JP2012194011A - Fm-cw radar system and moving target signal detection method used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FM-CW radar system capable of detecting a moving target signal even under the environment where an unwanted signal is present within the same distance.SOLUTION: An FM-CW radar system includes: a normalization processor (20) which performs normalization processing in a time direction for each identical beat frequency on a spectrum obtained at a fixed time interval from a signal obtained by mixing a continuous wave signal and a reflection signal; a line segment detector (21) which performs line segment detection on a two-dimensional plane of a time-to-beat frequency obtained in the normalization processor; a frequency estimator (22) which estimates the beat frequency at a predetermined time from a line segment detected by the line segment detector; and a distance/speed detector (23) which computes target distance and speed from the beat frequency obtained by the frequency estimator.

Description

  The present invention relates to an FM-CW radar apparatus and a moving target signal detection method used therefor, and more particularly to an FM-CW (Frequency Modulated Continuous Waves) radar apparatus that detects a moving target.

  A radar device generally detects the presence of a target by irradiating a space with radio waves and receiving a reflected signal from the target, and observes its position, movement state, and the like. In the radar apparatus, the radio wave is irradiated from the aerial to the space, is reflected by hitting the target, is received again by the aerial, and is output as a radar reception signal to a receiver or the like.

  The radar received signal is frequency-converted by the receiver and then A / D (analog / digital) converted, and the digital received signal is detected as a target signal by threshold determination after various signal processing.

  The radar apparatus has applications, but particularly in the defense radar, there is a demand for detecting an object fired by an enemy to a short distance. As a radar system for measuring a short-range target, a continuous wave (CW) radar has been put to practical use, and in particular, frequency modulation (FM: Frequency Modulation) is applied to a CW signal in order to measure a distance. An FM-CW radar device that transmits a -CW signal is generally used.

  The principle is that when a CW signal with repeated triangular wave modulation is transmitted and mixed with a reflected signal from the target, a beat frequency corresponding to the distance and speed of the target signal is observed, and this beat frequency is used. From this, the target distance and speed are calculated (for example, see Non-Patent Document 1).

  FIG. 8 shows a configuration of a general FM-CW radar apparatus shown in Non-Patent Document 1 and the like, and the operation of the FM-CW radar apparatus will be described with reference to FIG.

  First, the triangular wave generator 18 generates a triangular wave modulation signal. The voltage controlled oscillator 17 generates a transmission signal obtained by modulating a triangular wave to a CW signal having a predetermined frequency by the triangular wave generated by the triangular wave generator 18 and outputs the transmission signal to the directional coupler 12. The directional coupler 12 outputs the transmission signal input from the voltage controlled oscillator 17 to the antenna 11. The antenna 11 irradiates the space with a transmission signal from the directional coupler 12 as radio waves.

  The aerial line 11 irradiates radio waves into the air, and simultaneously receives radio waves input from space and outputs them to the directional coupler 12. The directional coupler 12 outputs the received signal from the antenna 11 to the mixer 13. The mixer 13 mixes the reception signal input from the directional coupler 12 and the transmission signal input from the voltage controlled oscillator 17, and outputs the resulting signal to the low-pass filter 14.

  The low-pass filter 14 removes high-frequency components from the signal from the mixer 13, extracts the transmission signal and the beat signal of the reception signal, and outputs them to the A / D converter 15. The A / D converter 15 converts the analog signal from the low-pass filter 14 into a digital signal.

  The data extractor 16 extracts the received signal at the timing corresponding to the up-modulation of the triangular wave modulation signal and the received signal at the timing corresponding to the down-modulation as data, and outputs the data to the FFT (Fast Fourier Transform) processor 19. To do. The FFT processor 19 calculates the spectrum by performing FFT on each data.

  The frequency detector 31 detects a signal exceeding a predetermined threshold in the spectrum as a beat signal corresponding to the target reflected signal. The distance / speed detector 23 calculates a target distance and speed from the frequency of the obtained beat signal.

  Here, the principle of obtaining the target distance and speed from the beat frequency will be described. FIG. 9 is a schematic diagram for explaining a transmission signal and a beat signal of the FM-CW radar apparatus. The transmission signal is a signal obtained by modulating a CW signal having a center frequency f0 with a triangular wave having a modulation frequency width Δf and a modulation repetition frequency fm. FIG. 10 is a schematic diagram for explaining the spectrum of the beat signal.

The beat frequency fB is
fB = fR ± fV (1)
fR: distance frequency, fV: velocity frequency. In the equation (1), the + sign is the frequency of the beat signal (downbeat fBD) obtained in the interval in which the frequency of the transmission wave falls, and the-sign is the frequency of the beat signal (upbeat fBU) obtained in the ascending interval. .

fBD and fBU are
fBD = fR + fV (2)
fBU = fR−fV (3)
It is expressed by the formula.

FR and fV are expressed by the following equations.
fR = 4 · Δf · R · fm / C (4)
fV = 2 · f0 · V / C (5)
C: Radio wave propagation speed, fm: Triangular wave modulation frequency, f0: Center frequency,
Δf: modulation width of triangular wave, R: target distance, V: target relative speed

The distance R and the relative speed V are derived by the following equations from the equations (1) to (5).
R = (fBD + fBU) C / 8 · Δf · fm (6)
V = (fBD−fBU) C / 4 · f0 (7)
It is expressed by the formula.

  That is, the distance and the relative speed can be obtained by measuring the beat signal frequency fBU and the beat signal frequency fBD for each frequency increase / decrease section and calculating the sum and difference thereof.

  The principle of the FM-CW radar device described above shows the basic operation in an ideal environment where only the reflected signal from the target exists. In the case of an FM-CW radar device in an actual environment, a strong reflected signal from a nearby fixed object of a building or structure is simultaneously input as an unnecessary signal. There is a problem that the reflected signal cannot be observed.

  As a countermeasure for this problem, there is a technique described in Patent Document 1 below. FIG. 11 shows the configuration of the FM-CW radar apparatus described in Patent Document 1. The configuration of the FM-CW radar apparatus shown in FIG. 11 is the same as that of the FM-CW radar apparatus shown in FIG. 8 except that an amplitude equalizer 32 is added between the low-pass filter 14 and the A / D converter 15. The same components are denoted by the same reference numerals.

  The distance frequency fR increases as the distance R increases from the equation (4), and the beat signal frequency fBD and the beat signal frequency fBU increase from the equations (2) and (3). That is, a signal from a long-distance target has a higher beat frequency, but a long-distance target signal is weaker than a short-distance target, and thus needs to be amplified.

  This technology performs control to increase the amplification gain sequentially as the frequency of the beat signal increases. This makes the beat frequency amplitude constant regardless of the distance, and superimposes unnecessary signals from short-distance fixed objects. This is to reduce the fact that a long distance target is not detected.

  As another technique, there is a technique described in Patent Document 2 below. The configuration of the FM-CW radar apparatus described in Patent Document 2 is shown in FIG. The configuration of the FM-CW radar apparatus shown in FIG. 12 is the same as that of the FM-CW radar apparatus shown in FIG. 8 except that an own vehicle speed detector 33 and a threshold controller 34 are added. The same components are denoted by the same reference numerals.

  The technique described in Patent Document 2 assumes an in-vehicle FM-CW radar device, and aims to reduce the influence of a strong reflected signal from a building or structure near the road. . When traveling on a general road, there are many fixed objects in the vicinity, so the unnecessary signal is large, but the inter-vehicle distance is shortened and the target is a short distance, so the threshold is set high.

  On the other hand, when driving on an expressway, there are few fixed objects in the vicinity of the road, so unnecessary signals are small, and the threshold is set low in order to detect a weak signal of a long-distance target. In order to perform these controls, the own vehicle speed detector 32 detects the traveling speed of the own vehicle. Based on the speed detected by the own vehicle speed detector 32, the threshold controller 33 determines that the road is traveling on a general road when the vehicle is at a low speed, and sets the threshold high. And the threshold is set low.

JP 2001-215272 A Japanese Patent No. 3149142

"Revised radar technology Chapter 11 Special radar technology" (supervised by Takashi Yoshida, published by The Institute of Electronics, Information and Communication Engineers, 1996.0.01)

  In the above-described FM-CW radar apparatus related to the present invention, when detecting a target reflected signal in an environment where an unnecessary signal due to a fixed object exists, it is not possible to detect a moving target signal superimposed on an unnecessary signal of the same distance. There is a problem. The reason is that the focus is only on the difference between the target distance and the distance of the fixed object, and the amplification gain or threshold is changed according to the distance. This is because there is no consideration for distinguishing between and.

  Accordingly, an object of the present invention is to provide an FM-CW radar apparatus capable of detecting a moving target signal even in an environment where unnecessary signals are present at the same distance, and a moving target signal detecting method used therefor, which solve the above problems. There is to do.

The FM-CW radar apparatus according to the present invention transmits a continuous wave signal in which triangular wave modulation is repeated, mixes it with a reflected signal from the target, observes a beat frequency according to the distance and speed of the target signal, and An FM-CW (Frequency Modulated Continuous Waves) radar device that calculates the target distance and speed from a frequency,
A normalization processor that performs normalization processing in the time direction for each same beat frequency spectrum obtained at a constant time from a signal obtained by mixing the continuous wave signal and the reflected signal;
A line segment detector for performing line segment detection in a two-dimensional plane of time versus beat frequency obtained by the normalization processor;
A frequency estimator for estimating a beat frequency at a predetermined time from a line segment detected by the line segment detector;
A distance / speed detector for calculating a target distance and speed from the beat frequency obtained by the frequency estimator;

The moving target signal detection method according to the present invention transmits a continuous wave signal in which triangular wave modulation is repeated, mixes it with a reflected signal from the target, observes the beat frequency according to the distance and speed of the target signal, and A moving target signal detection method used in an FM-CW (Frequency Modulated Continuous Waves) radar device that calculates the distance and speed of the target from a frequency,
The FM-CW radar device is
A normalization process for performing a normalization process in the time direction for each same beat frequency spectrum obtained at a constant time from a signal obtained by mixing the continuous wave signal and the reflected signal;
A line segment detection process for performing line segment detection in a two-dimensional plane of time vs. beat frequency obtained by the normalization process;
A frequency estimation process for estimating a beat frequency at a predetermined time from the line segment detected in the line segment detection process;
A distance / speed detection process for calculating a target distance and speed from the beat frequency obtained by the frequency estimation process is executed.

  By adopting the above-described configuration and operation, the present invention provides an effect that a moving target signal can be detected even in an environment where unnecessary signals exist at the same distance.

It is a block diagram which shows the structural example of the FM-CW radar apparatus by the 1st Embodiment of this invention. It is a schematic diagram for demonstrating the normalization process by the 1st Embodiment of this invention. In the first embodiment of the present invention, the horizontal axis represents frequency, the vertical axis represents time, and the amplitude is represented by the size of each sample point. It is a block diagram which shows the structural example of the FM-CW radar apparatus by the 2nd Embodiment of this invention. It is a schematic diagram for demonstrating the operation | movement in the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the FM-CW radar apparatus by the 3rd Embodiment of this invention. It is a schematic diagram for demonstrating the operation | movement in the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the FM-CW radar apparatus relevant to this invention. It is a schematic diagram for demonstrating the transmission signal and beat signal of the FM-CW radar apparatus relevant to this invention. It is a schematic diagram explaining the spectrum of the beat signal shown in FIG. It is a block diagram which shows the structure of the FM-CW radar apparatus of patent document 1. As shown in FIG. It is a block diagram which shows the structure of the FM-CW radar apparatus of patent document 2. As shown in FIG.

  Next, embodiments of the present invention will be described with reference to the drawings. First, an outline of an FM-CW (Frequency Modulated Continuous Waves) radar apparatus according to the present invention will be described.

The FM-CW radar apparatus according to the present invention achieves the above-described object,
An antenna that emits radio waves in a predetermined direction and receives reflected radio waves from space, a triangular wave generator, a voltage-controlled oscillator, a directional coupler, a mixer, a low-pass filter, and A / D (analog / digital) Converter, data extractor, FFT (Fast Fourier Transform) processor, normalization processor, line segment detector, frequency estimator, distance / velocity detector, triangular wave generator, voltage control An oscillator, a directional coupler, a mixer, a low-pass filter,

  The antenna receives a reflected radio wave from space by radiating a radio wave in a predetermined direction. The triangular wave generator generates a triangular wave modulation signal. The voltage controlled oscillator generates a transmission signal obtained by modulating a triangular wave to a CW (Continuous Wave) signal having a predetermined frequency by the triangular wave generated by the triangular wave generator, and outputs the transmission signal to the directional coupler and the mixer.

  The directional coupler outputs a transmission signal input from the voltage controlled oscillator to the antenna and outputs a reception signal from the antenna to the mixer. The mixer mixes the reception signal input from the directional coupler and the transmission signal input from the voltage controlled oscillator, and outputs the resulting signal to the low-pass filter.

  The low-pass filter removes high frequency components, extracts the beat signals of the transmission signal and the reception signal, and outputs them to the A / D converter. The A / D converter converts an analog signal into a digital signal. The data extractor separates the received signal at the timing corresponding to the up-modulation of the triangular wave modulation signal and the received signal at the timing corresponding to the down-modulation as data, and outputs the data to the FFT processor.

  The FFT processor calculates the spectrum on the frequency axis by performing FFT on the extracted data. The normalization processor performs normalization processing on the spectrum obtained at regular intervals in the time direction at the same beat frequency. The line segment detector performs line segment detection in a two-dimensional plane of time versus beat frequency. The frequency estimator estimates a beat frequency at a predetermined time from the detected line segment. The distance / speed detector calculates the target distance and speed from the obtained beat frequency.

  FIG. 1 is a block diagram showing a configuration example of an FM-CW radar apparatus according to the first embodiment of the present invention. In FIG. 1, an FM-CW radar apparatus according to the first embodiment of the present invention includes an antenna 11, a directional coupler 12, a mixer 13, a low-pass filter 14, an A / D converter 15, and data. Extractor 16, voltage controlled oscillator 17, triangular wave generator 18, FFT processor 19, normalization processor 20, line segment detector 21, frequency estimator 22, distance / speed detector 23, It is composed of

  The antenna 11 radiates radio waves in a predetermined direction and receives reflected radio waves from the space. The triangular wave generator 18 generates a triangular wave modulation signal. The voltage controlled oscillator 17 generates a transmission signal obtained by modulating a CW signal having a predetermined frequency with the triangular wave generated by the triangular wave generator 18 and outputs the transmission signal to the directional coupler 12 and the mixer 13.

  The directional coupler 12 outputs a transmission signal input from the voltage controlled oscillator 17 to the antenna 11 and outputs a reception signal from the antenna 11 to the mixer 13. The mixer 13 mixes the reception signal input from the directional coupler 12 and the transmission signal input from the voltage controlled oscillator 17, and outputs the resulting signal to the low-pass filter 14.

  The low-pass filter 14 removes the high frequency component, extracts the transmission signal and the beat signal of the reception signal, and outputs them to the A / D converter 15. The A / D converter 15 converts an analog signal into a digital signal.

  The data extractor 16 divides the received signal at the timing corresponding to the up-modulation of the triangular wave modulation signal and the received signal at the timing corresponding to the down-modulation as data, and outputs the data to the FFT processor 19. The FFT processor 19 calculates a spectrum by performing FFT on the data extracted by the data extractor 16.

  The normalization processor 20 divides the spectrum obtained at regular time intervals for the same beat frequency, and performs normalization processing in the time direction. The line segment detector 21 performs line segment detection on a two-dimensional plane of time versus beat frequency. The frequency estimator 22 estimates a beat frequency at a predetermined time from the detected line segment. The distance / speed detector 23 calculates a target distance and speed from the estimated beat frequency.

  The antenna 11 emits radio waves in a predetermined direction and receives reflected radio waves from space. The triangular wave generator 18 generates a triangular wave modulation signal. The voltage controlled oscillator 17 generates a transmission signal obtained by modulating a CW signal having a predetermined frequency with the triangular wave generated by the triangular wave generator 18 and outputs the transmission signal to the directional coupler 12 and the mixer 13.

  The directional coupler 12 outputs a transmission signal input from the voltage controlled oscillator 17 to the antenna 11 and outputs a reception signal from the antenna 11 to the mixer 13. The mixer 13 mixes the reception signal input from the directional coupler 12 and the transmission signal input from the voltage controlled oscillator 17, and outputs the resulting signal to the low-pass filter 14.

  The low-pass filter 14 removes the high frequency component, extracts the transmission signal and the beat signal of the reception signal, and outputs them to the A / D converter 15. The A / D converter 15 converts the analog signal from the low-pass filter 14 into a digital signal.

  The data extractor 16 separates the received signal at the timing corresponding to the up-modulation of the triangular wave modulation signal and the received signal at the timing corresponding to the down-modulation as data, and outputs the data to the FFT processor 19. The FFT processor 19 calculates a spectrum by performing FFT on the data extracted by the data extractor 16.

  The operations of the antenna 11, the directional coupler 12, the mixer 13, the low pass filter 14, the A / D converter 15, the data extractor 16, the voltage controlled oscillator 17, the triangular wave generator 18, and the FFT processor 19 are shown in FIG. 8 is similar to the FM-CW radar apparatus related to the present invention shown in FIG. 8, and the relationship between the transmission signal and the beat signal and the spectrum of the beat signal are the same as the schematic diagram shown in FIG. 9 and the schematic diagram shown in FIG. is there.

  Since the spectrum is obtained at regular time intervals, the spectrum obtained at each time can be arranged in time series so that it can be considered on a two-dimensional plane of time versus beat frequency with the height direction regarded as the amplitude direction.

  FIG. 3 is a schematic diagram in which the horizontal axis represents frequency, the vertical axis represents time, and the amplitude magnitude is represented by the size of each sample point in the first embodiment of the present invention. FIG. 3A shows a state in which the spectrum of the output of the FFT processor 19 is arranged on a two-dimensional plane. In FIG. 3A, since the unnecessary signal has a large amplitude but the relative speed is 0, a large point at the same beat frequency, and a moving target signal has an intermediate point at which the beat frequency changes in the time direction. Sample points with noise only are represented by small dots.

  The reflected signal from a fixed object such as a nearby building or structure is generally strong, but the beat frequency does not change in the time direction because the relative speed is 0 when the radar apparatus is stopped. For this reason, the normalization processor 20 divides the spectrum obtained at regular intervals for each beat frequency and performs normalization processing in the time direction.

  FIG. 2 is a schematic diagram for explaining normalization processing according to the first embodiment of the present invention. In FIG. 2, the horizontal axis represents the beat frequency and the vertical axis represents the amplitude. FIG. 2A shows a state where the target signal is observed at a beat frequency that does not overlap with the unnecessary signal. The normalization process is performed by dividing the amplitude of the time of interest by the average value of the amplitude before and after the time of interest. FIG. 2B is a waveform after the normalization process of FIG. 2A, and as shown in FIG. 2B, the target signal becomes higher than the noise even after the normalization process, and can be detected. .

  On the other hand, FIG. 2C shows a time change in the amplitude of the beat frequency where an unnecessary signal due to a fixed object exists. Although the unnecessary signal has a larger amplitude than the noise or the target signal, it is continuously present at the same beat frequency without much change in amplitude, so the average value of the amplitude before and after the time of interest is also the time of interest. It becomes almost the same level as the unnecessary signal. For this reason, as shown in FIG. 2D, the amplitude of the unnecessary signal normalization processing error is equal to that after the noise level normalization processing.

  FIG. 3B shows the result of normalizing the time shown in FIG. 3A at each beat frequency in the time direction. Unnecessary signals that are continuous at the same beat frequency are equal to the noise level by the normalization process. On the other hand, the target signal is lined up on the line segment excluding the sample point of the beat frequency superimposed on the unnecessary signal.

  The line segment detector 21 performs a process of detecting a line segment on a two-dimensional plane of time versus beat frequency after the normalization process. As a technique for detecting a line segment on a two-dimensional plane, a general technique such as a line segment detection filter or Hough transform used in image processing or the like can be used.

  The frequency estimator 22 estimates the downbeat frequency and the upbeat frequency at a predetermined time for the line segment detected by the line segment extractor 21 by extrapolation. FIG. 3B shows an example in which the downbeat frequency at the time of interest is estimated by this processing because the downbeat frequency cannot be observed superimposed on the unnecessary signal.

  The distance / speed detector 23 calculates the target distance and speed from the downbeat frequency and the upbeat frequency according to the equations (6) and (7). The FM- related to the present invention shown in FIG. The operation is the same as that of the CW radar device.

  As described above, in the present embodiment, it is possible to obtain an effect that the moving target signal superimposed on the unnecessary signal of the same distance can be detected.

  Next, an FM-CW radar apparatus according to a second embodiment of the present invention will be described with reference to FIGS. The FM-CW radar apparatus according to the second embodiment of the present invention operates in consideration of detecting a low-speed target.

  FIG. 4 is a block diagram showing a configuration example of an FM-CW radar apparatus according to the second embodiment of the present invention, and FIG. 5 is a schematic diagram for explaining the operation in the second embodiment of the present invention. is there. 4, the FM-CW radar apparatus according to the second embodiment of the present invention is the same as the FM-CW radar apparatus according to the first embodiment of the present invention shown in FIG. 1 except that an adder 24 is added. It has the same structure, and the same code | symbol is attached | subjected to the same component. The operation of the same components is the same as that of the FM-CW radar apparatus according to the first embodiment of the present invention.

  When the target is a low speed, as shown in FIG. 5A, the frequency does not change at every observation timing, but changes at regular intervals. For this reason, the adder 24 groups the observed times at a plurality of times, adds the amplitudes for each group, and converts them into amplitude data with a wide time interval as shown in FIG. 5B.

  In this embodiment, by performing line segment extraction on a two-dimensional plane, line segment extraction can be performed correctly even for a low-speed target, and target detection can be performed. The numbers to be grouped and added are divided into cases for each assumed speed and parallel processing is performed, so that a target of an arbitrary speed can be detected.

  Next, an FM-CW radar apparatus according to a third embodiment of the present invention will be described with reference to FIGS. The FM-CW radar apparatus according to the third embodiment of the present invention operates while moving when the radar apparatus is mounted on the vehicle.

  FIG. 6 is a block diagram showing a configuration example of an FM-CW radar apparatus according to the third embodiment of the present invention, and FIG. 7 is a schematic diagram for explaining the operation in the third embodiment of the present invention. is there. In FIG. 6, the FM-CW radar apparatus according to the third embodiment of the present invention is the same as that of the present invention shown in FIG. 1 except that an own vehicle speed detector 25 and an average value calculation range selector 26 are added. The configuration is the same as that of the FM-CW radar apparatus according to the first embodiment, and the same components are denoted by the same reference numerals. The operation of the same components is the same as that of the FM-CW radar apparatus according to the first embodiment of the present invention.

  When the radar apparatus moves, the distance between the fixed object and the radar apparatus changes with time, and the beat frequency also changes. For this reason, in the configuration of the FM-CW radar apparatus according to the first embodiment of the present invention shown in FIG. 1, the beat frequency of the unnecessary signal is also observed in the time direction as shown in FIG. 7A. Therefore, even if normalization processing is performed at the same beat frequency, it is not possible to suppress the noise level.

  For this reason, in the present embodiment, first, the own vehicle speed of the vehicle or the like on which the radar apparatus is mounted is detected by the own vehicle speed detector 25. For a fixed object, the vehicle speed is a relative speed.

Radar device distance R is determined by relative speed V and time t.
R = V · t (8)
It is expressed by the formula.

From the equations (2), (4), (5), and (8), the downbeat frequency fBD is
fBD = 4 · Δf · V · t · fm / C + 2 · f0 · V / C
... (9)
It is expressed by the formula.

  In the two-dimensional plane of time vs. beat frequency according to the equation (9), the reflection signal of the fixed object exists on a line segment having an inclination with the relative velocity V as a parameter. For this reason, the average value calculation range controller 26 calculates an average value by selecting an average value calculation range from the above-described slope line segments for each focused time and beat frequency.

  Thereby, in the present embodiment, since the amplitude of the sample point where the unnecessary signal exists is selected and the normalization process is performed, it is possible to suppress the unnecessary signal and detect the target signal.

  The present invention pays attention only to the difference between the target distance and the distance of the fixed object, and does not require the same distance that is difficult in the technology related to the present invention in which the amplification gain is changed or the threshold is changed according to the distance. The moving target signal superimposed on the signal can be detected.

  The reason for this is that the technology related to the present invention focuses only on the difference between the target distance and the distance of the fixed object and does not take into account the distinction between the target and the unnecessary signal of the same distance, This is because, in the present invention, the beat frequency is detected in a two-dimensional plane of time vs. beat frequency by paying attention to the fact that the distance of the moving target changes with time and the beat frequency changes accordingly.

  Further, in the detection, unnecessary signals are stopped and the beat frequency does not change, while the target is focused on the fact that the beat frequency changes. This is because it is possible to distinguish between the target and the unnecessary signal by detecting only the line segment in which the change occurs.

DESCRIPTION OF SYMBOLS 11 Antenna 12 Directional coupler 13 Mixer 14 Low pass filter 15 A / D converter 16 Data extractor 17 Voltage control oscillator 18 Triangle wave generator 19 FFT processor 20 Normalization processor 21 Line segment detector 22 Frequency estimator 23 Distance・ Speed detector 24 Adder 25 Own vehicle speed detector 26 Average value calculation range selector

Claims (6)

Transmits a continuous wave signal with repeated triangular wave modulation, mixes it with the reflected signal from the target, observes the beat frequency according to the distance and speed of the target signal, and determines the distance and speed of the target from the beat frequency. An FM-CW (Frequency Modulated Continuous Waves) radar device for calculating,
A normalization processor that performs normalization processing in the time direction for each same beat frequency spectrum obtained at a constant time from a signal obtained by mixing the continuous wave signal and the reflected signal;
A line segment detector for performing line segment detection in a two-dimensional plane of time versus beat frequency obtained by the normalization processor;
A frequency estimator for estimating a beat frequency at a predetermined time from a line segment detected by the line segment detector;
An FM-CW radar apparatus comprising: a distance / speed detector that calculates a target distance and speed from a beat frequency obtained by the frequency estimator. The observed time is grouped at a plurality of times, and an adder that converts the amplitude for each group into amplitude data with a wide time interval is disposed in the preceding stage of the normalization processor,
The FM-CW radar apparatus according to claim 1, wherein the normalization processor performs the normalization process on the amplitude data converted by the adder. A vehicle speed detector that detects a relative speed with respect to a fixed object by detecting the vehicle speed;
An average value calculation range controller that calculates and calculates an average value calculation range for each beat frequency and an average value calculation range from a line segment in which the reflection signal of the fixed object exists and the relative speed is a parameter;
The FM-CW radar apparatus according to claim 1, wherein the normalization processor performs the normalization process in the average value calculation range calculated by the average value calculation range controller. Transmits a continuous wave signal with repeated triangular wave modulation, mixes it with the reflected signal from the target, observes the beat frequency according to the distance and speed of the target signal, and determines the distance and speed of the target from the beat frequency. An FM-CW (Frequency Modulated Continuous Waves) radar device for calculating a moving target signal,
The FM-CW radar device is
A normalization process for performing a normalization process in the time direction for each same beat frequency spectrum obtained at a constant time from a signal obtained by mixing the continuous wave signal and the reflected signal;
A line segment detection process for performing line segment detection in a two-dimensional plane of time vs. beat frequency obtained by the normalization process;
A frequency estimation process for estimating a beat frequency at a predetermined time from the line segment detected in the line segment detection process;
A distance / speed detection process for calculating a target distance and speed from a beat frequency obtained by the frequency estimation process is executed. In the preceding stage of the normalization process, the FM-CW radar apparatus performs an addition process of grouping observed times at a plurality of times and adding amplitude for each group to convert the data into amplitude data having a wide time interval. Run,
5. The moving target signal detection method according to claim 4, wherein, in the normalization process, the normalization is performed on the amplitude data converted by the adder. The FM-CW radar device is
A vehicle speed detection process for detecting a relative speed with respect to a fixed object by detecting the vehicle speed;
An average value calculation range control process for calculating and calculating an average value calculation range for each time of interest and the beat frequency by selecting from a line segment in which the reflection signal of the fixed object exists and the relative speed is a parameter,
5. The moving target signal detection method according to claim 4, wherein, in the normalization process, the normalization is performed in the average value calculation range calculated in the average value calculation range control process.

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