JPH05256936A - Onboard radar apparatus - Google Patents

Abstract

PURPOSE:To obtain an onboard radar apparatus robust against interferences and obstructions. CONSTITUTION:The distance to a target is measured by the spread spectrum system, whereby tone resistance to interferences and obstructions is enhanced. A reference transmission pseudo noise (PN) signal is delayed in two stages by delay circuits 36, 38 to ensure a coarse distance resolution by the delay circuit 36 and a fine distance resolution by the delay circuit 38. The relative speed to the target is obtained by controlling the frequency of a VCO 34 so as to make the output of a comparator 44 maximum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle radar device which is mounted on a vehicle and used for forward warning and the like.

[0002]

2. Description of the Related Art In order to safely operate a vehicle, it is necessary to detect an object in front of the vehicle, such as another vehicle, a person, a wall or a guardrail, at an early stage. Conventionally, as a device for this purpose, various forward warning devices using radio waves or light have been developed.

A device using radio waves is, for example, FM-C.
A W type or pulse Doppler type radar device is mounted on a vehicle. This type of device has the advantage that it is resistant to bad weather such as rain, snow and fog. Further, as a device using light, there is a device using a laser, an infrared ray, or a CCD, and these have an advantage that they are relatively resistant to interference and interference as compared with the radio wave type.

[0004]

This advantage indicates that, on the contrary, the vehicle-mounted radar device is relatively vulnerable to interference and interference. For example, in the FM-CW system, in which a signal whose frequency changes regularly is transmitted as a radio wave to the front of the vehicle to obtain the beat of the reflected wave to measure the distance, frequency modulation similar to the transmitted wave is added. When a radio wave is received, it will be mistakenly recognized as a target.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an on-vehicle radar device which is more resistant to interference and interference.

[0006]

In order to achieve such an object, the present invention provides pseudo noise for transmission.
A transmitting unit for generating a signal, phase-modulating a carrier wave by the transmitting PN signal and wirelessly transmitting the signal to the front of the vehicle; a receiving unit for receiving and demodulating a reflected wave from the front of the vehicle and outputting a transmitting PN signal; Means for synchronously generating a reference PN signal having a correlation with the transmission PN signal, and a plurality of types of reference PNs that delay the reference PN signal in units of a predetermined time and differ in delay amount by the unit time. A delay means for outputting a signal, a correlation means for determining which reference PN signal output from the delay means has a correlation with the output of the receiving means, and a delay means for the correlated reference PN signal. Distance output means for outputting the amount of delay as a signal representing the distance between the vehicle and the target.

In the second aspect, the delay means is the reference P
A first delay device that sequentially delays the N signal by using 1 bit of the transmission PN signal as a delay unit, and a first delay device that uses the time obtained by dividing the delay unit of the first delay device into integer fractions A second delay device that delays the output and outputs a plurality of types of reference PN signals whose delay amounts differ from each other by the unit time to the correlating means. It is characterized in that a fine delay resolution is obtained by the delay device of 2.

According to a third aspect of the present invention, the correlation output between the reference PN signal and the output of the receiving means is a sinusoidal square wave.
It is characterized by comprising frequency control means for changing the frequency of the reference PN signal from the initial value and outputting the changed amount as a signal representing the relative speed of the target with respect to the vehicle.

[0009]

In the present invention, first, the transmission PN signal and the reference PN signal are generated. These PN signals are, for example, the longest code series such as M series, and the carrier wave is the transmission PN.
The signal is phase-modulated and wirelessly transmitted in front of the vehicle.
When a target such as another vehicle exists in front of the vehicle, the transmitted phase-modulated wave is reflected by this and the reflected wave is received. Demodulation processing such as down conversion is further performed on the received phase-modulated wave. The transmission PN signal obtained as a result of reception is delayed from the transmitted transmission PN signal by the time required for the radio waves to travel back and forth between the vehicle and the target.

On the other hand, the reference PN signal is generated in synchronization with the transmission and delayed by the delay means. The delay means delays the reference PN signal by different delay amounts to generate a plurality of types of reference PN signals. The plurality of types of reference PN signals are input to the correlator and are subjected to correlation detection with the output of the receiver.

Here, since the transmission PN signal generated first has a correlation with the reference PN signal, among the plurality of types of reference PN signals output from the delay means, from the reception means. The delay amount for the reference PN signal that has a correlation with the output transmission PN signal corresponds to the time required for the radio wave to travel back and forth between the vehicle and the target. Therefore, by outputting a signal of this delay amount to an alarm device or the like, forward warning can be implemented. The PN signal, which is a sequence such as the M sequence, has a spread spectrum, and thus is less susceptible to interference and interference. Thus, in the present invention, spread spectrum (Spread Spectrum)
) Method, it is possible to realize an on-vehicle radar device that is resistant to interference, etc., with almost a digital circuit.

According to a second aspect of the present invention, the delay means includes a first delay device and a second delay device, and the first delay device has a distance resolution equivalent to 1 bit of M sequence.
With the second delay device, a fine range resolution within 1 bit of the M sequence can be obtained. The first delay device sequentially delays the reference PN signal using 1 bit of the transmission PN signal as a delay unit. The second delay device delays the output of the first delay device by a unit time (for example, 1 / n bit, n: natural number) obtained by dividing the predetermined number of bits into smaller parts, and thereby, for example, n.
A kind of reference PN signal is supplied to the correlation means. Therefore, in this claim, high resolution and high-speed calculation are realized with a relatively simple circuit configuration.

In the third aspect, the reference PN
The frequency of the reference PN signal is controlled so that the correlation output between the signal and the output of the receiving means becomes a sinusoidal square wave. That is, the Doppler shift caused by the relative speed between the vehicle and the target is controlled to be canceled out. Therefore, the frequency change of the reference PN signal due to this control indicates the relative speed of the target with respect to the vehicle. As described above, according to the present invention, the relative velocity can be detected in the spread spectrum method in which it is theoretically difficult to detect the Doppler shift due to the digital modulation, and more suitable forward warning can be performed.

[0014]

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 configuration of an on-vehicle radar device according to an embodiment of the present invention. The device shown in this figure is a radar device using a spread spectrum system,
It is a device that can determine the distance and relative speed to a target in front.

The radar system of this embodiment comprises a transmitting antenna 10 and a receiving antenna 12. These antennas 10 and 12 are arranged at the front of the vehicle and transmit and receive radio waves in front of the vehicle. The antennas 10 and 12 may be shared.

What is transmitted to the front of the vehicle by the antenna 10 is a radio wave which is PSK-modulated by the PSK modulator 14. The PSK modulator 14 supplies the PN signal generator 1 with a carrier wave of, for example, 24 GHz supplied from the carrier wave oscillator 16.
Two-phase PSK modulation is performed by the PN signal from 8. It should be noted that the present invention may use another PSK method. PN signal generator 1
8 corresponds to the transmission trigger from the transmission trigger generator 20,
Also, the transmission PN signal is generated at the clock frequency from the oscillator 22.

The receiving antenna 12 receives the reflected wave from the target. That is, as described above, the transmitting antenna 1
A radio wave transmitted from 0 to the front of the vehicle is reflected by a target such as another vehicle and is received by the receiving antenna 12. A mixer 24 and an amplifier 26 are connected downstream of the reception antenna 12, and the reception output of the reception antenna 12 is mixed with the output of the local oscillator 28 by the mixer 24. The down-converted signal is amplified and digitized by the amplifier 26 and input to the EOR 30 described later.

On the other hand, the apparatus of this embodiment is provided with 32 in addition to 18 as the PN signal generator. The PN signal generator 32 generates a reference PN signal at the clock frequency from the VCO 34 in response to the transmission trigger, and outputs it to 38 through the delay device 36.

Here, the PN signal for transmission and the PN signal for reference are, for example, longest code sequences such as M sequences, and are signals having correlation with each other. The clock frequency of the VCO 34 can be raised or lowered based on the clock frequency of the oscillator 22.

"Having correlation" means a relationship as shown in FIG. That is, when an exclusive OR of both PN signals is obtained and converted to a DC value by detection, an exclusive OR value shown as “BPF input” in FIG. 2A is obtained so that the value becomes maximum. It is in a state of being sine wave (sine wave square wave). The transmission PN signal output from the PN signal generator 18 and the reference PN signal output from the PN signal generator 32 are set to have "correlation" shown in this figure.

On the other hand, the PN signal for transmission output from the PN signal generator 18 is, after being modulated, reflected by the target existing in front of the vehicle and received by the antenna 12 for reception. The transmission PN signal output from the PN signal generator 18 is delayed by a time corresponding to the time required for the radio wave to travel back and forth between the vehicle and the target. Thus, when the exclusive OR of the transmission PN signal delayed with respect to the transmission PN signal output from the PN signal generator 18 and the undelayed reference PN signal is obtained, As shown as "BPF input" in FIG. 2B, even if the detection is performed, only a detection value smaller than that in the case of "having a correlation" is obtained.

Therefore, a plurality of types of reference PN signals are generated by delaying the reference PN signal output from the PN signal generator 32 with different delay amounts, and the exclusive OR of these and the output of the amplifier 26 is obtained. By obtaining the respective values and comparing the detected values, the delay amount exhibiting the maximum detected value can be known. This delay amount is an amount that represents the time required for the radio waves to travel back and forth between the vehicle and the target, that is, the distance.

In this embodiment, in order to perform this distance detection, the delay devices 36 and 38, the EOR 30, the BPF 40,
The detector 42 and the comparator 44 are used. The delay devices 36 and 38 output the reference P output from the PN signal generator 32.
The N signal is delayed in two steps, and the transmission PN signal is set to 1
Outputs n types of reference PN signals having different delay amounts by / n bits (n: natural number). Each of these reference PN signals is input to the EOR 30, and the EOR 30 is connected to the delay unit 3
The exclusive OR of the reference PN signal input from 8 and the transmission PN signal input from the amplifier 26 is obtained. BP
F40 filters this, and detector 42 detects the output of BPF40. The DC value obtained by the detection is compared by the comparator 44. The delay amount of the reference PN signal corresponding to the maximum detected detection value as a result of this comparison is output to a warning device or a braking control device as a signal indicating the distance.

Therefore, according to the present embodiment, an on-vehicle radar device having improved performance can be obtained by applying the spread spectrum method which is less likely to be affected by interference or recommendation.

By the way, the delay devices 36 and 38 delay the reference PN signal in two stages. The delay amount of the delay device 36 is in units of 1 bit of the transmission PN signal.
The delay amount of 8 is in units of 1 / n bit. Therefore, by performing the correlation detection based on the above principle while sequentially changing the delay amount of the delay device 36 bit by bit, it is possible to obtain a distance resolution higher than one bit of the transmission PN signal. For example, when 1 bit of the transmission PN signal corresponds to a distance resolution of 1 m and n = 10, 10
A distance resolution of cm can be obtained. Further, by configuring the delay means in two stages in this way, the number of EORs 30 etc. is reduced and the processing speed is increased as compared with the case where a distance resolution of 10 cm is obtained by one delay device, for example. The number of stages of the delay means is not limited to two.

Further, in this embodiment, the oscillation frequency of the VCO 34 is controlled according to the output of the comparator 44. That is, the VCO control circuit 46 controls the oscillation frequency of the VCO 34 so as to maximize the output of the comparator 44, and changes the frequency of the reference PN signal. As a result, the amplifier 26
The relative speed between the vehicle and the target can be obtained by utilizing the fact that the transmission PN signal output from is subjected to Doppler shift.

That is, the transmission PN signal output from the amplifier 26 differs in frequency from the transmission PN signal output from the PN signal generator 18 by the amount of Doppler shift. In the state where there is no Doppler shift, that is, in the state where the relative velocity is 0, the phase of the delay 38 output and the output of the amplifier 26 are more preferably matched and the output of the comparator 44 is compared to the state where Doppler shift occurs. Get bigger. Therefore, the VCO3 should be set so that the output of the comparator 44 becomes maximum.
Controlling the oscillation frequency of 4 and VC in the state where the relative speed is 0
By obtaining the difference between the oscillation frequency of O34 and the relative speed between the vehicle and the target, it is possible to know the relative speed. In this embodiment, this relative speed can be used for forward warning.

[0029]

As described above, according to the present invention,
Since the in-vehicle radar device is configured by applying the spread spectrum method, the in-vehicle radar device that is not easily affected by interference and interference can be realized by a digital circuit.

Further, according to the second aspect, since the coarse distance resolution is obtained by the first delay device and the fine distance resolution is obtained by the second delay device, respectively, the high resolution can be achieved by the relatively simple and high-speed circuit. Can be obtained.

According to the third aspect, the frequency of the reference PN signal is controlled so that the Doppler shift caused by the relative speed between the vehicle and the target is canceled.
The relative speed of the target with respect to the vehicle can be detected.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an on-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 Transmitting antenna 12 Receiving antenna 14 PSK modulator 18, 32 PN signal generator 24 Mixer 30 EOR 34 VCO 36, 38 Delay device 42 Detector 44 Comparator 46 VCO control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junji Sugawara 5-1-1 Shimorenjaku, Mitaka City, Tokyo Japan Radio Co., Ltd.

Claims (3)

[Claims] 1. A transmission means for generating a pseudo noise signal for transmission, phase-modulating a carrier wave by the pseudo noise signal for transmission, and wirelessly transmitting the carrier wave in front of the vehicle; Receiving means for outputting a noise signal, means for generating a reference pseudo noise signal having a correlation with a transmission pseudo noise signal in synchronization with transmission, and delaying the reference pseudo noise signal in units of a predetermined time,
Determining which of the reference pseudo noise signals output from the delay means has a correlation with the output of the receiving means, and the delay means that outputs a plurality of types of reference pseudo noise signals whose delay amounts differ from each other by the unit time An in-vehicle radar, comprising: a correlating unit, and a distance output unit that outputs a delay amount of the correlated pseudo noise signal for reference by the delay unit as a signal representing the distance between the vehicle and the target. apparatus. 2. The on-vehicle radar device according to claim 1, wherein the delay means sequentially delays the reference pseudo noise signal by using 1 bit of the transmission pseudo noise signal as a delay unit, and a first delay device. The output of the first delay device is delayed in units of time obtained by dividing the delay unit of the delay device into integers, and a plurality of types of reference pseudo noise signals having different delay amounts by the unit time are used as correlation means. And a second delay device for outputting, wherein the first delay device obtains a coarse distance resolution and the second delay device obtains a fine distance resolution. 3. The on-vehicle radar device according to claim 1, wherein the frequency of the reference pseudo noise signal is changed from an initial value so that the correlation output between the reference pseudo noise signal and the output of the receiving means becomes a sinusoidal square wave. An on-vehicle radar device comprising: frequency control means for outputting this change as a signal representing the relative speed of the target with respect to the vehicle.