JP3056579B2 - In-vehicle radar device - Google Patents

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 find an object existing ahead, for example, another vehicle, a person, a wall, a guardrail, or the like at an early stage. Conventionally, various forward warning devices using radio waves or light have been developed as devices for this purpose.

As a device using radio waves, 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 of being resistant to bad weather such as rain, snow and fog. In addition, as a device using light, there is a device using a laser, an infrared ray, or a CCD, and these devices have an advantage that they are relatively strong against interference or interference as compared with a radio wave type.

[0004]

This advantage, on the other hand, indicates that on-board radar systems are relatively vulnerable to interference and jamming. For example, in a system such as the FM-CW system in which a signal whose frequency changes regularly is transmitted as a radio wave to the front of the vehicle and a distance between the signal and the reflected wave is determined to measure the distance, a frequency modulation similar to the transmission wave is applied. If a radio wave is received, it is erroneously recognized as a target.

[0005] The present invention has been made to solve such problems, and an object of the present invention is to provide a vehicle-mounted radar device that is more resistant to interference and interference.

[0006]

In order to achieve the above object, the present invention provides a pseudo noise for transmission.
A transmitting means for generating a signal, phase-modulating a carrier with a transmitting PN signal and wirelessly transmitting the signal to the front of the vehicle, receiving means 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 each of which delays the reference PN signal in units of a predetermined time and in which the delay amounts are different from each other 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 reception means, and a delay means for the reference PN signal which has been correlated. A distance output unit that outputs the delay amount as a signal indicating a distance between the vehicle and the target, and a reference PN signal;
The correlation output with the output of the receiving means will be a sinusoidal square wave
By changing the frequency of the reference PN signal from the initial value,
Is a signal representing the relative speed of the target with respect to the vehicle.
And frequency control means for outputting the frequency .

In a preferred embodiment, the delay means includes a reference P
A first delay unit for successively delaying the N signal using one bit of the transmission PN signal as a delay unit, and a first delay unit in units of time obtained by dividing the delay unit of the first delay unit into integer fractions. A second delay unit for delaying the output and outputting a plurality of types of reference PN signals having a delay amount different from each other by the unit time to the correlating means, wherein a coarse distance resolution is obtained by the first delay unit. It is characterized in that a narrow distance resolution is obtained by the two delay units.

[0008]

[0009]

In the present invention, first, a transmission PN signal and a reference PN signal are generated. These PN signals are, for example, the longest code sequences such as M sequences, and the carrier is a transmission PN signal.
The signal is phase-modulated and wirelessly transmitted to the front of the vehicle.
When a target such as another vehicle exists in front of the vehicle, the transmitted phase-modulated wave is reflected thereby, 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 the reception is delayed from the transmitted transmission PN signal by the time required for the radio wave to reciprocate between the vehicle and the target.

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

Here, since the transmission PN signal generated first has a correlation with the reference PN signal, of the plurality of types of reference PN signals outputted from the delay means, the transmission PN signal is generated from the reception means. The delay amount of the reference PN signal having a correlation with the output transmission PN signal corresponds to the time required for the radio wave to reciprocate between the vehicle and the target. Therefore, forward warning can be performed by outputting a signal of this delay amount to an alarm device or the like. The PN signal, which is a sequence such as the M sequence, has a spread spectrum, and is therefore less susceptible to interference or interference. Thus, in the present invention, Spread Spectrum
) By applying the method, it becomes possible to realize an in-vehicle radar device that is resistant to interference and the like by using a digital circuit.

In the present invention, a reference PN signal is further provided.
The output of the correlation between the signal and the output of the receiving means is a sinusoidal square wave.
Thus, the frequency of the reference PN signal is controlled. That is,
Doppler shift caused by the relative speed of the vehicle and the target
It is controlled to be offset. Therefore, this control
The frequency change of the reference PN signal is
Shows the relative speed of Thus, in the claims
In principle, digital modulation is used, and in principle Doppler shift
In a spread spectrum system where it is difficult to detect
Degree can be detected, and more suitable forward warning can be implemented.
Become.

Further , in claim 2, the delay means is provided with a
A first delay unit and a second delay unit.
The distance resolution equivalent to one bit of the M sequence by the delay unit is
Narrow distance resolution within 1 bit of M-sequence by second delay unit
Noh is obtained. The first delay unit transmits a reference PN signal
One bit of the PN signal for use as a delay unit.
You. The second delay unit divides the predetermined number of bits into smaller pieces.
Unit time (for example, 1 / n bit, n: natural number)
Delays the output of the first delay device, so that, for example, n
The kinds of reference PN signals are supplied to the correlation means. Accordingly
Therefore, in the claims, a relatively simple circuit configuration is used.
High resolution and high-speed operation are realized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments 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,
This is a device that can determine the distance and relative speed with the target ahead.

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

What is transmitted to the front of the vehicle by the antenna 10 is a radio wave that has been subjected to two-phase PSK modulation by the PSK modulator 14. The PSK modulator 14 converts a carrier of, for example, 24 GHz supplied from the carrier oscillator 16 into a PN signal generator 1.
8 is subjected to two-phase PSK modulation by the PN signal. It should be noted that the present invention may be applied to other PSK systems. PN signal generator 1
8 corresponds to a transmission trigger from the transmission trigger generator 20,
The PN signal for transmission is generated at the clock frequency from the oscillator 22.

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

On the other hand, the apparatus of this embodiment has 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 the generated PN signal to the 38 via the delay unit 36.

Here, the transmission PN signal and the reference PN signal are longest code sequences such as an M sequence, for example, and have correlation with each other. The clock frequency of the VCO 34 can be increased or decreased based on the clock frequency of the oscillator 22.

"Having a correlation" means a relationship as shown in FIG. 2 (a). That is, when the exclusive OR of both PN signals is obtained and converted into a DC value by detection, the exclusive OR value shown as “BPF input” in FIG. 2A is obtained so that the value becomes maximum. (Sinusoidal 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 FIG.

On the other hand, the transmission PN signal output from the PN signal generator 18 is reflected by the target existing in front of the vehicle after modulation and is received by the reception antenna 12, so that the output of the amplifier 26 is The transmission PN signal output from the PN signal generator 18 has a delay corresponding to the time required for the radio wave to reciprocate between the vehicle and the target. As described above, when the exclusive OR of the transmission PN signal delayed from 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 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 by different delay amounts, and the exclusive OR of these signals with the output of the amplifier 26 is calculated. By calculating the respective values and comparing the detected values, it is possible to know the amount of delay exhibiting the maximum detected value. The amount of delay is an amount representing the time required for the radio wave to reciprocate between the vehicle and the target, and thus the distance.

In this embodiment, in order to detect the distance, the delay units 36 and 38, the EOR 30, the BPF 40,
A detector 42 and a comparator 44 are used. The delay units 36 and 38 provide the reference P output from the PN signal generator 32.
The N signal is delayed in two stages, and the transmission PN signal 1
It outputs n kinds of reference PN signals having different delay amounts by / n bits (n: natural number). These reference PN signals are respectively input to the EOR 30, and the EOR 30
The exclusive OR of the reference PN signal input from the amplifier 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 detection value recognized as the maximum as a result of the comparison is output as a signal indicating the distance to, for example, an alarm device or a brake control device.

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

The delay units 36 and 38 delay the reference PN signal in two stages. The delay amount of the delay unit 36 is in units of one bit of the transmission PN signal.
The delay amount of 8 is in units of 1 / n bits. Therefore, by performing the correlation detection based on the above-described principle while sequentially changing the delay amount of the delay unit 36 bit by bit, it is possible to obtain a distance resolution higher than 1 bit equivalent of the transmission PN signal. For example, if one bit of the transmission PN signal corresponds to a distance resolution of 1 m and n = 10, then 10
cm distance resolution can be obtained. Further, by configuring the delay means in two stages, the number of the EOR 30 and the like is reduced and the processing speed is increased as compared with a case where a distance resolution of 10 cm is obtained by one delay unit, for example. Note that the number of stages of the delay unit is not limited to two.

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 and changes the frequency of the reference PN signal so that the output of the comparator 44 becomes maximum. Thereby, the amplifier 26
The relative speed between the vehicle and the target is obtained by utilizing the fact that the transmission PN signal output from the device has undergone the Doppler shift.

That is, the transmission PN signal output from the amplifier 26 is different in frequency from the transmission PN signal output from the PN signal generator 18 by the Doppler shift. In a state where there is no Doppler shift, that is, in a state where the relative speed is 0, the phase of the output of the delay unit 38 and the output of the amplifier 26 are more preferably matched as compared with the state where the Doppler shift occurs, and the output of the comparator 44 is Be larger. Therefore, VCO3 is set so that the output of comparator 44 becomes maximum.
VC when the relative speed is 0 by controlling the oscillation frequency of
The relative speed between the vehicle and the target can be determined by calculating the difference between the oscillation frequency of O34 and the target. In the present embodiment, this relative speed can be used for forward warning.

[0029]

As described above, according to the present invention,
Since the on-vehicle radar device is configured by applying the spread spectrum method, the on-vehicle radar device which is hardly affected by interference or interference can be realized by a digital circuit. Also, vehicles and objects
Doppler shift caused by the relative speed of the target is offset
So that the frequency of the reference PN signal is controlled.
Therefore, the relative speed of the target with respect to the vehicle can be detected.

According to the second aspect of the present invention, a coarse distance resolution is obtained by the first delay unit, and a fine distance resolution is obtained by the second delay unit. Can be obtained.

[0031]

[Brief description of the drawings]

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

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

[Explanation of symbols]

 Reference Signs List 10 antenna for transmission 12 antenna for reception 14 PSK modulator 18, 32 PN signal generator 24 mixer 30 EOR 34 VCO 36, 38 delay unit 42 detector 44 comparator 46 VCO control circuit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junji Sugawara 5-1-1 Shimorenjaku, Mitaka-shi, Tokyo Japan Radio Co., Ltd. (56) References JP-A-62-25276 (JP, A) JP-A Sho JP-A-62-54190 (JP, A) JP-A-62-54191 (JP, A) JP-A-5-164852 (JP, A) JP-A-5-223932 (JP, A) A) Patent 2955789 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (2)

(57) [Claims] A transmitting means for generating a pseudo-noise signal for transmission, phase-modulating a carrier with the pseudo-noise signal for transmission, and wirelessly transmitting the reflected wave to the front of the vehicle; Receiving means for outputting a noise signal; means for generating a reference pseudo-noise signal having a correlation with the transmission pseudo-noise signal in synchronization with the transmission; delaying the reference pseudo-noise signal by a predetermined time unit;
A delay unit that outputs a plurality of types of reference pseudo noise signals whose delay amounts are different from each other by the unit time, and which reference pseudo noise signal output from the delay unit has a correlation with the output of the reception unit Correlation means; distance output means for outputting a delay amount of the reference pseudo-noise signal regarded as correlated by the delay means as a signal representing the distance between the vehicle and the target; output of the reference pseudo-noise signal and reception means Output is sine
Change the frequency of the reference pseudo-noise signal so that it becomes a wavy square wave.
It changes from the initial value, and this change is
A vehicle-mounted radar device , comprising: frequency control means for outputting a signal representing a relative speed . 2. The on-vehicle radar device according to claim 1, wherein the delay means sequentially delays the reference pseudo-noise signal by using one bit of the transmission pseudo-noise signal as a delay unit; The output of the first delay unit is delayed in units of time obtained by dividing the delay unit of the delay unit into integer fractions, and a plurality of types of reference pseudo noise signals whose delay amounts are different from each other by the unit time are used as correlation units. An on-vehicle radar device, comprising: a second delay unit that outputs a signal; and a coarse distance resolution is obtained by the first delay device and a fine distance resolution is obtained by the second delay device.