JPH11183601A - Signal processing method for radar apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a radar apparatus and to enhance its accuracy. SOLUTION: In a radar apparatus of an FM-CW system, a beat signal is frequency-converted by an FFT circuit 40. A signal processing circuit 44 first finds distribution of the signal level of the beat signal with reference to a frequency and to a measuring angle, by using the frequency component of the beat signal obtained in every period of every increase period and every decrease period. The signal level Lp and the frequency fp of the maximum point of a curved surface which expresses the distribution of every period as well as the central angle θm and the angle width Δθa of an angle range are found as variables of data on the maximum point. In addition, data on maximum points in both periods are compared. The combination of the maximum points in which the difference between the variables is less than a reference value is found. On the basis of the data on the maximum points, the relative distance between a target and the radar apparatus and their relative speed as well as the position and the size of the target are found. As a result, the position and the size of the target can be found without narrowing the beam width of transmitting waves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing method for a radar apparatus suitably used for detecting an object around a vehicle.

[0002]

2. Description of the Related Art A vehicle is provided with a radar device for detecting a relative distance and a relative speed between the target and the vehicle in order to detect a target such as a preceding vehicle traveling ahead of the same road as the host vehicle. Be provided.

[0003] A transmitting antenna 1 and a receiving antenna 2 of a first prior art radar device are installed in, for example, a front grill of a vehicle 3 as shown in FIG. From the transmitting antenna 1, an electromagnetic wave having a predetermined wavelength having directivity is emitted as a transmitting wave 5 while the radiation direction thereof is angularly displaced in the horizontal direction 6 with the passage of time. This transmitted wave 5
Is, for example, 2 to 3 degrees. Transmitted wave 5
Is reflected by the target 7, returned as a reflected wave, and received by the receiving antenna 2. The radar apparatus first obtains the distribution of the received electric field strength of the reflected wave using the measurement angle as a variable. The measurement angle is the angle between the radiation direction of the transmitted wave and a predetermined forward direction perpendicular to the axle of the vehicle and parallel to the ground. Next, the measurement angle of the maximum point of the distribution is obtained, and the position of the target object with respect to the vehicle is calculated based on the relative distance between the target object and the vehicle and the measurement angle of the maximum point.

FIG. 14 is a graph showing the distribution of the received electric field strength of the reflected wave with respect to the measurement angle in the radar device of the first prior art. In this graph, the received electric field strength of the actually measured reflected wave is represented by a thick solid line, and the distribution estimated from the received electric field strength is represented by a curve 9. When a transmission wave having a beam width of 2 to 3 degrees is used, the interval 8 between the measurement angles at which the transmission wave is actually emitted is relatively large. As described above, in the radar device of the first prior art, since the number of actually measured reflected waves is small, it has been difficult to obtain the exact position of the target.

For this purpose, as a second prior art radar apparatus, a radar apparatus which emits a transmission wave having a beam width of 0.1 to 0.9 degrees is used. As shown in FIG. 15, this radar device has the same installation positions of the transmitting antenna 11 and the receiving antenna 12, and the behavior of radiating the transmitting wave and receiving the reflected wave as the radar device of the first prior art.
Only the structure and the beam width of the antennas 11 and 12 are different.

FIG. 16 is a graph showing the distribution of the received electric field strength of the reflected wave of the transmission wave 15 with respect to the measurement angle in the radar device of the second prior art. Beam width 0.1 ~
When a transmission wave of 0.9 degrees is used, the interval 18 between the actually emitted measurement angles is smaller than the interval 8 of the first prior art radar apparatus. For this reason, the transmission wave is radiated a plurality of times within the angle range where the vehicle exists, and the reception electric field strength of the reflected wave clearly changes inside and outside the angle range. Therefore, the size and position of the target are determined based on the range 19 in which the received electric field strength exceeds a certain threshold.
However, in order to reduce the beam width, it is necessary to increase the aperture area of the transmitting antenna, so that it has been difficult to reduce the size of the radar device.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a signal processing method for a radar apparatus capable of accurately determining the size and position of a target irrespective of the beam width.

[0008]

According to the present invention, a transmission wave, which is an electromagnetic wave whose frequency increases and decreases with time, is transmitted while the radiation direction is angularly displaced, and the transmission wave is reflected by a target. In a signal processing method for a radar device, which receives a reflected wave and obtains information on a position of a target based on a mixed signal obtained by mixing the transmitted wave and the reflected wave, an increase period in which the frequency of the transmitted wave is increased, and a frequency of the transmitted wave. For each decrease period in which is decreased, the distribution of the signal level of the mixed signal with respect to the frequency and the angle between the predetermined reference direction and the radiation direction of the transmission wave is obtained, and the curves representing the distribution of the increase period and the decrease period are compared. A maximum point having a similar curve shape in a predetermined range including the maximum point is obtained, and the relative distance between the target and the radar device is determined based on the obtained frequency of the maximum point in the increasing period and the decreasing period. Obtains a release and a relative speed, based on the distribution of the range including the ultra large point, is a signal processing method of the radar device characterized by determining the position and size of the target.

According to the present invention, in the signal processing method of the radar apparatus, as described above, first, the distribution of the signal level of the mixed signal with respect to the frequency and the angle is created, and based on the distribution, the position of the target and the position of the target are determined. The size and the relative distance and relative speed between the target and the radar device are calculated. If the electric field strength of the transmitted wave is constant, the signal level of the mixed signal is
It increases and decreases as the received electric field strength of the reflected wave increases and decreases.
Therefore, performing processing based on the signal level of the mixed signal as described above is equivalent to performing processing based on the received electric field strength of the reflected wave. Thus, the position and size of the target can be accurately calculated regardless of the beam width of the transmission wave. Further, since the beam width of the transmission wave is not limited, the beam width can be made wider than that of the second prior art radar apparatus. This makes it possible to easily reduce the size of the radar device.

Further, since the combination of the maximum points of the increasing period and the decreasing period is obtained by using the distribution, the angle formed by the emission angle of the transmission wave and the reference angle can be referred to in order to obtain the combination. . Accordingly, it is possible to prevent a combination of the local maximum points representing the reflected waves from different targets, thereby preventing a calculation error of the relative distance and the relative speed. Therefore, the calculation accuracy of the relative distance and the relative speed can be improved.

According to the present invention, for each distribution of signal levels having the same frequency in the increasing period and the decreasing period, the first signal level includes the angle of the maximum point of the distribution, and the signal level is smaller by a predetermined reference level than the signal level of the maximum point. And an angle range having both ends of the first angle and the second angle at which the signal level decreases as the angle approaches the first and second angles from the angle of the maximum point, and the distribution of the increase period and the decrease period The frequency of the local maximum point, the signal level, and the angle range are compared, and the combination of the local maximum point having the same signal level, the angular range, and the frequency is set as a local maximum point having a similar curve shape.

According to the present invention, in the signal processing method of the radar apparatus, the signal level and frequency of the maximum point in both periods and the angle range including the maximum point are compared in order to find the maximum point having a similar curve shape. I do. by this,
By comparing numerical values, the similar maximum point can be obtained. Therefore, arithmetic processing can be facilitated.

According to the present invention, when there are a plurality of maximum points in the distribution of signal levels having the same frequency in the increasing period and the decreasing period,
An angle range is obtained for each local maximum point, and the position and size of the target are obtained based on the angular range of the local maximum point having the highest signal level among a plurality of local maximum points.

According to the present invention, in the signal processing method of the radar apparatus, when there are a plurality of maximum points of a certain frequency distribution, the size and the position of the target are determined based on the maximum point of the signal level. Ask. Thus, for example, even when a large number of noise components are mixed in the reflected wave and the received electric field strength of the reflected wave from the target is close to the received electric field intensity of the noise component, the size and position of the target can be reliably determined. Can be sought.

According to the present invention, when there are a plurality of maximum points in the distribution of signal levels having the same frequency in the increasing period and the decreasing period,
An angle range is obtained for each local maximum point, and a position and a size of a single target are obtained based on mutually overlapping angular ranges among the angular ranges of the local maximum points.

According to the signal processing method of the radar apparatus according to the present invention, when there are a plurality of local maximum points of a certain frequency distribution and the angular ranges of the local maximum points overlap each other, the whole curve of the overlapping angular range Is regarded as representing a reflected wave from a certain target, and the size and position of the target are obtained. Accordingly, even when interference occurs in the reflected wave because the beam width of the transmission wave is smaller than the angle range in which the target exists, the size and position of the target can be reliably obtained.

According to the present invention, the frequency difference, the difference between the center angles of the angle ranges, the difference between the magnitudes of the angle ranges, and the difference between the signal levels are obtained for each maximum point of the distribution of the increase period and the decrease period. Is less than a predetermined first reference value, the difference in the center angle of the angle range is less than a second reference value, the difference in the size of the angle range is less than a third reference value, and The maximum point of the distribution of the increasing period and the decreasing period in which the difference in the signal level is less than the predetermined fourth reference value is a maximum point having a similar curve shape.

According to the present invention, in the signal processing method of the radar apparatus, when there are a plurality of maximum points in the distribution of the increasing period and the decreasing period, the maximum point of the increasing period and the maximum point of the decreasing period are combined, and these are combined. , The difference in the center angle, the difference in the size of the angle range, and the difference in the frequency. The difference between these variables is obtained by changing the combination of the maximum points, and the combination of the maximum points where each difference is less than the reference value is regarded as the combination of the maximum points having similar curve shapes. Accordingly, even if each variable of the maximum point of the distribution of the increasing period and the decreasing period representing the reflected wave from the same target has a small error, the relative distance and the relative speed and the target Size and position can be reliably obtained.

According to the present invention, when there are a plurality of combinations of the maximum points where each of the differences is less than each of the reference values, the maximum point of the combination having the smallest frequency difference is set to the maximum point having a similar curve shape. It is characterized by.

According to the present invention, when the difference between the variables is obtained by combining the maximum point in the increasing period and the maximum point in the decreasing period,
When there are a plurality of combinations of the maximum points where the difference between the variables is less than the reference value, the combination having the minimum frequency difference is set as the combination of the maximum points having similar curve shapes. by this,
Even in the above case, it is possible to reliably determine the relative distance and the relative velocity and the size and the position of the target by selecting a combination of the maximum points that are likely to represent the reflected wave from the same target.

According to the present invention, when there are a plurality of combinations of the maximum points where each of the differences is smaller than each of the reference values, the maximum point of the combination having the smallest difference in the signal level is the maximum point having a similar curve shape. It is characterized by the following.

According to the present invention, when the difference between the variables is obtained by combining the maximum point in the increasing period and the maximum point in the decreasing period,
When there are a plurality of combinations of the maximum points in which the difference between the variables is less than the reference value, the combination in which the difference between the signal levels is the smallest is a combination of the maximum points having similar curve shapes. Thus, even in the case described above, the combination of the maximum points that are likely to represent the reflected wave from the same target can be selected, and the relative distance and the relative speed and the size and the position of the target can be reliably obtained. .

According to the present invention, when there are a plurality of combinations of the maximum points where each of the differences is less than each of the reference values, the maximum point having the smallest difference between the center angles of the angle ranges is determined as the maximum having the similar curve shape. It is characterized by a point.

According to the present invention, when the difference between the variables is obtained by combining the maximum point in the increasing period and the maximum point in the decreasing period,
When there are a plurality of combinations of the maximum points in which the difference between the variables is less than the reference value, the combination in which the difference between the center angles of the angle ranges is the smallest is a combination of the maximum points having similar curve shapes. Thus, even in the case described above, the combination of the maximum points that are likely to represent the reflected wave from the same target can be selected, and the relative distance and the relative speed and the size and the position of the target can be reliably obtained. .

According to the present invention, when there are a plurality of combinations of the maximum points where each of the differences is less than each of the reference values, the maximum point of the combination having the smallest difference in the magnitude of the angle range is determined by the maximum having the similar curve shape. It is characterized by a point.

According to the present invention, when the difference between the variables is obtained by combining the maximum point in the increasing period and the maximum point in the decreasing period,
When there are a plurality of combinations of the maximum points in which the difference between the variables is less than the reference value, the combination in which the difference in the magnitude of the angle range is the smallest is a combination of the maximum points having similar curve shapes. Thus, even in the case described above, the combination of the maximum points that are likely to represent the reflected wave from the same target can be selected, and the relative distance and the relative speed and the size and the position of the target can be reliably obtained. .

According to the present invention, a transmission wave, which is an electromagnetic wave whose frequency increases and decreases with time, is transmitted while the radiation direction is angularly displaced, and the transmission wave receives a reflected wave reflected by a target and transmits the transmission wave. In a signal processing method of a radar apparatus for obtaining information on a position of a target based on a mixed signal obtained by mixing a wave and a reflected wave, a mixing of an increasing period in which the frequency of the transmitting wave increases and a decreasing period in which the frequency of the transmitting wave decreases Based on the frequency of the signal, the relative distance and the relative speed are obtained, the relative speed, the relative distance, and the distribution of the signal level of the mixed signal with respect to the angle between the predetermined reference direction and the emission direction of the transmission wave are obtained. The local maximum point of a curve representing the distribution of the signal level of the mixed signal having the same relative distance with respect to the angle is obtained, and based on the curve shape in the range including the obtained local maximum point, A signal processing method of the radar device characterized by determining the position and size of the object.

According to the present invention, in the signal processing method of the radar device, as described above, first, the relative distance and the relative speed are obtained, and then the distribution of the signal level of the mixed signal with respect to the relative distance, the relative speed and the angle is obtained. Then, the position and size of the target are obtained based on this distribution. When the electric field strength of the transmission wave is constant, the signal level of the mixed signal increases and decreases as the reception electric field strength of the reflected wave increases and decreases. Therefore, performing processing based on the signal level of the mixed signal as described above is equivalent to performing processing based on the received electric field strength of the reflected wave. The distribution is created, for example, by collecting a mixed signal of a reflected wave and a transmitted wave reflected by a target having the same relative velocity, and determining a distribution of a signal level of the mixed signal with respect to a relative distance and an angle. Thus, the position and size of the target can be accurately calculated regardless of the beam width of the transmission wave. Further, since the beam width of the transmission wave is not limited, the beam width can be made wider than that of the second prior art radar apparatus. This makes it possible to easily reduce the size of the radar device.

According to the present invention, the distribution of the reception electric field strength of the mixed signal is created by collecting mixed signals obtained by mixing a reflected wave from a target object and a transmitted wave included in a predetermined range of a relative velocity. It is characterized by.

According to the present invention, the signal level distribution of the mixed signal is created as described above. Thus, even when there is a small error in the relative speed, the position and the size of the target can be calculated based on the curve shape of the maximum point representing the reflected wave from the same target.

[0031]

FIG. 1 shows a radar apparatus 31 using a signal processing method for a radar apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an electrical configuration of the embodiment. Radar device 31
Is a so-called FM-CW radar device, which is mounted on a vehicle, for example, and is used for detecting a preceding vehicle in an auto cruise device. The radar device 31 includes a transmission antenna 33, a reception antenna 34, an oscillation circuit 35, a local oscillator 36, a directional coupler 37, a mixing circuit 38, an amplification circuit 39, an FFT circuit 40, a displacement device 41, and a signal processing circuit 44. . Further, an application device 45 is provided in association with the radar device 31. Transmitting and receiving antennas 33 and 34, an oscillation circuit 35, a local oscillator 36, a directional coupler 37, a mixing circuit 38, and an amplification circuit 39
Are housed in a single housing as the sensor device 46.

The transmitting and receiving antennas 33 and 34 are antennas having high directivity, and the beam width θb of the main lobe of the transmitting antenna 33 is, for example, about 2 to 3 degrees. The transmitting antenna 33 is installed at a position where electromagnetic waves can be emitted forward in the traveling direction of the vehicle, for example. The receiving antenna 34 is installed at a position where it can receive electromagnetic waves from the front in the traveling direction of the vehicle. Such a position is, for example, in the front grill in front of the vehicle body of the vehicle. The transmitting and receiving antennas 33 and 34 may be realized by a configuration sharing a single antenna.

The oscillating circuit 35 generates an oscillating signal whose voltage increases and decreases according to the FM frequency of about 750 Hz, and supplies the oscillating signal to the local oscillator 36. The local oscillator 36 generates a local oscillation signal having a frequency corresponding to the voltage of the oscillation signal. The local oscillation signal is provided from the local oscillator 36 to the transmission antenna 33 via the directional coupler 37. The local oscillation signal is, for example, an AC power signal whose frequency shifts with time, and its intensity is always constant. The transmission antenna 33 radiates a transmission wave, which is an electromagnetic wave having the same frequency as the local oscillation signal, in a beam shape. This transmission wave is reflected by a target object ahead in the traveling direction of the vehicle, and returns as a reflected wave. The reflected wave is delayed according to the relative distance between the target and the radar device 31,
The frequency shifts in accordance with the relative speed between the target and the radar device 31.

The receiving antenna 34 receives an electromagnetic wave including a reflected wave and a noise component, and derives a received signal indicating the received electric field strength of the electromagnetic wave to the mixing circuit 38. The signal level of the received signal increases in proportion to the level of the received electric field strength. In addition to the received signal, the local oscillator 3
6 is provided via a directional coupler 37. The mixing circuit 38 mixes the local oscillation signal and the received signal to generate a beat signal that is a mixed signal of the two signals. This beat signal is supplied to the FFT circuit 40 after being amplified by the amplifier circuit 39.

The FFT circuit 40 first samples the signal level of the beat signal from the predetermined observation start time a predetermined number N with the passage of time to obtain N signal level values L1 to LN. This sampling is
It is repeated at a predetermined cycle. The number of times N of the above-mentioned sampling is, for example, 128 times. Next, by converting the signal level values L1 to LN of the beat signal into frequencies, the frequency components of the signal level of the beat signal at the observation start time are converted to the frequencies f1 to fN of the N observation points on the frequency axis.
Get every time. The FFT circuit 40 is realized by, for example, an arithmetic circuit that performs a frequency conversion operation, and the above-described frequency components of the beat signal are obtained by Fourier transform using the signal level values L1 to LN of the beat signal. The frequency component of each frequency is provided to the signal processing circuit 42.

The displacement device 41 periodically angularly displaces the radiation direction of the transmission wave so that the transmission wave scans a predetermined scanning range θs at a predetermined scanning speed. The transmission wave is, for example, angularly displaced parallel to the ground surface, and periodically scans the scanning range θs. The scanning range θs is, for example, 10 degrees to 15 degrees in a direction in which the measurement angle increases and decreases in a direction from the reference direction, and is assumed to be a range of 20 degrees to 30 degrees in total. The measurement angle is an angle between the radiation direction of the transmission wave and the reference direction in advance.

For example, the displacement device 41 includes the sensor device 4
6 is mechanically angularly displaced using a motor or the like to angularly displace the radiation direction of the transmission wave. Further, the displacement device 41 may have a structure in which only the transmitting and receiving antennas 33 and 34 are mechanically angularly displaced. Further, the angular displacement of the transmission wave in the radiation direction may be performed not only by the above-described mechanical method but also by an electric method. As an electrical method, for example, a method of using a phased array antenna as the transmitting antenna 33 and changing the phase difference of electromagnetic waves radiated from each antenna element of the phased array antenna to change the direction of the radiation beam is exemplified. .

The signal processing circuit 44 is supplied with the frequency component of each frequency of the signal level of the beat signal from the FFT circuit 40, and the displacement device 41 is supplied with the measurement angle of the transmission wave. In the present embodiment, it is assumed that the reference direction is a forward direction perpendicular to the axle of the vehicle and parallel to the ground surface. The signal processing circuit 44 obtains a distribution of the signal level of the beat signal with respect to the measurement angle and the frequency, and based on the distribution,
Calculate the position and size of the target. Further, a relative distance and a relative speed between the target and the vehicle are calculated based on the frequency of the beat signal.

The application device 45 receives the position and size of the target from the signal processing circuit 44 and controls the behavior of the vehicle based on the position and size. For example, the application device 45 determines whether or not the target obstructs the traveling of the vehicle. When it is determined that the target obstructs the traveling of the vehicle, the application device 45 controls the parts of the vehicle to perform an avoidance operation for avoiding the target. Do.

FIG. 2 shows transmitting and receiving antennas 33 and 3.
6 is a graph showing directivity of No. 4; The vertical axis of this graph is the electric field strength (unit: dB), and the horizontal axis is the radiation direction. In this graph, it is assumed that the radiation direction increases clockwise with the maximum radiation direction of the antenna being 0 degrees. The transmitting and receiving antennas 33 and 34 have directional characteristics such that the main lobe 51 is several times larger than the sub lobe 52. The beam width θb of the transmission wave is a width between points pb1 and pb2 on the curve representing the main lobe 51, which corresponds to an electric field intensity Em that is 3 dB lower than the electric field intensity Ep in the maximum radiation direction.

In the following, in order to explain the behavior of the FM-CW type radar device, the behavior of the transmitted wave, the reflected wave, and the beat signal will be described in detail. FIG. 3A is a graph for explaining the temporal shift of the frequency of the transmission wave and the reflection wave. The solid line 51 represents the temporal shift of the frequency of the transmission wave, and the solid line 52 represents the temporal shift of the frequency of the reflected wave returned by the transmission wave of the solid line 51 being reflected by the target.

The frequency of the transmitted wave is shifted around a predetermined center frequency F0 by a predetermined modulation width δf so as to periodically increase and decrease at a predetermined sweep period W1. Examples of the shift mode include a triangular wave sweep, a sawtooth sweep, and a sine wave sweep. In the present embodiment, a triangular wave sweep is performed. Specifically, the frequency of the transmission wave is the increasing period W from time t0 to time t2.
2, the frequency increases from the predetermined minimum frequency fmin to the predetermined maximum frequency fmax in proportion to the passage of time, and the time t
The maximum frequency fma in the decrease period W3 from 2 to time t4
It decreases in proportion to time from x to the minimum frequency fmin. The maximum and minimum frequencies fmax and fmin are frequencies that are increased and decreased from the center frequency F0 by half the frequency of the modulation width δf, respectively. Center frequency F0 is, for example, 60 GHz, and modulation width δf is, for example, 7 GHz.
5 MHz. The vibration frequency of the transmission wave at this time is, for example, 750 Hz, and the sweep cycle W1 is, for example, 1.3.
m seconds. The lengths of the increase and decrease periods W2 and W3 are the same, and are half the time of the sweep cycle W1. Further, the absolute values of the time change rates of the frequency increase and decrease are equal.

The delay time W4 from the emission time of the transmission wave to the reception time of the reflected wave of the transmission wave increases in proportion to the relative distance between the target and the radar device 31. The frequency difference δfcw between the maximum and minimum frequencies fmax and fmin of the transmitted wave and the maximum and minimum frequencies fmaxa and fmina of the reflected wave increases in proportion to the relative speed between the target and the radar device 31. Therefore, the behavior of the frequency shift of the reflected wave is such that the frequency shift timing is delayed from the frequency shift timing of the transmission wave by the delay time W4, and the maximum and minimum frequencies and the center frequency are different in frequency difference δf.
The difference is that the frequency changes by cw, and the time change rate of the frequency, the modulation width δf, and the sweep period W1 are equal. Therefore, the reflected wave increases in proportion to the passage of time from the start time t1 of the frequency increase to the decrease start time t3 via the time t2, and in proportion to the passage of time from the decrease start time t3 to the decrease end time t5 via the time t4. Decrease. The times t1, t3, and t5 are times delayed by the delay time W4 from the times t0, t2, and t4 of the frequency shift of the transmission wave, respectively.

FIG. 3B is a graph showing a beat signal generated by mixing the transmitted wave and the reflected wave shown in FIG. 3A. The beat frequency of the beat signal keeps the beat frequency Fup of the increase period W2 from the start time t1 of the increase in the frequency of the reflected wave to the start time t2 of the decrease in the frequency of the transmitted wave, and starts from the start time t3 of the frequency decrease of the reflected wave. The beat frequency Fdn of the decrease period W3 is maintained until the end time t14 of the frequency decrease. The beat signal obtained during the increasing period W2 is referred to as a beat signal Bpnn, and the beat signal obtained during the decreasing period W3 is referred to as a beat signal Bdnn. n is one or more arbitrary integers.

The beat frequencies Fup and Fdn of the beat signals Bupn and Bdnn are beat frequencies of the transmitted wave and the reflected wave, and become larger as the relative distance and the relative speed between the target and the radar device 31 are larger. In addition, the signal level of the local transmission signal always keeps a predetermined level, and the signal level of the reception signal fluctuates according to the change over time in the reception electric field strength of the reflected wave. For this reason, the beat signal is a pulsating signal whose signal level changes in accordance with the temporal change in the received electric field strength of the reflected wave, and the change in the amplitude of the AC component of the signal level is the temporal change in the received electrification intensity of the reflected wave. Corresponding to

FIG. 4 is a graph showing the distribution of the signal level of the beat signal Bpn during the increasing period with respect to the measurement angle and the frequency. This graph has three mutually orthogonal axes, with the horizontal axis representing the measurement angle, the depth axis representing the frequency and the vertical axis representing the signal level of the beat signal in the drawing. . The height from a certain point in the reference plane defined by the axis representing the measurement angle and the axis representing the frequency to the curved surface 71 representing the distribution corresponds to the frequency component of the signal level of the beat signal. The distribution of the signal level of the beat signal Bdnn in the decreasing period with respect to the measurement angle and the frequency is substantially equal to the distribution of the beat signal Bpn in the increasing period immediately before the decreasing period, unless there is an influence of noise, multipath interference, or the like.

The signal level locally increases, and the portion including the maximum point of the signal level corresponds to the reflected wave reflected by the target. This part is referred to as a noted part 75. When there is one target, there is one attention portion 75 as shown in FIG. 4, and when there are two targets, there are two attention portions 75 as shown in FIG. That is, when there is no interference or the like in the reflected waves, the curved surface representing the distribution has the same number of target portions 75 as the number of target objects. Within the angle range of the portion of interest, there is an angle formed by the direction in which the center of the target is viewed from the radar device 31 and the reference direction.

As described above, when the distribution of the received electric field strength is obtained by using the measured angle and the frequency as variables, the signal level of the beat signal is in a range defined by the direction from the radar device 31 toward the center of the target and the frequency of the beat signal. Increases locally. Therefore, the position of the center of the target and the size of the target can be obtained based on the position and the shape of the target portion 75 of the curved surface 71 representing this distribution.

The relationship between the shift of the frequency of the beat signal and the angular displacement of the transmission wave in the radiation direction will be described below. FIG. 6 is a graph showing the change over time of the frequency of the transmission wave. In order to prevent the frequency of the beat signal from being affected by the angular displacement of the transmission wave in the radiation direction, the radiation direction of the transmission wave is fixed while obtaining the beat signals Bupn and Bdnn to be sampled by the FFT circuit 40. Is preferred. For this purpose, for example, the radiation direction of the transmission wave is angularly displaced by the displacement device 41 within a period W11 that is an integral multiple of the sweep period W1, and the receiving antenna 34, the mixing circuit 38, With the circuit 39, beat signals Bpn and Bdnn are obtained. The transmitted wave is
The light may be continuously emitted over the periods W11 and W12, or may be emitted only during the period W12.

In this embodiment, the period W11 is the sweep cycle W
2, and the period W12 is assumed to be equal to the sweep period W2. The observation start time of the sampling described above corresponds to, for example, the start time of the period W12, and the cycle of the observation start time is equal to the sum of the periods W11 and W12. The amount of angular displacement in the radial direction within the period W11 is, for example, the beam width θb of the transmission wave.
Smaller than, for example, 0.1 degree to 1.0 degree. If you want to change the emission direction of the transmitted wave by electrical means,
The radiation direction of the transmission wave may be changed in such a procedure.

Further, when changing the radiation direction of the transmission wave by a mechanical method using a motor or the like, a load is applied to the motor when stopping the motor. Therefore, in order to reduce the load on the motor, the radiation direction of the transmission wave may be constantly angularly displaced at an angular velocity that does not affect the frequency shift of the transmission wave. For example, the radiation direction of the transmission wave is angularly displaced by the angular displacement while the sweep of the frequency of the transmission wave from the minimum frequency to the maximum frequency and back to the initial frequency is repeated a plurality of times. The receiving antenna 34, the mixing circuit 38, and the amplifying circuit 39 perform the beat signals Bpn, Bdnn in any one of the plurality of sweeps.
To get. In the present embodiment, the number of sweeps is set to, for example, 5
Times. Thus, it is possible to prevent the beat signal from being affected by the angular displacement of the transmission wave in the radiation direction without applying a load to the motor.

FIG. 7 is a flowchart for explaining the signal processing operation of the radar device 31. Radar device 31
Is activated, the process proceeds from step a1 to step a2. In step a2, first, the displacement device 41 changes the radiation direction of the transmission wave to a direction shifted from the reference direction by the measurement angle θn. n is any integer of 0 or more. Next, the oscillation circuit 35, the local oscillator 36, and the transmission antenna 33
Then, a transmission wave is emitted. In step a3,
The reception antenna 34 receives the electromagnetic wave to generate a reception signal, and supplies the reception signal to the mixing circuit 38 to generate a beat signal.

In step a4, the FFT circuit 40 performs a beat signal sampling process and a frequency conversion process to determine the frequency components of the signal levels of the beat signal at frequencies f1 to fN. The frequency conversion process is a process for rearranging the signal levels L1 to LN using the sampling time as a variable and obtaining the distribution by using the frequency as a variable. Specifically, for example, a fast Fourier transform method of N points is used for the frequency conversion process. The number N of the Fourier transform is, for example, 128 points. Equation 1 is a conversion equation of a fast Fourier transform method for obtaining a frequency component cn (tam) of an arbitrary frequency fn among the frequencies f1 to fN in the frequency conversion processing at the observation start time tam where the measurement angle is the angle θn. It is. Obtained frequency component c1 (tam)-
The cM (tam) and the measurement angle θn are stored in, for example, a memory inside the signal processing circuit 44 in association with each other.

[0054]

(Equation 1)

In step a5, it is determined whether or not the operations in steps a2 to a4 have been executed N times. Number of executions is N
If it is less than the number of times, the process returns from step a5 to step a2, and the displacement device 41 increases the measurement angle θn by the predetermined angular displacement, and repeats the processes of steps a2 to a4. The number of executions N is, for example, 40 times. When the number of executions is N or more, the process proceeds from step a5 to step a6. The processing operations of steps a2 to a5 are performed within a time period that can prevent the relative distance from being corrected due to the movement of the target during this processing operation. This time is, for example, 0.1 second.

In steps a6 and a7, the signal processing circuit 4
4 operates as means for detecting the maximum point of the signal level distribution of the beat signal. This operation will be described with reference to FIG. FIG. 8 is a simplified graph of the distribution shown in FIGS. First, in step a6, the signal processing circuit 44 outputs the beat signal B in the increasing period and the decreasing period.
step a for each of upn and Bdnn
Among the frequency components of all the signal levels obtained by the processes 2 to a5, the frequency at the maximum point of the curve representing the distribution of the signal level of the beat signal with respect to the frequency is obtained by using the frequency components having the same measurement angle.

In this process, first, a curved surface 71 representing a distribution is first obtained by a plane which is perpendicular to the reference plane, parallel to the axis in the depth direction, and passes through a point representing the measurement angle θx on the axis in the horizontal direction. To obtain a curve 72 representing the cross section. FIG. 9 is a graph showing the distribution of the signal level of the beat signal with respect to the frequency at a certain measurement angle θx, and corresponds to the above-described cross section. Next, the signal level Lp at the maximum point of the curve 72 is searched. The signal level Lp at the local maximum point is, for example, equal to or higher than a predetermined reference level, and is the largest signal level corresponding to a measurement angle within a predetermined angle range centered on the measurement angle corresponding to the signal level. And Finally, the frequency at the obtained signal level Lp is obtained as the frequency fp of the local maximum point. This process is performed for each measurement angle, for example, by increasing or decreasing the measurement angle θx in units of the angular displacement.

Next, in step a7, for each of the beat signals Bupn and Bdnn in the increasing period and the decreasing period, of the frequency components of all signal levels obtained by the processing in steps a2 to a5, the frequency components obtained in step a6 are obtained. Using the frequency component corresponding to the obtained maximum point frequency fp, the measurement angle of the maximum point of the curve representing the distribution of the signal level of the beat signal with respect to the measurement angle is obtained. In this process, first, a curved surface 71 representing the distribution is first expressed by:
A plane that is perpendicular to the reference plane and parallel to the horizontal axis and passes through a point representing the frequency fp of the maximum point on the axis in the depth direction is cut out, and a curve 73 representing the cross section is obtained. FIG. 10 is a graph showing the distribution of the signal level of the beat signal with respect to the measurement angle at the frequency fp of the maximum point, and corresponds to the above-described cross section. Next, on the curve 73, a point where the signal level is the signal level Lp is searched, and the measurement angle of the point is obtained. When a plurality of maximum points are obtained, the process of step a7 is performed for each maximum point.

In step a8, the signal processing circuit 44
It operates as a means for extracting a portion of interest on a curved surface representing the distribution of the signal level of the beat signal. For this purpose, the signal processing circuit 44 determines the angle range in which the target exists. The angle range in which the target is present when viewed from the radar device 31 includes a measurement angle θL when a transmission wave is applied to one end of the surface of the target facing the radar device 31 in the horizontal direction, and a horizontal direction of the surface. Angle θ when transmission wave hits the other end of
Let R be both ends. This angle range is
This corresponds to the angle range of the portion of interest in the graphs of FIGS.

Specifically, first, the signal processing circuit 44
Beat signals Bpn, Bdn in the increasing period and the decreasing period
n individually for each of the measurement angles θL, θ at both ends of the angle range based on the signal level distribution with respect to the measurement angle at the frequency fp of the maximum point obtained in step a6.
Look for R. Specifically, as shown in FIG. 10, the measurement angles θL and θR are measurement angles corresponding to a signal level Lb smaller than the signal level Lp at the local maximum point by a predetermined reference level ΔL. Reference level ΔL is, for example, 10 dB to 20 dB.

Next, the signal processing circuit 44 obtains the angle width Δθa of the angle range. The angle width Δθa is calculated by, for example, Equation 2.
Is the difference obtained by subtracting the measurement angle θL from the measurement angle θR. Further, the signal processing circuit 44 calculates the center angle θm of the angle range. The center angle θm is calculated by, for example, Equation 3.
Is an intermediate angle between the measurement angles θL and θR. The angle width Δθa and the center angle θm are stored in the memory in association with the signal level Lp and the frequency fp of the local maximum used in the calculation. When there are a plurality of maximum points, the process of step a8 is performed for each maximum point. Δθa = θR−θL (2) θm = (θR−θL) / 2 + θL (3)

When the angle width Δθa is smaller than the beam width θb, the angle width Δθa is considered to be a value that increases and decreases using the reference angle width θc determined based on the antenna characteristics of the transmitting antenna 33 as a variable. The reference angle width θc is the electric field strength En lower than the electric field strength Ep in the maximum radiation direction by a predetermined electric field strength ΔL on the curve representing the main lobe 51 in FIG.
Is the width between the points pb3 and pb4. Experimentally, the angle width Δθa was substantially equal to the reference angle width θc.

Referring again to FIG. In step a9,
The signal processing circuit 44 functions as a determination unit, and determines whether or not the angular ranges obtained in step a8 overlap with each other for each signal level distribution of the beat signal in the increasing period and the decreasing period. When the angle ranges overlap, the process proceeds from Step a9 to Step a10. When the angle ranges do not overlap, Step a9
The process proceeds from step 9 to step a11. In step a10, the signal processing circuit 44 resets the angle range based on the local maximum point of the plurality of overlapping angle ranges to reduce the plurality of angle ranges to one. After resetting, steps a10 to a
Proceed to 11.

By the processing in steps a6 to a10, the beat signals in the increasing period and the decreasing period are
As variables of the data of the local maximum point of the distribution of the beat signal, the frequency fp and the signal level Lp of the local maximum point, the angle width Δθa of the angle range including the local maximum point, and the center angle θm are obtained. The data of the local maximum point represents a curved shape representing a cross section obtained by cutting a portion of interest including the local maximum point through the local maximum point and parallel to an axis representing an angle. Table 1 shows that the maximum points Pup1 to Pup of the beat signal in the increasing period and the decreasing period.
3, an example of data of Pdn1 to Pdn3.

[0065]

[Table 1]

At step a11, the signal processing circuit 44
Combines the noteworthy parts of the distribution of increasing and decreasing periods representing reflected waves from the same target. For this purpose, the signal processing circuit 44 determines the maximum point P of the beat signal Bpn during the increase period.
Upi data and the data of each maximum point Pdni of the beat signal Bdnn in the decreasing period are compared, and the combination of the data of the maximum point of the target portion which is located at substantially the same position on the reference plane and has almost the same shape is obtained by: It is selected as the data of the local maximum point of the portion of interest representing the reflected wave from the same target. i is an arbitrary natural number.

For example, first, an arbitrary maximum point Pupi,
Pupi is selected, the difference of the frequency fp, the signal level L
p, angular range center angle θm difference, and angular width Δ
The difference between θa is determined. Next, whether the difference of the frequency fp is less than a predetermined first reference value or not, the signal level L
whether the difference of p is less than a predetermined second reference value, whether the difference of the center angle θm of the angle range is less than a predetermined third reference value, and whether the difference of the angle width Δθa is the fourth predetermined value.
It is checked whether it is less than the reference value.

When all the differences are less than the reference value, it is considered that the shapes of the two target portions individually including the local maximum points Pupi and Pdni are similar, and the target portions recognize the reflected waves from the same target. It is determined that the information is to be represented. When any one difference is equal to or more than the reference value, the local maximum point Pu
It is considered that the shapes of two attention portions individually including pi and Pdni are different, and it is determined that the attention portions do not represent reflected waves from the same target.

This determination is made, for example, by determining the frequency f of the local maximum point.
local maximum points Pupi, Pd in which the difference of p is less than a predetermined value
ni to cover all combinations of ni
i, Pdni is changed and the repetition is performed, and the local maximum point P determined to indicate that the focused portion represents a reflected wave from the same target object
Upi and Pdni data are stored in the memory. Alternatively, an average value may be obtained for the values of the variables of the local maximum points Pupi and Pdni, and the average value may be stored together.

When a plurality of combinations in which all of the differences are less than the reference value are obtained by this determination, the maximum point Pupi of the combination in which the difference of the frequency fm is the smallest among these combinations is obtained. , Pdni are selected as corresponding to the reflected waves from the same target. In addition, the criteria for this selection are a difference in signal level Lp, a difference in center angle θm,
Alternatively, the difference between the angle widths Δθa may be used, and the difference between two or more of the four types of differences may be selected. Further, other variables may be used as long as the variables can compare the shape and position of the target portion.

For example, in the example of Table 1, the local maximum points Pup1, Pup
dn1 and the maximum points Pup2, Pdn1
Is considered, the difference between the variables of the data is smaller in the former case. Therefore, the former combination is selected. It can be seen from the center angles and the angle widths that the maximum points Pup1 and Pup2 have overlapping angle ranges. Therefore, the two noticeable portions individually including the local maximum points Pup1 and Pup2 are originally a single noticeable portion because, for example, the signal level of the reflected wave from a single target is locally reduced due to the interference of the reflected waves. It is considered that what is supposed to be a divided one. Therefore, by this combination process, the target portion divided into a plurality of portions for the above-described reason can be considered as one target portion, and the maximum point thereof can be used for the subsequent process.

In the example of Table 1, the maximum points Pup3, Pd
Considering the case where n2 is combined and the case where the maximal points Pup3 and Pdn3 are combined, the difference between the variables of both data is almost equal. Comparing the local maximum points Pdn2 and Pdn3, it can be seen that the frequency and signal level of the local maximum points are almost the same, and the angle ranges are also overlapping. For this reason,
It is considered that the two noticeable portions individually including the two maximum points are also divided from those originally supposed to be a single noticeable portion. In this case, the signal processing circuit 44 creates new maximum point data based on the values of the variables of the maximum points Pdn2 and Pdn3, and the data of this maximum point and the maximum point Pdn.
Up3 data is used in combination with the up3 data for subsequent processing.
The value of each variable of the new maximum point data is, for example, the average of the values of the maximum points Pdn2 and Pdn3. In the example of Table 1, the frequency is 75 Hz, the center angle is 4.1 degrees, and the angle width is 3 degrees. 0.8 degrees. Also according to this combination process, the attention portion divided into a plurality of portions for the above-described reason can be considered as one attention portion, and the maximum point thereof can be used for the subsequent processes.

Referring back to FIG. In step a12, the signal processing circuit 44 operates as a means for calculating the relative distance and the relative speed of the target. Specifically, the signal processing circuit 44 substitutes the frequency of the data of the maximum point combined in step a11 into Expressions 4 and 5, and calculates the relative distance R and the relative distance between the radar device 11 and the target. Calculate the speed v. It is assumed that the relative distance R is a length of a line segment having both ends of the antenna of the radar device 31 of the vehicle 61 and the surface of the target object that reflects the transmission wave, and is parallel to the reference direction 65. The relative velocity v represents a velocity in a direction in which the target approaches the radar device 11 by a positive value, and a velocity in a direction away from the radar apparatus 11 by a negative value.

In equations (4) and (5), “fup” is the frequency fp of the maximum point Pupi of the beat signal Bpn in the increasing period.
And “fdn” is the beat signal Bdnn in the decreasing period.
Is the frequency fp of the maximum point Pdni. The coefficient Kr is, as shown in Expression 6, the center frequency F0 of the transmission wave and the modulation width δf
Is determined by a predetermined function F () using The coefficient Kv is defined as shown in Expression 7.
c is the speed of light.

[0075]

(Equation 2)

Kr = F (F0, δf) (6) Kv = 2 · F0 / c (7) The data of the maximum point used in this calculation processing is the central angle θm of the angle range when they are combined. And angle width Δ
θa. As a result, since the shape of the target portion including the maximum point is compared, it is possible to prevent the maximum points of the target portion of the distribution of the increase and decrease periods corresponding to different targets from being combined beforehand. it can.
Therefore, when calculating the relative distance R and the relative speed v using the data combined in step a11, the accuracy can be improved more than the relative distance and the relative speed calculated by the conventional radar device.

At step a13, the signal processing circuit 44
Works as a means for calculating the center position of the target based on the position and shape of the target portion. Schematically, the circuit 44 determines that the center of the target is located in a direction in which the angle formed with the reference direction is the center angle θm, and determines the center position of the target as the relative distance R determined in step a12. And the angle width Δθa and the center angle θm of the data of the maximum point combined in step a11.
In the following equation, “(θR−θL) / 2 + θL” represents an angle between the direction in which the center of the target is located and the reference direction.

Specifically, assuming that the x-coordinate axis of the xy rectangular coordinate system is parallel to the reference direction, the y-coordinate axis is perpendicular to the reference direction and parallel to the ground, and the origin coincides with the radar device 31, The x coordinate of the center position of the object has a value equal to the relative distance R, and the y coordinate is obtained by the following equation. Thus, the position of the center of the target can be obtained without reducing the beam width of the transmission wave. Further, the local maximum point of the curve representing the distribution is directly used as y at the center position.
The center position of the target can be obtained more accurately than when the coordinates are used. Center position = R × tan {(θR−θL) / 2 + θL} = R × tan {Δθa / 2 + θL} (8)

At step a14, the signal processing circuit 44 functions as a determining means, and determines whether or not the relative distance R exceeds a predetermined reference distance Rth. When the relative distance R exceeds the reference distance Rth, the process proceeds to step a15. When the relative distance R is equal to or less than the reference distance Rth, the process proceeds to step a16.
Proceed to. In steps a15 and a16, the signal processing circuit 4
Reference numeral 4 serves as a means for calculating the width of the target in the direction parallel to the scanning direction based on the position and shape of the target portion.
Specifically, in step a15, the width is the angle width Δθ
The width is calculated based on the relative distance R and the measurement angles θR and θL of the angle range of the data of the local maximum point combined in step a11, considering that a is a variable.
Is calculated by In step a16, the width is calculated by Expression 10 based on the relative distance R and the measured angles θR and θL, assuming that the width increases or decreases using the difference between the angle width Δθa and the beam width θb as a variable. Width = R × tan θ R−R × tan θL (9) width = R × tan (θR−θb / 2) −R × tan (θL−θb / 2) (10)

The reason for changing the width calculation method according to the relative distance is as follows. The angle width Δθa decreases as the target moves away from the radar device. Therefore, even when the angular width Δθa and the beam width θb at which the target that is separated from the radar device 31 by a certain relative distance exists are equal,
If the target moves away from the radar device 31 by more than a certain relative distance, the angular width Δθa becomes less than the beam width θb, and if the target approaches the radar device 31 to less than a certain relative distance, the angular width Δθa becomes Exceeds the width θb. For this reason,
The relationship between the angle width Δθa, the relative distance R, and the size of the target changes according to the relative distance R. When the width of the target in the scanning direction is obtained by Expression 9, the error is small when the angle width Δθa exceeds the beam width θb, but an error occurs when the angle width Δθa is equal to or smaller than the beam width. Sometimes. In order to reduce this error, in the radar device 31 of the present embodiment, the formula for calculating the width is changed according to the magnitude relationship between the relative distance R and the reference distance Rth.
As a result, a width error can be reduced. When the width is calculated in any of Steps a15 and a16, the processing operation of the signal processing circuit 44 ends, and Step a17
Proceed to.

At step a17, the application device 45 functions as a judgment means, and based on the center position and width of the target obtained by the processing at steps a6 to a16, is there any possibility that the target obstructs the running of the vehicle? Determine whether or not. When the target obstructs the running of the vehicle, the process proceeds from step a17 to step a18. If it does not hinder, the process proceeds from step a17 to step a19, and the signal processing operation ends.

The determination as to whether or not the target obstructs the running of the vehicle is made, for example, by considering a virtual axis passing through the center of the vehicle and parallel to the forward direction. First, the positional relationship between the virtual axis and the center of the target is considered. Find out. If the position of the center of the target is on the virtual axis, it is considered that the target may obstruct the running of the vehicle. If the location of the center of the target is away from the virtual axis, then based on the width of the target,
It is checked whether or not the end of the target is on the virtual axis. For example, even when the position of the center of the target is very close to the virtual axis, if the width of the target is less than the distance between the center and the virtual axis, the target does not hinder the traveling of the vehicle. . Conversely, even when the center of the target is located far from the virtual axis, if the width of the target is equal to or greater than the distance between the center and the virtual axis, the end of the target is positioned on the virtual axis. Therefore, it is assumed that the target may hinder the running of the vehicle. As described above, in the radar device 31 of the present embodiment, since the accurate position and size of the target are known, it is possible to reliably determine whether the target obstructs the traveling of the vehicle.

The above-described determination may be made in consideration of not only the positional relationship between the target and the vehicle but also the traveling state of the vehicle and the traffic state of the road on which the vehicle is traveling. The running state of the vehicle is determined based on information measured by various sensors including a vehicle speed sensor, a yaw rate sensor, and a steering sensor, for example. The traffic condition of the road is obtained based on information measured by the navigation device and a sensor provided therein.

At step a18, the application device 45 controls parts of the vehicle to perform an avoiding operation for avoiding a target. For example, a warning device is attached to a vehicle, and when there is a target that hinders the running of the vehicle, a warning sound is generated by the warning device. As a result, the driver of the vehicle can recognize that there is a target that hinders the traveling of the vehicle, and can change the traveling direction of the vehicle. Therefore, the target can be avoided before the vehicle approaches the target. Also, an electrically controllable power source is attached to the shaft of the steering wheel, and when there is a target that hinders the running of the vehicle, the steering wheel is rotated by the power source so that the traveling direction of the vehicle can avoid the target. May be changed. Thereby, the target can be avoided before the vehicle approaches the target.

Further, an electrically controllable power source is mounted on the brake of the vehicle, and when there is a target that hinders the running of the vehicle, the brake is operated by the power source,
Decrease the running speed of the vehicle. As a result, the vehicle can be prevented from suddenly approaching a target that hinders the traveling of the vehicle. Furthermore, an electrically controllable power source is attached to the throttle valve of the vehicle, and when there is a target that hinders the running of the vehicle, the opening of the throttle valve is reduced by the power source to reduce the running speed of the vehicle. Let it. This can also prevent the vehicle from approaching a target that hinders the traveling of the vehicle. In these avoiding operations, the traveling speed of the vehicle may be reduced to such an extent that the vehicle stops, or the target may be tracked at such a speed that the relative distance to the target does not decrease. These four types of avoidance operations are examples, and other avoidance operations may be performed. Further, these avoiding operations may be executed individually, a part of the operations may be executed in combination, or all the operations may be executed at the same time.

When the object avoiding operation is completed, step a1 is executed.
At 9, the signal processing operation ends. With this series of operations, the radar device 31 can accurately calculate the position and size of the target irrespective of the beam width of the transmission wave. Also, since the beam width of the transmission wave is not limited,
By increasing the beam width compared to the second prior art radar device, the position and size of the target can be calculated with the same accuracy as the conventional radar device.
The size can be easily reduced.

The determination in step a9 is made for the following first and second reasons. The first reason is as follows. When the received electric field strength of the reflected wave is close to the noise component received by the receiving antenna 34, the portion including the maximum point caused by the increase in the signal level due to the increase in the noise component is the target portion. Mistaken for
The angle range may be required. For this purpose, the signal processing circuit 44 selects only the angle range of the target portion representing the reflected wave of the target from the overlapping angle ranges.

The second reason is as follows. If the surface of the target object that reflects the transmitted wave has irregularities and the like, the reflected waves from a plurality of points in the surface interfere with each other, and the received electric field strength may be reduced. For this reason, the received electric field strength of the reflected wave from the target object may be locally reduced in spite of the fact that the transmitted electric wave should have almost the same value no matter where the transmitted wave is reflected. Further, the reflectance may be different at a plurality of points on the reflecting surface, and in this case, the received electric field strength of the reflected wave may be locally reduced. This often occurs, for example, when the beam width of the transmitted wave is less than the angular range in which the target is located. At this time, although there is only one target, a plurality of portions of interest can be formed on the curved surface representing the distribution. Therefore, in this case, the signal processing circuit 44 integrates the plurality of attention portions as representing one target in step all, and resets the angle range based on the integrated attention portions.

The angle range resetting process will be described with reference to FIG. FIG. 11 is a graph showing the distribution of the signal level of the beat signal with respect to the measurement angle at the frequency fp of the maximum point when only one target exists. Among the maximum points of the curve 80 representing the distribution, the angle ranges of the maximum points 81 and 82 whose signal level is the reference level overlap. Maximum point 8
The angle width of the angle range of 1,82 is defined as angle width Δθa1, Δθ
a2. There are two methods for resetting the angle range.

In the first method of resetting the angle range, the maximum point 81 having the maximum signal level is selected from the maximum points 81 and 82 where the angle ranges overlap, and only the angle range of the maximum point 81 is selected. Adopted so that the angle range of the remaining maximum point 82 is not used in the subsequent processing. The angle width and the center angle are calculated based on the angle range of the local maximum point 81. When this method is used, when the angle ranges overlap due to the first reason, it is possible to prevent the angle range caused by the noise component from being used in the subsequent processing.

In the second method of resetting the angle range, first, the maximum point 81 having the highest signal level is selected from the maximum points 81 and 82 where the angle ranges overlap. Then
In the distribution of signal levels in the entire overlapping angle range, a point whose signal level is smaller by a predetermined level ΔL than the signal level of the selected maximum point 81 is detected. In the example of FIG. 11, points 83 to 88 are detected. Finally, the angles of the two outermost points among the detected points are determined by measuring angles θR,
It is acquired as θL. In the example of FIG. 11, the point 83 having the smallest measurement angle and the point 88 having the largest measurement angle are selected, and the measurement angles of these two points 83 and 88 are obtained as the measurement angles θR and θL. Using these measurement angles θR and θL, an angle width Δθa and a center angle θm are obtained by Expressions 2 and 3, and the angle width Δθa and the center angle θm are converted to the signal level and frequency of the selected local maximum point 81. The information is stored in the memory in association with each other.

When obtaining the measurement angles θR and θL,
The envelopes of the plurality of local maximum points 81 and 82 are obtained, and points on the envelope where the received electric field strength is smaller than the received electric field strength of the local maximum points by the electric field strength ΔL are detected, and the angles corresponding to these points are measured. The angles θR and θL may be used. When this method is used, when the angle ranges overlap for the second reason, the angle ranges can be combined to obtain an angle range corresponding to one target. Further, the entire overlapping angle range may be directly used as one angle range.

Hereinafter, a radar apparatus using the signal processing method for a radar apparatus according to the second embodiment of the present invention will be described. The electrical structure of the radar device of the second embodiment is the same as that of the first embodiment.
Compared to the radar device 31 of the embodiment,
The difference is that 0 is deleted and the output from the amplifier circuit 39 is directly supplied to the signal processing circuit 44. Also,
The signal processing operation of the signal processing circuit 44 has been changed. Components having the same structure and behavior are given the same reference numerals,
Description is omitted.

FIG. 12 is a flowchart for explaining the signal processing operation of the radar device of the second embodiment. This flowchart includes steps for performing operations similar to those of the flowchart of FIG. 7, and detailed description of those steps will be omitted. When the radar device is activated, the process proceeds from step a1 to step a2. The processing operations in steps b2 to b5 are the same as those in steps a2 to a except for the processing operation in step b4.
Equal to 5.

At step b4, the signal processing circuit 44 operates as a means for calculating the relative distance and the relative speed.
Specifically, first, for each of the beat signals Bupn, Bdnn in the increasing period and the decreasing period in which the measurement angle θn is equal, the beat frequencies fup,
fdn, and this beat frequency is set to the maximum point frequency fp.
Substituting into Equations 4 and 5 for the relative distance R and the relative velocity v. At this time, when there are a plurality of beat signals Bpn and Bdnn having the same measurement angle θn, for example, a combination of beat signals having the smallest difference in beat frequency,
Alternatively, a combination of beat signals having the smallest signal level difference is selected, and the above-described calculation processing is performed. The relative distance R and the relative velocity v are stored in association with the signal levels of the beat signals Bpn and Bdnn and the measurement angle θn. If the signal levels of both beat signals Bupn and Bdnn are different, the average value of the signal levels of both beat signals Bupn and Bdnn, or both beat signals Bupn and Bdn.
The higher level of dnn is associated.

In step b5, the same determination as in step a5 is performed. When the number of executions of the operations in steps b2 to b4 is less than N times, the process returns from step b5 to step b2, and the displacement device 41 sets the measurement angle θn to the angle. The processing of steps b2 to b4 is repeated with the displacement increased.
When the number of executions is N or more, the process proceeds from step b5 to step b6.

In steps b6 and b7, the signal processing circuit 4
4 operates as means for detecting the maximum point of the signal level distribution of the beat signal. First, in step a6, the signal processing circuit 44 calculates, for each of a plurality of predetermined relative speeds, the distribution of the signal level of the beat signal corresponding to the relative speed in the predetermined range including the relative speeds with respect to the measurement angle and the relative distance. Ask. The graph representing this distribution represents the variables represented by the axes in the depth direction of the graphs of FIGS.
It is replaced with the relative distance from the frequency. This graph is created for each of the plurality of relative speeds.
Further, the predetermined range is, for example, approximately the same as the resolution of the FFT processing.

In steps b7 and b8, the signal processing circuit 4
4 operates as a means for extracting a portion of interest of the distribution created in step b6 and calculating data representing its shape. Specifically, in step b7, the signal processing circuit 44 determines, for each signal level having the same relative distance, a local maximum of a curve representing the distribution of the signal level with respect to the measurement angle based on the distribution created for a certain relative speed. Find the measurement angle and relative distance of the point. The specific method of this process is different from the process of step a7 in that the process in step a6
The process performed only for the frequency of the maximum point obtained in
The difference is that the measurement is performed for a plurality of predetermined measurement angles θn, and the others are equal. In step b8, the signal processing circuit 44
Operates as means for calculating the angle range in which the target exists, and calculates the center angle θm and the angle width Δθa of the angle range by the same processing as in step a8. Angle width Δθa
And the center angle θm are stored in the memory in association with the signal level Lp and the relative distance of the local maximum point used for the calculation.

At step b9, the signal processing circuit 44 functions as a judging means, and judges whether or not the angle ranges obtained at step b8 overlap each other based on the distribution created for the relative speed. When the angle ranges overlap, the process proceeds from step b9 to step b10, where the angle range is reset, and the process proceeds to step a11. If they do not overlap, the process proceeds directly from step b9 to step b11. Steps b9 and b10 are performed in steps a9 and a9.
Equivalent to 10.

At step b11, the signal processing circuit 44
Functions as a means for calculating the center position of the target based on the position and shape of the target portion. In step b12,
The signal processing circuit 44 functions as a determination unit, and determines whether the relative distance R exceeds a predetermined reference distance Rth.
When the relative distance R exceeds the reference distance Rth, step b
When the relative distance R is equal to or smaller than the reference distance Rth, the process proceeds to step b14. In steps b13 and b14, the signal processing circuit 44 functions as a means for calculating the width of the target in the direction parallel to the scanning direction based on the position and shape of the target portion. The processing operations in steps b11 to b14 are different from the processing operations in steps a13 to a16 in that the angle range obtained in step b8 is used instead of the angle range obtained by the combination processing in step a11. And others are equal. When the width is calculated in one of steps b13 and b14, the processing operation of the signal processing circuit 44 ends, and the process proceeds to step b15.

In step b15, the signal processing circuit 44 operates as a judgment means, and performs the processing in steps b7 to b1 on the distributions of all the relative velocities created in step b6.
It is determined whether the process of No. 4 has been performed. When there is a process that has not been performed, the process returns from step b15 to step b7, and the above process is performed on a process that has not been performed. If it is determined that the processing has been performed on all the items, the process proceeds from step b15 to step b16.
Proceed to.

In step b16, as in step a17, the application device 45 functions as a judgment means, and the target obstructs the running of the vehicle based on the position and width of the target obtained by the processing in steps b7 to b14. It is determined whether or not it is in a possible position. If the target obstructs the travel of the vehicle, the process proceeds from step b16 to step b17, where the avoidance processing of the target is performed, and then the signal processing operation ends in step b18. Also,
If not hindered, the process proceeds directly from step b16 to step b18 to end the signal processing operation. Step b
Detailed operations of steps 16 and b17 are described in steps a17 and a18.
Is equal to

By the series of operations, the radar apparatus according to the second embodiment can accurately calculate the position and the size of the target irrespective of the beam width of the transmission wave.
Further, since the beam width of the transmission wave is not limited, the position and size of the target can be calculated with the same accuracy as that of the conventional radar device by making the beam width wider than that of the second conventional radar device. A possible radar device can be easily reduced in size.

The flowcharts of FIGS. 7 and 12 are examples, and the signal processing operations of the radar devices of the first and second embodiments may be such that only a part of the operations described in the flowcharts of FIGS. Good. For example, steps a9, 10; b9, b10 may be omitted. Steps a14 and b12 are deleted, and step a1
3, after completion of b11, steps a15, 16; b13,
One of the operations b14 may be executed. The processing in steps a4 and b4 is performed in step a
They may be executed collectively after 5 and b5.

Furthermore, the processing of the application device 45 is not limited to the above-described avoidance operation, but may be another operation. Further, the radar device 31 may calculate only the position or the size of the target in response to the operation of the application device. Further, in the above-described radar apparatus, the processing of steps a6 to a18; b6 to b17 is performed by the arithmetic processing of the signal processing circuit 44 and the application apparatus 45, but means for performing only the processing operation of each step are separately prepared. Then, they may be performed individually.

The radar apparatus of the first and second embodiments is an example of the signal processing method of the radar apparatus of the present invention, and can be implemented in other various forms if the main operations are the same. Particularly, detailed operations of each circuit and device are not limited thereto, and may be realized by other operations as long as the object is achieved. Also, the signal processing method of this radar device is as follows.
The present invention may be applied to a radar device other than the FM-CW type radar device. Furthermore, the signal processing method of the radar device is realized by storing in a storage medium of a computer software for executing the above-described signal processing method, and installing this software on a computer that controls the radar device. You may. The storage medium includes a CD-ROM and a floppy disk.

[0107]

As described above, according to the present invention, in the signal processing method of the radar apparatus, first, as described above, the distribution of the signal level of the beat signal with respect to the frequency and the angle is created.
Based on this distribution, the position and size of the target and the relative distance and relative speed between the target and the radar device are calculated. Thus, the position and size of the target can be accurately calculated regardless of the beam width of the transmission wave. Further, the radar device can be easily downsized. Further, the calculation accuracy of the relative distance and the relative speed can be improved.

Further, according to the present invention, in the signal processing method of the radar apparatus, in order to obtain a local maximum point having a similar curve shape, the signal level and the angle of the local maximum point are compared with an angle range including the local maximum point. . Thereby, the arithmetic processing can be facilitated.

Furthermore, according to the present invention, in the signal processing method of the radar apparatus, when there are a plurality of maximum points of a certain frequency distribution, the size of the target and the size of the target are determined based on the maximum point of the signal level. Find the position. According to the present invention, in the signal processing method of the radar device, when there are a plurality of local maximum points of a certain frequency distribution, and when the angular ranges of the local maximum points overlap each other, a curve of the entire curve of the overlapping angular range is obtained. The size and position of the target are determined based on the shape. As a result, the size and position of the target can be reliably obtained.

Further, according to the present invention, in the signal processing method of the radar apparatus, when there are a plurality of maximum points in the distribution of the increasing period and the decreasing period, a difference between the variables of the maximum points in both periods is obtained, and Are set as combinations of local maximum points having similar curve shapes. Thus, the relative distance and the relative speed, and the size and the position of the target can be reliably obtained.

Further, according to the present invention, when the difference between variables is obtained by combining the maximum points of the increasing period and the decreasing period, when there is a plurality of combinations of the maximum points where the difference of each variable is smaller than the reference value. , The combination in which the difference between any one of the variables is the smallest is a combination of the maximum points having similar curve shapes. Thus, even in the case described above, the relative distance and the relative speed, and the size and the position of the target can be reliably obtained.

Further, according to the present invention, in the signal processing method, first, a relative distance and a relative speed are obtained, and then the distribution of the signal level of the beat signal with respect to the relative distance, the relative speed and the angle is obtained, and based on the distribution, To determine the position and size of the target. Thus, the position and size of the target can be accurately calculated regardless of the beam width of the transmission wave. Further, the radar device can be easily downsized. Further, the calculation accuracy of the relative distance and the relative speed can be improved.

According to the present invention, the signal level distribution of the beat signal is created by collecting signal levels corresponding to a certain range of relative speed. Thus, even when there is a small error in the relative speed, the position and the size of the target can be reliably calculated.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an electrical configuration of a radar device 31 using a signal processing method for a radar device according to a first embodiment of the present invention.

FIG. 2 is a graph showing antenna characteristics of transmission and reception antennas 33 and 34.

FIG. 3 is a waveform diagram illustrating a change over time in the frequency of a transmitted wave and a reflected wave, and a waveform diagram illustrating beat signals Bupn and Bdnn.

FIG. 4 shows a beat signal Bu with respect to a measurement angle and a frequency.
It is a graph showing distribution of pn signal level.

FIG. 5 shows a beat signal Bu with respect to a measurement angle and a frequency.
It is a graph showing distribution of pn signal level.

FIG. 6 is a waveform diagram illustrating a change over time of the frequency of the transmission wave for explaining the relationship between the angular displacement of the transmission wave in the radiation direction and the shift of the frequency of the transmission wave.

FIG. 7 is a flowchart for explaining a signal processing operation of the radar device 31.

FIG. 8 shows a beat signal Bu with respect to a measurement angle and a frequency.
It is a schematic diagram which represents the graph which represents the distribution of the signal level of pn in a simplified manner.

FIG. 9 is a graph showing the distribution of the signal level of the beat signal Bpn with respect to the frequency at a certain measurement angle.

FIG. 10 is a graph showing a distribution of a signal level of a beat signal Bpn with respect to a measurement angle at a certain frequency.

FIG. 11 is a graph showing a distribution of a signal level of a beat signal Bpn with respect to a measurement angle at a certain frequency when there are a plurality of maximum points.

FIG. 12 is a flowchart illustrating a signal processing operation of the radar device according to the second embodiment.

FIG. 13 is a graph showing a positional relationship between a vehicle 3 on which the radar device of the first related art is mounted and a target 7.

FIG. 14 is a graph showing a distribution of a received electric field strength of a reflected wave received by the radar device of the first related art.

FIG. 15 is a graph showing a positional relationship between a vehicle 3 equipped with a radar device of the second prior art and a target 7;

FIG. 16 is a graph showing a distribution of a received electric field strength of a reflected wave received by the radar device of the second related art.

[Explanation of symbols]

 Reference Signs List 31 radar device 33 transmission antenna 34 reception antenna 40 FFT circuit 41 displacement device 44 signal processing circuit 45 application device 46 sensor device

Claims (11)

[Claims] 1. A transmission wave, which is an electromagnetic wave whose frequency increases and decreases with the passage of time, is transmitted while the radiation direction is angularly displaced, and the transmission wave receives a reflected wave reflected by a target object. In the signal processing method of the radar device for obtaining information on the position of the target based on a mixed signal obtained by mixing the reflected wave and the reflected wave, in each of an increasing period in which the frequency of the transmitting wave increases and a decreasing period in which the frequency of the transmitting wave decreases, Determine the distribution of the signal level of the mixed signal with respect to the frequency and the angle between the predetermined reference direction and the emission direction of the transmission wave, and compare the curves representing the distribution of the increasing period and the decreasing period,
Find a maximum point similar to the curve shape of a predetermined range including the maximum point, based on the frequency of the maximum point of the increasing period and the decreasing period, determine the relative distance and relative speed between the target and the radar device, A signal processing method for a radar device, wherein a position and a size of a target are obtained based on a distribution of the range including the maximum point. 2. For each distribution of signal levels at which the frequencies of the increasing and decreasing periods are equal, include the angle of the local maximum of the distribution;
First and second angles where the signal level is smaller by a predetermined reference level than the signal level of the local maximum point, and the signal level decreases as the angle of the local maximum point approaches the first and second angles. Calculate the angle range having two angles at both ends, compare the frequency of the maximum point of the distribution of the increasing period and the decreasing period, the signal level, and the angle range, and combine the maximum points where the signal level, the angle range, and the frequency are equal. 2. The signal processing method for a radar apparatus according to claim 1, wherein is a maximum point having a similar curve shape. 3. When there are a plurality of maximum points in the distribution of signal levels having the same frequency in the increasing period and the decreasing period, an angle range is determined for each of the maximum points, and the local maximum having the maximum signal level among the plurality of maximum points is obtained. 3. The signal processing method for a radar device according to claim 2, wherein the position and the size of the target are obtained based on the angle range of the point. 4. When there are a plurality of maximum points in the distribution of the signal level having the same frequency in the increasing period and the decreasing period, an angle range is obtained for each maximum point, and the angles overlapping each other in the angle range of each maximum point are determined. 3. The signal processing method for a radar device according to claim 2, wherein the position and the size of a single target are obtained based on the range. 5. A difference between a frequency, a difference between center angles of angle ranges, a difference between magnitudes of angle ranges, and a difference between signal levels at each local maximum point of the distribution of the increase period and the decrease period, and Is less than a predetermined first reference value, the difference between the center angles of the angle ranges is less than a predetermined second reference value,
Curve shapes are similar to local maximum points in the distribution of the increasing period and the decreasing period in which the difference in the size of the angle range is less than the third reference value and the difference in the signal level is less than the fourth reference value. 3. The signal processing method for a radar apparatus according to claim 2, wherein the signal is a maximum point. 6. When there are a plurality of combinations of the maximum points where each of the differences is less than each of the reference values, the maximum point of the combination having the smallest frequency difference is a maximum point having a similar curve shape. The signal processing method for a radar device according to claim 5, wherein 7. When there are a plurality of combinations of the maximum points where each of the differences is smaller than each of the reference values, the maximum point of the combination having the smallest difference in the signal level is determined to be the maximum point having a similar curve shape. 6. The signal processing method for a radar device according to claim 5, wherein: 8. When there are a plurality of combinations of the maximum points where each of the differences is less than each of the reference values, the maximum point of the combination having the smallest difference between the center angles of the angle ranges is defined as the maximum point having a similar curve shape. 6. The signal processing method for a radar device according to claim 5, wherein: 9. When there are a plurality of combinations of the maximum points where each difference is less than each reference value, the maximum point of the combination having the smallest difference in the size of the angle range is defined as the maximum point having a similar curve shape. 6. The signal processing method for a radar device according to claim 5, wherein: 10. A transmission wave, which is an electromagnetic wave whose frequency increases and decreases with the passage of time, is transmitted while the radiation direction is angularly displaced, and the transmission wave receives a reflection wave reflected by a target, and transmits the transmission wave. In a signal processing method of a radar device for obtaining information on the position of a target based on a mixed signal obtained by mixing a reflected wave, a mixed signal of a mixed signal in an increasing period in which the frequency of the transmitting wave increases and a decreasing period in which the frequency of the transmitting wave decreases. Based on the frequency, the relative distance and the relative speed are obtained.The relative speed, the relative distance, and the distribution of the signal level of the mixed signal with respect to the angle between the predetermined reference direction and the transmission wave radiation direction are obtained. The maximum point of the curve representing the distribution of the signal level of the mixed signal with respect to the angle is determined. Signal processing method of the radar device characterized by determining the location and size. 11. The distribution of the received electric field intensity of the mixed signal is created by collecting mixed signals obtained by mixing a reflected wave and a transmitted wave from a target whose relative velocity falls within a predetermined range. The signal processing method for a radar device according to claim 10, wherein