JPH07151850A - Radar equipment for moving body - Google Patents

Abstract

PURPOSE:To make it possible to detect an obstacle and measure the distance thereto in a short time without degradation of precision in measurement. CONSTITUTION:In radar equipment for a moving body wherein radio waves modulated by a PN signal for transmission and constructed with a prescribed unit is transmitted in the direction of movement of the moving body from a transmission antenna 11, while reflected waves of the radio waves is received by a reception antenna 12, and the relative distance to an obstacle relating to the reflection is detected from the time of delay of the radio waves, a correlation computing part 25 changes the time of delay of a PN signal for reception in the amount of shift corresponding to a measuring distance for each transmission of the prescribed unit, executes computation of correlation of reception signals from mixers 17 and 18 with the PN signal for reception generated from a generating circuit of PN for reception and thereby conducts detection of the obstacle existing in a detecting range and measurement of the relative distance to the obstacle. In other words, the correlation computing part 25 enlarges the amount of shift when the measuring distance is long, while lessening it when this distance is short.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus for a mobile body for detecting an obstacle existing in the traveling direction of a mobile body such as an automobile.

[0002]

2. Description of the Related Art Conventionally, radar technology has been applied to a radar device of this type by, for example, emitting a specific radio wave in the traveling direction of a moving body to obtain information (for example, relative Information such as distance and relative speed) is acquired from the reflected waves from the obstacle, and warning indications and sounds are emitted based on this information to alert the occupants to ensure the safety of the moving body. There was something to secure and improve. In such a device, since it is mainly within the range of application of the radar technology using the millimeter wave band, various existing radar systems (for example, FM-CW, pulse, two-frequency) are used as a principle for obtaining information about the obstacle. CW, spread spectrum method, etc.) are known. The characteristics in terms of performance will change greatly depending on which of these radar devices is used to obtain information about the obstacle. Conventionally, for example, spread spectrum (Spread Sp
Japanese Patent Application Laid-Open No. 5-9377 using the ECTrum (SS) method.
There is a radar device described in Japanese Patent No. 6 publication. In such a radar device, a pseudo noise signal (PN signal) is transmitted, and a received signal reflected from an obstacle and a delay time unit for determining measurement accuracy are used. The relative distance was calculated by taking the correlation with the sequentially-shifted reception PN signal.

[0003]

However, in the above radar device, in order to improve the accuracy, it is necessary to reduce the shift amount, and if the required detection distance is detected,
Sometimes the number of shifts increased. For this reason, the above radar device has a problem that the number of times of performing the correlation calculation increases, and as a result, it takes a considerable time to obtain the correlation.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a radar apparatus for a mobile body which can detect an obstacle and measure the distance to the obstacle in a short time without lowering the measurement accuracy. To aim.

[0005]

In order to achieve the above object, according to the present invention, a radio wave modulated by a transmission PN signal in the traveling direction of a mobile body and composed of a predetermined unit is transmitted from a transmission antenna. In a mobile radar device that receives a reflected wave of the radio wave from a reception antenna and detects a relative distance to an obstacle related to the reflection from a delay time of the radio wave, the mobile rad device has the same structure as the transmission PN signal. And a signal generating means including a reception PN delay circuit and a reception PN generation circuit for generating a reception PN signal with a delay amount changed each time the radio wave is transmitted by a predetermined unit, and for each predetermined unit transmission When the delay amount of the reception PN signal is changed, the reception PN delay circuit is controlled to change the delay amount for each predetermined unit transmission by the change amount according to the measured distance. Provided is a radar apparatus for a mobile object, comprising: a stage, the reception signal, and a correlation calculation unit including a correlation calculation unit that performs a correlation calculation between the reception signal and the reception PN signal whose delay amount is sequentially changed for each predetermined unit transmission. To be done.

[0006]

Each time the transmission PN signal is transmitted by a predetermined unit, the correlation calculator changes the delay time of the reception PN signal by the shift amount according to the measurement distance to detect and detect an obstacle within the detection range. Measure the relative distance to the obstacle. That is, the shift amount is increased when the measured distance is in the far region, and the shift amount is decreased when the measured distance is in the near region.

Therefore, the number of shifts required for correlation can be reduced and the correlation distance with the obstacle can be detected without lowering the measurement accuracy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings of FIGS. FIG. 1 is a block diagram showing a first embodiment of the configuration of a mobile radar device according to the present invention. In the figure, the mobile radar device according to the present embodiment is one using the SS system, and includes a pair of transmission / reception antennas 11 and 12,
The phase modulation circuit 13, the transmission PN generation circuit 14, the transmission oscillation circuit 15, the code setting circuit 16, and the mixing /
Circuit (hereinafter referred to as "mixer") 17-20
, Phase shift circuit 21, and intermediate frequency oscillator circuit 22
, The reception PN delay circuit 23, and the reception PN generation circuit 2
4, a correlation calculator 25, and a Doppler counter 26.

The transmitting / receiving antennas 11 and 12 are arranged, for example, in front of the moving body. The transmitting antenna 11 is
It is connected to the phase modulation circuit 13 and transmits the signal supplied from the phase modulation circuit 13 to the front of the moving body as a radio wave, and has a predetermined directivity. Further, the receiving antenna 12 receives an electric wave reflected from the front of the moving body, and the received electric wave is the transmitting antenna 1
The radio wave transmitted from No. 1 is a reflected wave reflected by an obstacle ahead.

The phase modulating circuit 13 is connected to the transmitting PN generating circuit 14 and the transmitting oscillating circuit 15, and outputs the basic oscillation signal output from the transmitting oscillating circuit 15 from the transmitting PN generating circuit 14. By performing two-phase phase modulation on the transmitted transmission PN signal, the transmission antenna 1
1 is being generated. Based on the control of the code setting circuit 16, the transmission PN generation circuit 14 generates a transmission PN signal which is a pseudo noise signal for transmission configured as a longest code sequence (also referred to as an M sequence).

The transmission oscillating circuit 15 generates a basic oscillation signal having an optimum frequency for radar, and when the radar device of this embodiment is used in an automobile, the basic oscillation signal is not for a general automobile. Millimeter wave band, ie 60
The frequency is about GHZ. The code setting circuit 16 is connected to the transmission PN generation circuit 14 and the reception PN generation circuit 24, and the transmission PN generation circuit 14 and the reception P
The code is controlled so that the N generation circuit 24 generates the same code.

When the mobile body is an automobile, the signal received by the receiving antenna 12 is in the millimeter wave band of about 60 GHz, that is, an ultra high frequency. Therefore, even if the received signal is input to the correlation calculating unit 25 as it is, the correlation is obtained. There is an inconvenience that calculation cannot be performed. Therefore, it is necessary to remove the high-frequency component generated by the transmission oscillation circuit 15 with a mixer that is a multiplication circuit. However, if the high-frequency component is removed from the received signal, only the PN signal, that is, the digital signal is obtained. Therefore, when calculating the relative speed together with the relative distance, the Doppler frequency for calculating the relative speed can be counted. Disappear. Therefore, it is necessary to add a fundamental oscillation signal including a frequency component that can be easily processed by the Doppler counter 26. Intermediate frequency oscillation circuit 22
Generates the fundamental oscillation signal, and the mixers 19, 20
Is output to. The fundamental oscillation signal generated by the intermediate frequency oscillation circuit 22 preferably has a frequency of about 1 GHz.

The mixer 19 is connected to the intermediate frequency oscillating circuit 22 and the transmitting oscillating circuit 15, and synthesizes the basic oscillating signals from both circuits and outputs them to the mixer 18 and the phase shift circuit 21. This is two signal processes, namely 60 from the signal received at the receiving antenna 12.
The mixer 19 converts the oscillation frequency input from both circuits 15 and 22 into a signal of 61 GHz band and outputs it in order to remove the super high frequency component of about GHZ and to add an easy-to-handle intermediate frequency component of about 1 GHz. is doing.

The phase shift circuit 21 is connected to the mixer 17, and shifts the phase of the signal input from the mixer 19 by 90 ° and outputs it to the mixer 17. This is because the signal received by the receiving antenna 12 is out of phase due to reflection. This allows
When the phase of the received signal is shifted by 180 °, signal processing can be performed by the mixer 18, and when it is shifted by 90 °,
The mixer 17 can perform signal processing.

The mixers 17 and 18 are connected to the correlation calculation unit 25, and combine the received signal input from the reception antenna 12 and the signal input from the mixer 19 and output the combined signal to the correlation calculation unit 25. Also, the mixer 18
The combined signal is also output to the mixer 20. That is, the radio wave in the 60 GHz band reflected by the front obstacle undergoes Doppler shift and is received by the receiving antenna 12,
Further, the signals are separated into two systems and mixed by the mixers 17 and 18 with signals in the 61 GHz band having different phases, and are output to the correlation calculating section 25 as signals in the 1 GHz band which are easy to handle and have information on the front obstacle.

The reception PN delay circuit 23 is connected to each of the reception PN generation circuit 24 and the correlation calculation section 25. Based on the instruction of the correlation calculation section 25, the reception PN generation circuit 24 outputs the reception PN delay circuit 23. The delay amount of the PN signal is variably and sequentially changed. That is, the reception PN delay circuit 23, every time the transmission PN signal is transmitted in a predetermined unit, a specific number of times with a first shift amount of a fine unit (for example, when the measurement distance is a near region, The corresponding number of times), the delay amount of the reception PN signal is sequentially shifted, and then a second number of shifts, which is a unit somewhat rougher than the first shift amount, is performed for a specific number of times (for example, the measured distance is in the middle distance In this case, the delay amount of the reception PN signal is sequentially shifted by the number of times corresponding to the measured distance), and then a specific number of times by a third shift amount in a unit larger and rougher than the first shift amount ( For example, when the measurement distance is in the far area, the delay amount of the reception PN signal is sequentially shifted by the number of times corresponding to the measurement distance).

The reception PN generation circuit 24 includes a correlation calculation unit 2
5, the reception PN signal is sequentially shifted and generated based on the shift amount output from the reception PN delay circuit 23, and output to the correlation calculator 25. The correlation calculator 25 receives the reception signals input from the mixers 17 and 18 and the reception PN input from the reception PN generation circuit 24.
Performs correlation calculation with the signal. That is, the correlation calculation unit first performs the correlation calculation for the number of times corresponding to the measured distance of the neighboring region with the first shift amount of the fine unit, and then with the second shift amount of the slightly rough unit of the medium distance region. Correlation calculation is performed for the number of times corresponding to the measured distance, and then for the number of times corresponding to the measured distance of the distant region with the third shift amount of the rough unit.

Further, the mixer 20 is connected to the mixer 18 and the intermediate frequency oscillation circuit 22, and the mixer 1
The Doppler counter 26 is added to the composite signal input from 8.
Intermediate-frequency oscillator circuit 2 including frequency components that can be easily processed by
The fundamental oscillation signal of 2 is added to generate the Doppler frequency, and the Doppler frequency is set to the Doppler counter 26.
Is output to. The Doppler counter 26 counts the Doppler frequency for calculating the relative speed,
It is output to a calculation control unit (not shown).

Next, the principle of correlation calculation in this embodiment will be described with reference to the waveform diagram of FIG. First, the transmission wave transmitted from the transmission antenna 11 is modulated by the transmission PN signal having the configuration shown in FIG. Generally, a PN signal used in the SS system has one chip as a unit, and the above-mentioned aggregate of chips as an epoch.
In this embodiment, for example, one chip length is 50 ns and one epoch is 1024 chips.

With such a PN signal, the transmission wave modulated by the phase modulation circuit 13 is transmitted from the transmission antenna 11 to the front of the moving body, reflected by an obstacle and returned, and FIG.
Received waves as shown in are received by the receiving antenna 12. The received wave is obtained as a received signal delayed from the transmitted wave by the time T required for the wave to propagate between the obstacle and the obstacle.

On the other hand, the reception PN signal output from the reception PN generation circuit 24 has the same structure as the transmission PN signal, but the reception PN delay circuit 23 outputs 1 when the epoch is transmitted. Delayed by chip length. With respect to the reception signal and the reception PN signal, the negation of the exclusive OR is taken as a digital code in the correlation calculation unit 25, and the result is output as an integrated value. That is, when the chips of both signals match, the digital code becomes "1", and when they do not match, "-"
1 ”, and these values are integrated. When the received signal and the received PN signal match, the integrated value becomes the maximum value. Note that these operations performed by the correlation operation unit 25 are referred to as correlation operations. It is called that the correlation can be obtained when the result of this correlation calculation becomes the maximum value.

By the way, the reception signal and the reception PN signal substantially match, that is, the reception PN signal is as shown in FIG.
In the case of (1), the result of the correlation calculation becomes the maximum value. When the unit of the shift amount of the reception PN signal is about 50 ns and an obstacle up to 200 m is detected with a relative distance measurement accuracy of 8 m, for example, the time t required for distance calculation is t = 50 ns × 1024 chips. × (200m / 8m) = 1.28ms (1) However, the measurement accuracy of the relative distance in this case is 8
m, and considering the case of automobiles, the measurement accuracy of 8 m is too large. Therefore, it is considered that the measurement accuracy of about 1 m is appropriate. To improve the measurement accuracy,
The unit of the shift amount may be reduced, but if the relative calculation is performed from the beginning in a short shift time, the number of shifts increases. That is, the number of calculations increases and the time t for calculating the distance to 200 m is t = 50 ns × 1024 chips × (200 m / 1 m) = 10.24 ms (2)

The distance calculation of this embodiment is to detect the relative distance by changing the shift amount according to the measured distance. That is, in the present embodiment, for an obstacle in the range of measurement distance 0 to 70 m, it is detected with a measurement accuracy of 1 m, that is, a shift time of 6.25 ns, and for an obstacle in the range of 70 to 140 m. Is detected with a measurement accuracy of 2 m, that is, a shift time of 12.5 ns, and finally 140 to 200
An obstacle in the range of m is detected with a measurement accuracy of 4 m, that is, a shift time of 25.0 ns.

Therefore, for an obstacle within the required detection distance of 200 m, the time t required for detection and measurement is t = 50 ns × 1024 chips × (70 m / 1 m) +50 ns × 1024 chips × (70 m / 2m) + 50ns × 1024 chips × (60m / 4m) = 6.14ms (3)

As described above, in this embodiment, the formula (3) is changed to the formula
Compared to the case of (2), the measurement accuracy becomes worse as the distance to the obstacle increases, but the ratio of the measurement accuracy to the measurement distance is in a very close range (for example, 0 to 3 m).
It can be seen that the values are almost constant except for, that is, (measurement accuracy) / (measurement distance) <3%. In particular, when considering the application of the present embodiment to an inter-vehicle distance warning device of an automobile, it is considered that it is not necessary to detect the correlation distance with a certain accuracy for the entire detection range (required detection distance), Rather, it seems necessary to shorten the detection time.

Therefore, in the present embodiment, the number of calculations is reduced as compared with the case of the above equation (2), so that the detection time can be greatly shortened. In addition, the radar device of the present invention is shown in FIG.
Not only the configuration of the first embodiment shown in FIG. 4 but also a second embodiment having the configuration shown in FIG. 4 can be considered. In the second embodiment, the transmission / reception integrated antenna is used, and the transmission / reception signals are separated by the circulator 31. According to this embodiment, the same effect as that of the first embodiment can be obtained. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals.

[0027]

As described above, according to the present invention, the radio wave modulated by the pseudo signal for transmission in the traveling direction of the moving body and transmitted in the predetermined unit is transmitted and the reflected wave of the radio wave is received. A mobile radar device that receives a signal and detects the relative distance to an obstacle related to reflection from the delay time of the radio wave, has the same structure as the pseudo signal for transmission, and sets the radio wave in a predetermined unit. A signal generating means for generating a receiving pseudo signal with a changed delay amount each time transmission is performed, and a signal generating means for controlling the signal generating means when changing the delay amount of the receiving pseudo signal for each predetermined unit transmission. A delay amount changing means for changing a delay amount for each predetermined unit transmission by a change amount according to a measured distance; the reception signal; and a reception pseudo signal whose delay amount is sequentially changed for each predetermined unit transmission. Correlation performance that performs correlation calculation Because and means, without lowering the measurement accuracy, can measure the distance to the detection and obstacle in a short time obstacle.

[Brief description of drawings]

FIG. 1 is a first configuration of a mobile radar device according to the present invention.
It is a block diagram which shows an Example.

FIG. 2 is a waveform diagram for explaining the principle of correlation calculation in the first embodiment.

FIG. 3 is a diagram showing a correlation calculation result by a correlation calculation unit shown in FIG.

FIG. 4 is a second configuration of the mobile radar device according to the present invention.
It is a block diagram which shows an Example.

[Explanation of symbols]

 Reference Signs List 11 transmission antenna 12 reception antenna 13 phase modulation circuit 14 transmission PN generation circuit 15 transmission oscillation circuit 16 code setting circuit 17 to 20 mixer 21 phase shift circuit 22 intermediate frequency oscillation circuit 23 reception PN delay circuit 24 reception PN generation circuit 25 Correlation calculator

Claims (2)

[Claims] 1. A radio wave that is modulated by a pseudo signal for transmission in a traveling direction of a mobile body and is composed of a predetermined unit is transmitted, and a reflected wave of the radio wave is received as a reception signal,
A mobile radar device for detecting a relative distance from an obstacle related to reflection from a delay time of the radio wave, having the same structure as the pseudo signal for transmission, and delaying each time the radio wave is transmitted in a predetermined unit. A signal generating means for generating a pseudo signal for reception whose amount is changed, and a signal generating means for controlling the signal generation means when changing the delay amount of the pseudo signal for reception for each predetermined unit transmission, according to the measured distance. A delay amount changing unit that changes the delay amount for each predetermined unit transmission by a change amount, a correlation calculation for performing a correlation calculation between the reception signal and the reception pseudo signal whose delay amount is sequentially changed for each predetermined unit transmission. A radar device for a mobile body, comprising: 2. The delay amount changing means changes the change amount of the delay amount for each predetermined unit transmission according to the measured distance so that the ratio of the measurement accuracy to the measured distance falls within a predetermined range. The radar apparatus for a mobile body according to claim 1.