JPH0712930A - Distance/relative speed detection circuit and radar equipment for vehicle using it - Google Patents

Abstract

PURPOSE:To detect the distance to an object from its own vehicle and relative speed of the object against its own vehicle without using any costas loop, etc. CONSTITUTION:A delayed PN(pseudo noise) code delayed against a PN code used for phase modulation at the time of transmission is generated by means of a PN generator 28 and delay circuit 30. Received signals outputted from an reception antenna 30 are multiplied by the delayed PN code by means of a multiplier 26 after the frequency of the signals is converted into a first IF signal by means of a frequency conversion circuit 24. The output of the multiplier 26 is limited in band and, by discriminating the correlation of the signals obtained by limiting the band, the delaying amount corresponding to the time required for radio waves to go to and come back from an object from and to its own vehicle is detected. A distance detecting circuit 36 calculates the distance to the object based on the detected delaying amount. The output of the BPF 32 is further frequency-converted by means of another frequency conversion circuit 40 and converted into a voltage by means of an F-V converter 42. The output of the converter 42 contains a voltage component related to a Doppler frequency and a relative speed calculating circuit 44 calculates the relative speed of the object from the component related to the Doppler frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle radar device mounted on a vehicle, and more particularly to a circuit for detecting a distance between an own vehicle and an object and a relative speed of the object with respect to the own vehicle.

[0002]

2. Description of the Related Art A vehicular radar system is a radar system used to detect an object (other vehicle, guardrail, building, etc.) existing in front of or behind a vehicle. Vehicle radar devices are roughly classified into optical type and radio type. In the optical system, laser or infrared is used as a carrier wave. In the radio wave method, a modulation method such as a pulse method or an FM-CW method is used.

[0003]

As a vehicle radar device, a device using a spread spectrum system has been developed in recent years. Direct spread (DS) method and frequency hopping (FH) method are known as the spread spectrum method, but the DS method used in the vehicle radar device is a pseudo noise (PN) method. In this method, a carrier wave is phase-modulated by a code and the phase-modulated signal is used as a transmission signal. The transmission signal is reflected by the object and input to a carrier synchronization circuit such as Costas loop. Therefore, in this method, since a signal that is phase / frequency synchronized with the received signal is obtained, it is possible to extract the Doppler frequency, that is, to detect the relative speed of the object with respect to the own vehicle.

The distance measuring range required for the vehicle radar device is a short distance of several hundred meters. Therefore, when the spread spectrum method using the carrier synchronization circuit described above is adopted, it is necessary to realize high-speed phase / frequency synchronization. This increases the cost for implementing the vehicle radar device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and has been made to solve such problems.
It is an object of the present invention to realize a device capable of detecting a relative speed at a lower cost.

[0006]

In order to achieve such an object, the distance / relative velocity detection circuit of the present invention is designed to provide a predetermined PN code for phase modulation of a transmission signal to an object. And means for generating a delayed PN code having a phase delayed by the delay amount while changing the delay amount, and means for multiplying the received signal, which is a signal obtained by down-converting the reflected wave received from the object, by the delayed PN code. , Means for extracting a frequency component in the vicinity of the fundamental frequency of the received signal after being multiplied by the delayed PN code, means for detecting a delay amount when the level of the extracted frequency component is maximum, and detection A means for calculating the distance between the vehicle and the object based on the amount of delay, a means for further down-converting the extracted frequency component, and a frequency of the signal obtained by this down-conversion. Based on the detected Doppler shift, means for detecting the Doppler shift caused by the relative movement of the target object with respect to the own vehicle, and a means for calculating the relative speed of the target object with respect to the own vehicle are installed in the vehicle. It is characterized by

The vehicle radar device of the present invention is a PN
Code generating means, phase modulating a carrier wave by the generated PN code and transmitting it as a transmission signal to an object, means for receiving a reflected wave from the object, distance / relative speed detection circuit of the present invention And is mounted on a vehicle.

[0008]

In the distance / relative speed detection circuit of the present invention,
First, a delayed PN code is generated. This delayed PN code has a phase delayed by a predetermined delay amount with respect to the PN code used at the time of transmission. Furthermore, this delayed PN code is multiplied on the received signal. This received signal is a signal obtained by down-converting the reflected wave received from the object.
At this time, the delay amount of the delayed PN code with respect to the PN code used at the time of transmission corresponds to the time required from the transmission of the transmission signal to the reception of the reflected wave, that is, the time corresponding to the round-trip distance between the vehicle and the object. If they are substantially the same, the received signal after being multiplied by the delayed PN code is a signal including only a single frequency component. On the other hand, if the delay amount of the delayed PN code with respect to the PN code used for transmission does not match the time from the transmission of the transmission signal to the reception of the reflected wave, the delay P
The received signal after being multiplied by the N code becomes a signal containing many frequency components. Therefore, by extracting only the frequency component in the vicinity of the fundamental frequency from the received signal after being multiplied by the delayed PN code by using a filter and monitoring the level of the extracted frequency component, the distance between the own vehicle and the object can be determined. Can be detected. That is, in the present invention, the delay amount when the level of the extracted frequency component becomes maximum is detected, and the distance between the vehicle and the object is calculated based on the detected delay amount. Therefore, in the present invention, the distance between the own vehicle and the object is detected without using a Costas loop or the like, and a circuit that can perform high-speed processing at a relatively low cost is realized.

Further, according to the present invention, the frequency component extracted from the received signal after being multiplied by the delayed PN code is further down-converted. The frequency of the signal obtained by this shows the relative speed of the object with respect to the own vehicle.
That is, by monitoring the frequency of this signal, the Doppler shift caused by the relative movement of the object with respect to the own vehicle can be detected. In the present invention, the relative speed of the object with respect to the own vehicle is calculated based on the detected Doppler shift. Therefore, in the relative speed detection circuit of the present invention, the relative speed of the object with respect to the own vehicle is detected at high speed without using a carrier synchronization circuit such as Costas loop.

The vehicle radar device according to the present invention includes:
The distance / relative speed detection circuit of the present invention described above is mounted. That is, in the present invention, the distance between the own vehicle and the object or the relative speed of the object with respect to the own vehicle is detected at high speed, and the cost of the apparatus is reduced.

[0011]

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

FIG. 1 shows the structure of a vehicle radar device according to an embodiment of the present invention. Further, FIG. 2 shows the operation of each part of this embodiment.

In the vehicle radar system shown in FIG. 1, first, a transmission oscillator 10, a transmission trigger circuit 12, a PN generator 14, a phase modulator 16 and a transmission antenna 18 are provided as means for transmitting a signal to an object. Is equipped with. The transmission trigger circuit 12 supplies a transmission trigger to the PN generator 14, and the PN generator 14 responds to the transmission trigger by transmitting P.
Generate an N code. On the other hand, the transmission oscillator 10 generates a carrier wave. The carrier wave has a waveform as shown in FIG. 2A, and the transmission PN code is shown in FIG.
It is a code as shown in (b). Phase modulator 16
Supplies the phase-modulated carrier wave with the transmitting PN code and supplies it to the transmitting antenna 18. The transmission antenna 18 is provided, for example, at the front or rear of the vehicle, and transmits a phase-modulated carrier wave to an object (other vehicle or the like). When the carrier wave shown in FIG. 2A is phase-modulated by the transmission PN code shown in FIG. 2B, the transmission antenna 1
The transmission wave (modulation wave) transmitted from 8 to the target becomes a wave as shown in FIG.

The transmitted wave transmitted from the transmitting antenna 18 is reflected by the object and received by the receiving antenna 20. The receiving antenna 20 is arranged, for example, in the front part or the rear part of the vehicle. When the transmission wave transmitted by the transmission antenna 18 is a signal as shown in FIG. 2C, the signal received by the reception antenna 20 is a signal obtained by delaying the transmitted signal, for example, FIG. ) Will be a signal as shown in. The amount of delay is the antenna 1 for transmission.
This corresponds to the time required for the radio wave to propagate the distance from 8 to the receiving antenna 20 through the object. Therefore,
If this delay amount can be detected, the transmitting antenna 1
It is possible to detect the distance from the vehicle (own vehicle) equipped with the antenna 8 and the receiving antenna 20 to the object.

The vehicle radar system shown in FIG. 1 includes a local oscillator 22 and a frequency conversion circuit 24 as means for converting the signal received by the receiving antenna 20 into a first intermediate frequency (IF) signal. That is, the local oscillator 22 generates a first local oscillation signal having a predetermined frequency, and the frequency conversion circuit 24 mixes the first local oscillation signal with the signal received by the receiving antenna 20 to generate the first IF signal. Generate.

The distance detection and the relative speed detection according to the features of the present embodiment can be realized by multiplying the first IF signal by the delayed PN code and further limiting the band. In the present embodiment, the delayed PN code is generated by the PN generator 28 and the delay circuit 30, the multiplication of the delayed PN code and the first IF signal is executed by the multiplier 26, and the band limitation is executed by the BPF 30.

First, the PN generator 28 generates a PN code according to the transmission trigger supplied from the transmission trigger circuit 12. The delay circuit 30 delays the PN code generated by the PN generator 28 in response to the supply of the transmission trigger from the transmission trigger circuit 12, thereby generating the delayed PN code. The delay amount is set to be gradually increased / decreased at least until it is determined that there is a correlation (described later). The delayed PN code output from the delay circuit 30 is supplied to the multiplier 26, which multiplies the delayed PN code by the first IF signal (direct despreading). The resulting signal is the BPF
32, and only the frequency component near the fundamental frequency of the first IF signal is extracted.

Here, the delay PN for the transmission PN code is used.
When the delay amount of the code is significantly different from the time required for the radio waves to travel back and forth between the vehicle and the object, the level of the fundamental frequency component of the signal output from the multiplier 26 becomes low.
For example, when the delay PN code output from the delay circuit 30 is a delay PN code having a delay amount of 0 with respect to the transmission PN code shown in FIG. 2B, that is, as shown in FIG. In the case of a delayed PN code, the signal obtained as a result of multiplying the first IF signal by this delayed PN code becomes a signal as shown in FIG. 2 (f). On the other hand, when the delay amount of the delayed PN code with respect to the transmission PN code is substantially equal to the time required for the radio wave to travel back and forth between the vehicle and the object, that is, the delayed PN code is 2 (g), the signal output from the multiplier 26 has a substantially single frequency component (fundamental frequency component) as shown in FIG. 2 (h). Becomes Therefore, the level of the signal output from the BPF 32 becomes high.

Correlation determination circuit 34 and distance calculation circuit 36
Is a means for detecting the distance between the vehicle and the object by utilizing such a phenomenon. That is, the correlation determination circuit 34
When the output level of the PF 32 is high (when it is the maximum), it is determined that there is a correlation, and the distance calculation circuit 36 is instructed to calculate the distance data. The distance calculation circuit 36 responds to the transmission trigger supplied from the transmission trigger circuit 12 by the delay circuit 30.
The delay amount of is input and this delay amount is converted into the distance between the vehicle and the object. The distance obtained by this conversion is output to a circuit (not shown) as distance data.

As described above, in the present embodiment, distance detection is executed without using a carrier synchronizing circuit such as Costas loop.

The vehicle radar apparatus of this embodiment further includes
A local oscillator 38, a frequency conversion circuit 40, an FV converter 42, and a relative speed calculation circuit 44 are provided as means for detecting the relative speed. Among these circuits, the local oscillator 38 and the frequency conversion circuit 40 output the first IF signal multiplied by the delayed PN code output from the BPF 32 to the second IF signal.
It is a means of converting into a signal. That is, the local oscillator 38
Oscillates at a predetermined frequency, and the frequency conversion circuit 40 outputs the output (second local oscillation signal) of the local oscillator 38 to the BPF 32.
The output of the BPF 32 is converted to a lower frequency component by mixing with the output of the. The frequency of the resulting signal has a Doppler shift ± Δfd caused by the relative movement of the object with respect to the vehicle. That is, the frequency conversion circuit 40 when the object is stationary with respect to the own vehicle
Where f is the output frequency of, the output frequency of the frequency conversion circuit 40 when the object is moving relative to the own vehicle is f ± Δfd. The FV converter 42 converts the output frequency f ± Δfd of the frequency conversion circuit 40 into a voltage and supplies the voltage to the relative speed calculation circuit 44. On the other hand, the correlation determination circuit 34 determines that there is a correlation when the output level of the BPF 32 is high (when the output level is the maximum), and instructs the relative speed calculation circuit 44 to calculate the relative speed data.

The relative speed calculation circuit 44 uses the voltage supplied from the FV converter 42, that is, the Doppler shift ± Δf.
Based on the voltage including d as a component and in response to a command from the correlation determination circuit 34, the relative speed of the object with respect to the own vehicle is calculated and output as relative speed data. The frequency f must be sufficiently low so that the FV converter 42 can operate with high accuracy. The relative speed data output from the relative speed calculation circuit 44 is positive and negative relative speed data.

Therefore, in this embodiment, the relative speed of the object with respect to the own vehicle is calculated without using the Costas loop or the like.

[0024]

As described above, according to the present invention,
Since the direct despreading operation of multiplying the received signal by the delayed PN code delayed with respect to the PN code used at the time of transmission and the filtering of the signal obtained by this are executed, the correlation judgment concerning the extracted frequency component ( It is possible to measure the distance to the object by detecting the delay amount that maximizes the level of the extracted frequency component. Also,
By down-converting the extracted frequency component, it becomes possible to detect the relative speed of the object with respect to the own vehicle as a Doppler shift. As a result, it is possible to detect the distance and the relative speed at high speed without using a carrier synchronization circuit such as Costas loop, and thus without increasing the cost of the device, and to provide a vehicle radar device that is significant for vehicle safety. Can be realized.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an operation of this embodiment.

[Explanation of symbols]

 10 Transmitter Oscillator 12 Transmission Trigger Circuit 14, 28 PN Generator 16 Phase Modulator 18 Transmitting Antenna 20 Receiver Antenna 22, 38 Local Oscillator 24, 40 Frequency Converter Circuit 26 Multiplier 30 Delay Circuit 32 BPF 34 Correlation Judgment Circuit 36 Distance calculation circuit 42 FV converter 44 Relative speed calculation circuit

Claims (2)

[Claims] 1. A means for generating a delayed pseudo-noise code having a phase delayed by a predetermined delay amount with respect to the pseudo-noise code used when phase-modulating a transmission signal to an object, while varying the delay amount. A means for multiplying the received pseudo-noise code, which is a signal obtained by down-converting the reflected wave received from the object, by a delayed pseudo-noise code, and a frequency near the fundamental frequency of the received signal from the received signal after the delayed pseudo-noise code is multiplied. A means for extracting the component, a means for detecting the delay amount when the level of the extracted frequency component becomes maximum, a means for calculating the distance between the vehicle and the target object based on the detected delay amount, and Based on the frequency of the signal obtained by this down conversion and the means for further down converting the frequency component A distance / relative speed detection circuit, which is mounted on a vehicle, comprising: a means for outputting the speed and a means for calculating the relative speed of the object with respect to the own vehicle based on the detected Doppler shift. 2. A means for generating a pseudo-noise code, a means for phase-modulating a carrier wave by the generated pseudo-noise code and transmitting it as a transmission signal to an object, and means for receiving a reflected wave from the object. A distance / relative velocity detection circuit according to item 1, and a radar device for a vehicle, which is mounted on a vehicle.