JPH0593776A - Collision preventive radar device for automobile - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a device which uses a spread spectrum and has a high obstacle detection speed by using a PN signal having an epoch as short as possible. A receiving PN (pseudo noise) signal is delayed by a predetermined phase for each single or multiple epochs, and the product of the output of the receiving unit 30 is integrated. The epoch of the transmission PN signal included in the output of the reception unit 30 at the M-th epoch and the reception PN
When the epochs of the signals match, the integrated output of the signal detection unit 50 becomes large. The arithmetic controller 600 detects this by the threshold value determination, and takes in the count value related to M · Δt from the delay amount arithmetic unit 500. At this time, M · Δt substantially matches the delay time td related to the reflection of the radio wave, and the distance can be obtained. The transmission PN signal generator 200 and the reception PN signal generator 300 generate PN signals of the same type for both designated by the code setting unit 800, but different types for each device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle collision prevention radar device for detecting an obstacle existing in a traveling direction of an automobile by using radio waves and issuing an alarm to an occupant of the automobile.

[0002]

2. Description of the Related Art When an obstacle exists in the traveling direction of an automobile, the occupant of the automobile avoids the obstacle and travels safely. Therefore, in order to safely drive the automobile, it is preferable to have a device that automatically detects an obstacle and warns an occupant. Devices used for such applications include, for example, a device that detects an obstacle by radio waves and a device that detects an obstacle by ultrasonic waves, but in order to detect an obstacle at a longer distance, the former, that is, radio waves. A collision prevention radar device for automobiles is used.

This device is an application of radar technology, and a structure based on various systems such as a pulse radar and an FM-CW radar has been conventionally studied.

[0004]

However, in devices using pulse radar, FM-CW radar and the like, for example, the peak power of the transmission pulse becomes large, and interference with similar devices mounted in other vehicles may occur. There are problems such as occurrence. In order to solve such a problem, the applicant of the present application previously applied for an apparatus to which spread spectrum is applied (Japanese Patent Application No. 3-52893).
issue). In this prior application, pseudo noise of a structure having a chip length and a epoch length that are sufficiently shorter than the maximum propagation time required for a radio wave to travel the maximum measurement distance back and forth.
O noise (PN) is used to prevent interference with similar devices installed in other vehicles.

As described above, means for solving the problems in the pulse radar, the FM-CW radar and the like have already been proposed, but on the other hand, in order to sufficiently remove the interference with the same type device mounted in another vehicle. Has to have a sufficiently long length of PN, and there is a certain limit to the time required to detect an obstacle, that is, the detection speed. The device according to the prior application is also a device that can reduce interference from similar devices mounted on other vehicles and can be realized at low cost as compared with pulse radars, FM-CW radars, etc. It goes without saying that it is preferable if it can be used as a fast device.

[0006] The present invention detects obstacles at a higher speed and alerts the occupant more quickly while securing advantages such as the interference elimination obtained in the prior application that can be made cheaper and integrated into an IC. The aim is to realize a possible device.

[0007]

In order to achieve such an object, the present invention uses an antenna that transmits and receives radio waves in the traveling direction of a vehicle and a maximum propagation time required for the radio waves to travel back and forth over a maximum measurement distance. A transmission PN generator capable of setting a plurality of types of codes for generating a transmission PN signal having a sufficiently short chip length and at least an epoch length longer than the maximum propagation and as short as possible, and an antenna for a transmission signal modulated by the transmission PN signal. And a receiver for converting the signal related to the reflected wave received by the antenna to a predetermined frequency and outputting the same, and a receiver P having the same structure as the transmitter PN signal.
A reception PN generator in which a code for generating an N signal can be set, and a code setting device for sequentially setting the plurality of types of codes common to the reception PN generator and the transmission PN generator for each device of the present application, A signal detector that integrates and outputs the output of the receiver and the amplitude component of the reception PN signal, a phase shift controller that delays the reception PN signal by a predetermined phase Δt for each single or multiple epochs, and a phase shift Total delay M of receiving PN signal by controller
The epoch of the transmission PN signal and the epoch of the reception PN signal included in the output of the reception unit match when the output Σ1 of the signal detection unit and the output Σ1 of the signal detection unit become equal to or more than the predetermined value TH1. And the stored value M of the delay amount calculator
And an arithmetic controller for calculating a distance to an obstacle related to the reflection of radio waves based on the stored value M and supplying the distance to an alarm device. An epoch of a PN signal for transmission and a PN for reception included in the output of the receiving unit. It is characterized in that the distance is measured based on the total delay amount MΔt of the reception PN signal when the epochs of the signals match.

According to a second aspect of the present invention, the signal detecting section includes a Doppler counter for counting the Doppler frequency of the signal from which the pseudo noise signal component for transmission is removed, including means for removing the pseudo noise signal component for transmission from the obtained product. The arithmetic controller determines the relative speed to the obstacle based on the Doppler frequency obtained by counting, and supplies a signal to the alarm device according to a predetermined rule.

[0009]

In the present invention, the signal which is two-phase modulated with the transmission PN signal is transmitted as a radio wave from the antenna in the traveling direction of the vehicle, and when there is an obstacle in that direction, the reflected wave is received by the antenna. ..

Here, the transmission PN signal is generated by the transmission PN generator. The transmission PN signal is composed of chips having a length sufficiently shorter than the maximum propagation time (corresponding to the maximum measurable distance), and the epoch, which is a set of a plurality of chips, is set to be at least longer than the maximum propagation time but as short as possible. ..

Further, the PN code of the transmission PN signal can be set by the code setting device.
Ten different codes are sequentially set in correspondence with the smallest digit of the serial number of the device of the present application. The process related to transmission such as two-phase modulation is executed by the transmission unit.

A signal relating to the received reflected wave is taken into the receiving unit. The signal is converted into a predetermined frequency in the receiving section. The converted signal is a signal delayed by a delay time td corresponding to the time required for the radio waves to travel back and forth between the obstacle and also includes a Doppler component corresponding to the relative speed with the obstacle. The output of the receiver is captured by the signal detector.

On the other hand, the receiving PN signal is also fetched in the signal detecting section. This reception PN signal is generated by the reception PN generator and has the same structure as the transmission PN signal. The reception PN signal is set at the same time when the transmission PN signal is selected and set by the code setting device from a plurality of types. However, the phase thereof is different from that of the transmitting PN signal by the phase shift controller. That is, in the present invention, the reception PN signal supplied to the signal detection unit is sequentially delayed by a predetermined phase Δt for each single or multiple epochs based on the reset time.

When this delay is repeated a plurality of times (M times), the cumulative value MΔt of the delay amount Δt matches the delay time td of the output of the receiving unit at any time. Therefore, when the product of the output of the receiving unit and the receiving PN signal is obtained and the amplitude component is integrated in the signal detecting unit, the integrated value Σ1 increases at a certain point. It is at this point that the accumulated delay amount MΣΔ
This is the time when t matches the delay time td.

On the other hand, in the present invention, a delay amount computing unit is provided, and the delay amount computing unit executes the counting related to the phase shift amount (delay amount). With this, it is possible to know how many times the delay amount Δt has arrived from the time of resetting to the increase of the integral value. Therefore, the delay time t, that is, the distance to the obstacle can be calculated based on the number of delays M, and this calculation is performed by the calculation controller. The arithmetic controller resets the delay amount arithmetic unit accordingly, and prepares for the next arithmetic calculation.

As described above, in the present invention, the delay amount Δ
The distance is measured by accumulating t. In the device of the present application, since the PN signal is used as in the device of the above-mentioned prior application, an action such as interference elimination with a similar device mounted on another vehicle is secured by spread spectrum, and a reception gain is secured by spectrum recombining and low power transmission etc. Is possible, but P
Since the length of the N signal is short, the time required for distance measurement is shortened. However, because the length of the PN signal is shortened, there is a drawback that it becomes more susceptible to interference from other vehicles equipped with the same type of device. Therefore, a plurality of different types of PN signals are used, and the PN signal is different for each device. This defect was solved by setting the thing. The interference removal effect of the present invention is equivalent to the case of using a PN signal whose length is a multiple of the number of different types of PN signals.

In the present invention, the Doppler frequency is counted by the Doppler counter. This counting is performed based on the product obtained in the signal detecting section and the fundamental frequency output of the receiving section. As the former, the one in which the component of the PN signal for transmission is removed in the signal detector may be used, and in the latter, for example, the output of the oscillator included in the receiver may be taken in. The Doppler frequency thus obtained is used as one of the parameters relating to the alarm signal generation in the alarm device. For example, the alarm device sets a larger distance at which the alarm should be issued when the relative speed corresponding to the Doppler frequency is high. In this way, it is possible to generate a suitable alarm that is more suitable for actual conditions.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

(1) Overall Configuration of Embodiment FIG. 1 shows the overall configuration of a vehicle collision prevention radar device according to an embodiment of the present invention. As shown in this figure, this embodiment includes an antenna 10, a transmitter 20, and a receiver 30.

The antenna 10 is arranged at a predetermined position of the vehicle, for example, the front part. The antenna 10 is an antenna that transmits the signal supplied from the transmitter 20 to the front of the vehicle, and has a predetermined directivity. The transmitter 20 supplies a signal to be transmitted to the antenna 10, and the signal is a signal which is two-phase modulated by a pseudo noise signal having a structure described later. In the following description, this pseudo noise signal is called a transmission PN signal. Further, the transmission PN signal is generated as a longest code sequence (also referred to as N sequence) by the transmission PN generator 200 including a shift register or the like using the output of the reference oscillator 100.

The antenna 10 also supplies a signal to the receiver 30 via a circulator inside the transmitter 20. This signal is a signal relating to an electric wave reflected from an obstacle existing in the front, for example, another vehicle traveling in the same lane.
Therefore, the time td required for the radio wave to make a round trip to the obstacle is td.
Is delayed from the signal related to transmission, and is further subjected to Doppler shift due to the speed difference (relative speed) with the obstacle. Further, the operation of the transmitter 20 includes a modulation component related to the transmission PN signal.

A local signal generator 40 is attached to the receiver 30. The local signal generating section 40 is provided in the receiving section 30,
A signal having a predetermined frequency is supplied, and the receiving unit 30 converts the signal related to the output of the antenna 10 into a different frequency based on this signal.

A signal detecting section 50 and a precision distance detecting section 60 are provided downstream of the receiving section 30. These circuits 50 and 60 take in the output of the receiving section 30 and output an integral value which is the basis for the condition judgment of the distance and relative speed detection in this embodiment. Also, these circuits 50 and 60
As a premise of the integral value calculation, takes in a pseudo noise signal related to the receiving PN signal and executes a predetermined process on the output of the receiving unit 30. This pseudo noise signal has the same structure as the transmission PN signal supplied to the transmission unit 20, but differs in that it is delayed by the phase shift control. In the following description, the pseudo noise signal supplied to the signal detection unit 50 and the precision distance detection unit 60 will be referred to as a reception PN signal. The phase shift control and the distance detection will be described later in detail.

The reception PN signal is transmitted to the transmission PN generator 20.
As with 0, using the output of the reference oscillator 100,
Generated by N generator 300. However, the receiving PN
The reception PN signal generated by the generator 300 is not directly supplied to the signal detection unit 50 or the like, but the reception PN signal delayed by a predetermined delay by the delay circuit 70 is supplied. That is, the signal detecting unit 50 receives the receiving PN signal obtained by delaying the output of the receiving PN generator 300 by 1/2 chip, and the distance precision detecting unit 60 receives the signal detecting unit 5.
Two types of signals before and after the receiving PN signal supplied to 0 ± 1/2 chip (that is, the receiving PN generator 3
00 output and a signal delayed by 1 chip for this)
Are supplied respectively. In addition, although one reference oscillator 100 is shown in this drawing, two reference oscillators 100 may be provided for each of transmission and reception.

A code setting unit 800 is connected to the transmission PN generator 200 and the reception PN generator 300, and the transmission PN generator 200 is provided so that the transmission PN signal and the reception PN signal have the same code. And receiving PN generator 300
Set the state of. The code setting device 800 is, for example, 10
Various types of devices can be installed and fixed at the manufacturing stage so that the codes are repeatedly set in order of the manufacturing number of the device of the present application.

A phase shift controller 400 is attached to the receiving PN generator 300. The phase shift controller 400 takes in the epoch generation timing from the reception PN generator 300, and delays the reception PN signal by a predetermined time Δt each time a single epoch occurs. In addition, the phase shift controller 400
A delay amount calculator 500 is provided for calculating the total delay amount corresponding to the delay of the receiving PN signal. The calculated value of the delay amount calculator 500 represents the delay time td, and thus the distance to the obstacle, when the outputs of the signal detection unit 50 and the precision distance detection unit 60 satisfy a predetermined condition.

Further, the gain controller 8 which controls the amplification gain in the receiving section 30 according to the output of the delay amount calculator 500.
0 is provided. In addition, the local signal generator 40 uses the frequency generated by the local oscillator to detect the signal detector 50.
There is provided a Doppler counter 90 that obtains only the Doppler shift component from the frequency (the sum of the intermediate frequency and the Doppler shift component) of the signal generated in. The former covers the attenuation of the received power which is generally inversely proportional to the fourth power of the distance, and further covers the fluctuation of the received power due to the directivity of the antenna 10, and the latter covers the relative speed calculation and the alarm condition based on the result. This is a configuration used for optimization (setting of alarm distance corresponding to speed).

In the present embodiment, the arithmetic controller 6
00 is provided. The calculation controller 600 takes in an integrated value from the signal detection unit 50 and the distance precise detection unit 60, executes a judgment on this integrated value, and according to the result of the judgment, the calculation contents of the delay amount calculation unit 500 and the Doppler counter 90. Capture the counting contents. The arithmetic and control unit 600 obtains the distance to the obstacle and the relative speed in accordance with the taken-in contents, and gives it to the alarm unit 700. The alarm device 700 makes an alarm determination according to a predetermined alarm condition, and notifies an occupant of the presence of an obstacle or a necessary vehicle operation in the form of sound, light, or the like. The arithmetic and control unit 600 starts the operation as described above and the PN generator for transmission 200 and the PN generator for reception 30.
0, a reset pulse is supplied to the delay amount calculator 500, and the epoch generation timing is fetched from the reception PN generator 300 as a calculation control start signal.

(2) Distance Measuring Principle of Embodiment Next, the distance measuring principle will be described with reference to an embodiment before explaining the detailed structure and operation of this embodiment.

FIG. 2 shows the structure of the signal transmitted in this embodiment. First, the signal supplied from the transmitter 20 to the antenna 10 and transmitted from the antenna 10 to the front of the vehicle is a transmission PN having a configuration as shown in FIG.
It is modulated by the signal. Generally, a pseudo noise signal used in spread spectrum has a configuration in which chips are set as a unit and an epoch, which is a set of chips, repeats. The PN signal for transmission in this embodiment is
It is a pseudo noise signal having a chip length CH, an epoch length EP, and the number of chips N in one epoch.

Further, in this embodiment, the chip length CH
Is sufficiently shorter than the maximum measurement distance (maximum distance at which an obstacle can be detected), and the epoch length EP is set to be at least longer than the maximum measurement distance. For example, when the maximum measurement distance determined by the transmission power, the frequency used, etc. is 150 m, the time required for the radio wave to travel back and forth over this distance (maximum propagation time)
Is 1 μsec. Corresponding to this, for example, chip length C
H is 0.2 μsec, Epoch length EP is 100 μsec
Is set to. As will be described later, the probability of interference with another vehicle device is determined by the maximum propagation time / epoch length EP × the number of types of codes, and the frequency division corresponding to the output of the reference oscillator 100 is determined by the chip length CH and the required distance resolution. The ratio p is determined.

When a signal modulated by such a transmission PN signal is transmitted from the antenna 10, a signal having a configuration as shown in FIG. 2 (2) is obtained in the antenna 10 as a reflected wave from an obstacle. Be done. That is, a signal delayed by the time td required for the radio wave to propagate between the obstacles can be obtained. Such signals are supplied to the signal detection unit 50 and the distance precision detection unit 60.

On the other hand, the reception PN signal has the same structure as the transmission PN signal, but is delayed by Δt for each single or plural epochs set in advance in the design stage. However, for simplicity of explanation, only the case of delaying by Δtd for each single epoch will be described below. That is, based on the reset pulse supply timing by the arithmetic and control unit 600, FIG.
As shown in FIG. Signal detector 5
At 0, the signal shown in FIG. 2 (2) and the signal shown in FIG.
The product with the signal shown in is obtained and the phase is detected. The DC signal obtained as a result of the phase detection reaches the maximum level when the phases of both signals match. In this embodiment, the coincidence point is detected by the arithmetic controller 600 by the magnitude of the output supplied from the signal detecting section 50 to the arithmetic controller 600 by integrating the phase detection result.

If this integrated value is represented by Σ1, as shown in FIG. 3 (4), the maximum value N is reached at the time when the phases of both signals match, and one chip before and after the maximum value N is left. Is 0. Therefore, if the threshold value determination is performed on the integrated value Σ1, it is possible to determine the coincidence of the phases of both signals. This determination is made in the arithmetic and control unit 600.

If the result of determination is that the threshold value is exceeded, the operation controller 600 causes the delay amount calculator 50 to operate.
A calculated value of 0 is fetched. The delay amount calculator 500 executes the calculation of the total delay amount corresponding to the phase shift control with the reset time point as a reference, and the calculated value corresponds to the accumulated value MΔt of the delay amounts up to the present time. However, M is the number of phase shift control operations that have occurred up to that point. The fact that the phases of the two signals are the same does not mean that the delay time t
It indicates that d substantially matches the cumulative value MΔt of the delay amount. Therefore, the delay time td is detected by taking in the calculated value of the delay amount calculator 500, and the calculation controller 60
0 calculates the distance to the obstacle based on this.

In this way, the distance measurement is performed in this embodiment, and the distance precision detection unit 60 is further used to improve the accuracy. In the distance precise detection unit 60, the product of the reception PN signal having a phase of about 1/2 chip with respect to the reception PN signal supplied to the distance detection unit 50 and the output of the reception unit 30 is obtained. , Phase detected. Therefore, the two types of DC signals obtained as a result of the phase detection are related to a signal that is advanced by 1/2 chip and a signal that is delayed by 1/2 chip with respect to the reception PN signal supplied to the distance detection unit 50. There are two types: signal. When these are respectively integrated, the figure has a value obtained by moving the figure in FIG. 3 (4) forward and backward by 1/2 chip as indicated by the broken line in FIG. 3 (5). In the present embodiment, the difference between the two types of DC signals obtained as a result of the phase detection is obtained and then integrated. As a result, the integrated value Σ2 as shown by the solid line in FIG. 3 (5) is obtained.

This integrated value Σ2 is, therefore, calculated by the distance detecting section 5
When the phase of the reception PN signal supplied to 0 and the phase of the modulation component by the transmission PN signal included in the output of the reception unit 30 match, the absolute value minimum = 0. If this is utilized, the timing of taking the calculated value from the delay amount calculator 500 to the calculation controller 600 can be determined more accurately. For example, in addition to the determination on the output of the signal detection unit 50, it may be determined whether or not the output of the precision distance detection unit 60 is below a predetermined threshold value.

As described above, in this embodiment, the distance is precisely detected. In the above description, the delay circuit 7
Although the 1/2 chip delay at 0 is neglected, the chip length CH is already known, so it may be supplemented by the calculation in the calculation controller 600.

(3) Partial Configuration of the Embodiment-Transmission / Reception FIG. 4 shows a configuration related to transmission / reception among the configurations of this embodiment.

As shown in this figure, the transmitting PN generator 200 includes a frequency divider 201 and a first PN generator 202.

The frequency divider 201 takes in the signal of the reference frequency from the reference oscillator 100 and divides it by a predetermined frequency division ratio p.
The frequency division ratio p is determined according to the required distance resolution. For example, when it is desired to measure distance resolution up to 1.5 m, if the chip length CH is 0.2 μsec as described above, the frequency division ratio p is 0.2 μsec / 0.01 μ.
It is sufficient to set sec = 20. However, 0.01 μsec
Is the time required for a radio wave to make a round trip of 1.5 m. The first PN generator 202 has a configuration including, for example, a shift register, and generates a transmission PN signal based on the signal output from the frequency divider 201.

The transmitting section 20 has a transmitting oscillator 21, a phase modulator 22 and a circulator 23. The output of the predetermined frequency of the transmission oscillator 21 is supplied to the phase modulator 22 and is phase-modulated by the transmission PN signal. The modulated signal is supplied to the antenna 10 via the circulator 23.

The receiving section 30 has a first mixer 31 that works on the received output of the antenna 10 via the circulator 23. The first mixer 31 mixes the signal from the local signal generator 40 with the received output, and outputs the obtained signal to the amplifier 32. The amplifier 32 amplifies the signal and outputs it to the signal detection unit 50 and the like while receiving the gain control by the gain controller 80.

The local signal generator 40 has a structure including a local oscillator 41 and a second mixer 42. Local oscillator 41
Oscillates at a predetermined intermediate frequency and gives an oscillation output to the second mixer 42. The second mixer 42 takes in the output of the transmitter oscillator 21 of the transmitter 20 and mixes it with the output of the local oscillator 41. Therefore, the frequency of the signal output from the second mixer 42 is the transmission frequency + the intermediate frequency. When a signal having such a frequency is supplied to the first mixer 31, the first mixer 31
The frequency of the signal output from the mixer 31 is an intermediate frequency. However, it goes without saying that it includes the Doppler shift amount due to the relative speed with respect to the obstacle and also includes the modulation component by the transmission PN signal.

(4) Partial Configuration of Embodiment-Distance and Relative Velocity Detection FIG. 5 shows a partial configuration of this embodiment, particularly a configuration for performing distance detection and the like according to the features of the present invention.

As shown in this figure, the signal detector 50
Is a third mixer 51, a PLL 52, a first phase detector 53
And a first integrator 54. Third mixer 5
1 mixes the output from the receiving unit 30 and the output from the delay circuit 70, and supplies them to the first phase detector 53 via the PLL 52 and directly. The delay circuit 70 has a first 1 /
2-chip delay device 71 and second 1 / 2-chip delay device 72
It is a configuration in which are connected in cascade. The first half-chip delay unit 71 is supplied from the delay circuit 70 to the third mixer 51.
The receiving PN signal is delayed by 1/2 chip, and the receiving PN signal is a signal having the same configuration as the transmitting PN signal included in the output from the receiving unit 30 and having a different phase. Therefore, the output of the third mixer 51 becomes a signal from which the modulation component due to the PN signal is removed when the phase of the output from the receiving unit 30 and the phase of the output from the delay circuit 70 match. The PLL 52 operates as a narrow band filter including the intermediate frequency in the pass band, and by passing this, unnecessary components such as the intensity fluctuation of the interfering wave and the received wave are removed.

The first phase detector 53 phase-detects the output of the third mixer 51 with the output of the PLL 52, and the receiving section 30
And the output from the delay circuit 70 output the maximum DC component when the phase difference is zero. This output is supplied to the first integrator 54, whereby the integrated value Σ1 as shown in FIG. 3 (4) is obtained and supplied to the arithmetic controller 600. This integrated value Σ1 is used as a basis for the determination in the arithmetic and control unit 600. Since the output of the third mixer 51 contains the Doppler component, the Doppler frequency can be obtained by measuring the frequency of this signal. For this reason, a Doppler counter 90 is provided, and as a signal of a frequency that is a reference for counting by the Doppler counter 90,
The output of the local oscillator 41 is used.

The distance precision detecting section 60 is composed of a fourth mixer 61, a fifth mixer 62, a second phase detector 63, a third phase detector 64, a subtractor 65 and a second integrator 66. .. The fourth mixer 61 and the fifth mixer 62 both take in the output of the receiving section 30 and take in the receiving PN signal, and output the product of both. The reception PN signal captured by the fourth mixer 61 is the output of the second 1/2 chip delay device 72, and is 1/2 chip delayed as compared with the reception PN signal captured by the third mixer 51.

On the contrary, the reception PN signal fetched by the fifth mixer 62 is the output of the reception PN generator 300, that is, the signal before being delayed by the first 1/2 chip delay device 71. Therefore, the fourth mixer 61 and the fifth mixer 62
The output of each is 1/2 compared with the output of the third mixer 51.
It is an output related to a receiving PN signal having a phase before and after the chip. These signals are phase-detected by the output of the PLL 52 in the second phase detector 63 and the third phase detector 64, respectively, and if the difference is integrated, an integrated value Σ2 as shown in FIG. 3 (5) can be obtained. .. Difference is subtractor 65
Thus, the integrated value Σ2 is obtained by the second integrator 66. The integrated value Σ2 is used as a basis for the determination in the arithmetic controller 600.

The receiving PN signal is generated by the receiving PN generator 300. Reception PN generator 300
Has the same configuration as the transmitting PN generator 200. That is, a frequency divider 301 having a frequency division ratio p that takes in the output from the reference oscillator 100, and a shift register that generates 10 types of reception PN signals designated by the code setting device 800 based on the output of the frequency divider 301. It includes a second PN generator 302 configured by

The receiving PN generator 300 is different from the transmitting PN generator 200 in that it is subjected to the phase shift control by the phase shift controller 400. For this control, the phase shift controller 400 that gives the phase shift amount Δt to the frequency divider 301 is used, and the epoch is supplied from the second PN generator 302 to the phase shift controller 400. That is, at the time point when the PN signal for reception, which is the output of the second PN generator 302, reaches the epoch, the phase shift controller 400 gives the frequency shift amount Δt to the frequency divider 301 and delays the PN signal for reception sequentially. The initial timing of the reception PN signal is set by a reset pulse from the arithmetic and control unit 600. As a result, the reception PN signal as shown in FIG. 2C is generated.

The phase shift controller 400 includes a delay amount calculator 50.
0 is connected, and the delay amount calculator 500 calculates according to the phase shift amount Δt output from the phase shift controller 400. For example, the number of operations of the phase shifter 400 is counted. By performing such an operation based on the time of reset, the delay amount computing unit 500 causes the transmission PN included in the output of the receiving unit 30.
The phase matching timing M of the signal and the reception PN signal supplied to the third mixer 51 is obtained. The product of M and the amount of phase shift Δt represents the delay time td, and corresponds to the distance to the obstacle.

In this embodiment, further, the output level of the receiving section 30 is maintained at a predetermined value even if there is a change in the received signal due to the distance to the obstacle or the directivity of the antenna 10, and suitable signal detection, etc. The gain controller 80 is provided to perform the above operation, and the amplification gain of the amplifier 32 is controlled according to the calculation result of the delay amount calculator 500.

(5) Distance and Relative Velocity Detection Operation FIG. 6 shows a distance and relative velocity detection operation in this embodiment as a control flowchart of the arithmetic controller 600.

First, in this embodiment, the arithmetic and control unit 600 resets each member immediately after the operation is started (S1) by turning on the power (S2). That is, the frequency divider 20
The reset pulse is supplied to 1 and 301, the PN generators 202 and 302, the phase shift controller 400, and the delay amount calculator 500.

After that, the integrated values Σ1 and Σ2 are fetched from the signal detecting section 50 and the precision distance detecting section 60 into the arithmetic controller 600 (S3). The arithmetic controller 600 has an integrated value Σ1.
Is greater than or equal to the threshold value TH1 (S4),
When it is determined that the threshold value TH1 or more, the integrated value Σ2 is further determined whether or not the threshold value TH2 (S5).

As described above with reference to FIG. 3 (4), the case where the integrated value Σ1 takes a large value means that the product of the count value M of the delay amount calculator 500 and the phase shift amount Δt is delayed. This is the case when it is almost equal to the time td. Further, as described with reference to FIG. 3 (5), the same applies to the case where the integrated value Σ2 has a small value. However, the absolute value of the integrated value Σ2 is considered here.

Therefore, if either of the conditions of steps S4 and S5 is not satisfied, it can be considered that MΔt does not match td yet, so that the process returns to step S3 after execution of steps S6 and S7. In step S6, the phase shift controller 400 is instructed to shift the output of the receiving PN generator 300, and in step S7, the calculation content of the delay amount calculator 500 is incremented by Δt.

When both the conditions of steps S4 and S5 are satisfied, the product of the count value M and the phase shift amount Δt is the delay time td.
Since it can be considered that the case is almost equal to
00 takes in the calculated value of the delay amount calculator 500 and the count value of the Doppler counter 90 (S8). The former calculated value is
It corresponds to the distance to the obstacle based on the above-mentioned principle, and the latter count value is the Doppler frequency and corresponds to the relative speed to the obstacle. The arithmetic and control unit 600 is
Based on these information, the relative speed to the obstacle and the distance to the obstacle are calculated and sent to the alarm device 700 Step 2
Return to. Based on these pieces of information, the alarm device 700 determines whether or not the obstacle is at an alarm distance (a distance at which an occupant should be alarmed) (S9), and if there is, an alarm is generated.

In the above operation, step S8
The transition condition to is set to the AND condition of steps S4 and S5, in order to make the phase matching detection accuracy high. In addition, the determination algorithm in step S9 may be such that an alarm is issued at a larger distance when the relative speed is high, for example.

(6) Effects of the Embodiment As described above, according to this embodiment, the P of the epoch as short as possible is obtained.
Since the radio wave modulated by the N signal is used as the radar radio wave, the obstacle can be determined in a short time. However, since a plurality of PN signals sequentially different for each device are used, a long epoch As in the case of using the PN signal, it is possible to eliminate interference from the same type device mounted in another vehicle.

For example, as shown in FIG. 7, when another vehicle (obstacle) B is traveling in front of a vehicle (own vehicle) A equipped with the device of this embodiment, Even when the radio wave from the vehicle C traveling in parallel is reflected by the obstacle B, erroneous detection due to the reception of this radio wave is significantly suppressed. The same applies when the radio wave of the vehicle D traveling from the front is received. In terms of the interference probability, if the maximum measurement distance is 150 m, the epoch length is 0.1 msec, and the number of code types of the PN signal is set to 10 and 1 μsec / 0.1 ms
ec × 10 = 1/1000, which is equivalent to the case of using a 10 times longer epoch, which is practically not a problem.

Further, according to this embodiment, it is not necessary to increase the transmission power. This is because the continuous signal obtained by removing the PN modulation component from the received signal is used. Therefore, the device has low power consumption and high sensitivity. Further, since the output level of the receiving unit 30 is adjusted according to the distance, the influence of the reflection level variation corresponding to the distance can be eliminated.

Further, since the distance and the relative speed can be detected at the same time, the alarm can be issued under the condition more practically necessary. In addition, instead of the alarm device 700,
A signal may be supplied to the steering / braking control system.

Since the device of this embodiment is driven with low power by utilizing digital processing without using special parts such as a matched filter formed by SAW, it is realized with a simple structure despite high accuracy. it can. For example, it can be constructed inexpensively and compactly by using an IC.

[0066]

According to the present invention, the epoch of the PN signal is shortened as much as possible by sequentially using a plurality of types of PN signals which are different for each device. Therefore, the effect according to the previous proposal, for example, the interference elimination with the same type device mounted on another vehicle, This has the effect of reducing the detection speed of an obstacle in inverse proportion to the number of types of PN signals while ensuring low power transmission and the like.

According to the second aspect, since the Doppler frequency is counted by the Doppler counter, the distance and the relative velocity can be simultaneously measured. Further, it can be used as one of the parameters relating to the alarm signal generating condition, and a more suitable alarm can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a vehicle collision prevention radar device according to an embodiment of the present invention.

2A and 2B are diagrams showing the principle of distance measurement in this embodiment, FIG. 1A is a diagram showing a configuration of a PN signal in a transmission wave, and FIG. 2B is a propagation of the transmission wave in FIG. 2A. 2 is a diagram showing a received wave delayed by a time td, and FIG. 2C is a diagram showing the operation of the receiving PN signal and the distance counter.

FIG. 3 is a diagram showing information as a basis of distance measurement in this embodiment, FIG. 3 (4) shows an output of the first integrator, and FIG. 3 (5) shows an output of the second integrator. Is.

FIG. 4 is a block diagram showing a partial configuration of this embodiment, particularly a configuration relating to transmission and reception.

FIG. 5 is a block diagram showing a partial configuration of this embodiment, particularly a configuration relating to distance and relative velocity measurement.

FIG. 6 is a flowchart showing a flow of operation of distance and relative velocity measurement in this embodiment.

FIG. 7 is a diagram showing an effect of eliminating interference with another vehicle in this embodiment.

[Explanation of symbols]

 10 antenna 20 transmitter 30 receiver 32 amplifier 40 local signal generator 41 local oscillator 50 signal detector 52 PLL 53 first phase detector 54 first integrator 60 distance precise detector 63 second phase detector 64 third phase Detector 65 Subtractor 66 Second integrator 70 Delay circuit 71 First 1/2 chip delay 72 Second 1/2 chip delay 80 Gain controller 90 Doppler counter 100 Reference oscillator 200 Transmission PN generator 202 First PN generator 300 Receiving PN generator 302 Second PN generator 400 Phase shift controller 500 Delay amount calculator 600 Calculation controller 700 Alarm device 800 Code setting device EP Epoch CH chip td Delay time Δt Phase shift amount M Epoch number Σ1 integrated value of the first integrator Σ2 integrated value of the second integrator TH1 Threshold for have value TH2 distance precision detector output

Claims (2)

[Claims] 1. An antenna for transmitting and receiving radio waves in the traveling direction of a vehicle, a chip length sufficiently shorter than the maximum propagation time required for the radio waves to travel back and forth over the maximum measurement distance, and an epoch length at least longer than the maximum propagation time and as short as possible. A pseudo noise generator for transmission, which can set a code for generating a pseudo noise signal for transmission, a transmitter for supplying a transmission signal modulated by the pseudo noise signal for transmission to an antenna, and a reflected wave received by the antenna A receiving unit for converting a signal into a predetermined frequency and outputting the same, a receiving pseudo noise generator capable of setting a plurality of types of codes for generating a receiving pseudo noise signal having the same structure as the transmitting pseudo noise signal, and the receiving unit Setting unit for sequentially setting the plurality of types of codes common to the pseudo noise generator for transmission and the pseudo noise generator for transmission, the output of the receiving unit and the pseudo noise signal for reception , A signal detector that integrates and outputs the amplitude component of the product, a phase-shift controller that delays the receiving pseudo-noise signal by a predetermined phase for each single or multiple epochs, and a receiving pseudo-noise by the phase-shift controller. A delay amount calculator for calculating and storing the total delay amount of the signal, and an epoch of the pseudo noise signal for transmission and the pseudo noise signal for reception included in the output of the receiving unit when the output of the signal detecting unit exceeds a predetermined value. It is considered that the epochs match each other, the memory value of the delay amount calculator is taken in, and the arithmetic controller which obtains the distance to the obstacle related to the reflection of the radio wave based on this memory value and supplies it to the alarm device is provided. An automotive collision prevention radar device characterized by performing distance measurement based on a delay amount of a reception pseudo noise signal at a time point when an epoch of a transmission pseudo noise signal and an epoch of a reception pseudo noise signal included in an output match. 2. The vehicle collision prevention radar device according to claim 1, wherein the signal detecting unit includes means for removing a pseudo noise signal component for transmission from the obtained product, and a pseudo noise signal component for transmission is removed. The Doppler counter that counts the Doppler frequency of the signal is provided, and the arithmetic and control unit determines the relative speed with the obstacle based on the Doppler frequency obtained by counting, and supplies the signal to the alarm device according to a predetermined rule. A collision prevention radar device for automobiles.