JP2941075B2 - Automotive collision prevention radar system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art When an obstacle is present in the traveling direction of an automobile, the occupant of the automobile avoids the obstacle and drives safely. Therefore, for safe driving of an automobile, it is preferable to have a device that automatically detects an obstacle and alerts an occupant. Devices used for such applications include, for example, devices that detect obstacles by radio waves and devices that detect obstacles by ultrasonic waves. A collision prevention radar device is used.

This apparatus is an application of radar technology, and configurations based on various systems such as a pulse radar and an FM-CW radar have been studied.

[0004]

However, in a system using a pulse radar, an FM-CW radar, or the like, for example, the peak power of a transmission pulse becomes large, and interference with the same type device mounted on another vehicle is reduced. There is a problem that it occurs. In order to solve such a problem, the present applicant has previously filed an application to which spread spectrum is applied (Japanese Patent Application No. 3-51130). In this prior application, a PN having a structure in which the first and second pseudo noises (PN) are multiplexed is used to prevent interference with a similar device mounted on another vehicle.

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, since a special element such as a matched filter is used, there is a certain limit to cost reduction. There is. That is, the apparatus according to the prior application can be realized at a lower cost than the pulse radar, the FM-CW radar, and the like. However, it is needless to say that the apparatus can be further reduced in cost.

SUMMARY OF THE INVENTION It is an object of the present invention to realize an apparatus at a lower cost and as an IC, while securing advantages such as interference elimination obtained in the prior application.

[0007]

In order to achieve the above object, the present invention provides an antenna for transmitting and receiving radio waves in the traveling direction of a vehicle and a maximum propagation time required for the radio waves to reciprocate a maximum measurement distance. A transmitting PN generator for generating a transmitting PN signal having a sufficiently short chip length and a sufficiently long epoch length, a transmitting unit for two-phase modulating the transmitting PN signal and supplying it to the antenna as a signal to be transmitted, and receiving by the antenna A receiving unit that converts the signal related to the reflected wave into a predetermined frequency and outputs the same, and a receiving PN having the same structure as the transmitting PN signal.
A reception PN generator for generating a signal, a signal detection unit for integrating and outputting the output of the reception unit and the amplitude component of the reception PN signal, and a phase shift for delaying the reception PN signal by a predetermined phase Δt for each epoch Controller and PN for reception by phase shift controller
A distance counter that counts in accordance with the signal delay amount Δt, an epoch of the transmission PN signal included in the output of the reception unit when the output Σ1 of the signal detection unit becomes equal to or greater than a predetermined value TH1, and a reception PN signal The count value M of the distance counter is taken in assuming that the epochs match, the distance to the obstacle related to the reflection of the radio wave is calculated based on the count value M, and the distance counter is reset. And an arithmetic controller for supplying a signal to the alarm device when the PN signal becomes equal to the epoch of the PN signal for transmission and the epoch of the PN signal for reception included in the output of the receiving unit. Is characterized in that distance measurement is performed based on the total MΔt.

Further, the first delay means for delaying the reception PN signal by a time shorter than one chip and then supplying the delayed signal to the signal detection section, and the output of the first delay means is supplied to the first delay means.
Second delay means for delaying by the same amount of time as the delay means, means for detecting the product of the output of the reception unit and the reception PN signal relating to the output of the reception PN generator, and output of the second delay means. And a means for detecting and obtaining the product of the receiving PN signal and the output of the receiving section according to the above, and a distance precision detecting section including means for obtaining and integrating and outputting the difference between these two types of detection-related signals. The condition for taking in the count value M from the distance counter in the controller is that the absolute value | Σ2 | of the output of the distance precision detection unit is equal to or less than a predetermined value TH2 and / or that the output Σ1 of the signal detection unit is equal to or more than the predetermined value TH1. Has become
It is characterized by being.

A third aspect of the present invention provides a Doppler counter for counting the Doppler frequency of a signal from which the transmission pseudo noise signal component has been removed, wherein the signal detection unit includes means for removing the transmission pseudo noise signal component from the obtained product. The arithmetic and control unit determines a relative speed with respect to the obstacle based on the Doppler frequency obtained by counting, and supplies a signal to the alarm device according to a predetermined rule.

According to a fourth aspect of the present invention, the receiving section includes an amplifier for amplifying a signal related to the reflected wave, and a gain controller for controlling the gain of the amplifier according to the count value of the distance counter.

A fifth aspect of the present invention is characterized in that the transmitting PN generator and the receiving PN generator are provided with a reference oscillator for commonly supplying a signal of a reference frequency related to chip generation.

[0012]

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

The transmission PN signal is generated by a transmission PN generator. The transmission PN signal is composed of chips whose length is sufficiently shorter than the maximum propagation time (corresponding to the maximum measurable distance), and an epoch, which is a set of a plurality of chips, is set sufficiently longer than the maximum propagation time. Processing related to transmission such as two-phase modulation is executed by the transmission unit.

[0014] The received signal related to the reflected wave is taken into the receiving section. In the receiving section, the signal is converted into a predetermined frequency. Signal after the conversion is a signal delayed by a delay time t _d corresponding to the time that radio waves round trip between the obstacle and contains Doppler component corresponding to the relative speed of the obstacle I have. The output of the receiving unit is taken into the signal detecting unit.

On the other hand, a PN signal for reception is also taken into the signal detecting section. The reception PN signal is generated by the reception PN generator and has the same structure as the transmission PN signal. However, the phase is different depending on 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 epoch with reference to the reset time.

[0016] If the delay is repeated a plurality of times (M times), the cumulative value MΔt delay amount Δt corresponds to the delay time t _d of the output of the receiver at some point. Therefore, if the signal detector calculates the product of the output of the receiver and the PN signal for reception, and integrates the amplitude component, the integrated value Σ1 increases at a certain point in time. At this point, the total value of the delay amount MΔt
There is a point in time that matches the delay time t _d.

On the other hand, in the present invention, a distance counter is provided, and the distance counter performs counting relating to the phase shift amount (delay amount). This makes it possible to know how many times the epoch of the receiving PN signal has arrived from the time of reset until the integrated value increases. Therefore, the delay time t, that is, the distance to the obstacle, can be obtained based on the count value M, and this calculation is performed by the calculation controller. The arithmetic controller resets the distance counter in response to this, and prepares for the next and subsequent measurements.

As described above, in the present invention, the delay amount Δ
The distance is measured by the total of t. Since a special member such as a matched filter is not used, the configuration is inexpensive. Further, since the PN signal is used, the effect of eliminating interference with the same type device mounted on another vehicle is ensured by the spread spectrum, the reception gain is ensured by the spectrum resynthesis, and the transmission with reduced power can be performed.

According to the second aspect, while such an operation is ensured, there is an effect that the distance measurement accuracy is further improved.

First, the receiving PN supplied to the signal detecting section
A reception PN signal that is advanced by a predetermined time (for example, チ ッ プ of the chip length) with respect to the signal and a reception PN signal that is delayed by the same time are generated by delay, and these two types of reception PN are generated.
The signal is supplied to the distance precision detection unit. In the distance precise detection section, these two types of reception PN signals are each multiplied by the output of the reception section and detected. further,
The difference between the signals obtained by the detection is obtained and integrated.

In this way, the two types of receiving P
When the phase of the transmission PN signal included in the output of the reception unit belongs to the phase range defined by the N signal (for example, ± 1/2 chip length with respect to the reception PN signal supplied to the signal detection unit). , The absolute value of the integral value Σ2 in the precise distance detection unit becomes smaller. Therefore, when taking in the count value M from the distance counter, the integral value に お け る
If the threshold value determination based on the integral value Σ2 in the distance precision detection unit is performed in addition to the threshold value determination based on 1, the count value M from the distance counter can be captured at a more accurate time.

Based on such a principle, in claim 2, the absolute value | Σ2 | of the output of the precise distance detection unit is equal to or less than a predetermined value TH2, and the output Σ1 of the signal detection unit is equal to or greater than a predetermined value TH1. Under the condition that both or one of the conditions is met, the count value M is taken in from the distance counter, and the distance measurement accuracy is improved.

In the third aspect, the Doppler frequency is counted by the Doppler counter. This counting is performed based on the product obtained by the signal detection unit and the fundamental frequency output of the reception unit. As the former, a signal from which the component of the transmission PN signal has been removed in the signal detector may be used, and in the latter, for example, the output of an oscillator included in the receiver may be captured. The Doppler frequency obtained in this way is used as one of the parameters relating to the generation of an alarm signal in the arithmetic and control unit. For example, when the relative speed corresponding to the Doppler frequency is high, the arithmetic and control unit sets the distance at which an alarm should be issued longer. By doing so, it is possible to appropriately generate an alarm in conformity with the actual conditions.

According to the fourth aspect, the gain of the amplifier is controlled according to the distance, and the output level of the receiving section is controlled.
As a result, processing is performed on a signal for which a predetermined level has been ensured regardless of the directivity and distance of the antenna, and stable device operation is ensured.

In the present invention, the reference frequency of the transmission PN generator and the reference frequency of the reception PN generator are controlled by the same reference oscillator. Thus, the size of the device can be reduced.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments 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 an automobile collision prevention radar apparatus according to an embodiment of the present invention. As shown in this figure, this embodiment includes an antenna 10, a transmission unit 20, and a reception unit 30.

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

The antenna 10 supplies a signal to the receiving unit 30 via a circulator in the transmitting unit 20. This signal is a signal related to a radio wave reflected from an obstacle existing ahead, for example, another vehicle traveling in the same lane.
Therefore, the time t _d required for the radio wave to reciprocate to the obstacle is t _d
Only from the signal related to the transmission, and further undergoes a Doppler shift due to a speed difference (relative speed) from the obstacle. In addition, due to the operation of the transmission unit 20, a modulation component related to the transmission PN signal is included.

The receiving section 30 is provided with a local signal generating section 40. The local signal generator 40 supplies a signal of a predetermined frequency to the receiver 30, and the receiver 30 converts a signal related to the output of the antenna 10 into a different frequency based on the signal.

A signal detection unit 50 and a precise distance detection unit 60 are provided downstream of the reception unit 30. These circuits 50 and 60 take in the output of the receiving unit 30 and output an integral value which is the basis for determining the conditions for detecting the distance and the relative speed in the present embodiment. Also, these circuits 50 and 60
Performs a predetermined process on the output of the reception unit 30 by taking in a pseudo noise signal related to the reception PN signal as a premise of the integration value calculation. 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 phase shift control. In the following description, the pseudo noise signal supplied to the signal detection unit 50 and the distance precision detection unit 60 will be referred to as a reception PN signal. The phase shift control and the distance detection are operations according to the features of the present invention, and will be described later in detail.

The receiving PN signal is transmitted to the transmitting PN generator 20.
0, using the output of the reference oscillator 100
Generated by N generator 300. However, PN for reception
The reception PN signal generated by the generator 300 is not supplied to the signal detection unit 50 or the like as it is, but the reception PN signal delayed by a predetermined time by the delay circuit 70 is supplied. That is, the signal detection unit 50 receives the reception PN signal obtained by delaying the output of the reception PN generator 300 by チ ッ プ chip, and the distance precision detection unit 60 outputs the signal detection unit 5.
0, two signals before and after ± 1/2 chip with respect to the receiving PN signal supplied to the receiving PN signal (ie, receiving PN generator 3
00 output and the signal delayed by one chip)
Are supplied respectively. Although one reference oscillator 100 is shown in this figure, two reference oscillators may be provided separately for transmission and reception.

The receiving PN generator 300 is provided with a phase shift controller 400. The phase shift controller 400 captures the epoch occurrence timing from the reception PN generator 300, and outputs the reception PN signal for a predetermined time Δ every time an epoch occurs.
Delay by t. Further, a distance counter 500 is provided which performs counting in accordance with the delay of the receiving PN signal by the phase shift controller 400. The count value of the distance counter 500 indicates the delay time t _d , that is, 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, a gain controller 80 for controlling the amplification gain in the receiving unit 30 according to the output of the distance counter 500 is provided, and the local signal generating unit 40 generates the signal in the signal detecting unit 50 using the frequency generated by the local oscillator. A Doppler counter 90 is provided for calculating only the Doppler shift from the frequency of the signal to be performed (the sum of the intermediate frequency and the Doppler shift). 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. The latter covers the calculation of the relative speed and the appropriateness of the alarm condition based on the result. This is a configuration that is used for the configuration (setting of the alarm distance corresponding to the speed).

In this embodiment, the operation controller 6
00 is provided. The arithmetic and control unit 600 captures the integrated value from the signal detection unit 50 and the precise distance detection unit 60, performs a determination on the integrated value, and captures the count contents of the distance counter 500 and the Doppler counter 90 according to the determination result. . The arithmetic and control unit 600 obtains the distance and the relative speed to the obstacle according to the content of the acquired count, and gives a signal to the alarm 700 according to a predetermined alarm condition. The alarm 700 notifies the 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 sets the transmission PN at the start of such an operation.
The reset pulse is supplied to the generator 200, the receiving PN generator 300, and the distance counter 500, and the receiving PN generator 3
From 00, the epoch occurrence timing is taken in as an arithmetic control start signal.

(2) Distance Measurement Principle of Embodiment Next, before describing the detailed configuration and operation of this embodiment, the distance measurement principle according to the features of the present invention will be described in accordance with the embodiment.

FIG. 2 shows the configuration of signals transmitted and received in this embodiment. First, a signal supplied to the antenna 10 from the transmission unit 20 and transmitted from the antenna 10 to the front of the vehicle is a transmission P having a configuration as shown in FIG.
Modulated by N signals. In general, a pseudo-noise signal used in spread spectrum has a configuration in which a chip is a unit and an epoch, which is a set of chips, is repeated. The transmission PN signal in this embodiment is a pseudo noise signal having a chip length CH, an epoch length EP, and the number of chips N in an epoch.

In this embodiment, the chip length CH
Are sufficiently shorter than the maximum measurement distance (the maximum distance at which an obstacle can be detected), and the epoch length EP is sufficiently long. For example, when the maximum measurement distance determined according to the transmission power, the used frequency, and the like is 150 m, the time required for the radio wave to reciprocate over this distance (maximum propagation time) is 1 μsec.
c. Correspondingly, for example, the chip length CH is 0.2
μsec and the epoch length EP are set to 1 msec.
As will be described later, the probability of interference with other vehicle devices is determined by the maximum propagation time / epoch length EP, and the division ratio p with respect to the output of the reference oscillator 100 is determined by the chip length CH and the required distance resolution.

When a signal modulated by such a transmission PN signal is transmitted, the signal is reflected as a reflected wave from an obstacle in FIG.
A signal having a configuration as shown in (2) is obtained. That is, the time t _d required for the radio wave to propagate between the obstacle and the obstacle
Is obtained. Such a signal is supplied to the signal detection unit 50 and the distance precision detection unit 60.

On the other hand, the receiving PN signal has the same configuration as the transmitting PN signal, but is delayed by Δt for each epoch. That is, with reference to the reset pulse supply timing by the arithmetic and control unit 600 as a reference, FIG.
Is delayed by Δt. Signal detector 5
0, the signal shown in FIG. 2B and the signal shown in FIG.
Is obtained, and phase detection is performed. The DC signal obtained as a result of the phase detection reaches the maximum level when the phases of both signals match. In the present embodiment, the coincidence point is determined by integrating the phase detection result into the signal detection unit 50.
Are detected by the operation controller 600 based on the magnitude of the output supplied to the operation controller 600 from the CPU.

If this integral value is represented by Σ1, as shown in FIG. 3 (4), the maximum value N is reached when the phases of the two signals coincide with each other. Becomes 0. Therefore, if the threshold value is determined for the integral value Σ1, it is possible to determine the coincidence of the phases of the two signals. This determination is made in the arithmetic controller 600. If the result of the determination is that the threshold value is exceeded, the arithmetic controller 600 takes in the count value of the distance counter 500. The distance counter 500 executes a count corresponding to the phase shift control on the basis of the reset time point, and the count value corresponds to the accumulated value MΔt of the delay amount up to the present time. Here, M is the number of epochs generated up to that point. The fact that the phase of the two signals are coincident, take neither remedied, the delay time t _d is the delay amount of the cumulative value MΔ
This indicates that they substantially coincide with t. Therefore, by taking in the count value of the distance counter 500, the delay time t
_d is detected, and the arithmetic and control unit 600 calculates the distance to the obstacle based on the detected _d .

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

This integral value Σ2 is therefore calculated by the distance detection unit 5
When the phase of the reception PN signal supplied to 0 and the phase of the modulation component of the transmission PN signal included in the output of the reception unit 30 match, the absolute value becomes minimum = 0. By utilizing this, the timing of taking in the count value from the distance counter 500 to the arithmetic and control unit 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 distance precision detection unit 60 has become equal to or less than a predetermined threshold.

As described above, in this embodiment, precise detection of the distance is performed. In the above description, the delay circuit 7
Although the half chip delay at 0 is ignored, the chip length CH is already known, and thus may be supplemented by the calculation in the calculation controller 600.

(3) Partial Configuration of Embodiment—Transmission / Reception FIG. 4 shows a configuration related to transmission / reception in the configuration of the present embodiment.

As shown in the figure, the transmission 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 the frequency by a predetermined frequency division ratio p.
This division ratio p is determined according to the necessary distance resolution. For example, when it is desired to measure up to a distance resolution of 1.5 m, assuming that the chip length CH is 0.2 μsec as described above, the division ratio p is set to 0.2 μsec / 0.01 μ.
sec = 20. However, 0.01 μsec
Is the time required for a radio wave to reciprocate 1.5 m. The first PN generator 202 has a configuration including, for example, a shift register, and generates a transmission PN signal having the above-described configuration based on a signal output from the frequency divider 201.

The transmission section 20 has a transmission oscillator 21, a phase modulator 22, and a circulator 23. An output of a predetermined frequency of the transmission oscillator 21 is supplied to a phase modulator 22, and is phase-modulated by a 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 for receiving the output of the antenna 20 via the circulator 23. The first mixer 31 mixes the signal from the local signal generator 40 with the reception output, and outputs the obtained signal to the amplifier 32. The amplifier 32 amplifies the signal and outputs the signal 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 configuration including a local oscillator 41 and a second mixer 42. Local oscillator 41
Oscillates at a predetermined intermediate frequency and provides an oscillation output to the second mixer 42. The second mixer 42 takes in the output of the transmitting oscillator 21 of the transmitting unit 21 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 frequency of the signal output from the first mixer 31 becomes an intermediate frequency. However, it goes without saying that it includes the Doppler shift due to the relative speed with respect to the obstacle and includes the modulation component due to the transmission PN signal.

(4) Partial Configuration of Embodiment—Distance and Relative Speed Detection FIG. 5 shows a partial configuration of the present 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 detection unit 50
Are 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 the mixed output to the first phase detector 53 via the PLL 52 and directly. The delay circuit 70 has a first 1 /
Two-chip delay device 71 and second half-chip delay device 72
Are connected in cascade. The delay circuit 70 supplies the first half-chip delay 71 to the third mixer 51.
Is a PN signal for reception delayed by チ ッ プ chip.
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 becomes a signal from which the modulation component due to the PN signal has been 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 is a narrow band filter including an intermediate frequency in a pass band, and by passing through the filter, an unnecessary component such as an interference wave or a fluctuation in the intensity of a received wave is removed. The first phase detector 53 performs phase detection of the output of the third mixer by the output of the PLL 52, and outputs the maximum DC component when the phase difference between the output from the receiving unit 30 and the output from the delay circuit 70 is zero. .
This output is provided to a first integrator 54, which
An integral value Σ1 as shown in (4) is obtained and supplied to the arithmetic and control unit 600. The integral value Σ1 is used as a basis for determination in the arithmetic and control unit 600. Since the output of the third mixer 51 includes a Doppler component, the Doppler frequency can be obtained by measuring the frequency of this signal. For this purpose, a Doppler counter 90 is provided, and the output of the local oscillator 41 is used as a signal having a frequency that is a reference for counting by the Doppler counter 90.

The precise distance detecting section 60 includes 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 capture the output of the receiving unit 30 and capture the PN signal for reception, and output the product of both. The reception PN signal captured by the fourth mixer 61 is the output of the second half-chip delay unit 72, and is delayed by チ ッ プ chip compared to the reception PN signal captured by the third mixer 51. Conversely, the reception PN signal captured by the fifth mixer 62 is the output of the reception PN generator 300, that is, the first 1
This is a signal before being delayed by the / 2 chip delay unit 71. Therefore, the output of the fourth mixer 61 and the fifth mixer 62 is the third output.
This is an output related to the receiving PN signal having a phase of about 1/2 chip as compared with the output of the mixer 51. These are phase-detected by the output of the PLL 52 in the second phase detector 63 and the third phase detector 64, respectively, and the difference is integrated. As a result, the integrated value Σ as shown in FIG.
2 can be obtained. The difference is obtained by the subtractor 65, and the integrated value Σ2 is obtained by the second integrator 66. Integral value Σ
2 is the basis for the determination in the arithmetic and control unit 600.

The receiving PN signal is generated by the receiving PN generator 300. PN generator 300 for reception
Has the same configuration as the transmission PN generator 200. That is, a frequency divider 301 having a frequency division ratio p for taking in an output from the reference oscillator 100, and a second PN generator 302 configured by a shift register or the like to generate a reception PN signal based on the output of the frequency divider 301 are provided. Contains.

The PN generator 300 for reception differs from the PN generator 200 for transmission in that the PN generator 300 is subjected to phase shift control by a phase shift controller 400. For this control, a phase shift controller 400 that supplies the phase shift amount Δt to the frequency divider 301 is used, and the epoch is supplied to the phase shift controller 400 from the second PN generator 302. That is, 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 phase shift amount Δt to the frequency divider 301 to sequentially delay the PN signal for reception. Note that the initial timing of the reception PN signal is performed by a reset pulse from the arithmetic and control unit 600. As a result, a reception PN signal as shown in FIG. 2 (3) is generated.

The phase shift controller 400 includes a distance counter 50
0 is connected, and the distance counter 500 counts 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 counting based on the reset time, the distance counter 500 can determine the transmission PN included in the output of the receiving unit 30.
The phase matching timing M between the signal and the receiving PN signal supplied to the third mixer 51 is determined. Product of the M and the phase shift Δt represents a time delay t _d, which corresponds to the distance to the obstacle. In the present embodiment, furthermore, the output level of the receiving unit 30 is maintained at a predetermined value even if the received signal fluctuates due to the distance to the obstacle or the directivity of the antenna 10, and an operation such as suitable signal detection is performed. To provide a gain controller 80
The amplification gain of the amplifier 32 is controlled according to the counting result of the distance counter 500. (5) Operation of Detecting Distance and Relative Speed FIG. 6 is a control flowchart of the arithmetic and control unit 600 showing the operation of detecting distance and relative speed in the present embodiment.

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

Thereafter, the integral values Σ1 and Σ2 are taken into the arithmetic and control unit 600 from the signal detection unit 50 and the precise distance detection unit 60 (S3). The operation controller 600 calculates the integral value Σ1
Is greater than or equal to a threshold value TH1 (S4).
When it is determined that the above is the case, it is further determined whether or not the integral value Σ2 is equal to or less than the threshold value TH2 (S5).

Here, as described above with reference to FIG. 3D, the case where the integral value 大 き な 1 takes a large value means that the product of the count value M of the distance counter 500 and the phase shift amount Δt is the delay time t. _d . Further, as described with reference to FIG. 3 (5), the case where the integral value Σ2 takes a small value is the same case. However, here, the absolute value of the integral value Σ2 is considered.

[0059] Therefore, if not meet any of the conditions of steps S4 and S5, yet because regarded as MΔt does not match the t _d, the flow returns to step S3 after the execution of steps S6 and S7. In step S6, the reception PN generator 300 is sent to the phase shift controller 400.
A phase shift of the output is instructed, and in step S7, the content of the distance counter 500 is incremented.

If the conditions of steps S4 and S5 are both satisfied, the product of the count value M and the phase shift amount Δt is equal to the delay time t _d
It can be considered that the case is almost equal to
00 takes in the count values from the distance counter 500 and the Doppler counter 90 (S8). The former count value corresponds to the distance to the obstacle based on the above-described 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 determines whether or not the obstacle is within a warning distance (a distance at which a warning should be issued to an occupant) based on the information (S9). (S10), and if not, the process returns to step S2.

In the above operation, step S8
The condition for shifting to is the AND condition of steps S4 and S5, in order to raise the detection accuracy of the phase coincidence to a high level. Further, the determination algorithm in step S9 may be such that, for example, when the relative speed is large, an alarm is issued at a larger distance.

(6) Effects of Embodiment As described above, according to this embodiment, P having a sufficiently long epoch
Since the radio wave modulated by the N signal is used as the radar radio wave, interference from the same type device mounted on another vehicle can be eliminated. For example, as shown in FIG. 7, in a situation where another vehicle (obstacle) B is running in front of a vehicle (own vehicle) A on which the device of the present embodiment is mounted, the vehicle runs parallel to the vehicle A. Even when a radio wave from the vehicle C is reflected by the obstacle B, erroneous detection or the like due to reception of the radio wave is significantly suppressed. The same applies to the case where a radio wave of the vehicle D traveling from the front is received. Speaking of the interference probability, if the maximum measurement distance is 150 m and the epoch length is 1 μsec, 1 μ
sec / 1 msec = 1/1000, which is practically not a problem.

Further, according to the present embodiment, there is no need to increase the transmission power. This is because of a continuous signal. Therefore, the device has low power and high sensitivity. In addition, since the output level of the receiving unit 30 is adjusted according to the distance, it is possible to eliminate the influence of the reflection level fluctuation corresponding to the distance.

Further, since the distance and the relative speed can be detected simultaneously, an alarm can be generated under more actual conditions as required. In addition, instead of the alarm 700,
A signal may be supplied to the steering / braking control system.

Since the apparatus of this embodiment is driven by low power using digital processing without using special parts such as a matched filter constituted by SAW, it can be realized with a simple configuration despite high accuracy. it can. For example, an inexpensive and compact configuration can be achieved by using an IC.

[0066]

According to the present invention, since the PN signal is used based on the spread spectrum, the effects according to the prior proposals, for example, the elimination of interference with the same type device mounted on another vehicle, the transmission with reduced power, etc. are secured. In addition, since distance measurement is performed by accumulating the amount of phase shift, it can be configured without using a special element such as a matched filter, so that the device cost can be reduced and the IC can be easily integrated.

According to the second aspect, for the receiving PN signal supplied to the signal detecting section, for example, the difference threshold value is determined for the receiving PN signal having a phase of ± 1/2 × chip length,
Since the count value capturing condition is used, the distance measurement accuracy is further improved.

According to the third aspect, the Doppler frequency is counted by the Doppler counter, so that the distance and the relative speed can be measured simultaneously. Further, it can be used as one of the parameters related to the alarm signal generation condition, and more suitable alarm can be performed.

According to the fourth aspect, the output level of the receiving unit is controlled by the gain control of the amplifier, and stable device operation is possible.

According to the fifth aspect, the reference frequency in the transmitting and receiving PN generators is generated by the same reference oscillator, so that the device configuration can be downsized.

[Brief description of the drawings]

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

FIGS. 2A and 2B are diagrams showing the principle of distance measurement in this embodiment. FIG. 2A shows the configuration of a PN signal in a transmission wave, and FIG. 2B shows the propagation of the transmission wave in FIG. shows a received wave delayed by time t _d, the 2 (3) shows the operation of the reception PN signal and the distance counter.

FIGS. 3A and 3B are diagrams showing information serving as a basis for distance measurement in this embodiment. FIG. 3D shows an output of a first integrator, and FIG. 3F shows an output of a second integrator. It is.

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

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

FIG. 6 is a flowchart illustrating a flow of an operation of measuring a distance and a relative speed in the embodiment.

FIG. 7 is a diagram showing the effect of eliminating other vehicle interference in this embodiment.

[Explanation of symbols]

 Reference Signs List 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 unit 72 Second 1/2 chip delay unit 80 Gain controller 90 Doppler counter 100 Reference oscillator 200 Transmission PN generator 202 First PN generator 300 PN generator for reception 302 Second PN generator 400 Phase shift controller 500 Distance counter 600 Arithmetic controller 700 Alarm device EP Epoch CH chip td Delay time Δt Phase shift amount M Epoch number Σ1 First integrator Integral value 積分 2 Integral value of second integrator TH1 Threshold value for signal detector output TH2 Distance Threshold for dense detector output

Claims (5)

(57) [Claims] An antenna for transmitting and receiving radio waves in the traveling direction of a vehicle and a pseudo-noise signal for transmission having a chip length and an epoch length sufficiently shorter than a maximum propagation time required for the radio waves to reciprocate a maximum measurement distance are generated. A pseudo-noise generator for transmission, a transmitting unit that two-phase modulates the pseudo-noise signal for transmission and supplies the signal to the antenna as a signal to be transmitted, and converts a signal related to a reflected wave received by the antenna to a predetermined frequency and outputs the signal. A receiving unit, a receiving pseudo-noise generator that generates a receiving pseudo-noise signal having the same structure as the transmitting pseudo-noise signal, and integrating the amplitude component of the product of the output of the receiving unit and the receiving pseudo-noise signal. A signal detection unit to output, and a phase shift controller that delays the pseudo-noise signal for reception by a predetermined phase for each epoch,
A distance counter that counts according to the delay amount of the reception pseudo noise signal by the phase shift controller, and a transmission pseudo noise signal included in the output of the reception unit when the output of the signal detection unit becomes a predetermined value or more It is assumed that the epoch of the reception pseudo noise signal coincides with the epoch of the reception counter, and the count value of the distance counter is fetched. And an operation controller for supplying a signal to the alarm device when the pseudo-noise signal for transmission at the time when the epoch of the pseudo-noise signal for transmission and the epoch of the pseudo-noise signal for reception included in the output of the reception unit match each other. A collision prevention radar apparatus for an automobile, wherein the distance measurement is performed based on the total delay amount of a noise signal. 2. A collision prevention radar apparatus for an automobile according to claim 1, wherein said first pseudo noise signal is delayed by a time shorter than one chip, and is supplied to a signal detector. Second delay means for delaying the output of the delay means by the same time as the first delay means, and the product of the pseudo noise signal for reception relating to the output of the pseudo noise generator for reception and the output of the receiving section is detected. Means for obtaining the product of the pseudo-noise signal for reception relating to the output of the second delay means and the output of the receiving unit, and means for determining and integrating the difference between these two types of detection-related signals and outputting the result. And a condition for taking in the count value from the distance counter in the arithmetic and control unit is that the absolute value of the output of the distance precision detection unit is equal to or less than a predetermined value and / or the output of the signal detection unit is provided. It has exceeded the specified value Automotive collision prevention radar apparatus, characterized in that it. 3. The collision prevention radar apparatus for an automobile according to claim 1, wherein the signal detection unit includes means for removing a transmission pseudo noise signal component from the obtained product, and the transmission pseudo noise signal component is removed. A Doppler counter for counting the Doppler frequency of the signal obtained, wherein the arithmetic and control unit obtains a relative speed with respect to the obstacle based on the Doppler frequency obtained by counting, and supplies a signal to the alarm device according to a predetermined rule. A collision prevention radar device for automobiles, characterized by the following. 4. A collision prevention radar apparatus for an automobile according to claim 1, wherein the receiving unit includes an amplifier for amplifying a signal related to a reflected wave, and controls a gain of the amplifier according to a count value of a distance counter. An automobile collision prevention radar device comprising a gain controller. 5. A collision prevention radar apparatus for an automobile according to claim 1, further comprising a reference oscillator for commonly supplying a signal of a reference frequency related to chip generation to a pseudo-noise generator for transmission and a pseudo-noise generator for reception. An automobile collision prevention radar apparatus comprising: