signal. In this gain control, a gain is calculated by the noise signal adjustment unit 27 so that the input range width defined by the A / D converter 23 is obtained, and the calculation result is amplified via the D / A converter 28. 14 is reflected.

  In step 11 following step 10, a digital correction signal is acquired. First, a reception pulse in the reference environment is received by the reception antenna 11 and an analog reception signal sampled by the radar circuit 12 is output. Then, the analog reception signal is subtracted from the analog reference background signal by the analog subtractor 13 to output an analog subtraction signal. The output analog subtraction signal is amplified by the amplifier 14. The amplified analog subtraction signal is further digitized by the A / D converter 23 and stored in the storage unit 21 as a digital correction signal. The digital subtraction signal is input to the correction unit 24, but at this stage, the digital correction signal is not yet determined in the storage unit 21. Therefore, the correction unit 24 outputs the input digital subtraction signal as it is. Similarly to step 1, the control unit evaluates the digital correction signal. For example, when analog subtraction, amplification processing, A / D conversion processing, or the like is not normally performed and it is determined that the digital correction signal is not appropriate, acquisition of the digital correction signal is repeated until this is appropriately acquired.

  In step 12, a digital response signal is acquired. First, a reception pulse in a ranging environment is received by the reception antenna 11 and an analog reception signal sampled by the radar circuit 12 is output. Then, the analog subtractor 13 subtracts the analog reception signal and the analog reference background signal and outputs an analog subtraction signal. The output analog subtraction signal is amplified by the amplifier 14. The amplified analog subtraction signal is further digitized by the A / D converter 23 to become a digital subtraction signal. The digital subtraction signal in the ranging environment is subtracted from the digital correction signal by the correction unit 24 and stored in the storage unit 21 as a digital response signal. Thereafter, every time an analog reception signal is received / acquired, the digital background signal and the digital correction signal are read from the storage unit 21, and the subtraction / correction process based on them is repeated.

  FIG. 4 is an explanatory diagram of the D / A converter 22 in steps 2 and 6. As shown in FIG. 5A, when the output rate is low and the number of samples is small, the resolution of the delay amount is low and the removal rate of the digital reference background signal is low. Also, as shown in FIG. 5B, when the output rate is high and the number of samples is high, the resolution of the delay amount is also high. On the other hand, as the number of samples increases, the calculation load also increases, which may impair real-time processing. Therefore, as shown in FIG. 5C, the analog reference background signal is not changed without changing the data amount by increasing the output rate of the D / A converter 22 higher than the number of data points of the digital reference background signal while the number of samples is small. The resolution of the delay amount can be improved. Specifically, the D / A converter 22 interpolates between the sample points of the input digital reference background signal using the previous and subsequent sample values, thereby providing an analog reference having a higher resolution than the digital reference background signal. Outputs a background signal.

  FIG. 5 is a diagram for explaining the background signal removal simulation. FIG. 5A shows the characteristics of the analog reception signal and the background signal in the ranging environment before the background signal is removed. In order to extract the digital response signal from the analog reception signal, it is necessary to subtract the background signal in the reference environment. FIG. 6B shows the characteristics of the digital subtraction signal obtained by subtracting the digital reference background signal from the analog reception signal of FIG. The digital subtraction signal in the ranging environment includes a quantization error and an aperture error in the digital response signal to be measured. On the other hand, the digital subtraction signal in the reference environment is a quantization error and an aperture error itself. Accordingly, as shown in FIG. 5C, the response signal from the target T is digitally obtained by subtracting the digital subtraction signal in the ranging environment and that (digital correction signal) in the reference environment by the correction unit 24. A digital response signal can be obtained.

  As described above, in this embodiment, the background signal component included in the analog reception signal received by the reception antenna 11 is removed on an analog signal basis, and the error component included in the digital subtraction signal obtained by digitizing the processing result is obtained. Removal is performed on a digital signal basis using a digital correction signal. The digital correction signal is a signal for removing an error component superimposed on the signal by processing in the system including digitization and analogization of the signal, and is stored in the storage unit 21 in advance. As described above, both the quantization error in the A / D conversion and the aperture error in the D / A conversion are reproducible. This embodiment pays attention to this point, reproduces these error components in the reference environment, and generates a digital correction signal for removing them. Then, by performing the two-stage process of removing the background signal component and removing the error component, it is possible to effectively remove any of the background signal component, the quantization error, and the aperture error.

  According to this embodiment, it is not necessary to increase the number of output bits of the A / D converter 23 and the D / A converter 22, and even if the response signal intensity is equal to or less than the quantization error, the S / It becomes possible to improve the I ratio.

  Furthermore, according to the present embodiment, it is possible to effectively remove stationary interference waves such as direct waves from the transmitting antenna and ground reflected waves. The gain resolution generally depends on the number of output bits of A / D conversion, but according to the present embodiment, by performing subtraction on both the analog base and the digital base, the gain resolution can be reduced to “MIN ( A / D conversion bit number, D / A conversion bit number) + log2 (I / S) ". Although the present embodiment assumes removal of quantization error and aperture error, the present invention is not limited to this, and includes, for example, statistical errors such as glitches generated in the D / A converter 22. The present invention can be widely applied to various error components superimposed on a signal by processing in the system.

  In this embodiment, the digital reference background signal gain is adjusted (steps 6 to 9) after adjusting the delay amount of the digital reference background signal (steps 2 to 5). The delay amount adjustment may be performed after the above, or both may be performed in parallel.

  In this embodiment, the delay amount and gain of the digital reference background signal are adjusted on a digital basis. However, this adjustment may be performed on an analog basis. In this case, a delay amount / gain subtraction value between the digital reference background signal and the analog reception signal is obtained, and the delay amount / gain of the digital reference background signal with respect to the background signal adjustment unit 26 is adjusted based on the subtraction value. The evaluation unit 25 is not necessarily provided in the digital processing unit 2 and may read the analog subtraction signal and adjust the background signal adjustment unit 26. The evaluation unit 25 does not wait for the output of the analog subtraction signal from the analog subtractor 13 (input to the A / D converter 23), and the digital reference background signal read from the storage unit 21 and the radar circuit 12 output It is also possible to directly read and adjust the received analog received signal.

Illustration of background signal removal Configuration diagram of pulse radar device Background signal removal process flowchart Illustration of D / A converter Illustration of simulating background signal removal

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Analog processing part 11 Reception antenna 12 Radar circuit 13 Analog subtractor 14 Amplifier 15 Low pass filter 16 Attenuator 2 Digital processing part 21 Memory | storage part 22,28 D / A converter 23 A / D converter 24 Correction | amendment part 25 Evaluation part 26 Background signal adjustment unit 26a Delay adjustment unit 26b Gain adjustment unit 27 Noise signal adjustment unit

Claims (9)

Among the pulse signals radiated to the radiation space where the target to be measured exists, the pulse signal received by the receiving antenna is received as an analog received signal, and in the pulse radar device for measuring the target,
A digital reference background signal for removing a background signal component caused by a background other than the target included in the analog reception signal, and an error component superimposed on the signal by processing in the system including digitization and analogization of the signal A storage unit for storing a digital correction signal for removing
A digital-to-analog converter that outputs an analog reference background signal by analogizing the digital reference background signal read from the storage unit;
An analog subtractor that outputs an analog subtracted signal obtained by removing the background signal component from the analog received signal by subtracting the analog received signal and the analog reference background signal output from the digital-analog converter; ,
An analog-to-digital converter that outputs a digital subtraction signal by digitizing the analog subtraction signal;
Correction for outputting a digital response signal used for ranging of the target by correcting the digital subtraction signal output from the analog-to-digital converter based on the digital correction signal read from the storage unit. And a pulse radar device.   The digital reference background signal is a signal obtained by digitizing the analog reception signal received without the target in the radiation space by the analog-to-digital converter. Pulse radar equipment.   The digital correction signal is obtained by subtracting the analog reception signal received without the target in the radiation space and the analog reference background signal output from the digital-analog converter by the analog subtractor. 3. The pulse radar device according to claim 1, wherein the analog subtracted signal output from the analog subtractor is a signal obtained by digitizing the analog subtracted signal by the analog-digital converter.   4. The apparatus according to claim 1, further comprising a first attenuator that is provided between the digital-analog converter and the analog subtractor and attenuates a gain of the analog reference background signal. 5. The pulse radar device described in the above.   A delay adjustment unit is provided between the storage unit and the digital-analog converter and further adjusts a delay amount of the analog reference background signal output from the digital-analog converter. The pulse radar device according to any one of claims 1 to 4.   A second attenuating unit that is provided between the storage unit and the digital-analog converter and adjusts a gain of the analog reference background signal output from the digital-analog converter; The pulse radar device according to any one of claims 1 to 5.   Evaluation for adjusting the delay of the delay adjustment unit or the gain of the second attenuation unit based on the digital reference background signal and the analog reception signal received without the target in the radiation space The pulse radar device according to claim 5, further comprising a unit.   The digital-to-analog converter interpolates between the sample points of the input digital reference background signal using previous and subsequent sample values, thereby converting the analog reference background signal having higher resolution than the digital reference background signal. 8. The pulse radar device according to claim 1, wherein the pulse radar device outputs the pulse radar device. The digital-to-analog converter sets the gain of the analog reference background signal variably according to a duty ratio
The low-pass filter is provided between the digital-analog converter and the analog subtractor, and temporally equalizes the analog reference background signal output from the digital-analog converter. To 8. The pulse radar device according to any one of 8 to 8.

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