JP2856719B2 - Signal extraction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus having a function of compressing a received signal, and more particularly to a signal extracting apparatus which facilitates detection of a small signal buried in a range sidelobe of a large received signal.

[0002]

2. Description of the Related Art A radar apparatus having a function of compressing a received signal transmits a long pulse modulated with an appropriate modulation signal in order to increase an average transmission power (energy) and obtain a required distance resolution. A received signal is compressed by receiving a reflected signal from a target and performing a correlation process between the received signal and a modulated signal added to a transmission pulse. At this time,
Simply compressing the received signal not only compresses the received signal from each distance, but also generates an unnecessary signal called a range side lobe as shown in FIG. This will hinder the extraction of small received signals.

For this reason, a range side lobe has been reduced by selecting a modulation signal having a small range side lobe or by performing appropriate weighting on the modulation signal when performing a correlation process. However, it was difficult to make the range sidelobe sufficiently small.

FIG. 6 shows an example of the configuration of a conventional radar.
The transmitter 1 generates a transmission signal. At this time, the transmission signal is modulated with the modulation signal generated by the transmission modulation signal generator 2. The transmission / reception switch 3 converts the output signal of the transmitter 1 into an antenna 4
And sends the signal received by the antenna 4 to the receiver 5 side. The receiver 5 converts the received signal into Ι (In-phase
e) Component and Q (Quadrature-phase)
The component is converted to an analog video signal.

[0005] A coherent signal generator 6 generates a synchronizing signal necessary for generating a transmission signal and an analog video signal of an I component and a Q component. Analog-to-digital converters (hereinafter referred to as Α / D converters) 7 and 8 respectively convert Ι-component and Q-component analog video signals output from the receiver 5 into digital signals. The reception data compressor 9 performs a compression process on the reception signal by performing a correlation process between the reception signal and the transmission modulation signal from the transmission modulation signal generator 2. The output signal of the reception data compressor 9 is extracted and output by the target detector 17 by a threshold detection method with a signal having a predetermined amplitude (detection threshold) or more. The detection threshold is set from a detection rate required for the radar and a false alarm probability (probability of erroneously detecting noise), and a signal exceeding the detection threshold is unconditionally extracted as a target signal.

[0006]

The target signal extraction in this conventional radar apparatus extracts a signal having an amplitude value equal to or larger than a certain value unconditionally, so that a range side signal generated when a received signal is compressed is extracted. Due to the lobe, a small amplitude signal buried in the range side lobe of the large amplitude signal cannot be detected.

The present invention has been made to solve the above-described problem, and has as its object to prevent a range sidelobe of a large received signal from hindering the extraction of a small received signal.

[0008]

The present invention is based on the following concept. A signal obtained when one received signal to be extracted is compressed is composed of a compressed received signal and a range side lobe, as conceptually shown in FIG. When the received signal is composed of a large number of received signals, as shown in FIG. 7B, the received signal compressed by each received signal and the range side lobe are added. Therefore, a signal having a large amplitude value is obtained from the result of compression of the received signal, the pre-compressed estimated reception data to be given is generated and removed from the received signal, and the received signal is compressed again to obtain the large amplitude value. The range side lobe relating to the large amplitude signal is removed together with the signal, so that a smaller received signal can be easily extracted.

In order to generate estimated reception data, a transmission modulation signal is used, and the amplitude of the signal is changed so that the amplitude of the signal when compressed is the same as the amplitude of the signal after compression. Is possible.

In the above description, the estimated received data is removed from the received signal. However, a signal pattern including a range side lobe when the prepared received signal is compressed is prepared, and the amplitude of the signal pattern is removed. The same effect can be obtained by changing the amplitude of the received signal and removing it from the compression result of the received signal.

A signal extraction device according to the present invention is based on the above-described principle, and has a configuration in which a reception signal storage unit that stores a reception signal as reception data, and a correlation process between a modulation signal and reception data are performed. A reception data compressor for compressing data, a maximum signal detector for obtaining a maximum amplitude signal from an output signal of the reception data compressor, and giving the same amplitude value as the maximum amplitude signal when compressed by the reception data compressor. An estimated reception data generator that generates estimated reception data;
An unnecessary signal remover for subtracting and removing the estimated received data from the received data stored in the received signal storage, wherein the received data compressor stores the received data stored in the received signal storage. And a maximum amplitude signal is obtained from the output signal by the maximum signal detector, and is used as an output signal of the signal extraction device. Estimated reception data corresponding to the obtained maximum amplitude signal is obtained by the estimation reception data generator. A series of signal processing of generating and removing the received data from the received data with the unnecessary signal remover and replacing the received data in the received signal storage with the received data from which the estimated received data has been removed is performed at a required amplitude value. Is repeatedly performed until the output signal is obtained.

According to the present invention, a received data compressor for compressing a received signal by performing a correlation process between the received signal and the modulated signal, and a compressed data storage for storing an output signal of the received data compressor as compressed data A maximum signal detector for obtaining a maximum amplitude signal from the compressed data, and a reference compressed signal storage for storing a signal waveform obtained when the received signal to be extracted is compressed by the received data compressor as a reference compressed signal. An estimated compressed signal generator that generates an estimated compressed signal having an amplitude value of the maximum amplitude signal from the reference compressed signal; and an unnecessary signal eliminator that subtracts the estimated compressed signal from the compressed data to remove a maximum amplitude signal. A maximum amplitude signal is obtained from the output signal by the maximum signal detector, and the output signal of the signal extraction device is obtained. And an estimated compressed signal having an amplitude value of the determined maximum amplitude signal is generated by the estimated compressed signal generator, and the generated estimated compressed signal is removed from the compressed data by the unnecessary signal remover. A signal extraction device is obtained, wherein a series of signal processing of replacing the compressed data in the compressed data storage with the compressed data from which the signal has been removed is repeated until an output signal of a required amplitude value is obtained. .

It is to be noted that, instead of the method of sequentially obtaining the maximum amplitude signal, a set value for the output signal of the received data compressor is provided, and signals exceeding the set value are output collectively and signal processing for removing the signal is performed. Alternatively, the setting value may be sequentially reduced until an output signal having a required amplitude value is obtained.

Further, the apparatus further comprises an output signal storage unit for storing the output signal value by dividing the output signal value into attributes such as a distance and a Doppler frequency, and storing the same attribute as the output signal value already stored in the signal processing process. When a new output signal value is obtained, the output signal value may be added to the output signal value stored in the output signal storage, and the addition result may be output.

Further, a Doppler coefficient generator for generating a predetermined Doppler coefficient may be provided, and the reception data compressor may perform Doppler correction based on the Doppler coefficient and perform compression processing.

[0016]

Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a basic configuration of a signal extraction device according to the present invention, and FIG.
1 is a configuration diagram illustrating a first embodiment of the present invention in a case where the signal extraction device of FIG. 1 is applied to a radar device. That is, FIG.
Is a configuration in which a signal extraction device (within a broken line) according to the present invention is added to the configuration of the radar device having the pulse compression function shown in FIG. 6, and from the transmitter 1 to the A / D converters 7 and 8, FIG. It has the same configuration as a conventional radar device.

The transmitter 1 generates a transmission signal. At this time, an appropriate modulation signal is added to the transmission signal by the transmission modulation signal generator 2. The transmission / reception switch 3 sends the output signal of the transmitter 1 to the antenna 4 and sends the signal received by the antenna 4 to the receiver 5 side. The receiver 5 converts the received signal into an analog video signal having a Ι component and a Q component. The coherent signal generator 6 generates a synchronizing signal necessary for generating a transmission signal and generating analog video signals of the Ι component and the Q component. The Α / D converters 7 and 8 convert the ビ デ オ component and Q component analog video signals of the receiver 5 into digital signals, respectively.

The Ι component and Q component video signals converted into digital signals are stored in received signal storages 11 and 12, respectively. The reception data compressor 9 performs a compression process on the received signal by performing a correlation process between the stored reception signal and the transmission modulation signal from the transmission modulation signal generator 2. The maximum signal detector 10 detects the signal of the maximum amplitude among the compressed signals, outputs the signal as an output signal of the present apparatus, and outputs information on the amplitude and position of the detected signal to the estimated reception data generator 13. The estimated received data generator 13 generates a signal corresponding to the detected maximum amplitude signal (same amplitude) based on the information of the detected signal, the transmission modulation signal of the transmission modulation signal generator 2 and the compression ratio of the reception data compressor 9. , The same modulation, and the same position) as I-component and Q-component estimated reception data, and output them to the unnecessary signal removers 14 and 15. Unwanted signal removers 14, 1
5 is a received signal (digital video signal of I component and Q component) stored in the received signal storages 11 and 12, respectively.
Is subtracted from the estimated received data, and the data is updated with the processing result.

According to the above, the signal having the maximum amplitude is extracted from the received data and removed from the received data by one signal processing. If the above processing is repeated on the received data after processing until a signal having a required amplitude value is obtained, it is possible to sequentially extract large signals, and to successively remove them, to extract smaller signals. Can be prevented.

The above situation is shown in FIG. FIG. 3 shows an example in which a Μ-sequence phase code modulation signal having a code length of 10 is used as a transmission modulation signal. In FIG. 3, “0” indicates a phase of 0 °, and “1” indicates a phase of 180 °. FIG.
(A) shows the positional relationship of the targets and the reflected signals from each target. Note that the intensity of the reflected signal from each target was the same. The reflected signal from each target stores and receives the phase code information of the transmission modulation signal, but the positional relationship between targets 1 to 3 is such that each reflected signal overlaps and is received.
Will be obtained. This becomes the data of the reception signal storages 11 and 12.

Next, the stored received signal data (FIG. 3)
The compressed signal shown in FIG. 3C is obtained by correlating (b)) with the transmission modulation signal and performing compression processing. Goals 1 to 3
It can be seen that range side lobes are generated on both sides of. By performing the maximum signal detection process from this compressed signal,
The maximum amplitude signal is extracted at the position of the target 3. The estimated reception data shown in FIG. 3D is generated from the extracted maximum amplitude signal, and subtraction processing (removal of unnecessary signals) from the reception signal storage data shown in FIG. 3B is performed. Obtain the signal of e) and rewrite the received data in the received signal storage. By repeating the above processing, it is possible to sequentially extract targets from the large amplitude signal, and to sequentially suppress large signal components that are unnecessary for extraction in the next processing.

In FIG. 3, since the reflected signal intensities of the targets 1 to 3 are the same, although the range side lobe is affected in FIG.
It seems that 3 extractions are possible. However, in practice, when a signal reflected from the target is mixed and large and has a long transmission pulse length, the small-amplitude signal is buried in the range sidelobe of the large-amplitude signal as shown in FIG. Therefore, it is difficult to extract a small target using the conventional method.

FIG. 4 shows the configuration of another embodiment. In the present embodiment, the received signal compressed by the received data compressor 9 is stored in the compressed data storage 11a, and the maximum signal detector 10 detects the maximum amplitude signal from the stored compressed data and outputs it as an output signal. An estimated compressed signal generator 13a generates an estimated compressed signal from the detected maximum amplitude signal, and a subtraction process between the data stored in the compressed data storage 11a and the estimated compressed signal is performed by an unnecessary signal remover 14a. The data in the compressed data storage 11a is updated with the result. The reference compressed signal storage 18 stores a reference signal waveform obtained when the received signal to be extracted is compressed by the received data compressor 9 as a reference compressed signal. It is generated using the information (amplitude, position) of the maximum amplitude signal detected at 10 and the reference compressed signal stored in the reference compressed signal storage 18.

As described above, the signal having the maximum amplitude value is extracted and removed from the received data by one signal processing. If the above processing is repeated on the processed received data until a signal having a required amplitude value is obtained, it is possible to sequentially extract large signals, and to sequentially remove them, extract smaller signals. Can be prevented.

In the above-described two embodiments, the target extraction and the subtraction processing are performed by sequentially detecting the maximum amplitude signal. However, the detection value of the maximum signal detector 10 is set, and the set value is set. It is also possible to obtain a large-amplitude signal exceeding the above as an output signal and to remove the same repeatedly by lowering the detection value until an output signal having a required amplitude or more is obtained.

In the above embodiments, when the target Doppler shift frequency is large and the influence of the Doppler shift cannot be ignored in the correlation processing in the received data compressor, as shown in FIG. A coefficient generator 16 is added, and the received data compressor 9 includes a Doppler coefficient generator 16.
By performing Doppler correction using the Doppler coefficient (fd0 to fdm) and performing compression processing, a compression loss due to Doppler shift can be avoided.

When the reflected signals from a plurality of targets are superimposed and received, the amplitude value of the output signal of the compression processing is different from that of the signal received from a single target. In the case of FIG. 3, since the code length is 10, the amplitude value after compression in the case of a single target is 10, but as shown in FIGS. 3 (c) and 3 (f), it is slightly affected by the range side lobe. Error has occurred. Further, as described above, the Doppler shift component also causes an error.

Therefore, for example, an output signal storage for storing the output signal values from the target extraction device in the above two embodiments in the attributes of the distance axis and the Doppler frequency axis is added, and the above signal processing is sequentially performed. In the process of doing
If an output signal value with the same attribute as the already stored output signal value is obtained, the effect of the above error is reduced by adding the output signal value to the stored output signal. it can.

[0029]

As described above, the signal extracting apparatus according to the present invention obtains the maximum amplitude signal from the received signal, sets it as the output signal, and removes the estimated received data corresponding to the maximum amplitude signal from the received signal. Signal processing is repeated until an output signal having a required amplitude value or more is obtained, so that large signals can be sequentially extracted, and they are sequentially removed, so that extraction of a smaller signal is not hindered. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a signal extraction device of the present invention.

FIG. 2 is a diagram showing a configuration of a first embodiment of the present invention in a case where the signal extraction device of FIG. 1 is applied to a radar device.

FIG. 3 is a diagram for explaining an outline of processing in the embodiment shown in FIG. 2;

FIG. 4 is a diagram showing a configuration of another embodiment of the present invention.

FIG. 5 is a configuration diagram showing still another embodiment when Doppler correction is considered in the embodiment shown in FIG. 2;

FIG. 6 is a configuration diagram showing a conventional example.

FIG. 7 is a waveform diagram for explaining a compressed signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitter 2 Transmit modulation signal generator 3 Transmission / reception switch 4 Antenna 5 Receiver 6 Coherent signal generator 7,8 A / D converter 9 Receive data compressor 10 Maximum signal detector 11,12 Receive signal memory lla compression Data storage 13 Estimated reception data generator 13a Estimated compressed signal generator 14, 15 Unwanted signal remover 16 Doppler coefficient generator 17 Target detector 18 Reference compressed signal storage

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takaaki Hayashi 5-7-1 Shiba, Minato-ku, Tokyo Within NEC Corporation (72) Inventor Shigeharu Takemura 5-7-1 Shiba, Minato-ku, Tokyo NEC (72) Inventor Hiroshi Nakamura 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-9-90022 (JP, A) JP-A-9-26480 (JP JP-A-8-75846 (JP, A) JP-A-8-68851 (JP, A) JP-A-6-342062 (JP, A) JP-A-6-109833 (JP, A) 4-357485 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/95

Claims (8)

(57) [Claims] 1. A radar device for transmitting a signal modulated by a modulation signal, a reception signal storage device storing a reception signal as reception data, and performing a correlation process between the modulation signal and the reception data to compress the reception data. A reception data compressor, a maximum signal detector for obtaining a maximum amplitude signal from an output signal of the reception data compressor, and estimated reception data that gives the same amplitude value as the maximum amplitude signal when compressed by the reception data compressor. An estimated received data generator to generate, and an unnecessary signal remover that subtracts and removes the estimated received data from the received data stored in the received signal storage, and is stored in the received signal storage. Received data is compressed by the received data compressor, a maximum amplitude signal is obtained from the output signal by the maximum signal detector, and is used as an output signal of the signal extraction device. In addition, estimated reception data corresponding to the determined maximum amplitude signal is generated by the estimated reception data generator, and is removed from the reception data by the unnecessary signal remover. A signal extracting apparatus, wherein a series of signal processing of replacing the received data in a signal storage unit is repeated until an output signal having a required amplitude value is obtained. 2. The signal extraction device according to claim 1, wherein
Instead of a method of sequentially obtaining the maximum amplitude signal, a set value for the output signal of the received data compressor is provided, and a signal exceeding this set value is output collectively and the signal processing for eliminating the required amplitude value is performed. A signal extraction device for sequentially reducing the set value until an output signal is obtained. 3. The signal extraction device according to claim 1, further comprising an output signal storage unit that stores the output signal value in an attribute such as a distance or a Doppler frequency and stores the output signal value in a process of signal processing. When a new output signal value having the same attribute as the stored output signal value is obtained, the output signal value is added to the output signal value stored in the output signal storage, and the addition result is calculated. A signal extraction device for outputting. 4. The signal extracting apparatus according to claim 1, further comprising a Doppler coefficient generator for generating a predetermined Doppler coefficient, wherein the received data compressor includes a Doppler coefficient. A signal extraction device for performing Doppler correction and compression processing based on the Doppler correction. 5. A radar apparatus for transmitting a signal modulated by a modulated signal, a received data compressor for compressing a received signal by performing a correlation process between the received signal and the modulated signal, and an output signal of the received data compressor. A compressed data storage for storing the compressed data as compressed data; a maximum signal detector for obtaining a maximum amplitude signal from the compressed data; and a reference compression of a signal waveform obtained when a received signal to be extracted is compressed by the received data compressor. A reference compressed signal storage that holds the signal, an estimated compressed signal generator that generates an estimated compressed signal having an amplitude value of the maximum amplitude signal from the reference compressed signal, and subtracting the estimated compressed signal from the compressed data. An unnecessary signal remover for removing a maximum amplitude signal; compressing a received signal by the received data compressor; The estimated compressed signal having the amplitude value of the determined maximum amplitude signal is generated by the estimated compressed signal generator, and the generated estimated compressed signal is generated by the unnecessary compressed signal generator. A series of signal processing of removing the compressed data from the compressed data storage with the compressed data from which the estimated compressed signal has been removed, while removing the compressed data from the compressed data by the signal remover, is repeated until an output signal of a required amplitude value is obtained. A signal extraction device characterized by performing the above. 6. The signal extraction device according to claim 5,
Instead of a method of sequentially obtaining the maximum amplitude signal, a set value for the output signal of the received data compressor is provided, and a signal exceeding this set value is output collectively and the signal processing for eliminating the required amplitude value is performed. A signal extraction device for sequentially reducing the set value until an output signal is obtained. 7. The signal extraction device according to claim 5, further comprising an output signal storage unit that stores the output signal value in an attribute such as a distance or a Doppler frequency and stores the output signal value in a signal processing process. When a new output signal value having the same attribute as the stored output signal value is obtained, the output signal value is added to the output signal value stored in the output signal storage, and the addition result is calculated. A signal extraction device for outputting. 8. The signal extraction device according to claim 5, further comprising a Doppler coefficient generator that generates a predetermined Doppler coefficient, wherein the reception data compressor generates the Doppler coefficient. A signal extraction device for performing Doppler correction and compression processing based on the Doppler correction.