JPH0784035A - Front warning radar for automobile - Google Patents

Abstract

PURPOSE:To eliminate influence of radio interference due to a signal transmitted from an apparatus placed in the other vehicle. CONSTITUTION:An identification code(ID) inherent for an own vehicle is generated from an identification code generator 12. A logic calculator 13 executes a logic operation using the ID at a transmission pseudo-noise(PN) generated from a PN generator 11. An executed result is used for a phase modulation of the transmitted signal in a transmitter 14. In the case of reception, an ID output of outputs of a demodulator 32 is compared with an ID output of the generator 12. When both are not coincident as a result of its comparison, it is regarded as being radio interference to stop outputting of a distance, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile forward warning radar device for detecting an obstacle existing in front of an automobile, and more particularly to a pseudo noise (PN) code modulation type radar device.

[0002]

2. Description of the Related Art As a forward warning radar device for automobiles,
Besides the FM-CW radar device, a PN code modulation type radar device has been developed. In the PN code modulation type radar device, a PN code which is a code string of a predetermined length is generated, and the carrier wave is phase-modulated by the generated PN code. The obtained phase modulated wave is transmitted to the front of the vehicle from, for example, a transmitting antenna provided at the front of the vehicle. When an obstacle such as another vehicle exists in front of the vehicle, the transmitted phase modulated wave is reflected by the obstacle. The reflected phase-modulated wave is received by the receiving antenna that is placed side by side with the transmitting antenna or shared with the transmitting antenna.

When the reflected wave is received, the reflected wave and the receiving P
The correlation of N codes is calculated. Here, the reflected wave is delayed from the transmitted wave by a time corresponding to the round trip distance between the vehicle and the obstacle. Therefore, by controlling the phase of the receiving PN code, which is the same code string as the PN code (transmission PN code) used at the time of transmission, the presence of the obstacle and its distance can be detected. That is, when the correlation between the reflected wave and the reception PN code is maximized, the distance corresponding to the phase difference between the transmission PN code and the reception PN code at that time (the distance obtained by multiplying the phase difference by c / 2: c Can be considered to be the presence of an obstacle. Once the presence of an obstacle is detected, this obstacle is usually tracked.

[0004]

However, in the above-mentioned configuration, there is a possibility that radar signal interference may occur when the vehicle is traveling in a congested area, for example. That is, there is a possibility of receiving a radar signal from a similar device mounted on an accompanying vehicle or an oncoming vehicle, and this reception results in a determination that a front obstacle exists even though it does not actually exist. Connect As a method of avoiding such an inconvenience, for example, there is a method of giving a different PN code to each vehicle, but such a PN code becomes an extremely long code string. If the code string of the PN code becomes long, high-speed operation of the apparatus is required, and the apparatus configuration becomes complicated, and it takes time to detect an obstacle.

The present invention has been made to solve the above problems, and an object thereof is to prevent / eliminate erroneous determination due to interference without using a long PN code string.

[0006]

In order to achieve such an object, a forward warning radar device for an automobile according to the present invention has means for generating a transmission PN code which is a code string having a predetermined length, and is mounted on the vehicle. Identification code (ID) that differs from vehicle to vehicle
Means, a means for generating a modulation signal by a logical operation using a transmission PN code and an ID, a means for phase-modulating a carrier wave by the modulation signal and transmitting it to the front of the mounted vehicle, and a signal from the front of the vehicle. And a means for generating a receiving PN code having the same code string as the transmitting PN code while gradually increasing or decreasing the phase so that the phase difference between the transmitting PN code is within a predetermined range. , Means for calculating the correlation between the received signal and the PN code for reception, means for demodulating the received signal to detect the ID, and a correlation exceeding a predetermined value and the detected ID at the time of transmission. If there is an obstacle in front of the vehicle if it matches the generated ID, and if the detected ID does not match the ID generated at the time of transmission, it was mounted on another vehicle. Interference from the device When the determining means only when the vehicle front obstacle is determined to exist, the transmission P
A means for outputting information indicating that an obstacle exists at a distance corresponding to the phase difference between the N code and the receiving PN code and / or information indicating the distance is provided.

[0007]

In the forward warning radar device for an automobile according to the present invention, first, a transmission PN code, which is a code string having a predetermined length, and an ID different for each installed vehicle are generated, and then a predetermined logical operation is performed between the two codes. Is applied. Further, as a result, the carrier wave is phase-modulated, and the obtained phase-modulated wave is transmitted in front of the mounted vehicle.

When there is an obstacle ahead, the transmitted phase modulated wave is reflected by the obstacle. The received reflected wave is demodulated, and the correlation between the received reflected wave and the receiving PN code is calculated. The phase of the reception PN code, which is the same code string as the transmission PN code, is gradually increased or decreased so that the phase difference from the transmission PN code falls within a predetermined range.
If the correlation exceeds a predetermined value, it is determined whether the demodulated signal matches the ID, and only if it matches,
It is determined that an obstacle exists at a distance corresponding to the phase difference between the transmission PN code and the reception PN code. Thereby, an obstacle such as a vehicle ahead is detected.

In the present invention, since the obstacle detection operation is executed in this manner, malfunctions due to interference from radar devices other than the own vehicle are eliminated, and only front obstacles are correctly detected. For example, even if the correlation value exceeds a predetermined value due to interference from a radar device other than the own vehicle, the ID demodulated in this case is different from the ID given to the own vehicle. Erroneous judgments that mistake interference as a front obstacle are eliminated.

[0010]

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 a vehicle forward warning radar device according to an embodiment of the present invention. The radar apparatus shown in this figure first includes a PN generator 11, an identification code generator 12, a logical operation unit 13, a transmitter 14, and a transmitting antenna 15. The PN generator 11 generates a PN code which is a code string of a predetermined length, and the identification code generator 12
Generates an identification code (ID) which is different for each vehicle and is composed of, for example, a binary number. These two types of codes are subjected to a logical operation by the logical operation unit 13, for example, an exclusive OR operation, and the result is output to the transmitter 14 as a modulation signal. The transmitter 14 phase-modulates the carrier wave with the modulation signal supplied from the logical operation unit 13, and transmits the carrier wave in front of the vehicle via the transmitting antenna 15.

The radar device shown in this figure further comprises:
A reception antenna 21 and a receiver 22 are provided. The receiving antenna 21 receives the reflected wave coming from the front of the vehicle,
The receiver 22 performs processing such as amplification on this. The output of the receiver 22 is supplied to the product calculator 31.

The radar device shown in this figure is a receiver 2
It has a function of detecting an obstacle in front of the vehicle based on the output of 2. Therefore, the apparatus has a product calculator 31, a demodulator 32, a PN generator 33, a phase controller 34, and a control calculator 51.

The PN generator 33 generates a receiving PN code under the control of the phase controller 34. The reception PN code is the same code string as the transmission PN code generated by the PN generator 11, and the phase thereof, that is, the output phase of the PN generator 33 is a phase based on the phase of the transmission PN code. It is controlled by the controller 34. Phase controller 34
Is P in accordance with the phase information supplied from the control calculator 51.
The output phase of the N generator 33 is controlled. Therefore, the phase of the receiving PN code is controlled by the phase controller 34 under the control calculator 51.

The product calculator 31 inputs the signal relating to the reflected wave from the receiver 22 and calculates the product of the received wave and the PN code for reception supplied from the PN generator 33. The demodulator 32 demodulates the ID from the output of the product computing unit 31, obtains its amplitude, outputs it as amplitude information, and supplies it to the control computing unit 51. The control calculator 51 controls the phase of the receiving PN code via the phase controller 34, and inputs the amplitude information and the ID output of the demodulator 32. The control calculator 51 detects the presence of an obstacle in front of the vehicle and the distance thereof based on these. At this time, the control calculator 51 performs ID comparison as described later, and eliminates the influence of interference even if there is interference. The control calculator 51 supplies the presence or absence of an obstacle as an obstacle detection output and the distance as a distance output to, for example, a display device or the like.

FIG. 2 shows the operation of detecting the distance to the obstacle in this embodiment.

First, as shown in FIG. 2A, PN
The transmission PN code generated by the generator 11 is a code string that repeats with a certain time t _e as an epoch. PN
The generator 11 continuously generates the PN code for transmission with such an epoch t _e . On the other hand, the identification code generator 12
Generates an ID unique to the vehicle, that is, set to be different for each vehicle. The content of the ID is set, for example, at the manufacturing stage of the device. For these two types of codes, that is, the transmission PN code and the ID, for example, the exclusive OR is calculated by the logical operation unit 13. Therefore, the transmission signal transmitted from the transmitter 15 via the transmission antenna 13 is a signal phase-modulated by the transmission PN code and ID of the epoch t _e .

FIG. 3 shows an example of the ID structure. In the example shown in this figure, an epoch t having a plurality of IDs is used.
_It has a time length corresponding to _e . The ID needs to be sufficiently longer than the chip length of the PN code for transmission in order to appropriately execute demodulation, but it may be longer or shorter than the epoch t _e .

When a transmission signal as shown in FIG. 2A is transmitted in front of the vehicle and reflected by an obstacle, the reception signal received by the receiving antenna 21 and amplified by the receiver 22 is, for example, as shown in FIG. The signal is as shown in (b). As shown in this figure, the reception signal is a signal delayed from the transmission signal by the time (radio wave propagation time) t _d required for the radio waves to travel back and forth between the vehicle and the obstacle.

The receiving P generated by the PN generator 33.
As described above, the phase of the N code is controlled by the control calculator 51 via the phase controller 34 with the phase of the transmission PN code generated by the PN generator 11 as a reference. For example, the output phase of the PN generator 33 is controlled so that the phase difference from the PN code for transmission gradually increases from 0 to reach the epoch t _e . Here, in the control calculator 51, the correlation value is calculated by accumulating the amplitude information output of the demodulator 32. Therefore, as a result of this control, when the phase of the receiving PN code output from the PN generator 33 matches the radio wave propagation time t _d as shown in FIG. 2C, the correlation calculated by the control calculator 51. The value increases as shown in Figure 2 (e).

That is, in the product calculator 31, as shown in FIG.
The product of the reception signal shown in (b) and the reception PN code supplied from the PN generator 33 is obtained, and the demodulator 32 demodulates this and obtains amplitude information. Control calculator 5
1 is the amplitude information output obtained by the demodulator 32,
The correlation value between the received signal and the receiving PN code is calculated by accumulating over a predetermined time, for example, an integral multiple of the epoch. As shown in FIG. 2C, when the phase t _d1 of the reception PN code matches the phase of the reception signal (delay t _{d of the} reception signal with respect to the transmission signal), the cumulative value calculated by the control calculator 51 is obtained. The calculated value (correlation value) increases and exceeds the threshold value at some point. In other words, as shown in FIG. 2 (f), when the phase t _d1 of reception PN code is matched to the radio wave propagation time t _d, significantly increases the correlation values between the phase ± 1 chip Decreases rapidly at. Control calculator 5
1 detects the presence of an obstacle by thresholding this correlation value. The control calculator 51, together with this,
It is determined whether the ID (FIG. 2D), which is the demodulation output of the demodulator 32, and the ID generated by the identification code generator 12 match. If they match, the control calculator 51 determines that the phase of the receiving PN code at the time when the correlation value exceeds the threshold value (more precisely, the phase at which the correlation value becomes maximum), that is, the radio wave propagation time t. The distance to the obstacle is detected by multiplying _d by c / 2. Here, c is the propagation velocity of the radio wave.

The first feature of this embodiment is that when detecting an obstacle and its distance, I, which is a demodulation output of a received signal.
A point is provided to determine whether D matches the ID transmitted from the vehicle. The second feature of this embodiment is that
Only when the received ID matches the ID transmitted from the own vehicle, the control calculator 51 outputs the information indicating the existence of the obstacle and its distance. In this embodiment, with such a configuration, it is possible to eliminate a signal reception from a similar device mounted on another vehicle, that is, a malfunction due to interference. FIG. 4 shows the contents of this control, that is, the flow of operation of the control calculator 51.

First, the control calculator 51 first detects the PN generator 33.
The output phase t _d1 is gradually increased. That is, by giving a command to the phase controller 34, the PN generator 33
The output phase t _d1 of P is controlled to 0 (102), and then P
The output phase t _{d 1} of the N generator 33 is gradually increased by Δ (1
04). When step 104 is repeatedly executed, PN
The output phase t _d1 of the generator 33 gradually increases by Δ from the state of t _d1 = 0 (that is, the phase difference from the transmission PN code is 0), and when there is no obstacle, the PN code Epoch t _e is reached (106). When the condition of step 106 is satisfied, the control calculator 51 determines
02, the output phase t _d1 of the PN generator 33 is returned to the initial value.

While the condition of step 106 is not satisfied, the process proceeds from step 104 to step 106 and then to step 108. In step 108, the control calculator 51 determines whether the accumulated value (correlation value) of the amplitude information output which is one output of the demodulator 32 has reached a predetermined threshold value. If this condition is not satisfied, it can be considered that there is no obstacle, and therefore, the process returns to step 104, and the gradual increase control of the output phase t _d1 of the PN generator 33 is continuously executed. If the condition of step 108 is satisfied, there is a possibility that an obstacle exists, so the process proceeds to step 109.

At step 109, the other output of the demodulator 32, the ID output, matches the ID of the radar signal emitted from the vehicle, that is, the ID generated by the identification code generator 12. It is judged whether or not. If they do not match, the condition of step 108 is satisfied, but it is considered that this is because the signal due to the interference is received, and the process returns to step 104, and the output phase t _d1 of the PN generator 33 is gradually increased. It will continue to run. If they match, the control calculator 51 considers that an obstacle is present in the front, and outputs an obstacle detection output indicating that the obstacle is present or a distance output indicating the distance of the obstacle. Is output to a display or the like in the subsequent stage (110). The distance calculation in step 110 is executed by multiplying the output phase t _d1 of the PN generator 33 by c / 2, as described above.

In this way, when the received signal is detected by the obstacle detection system related to the PN generator 33, the control calculator 5
1 compares the output of the demodulator 32 with the output of the identification code generator 12, and only when they match, considers that there is an obstacle ahead and outputs the obstacle detection output and distance output to the display device in the subsequent stage.

Therefore, according to this embodiment, even if a signal modulated by the same PN code is received, if the ID does not match the ID of the own vehicle, it is not treated as a reflected signal from the obstacle ahead, Malfunction due to interference can be completely eliminated, and the safety of traveling of the vehicle can be further improved.

In the above description, the transmitting antenna 15 and the receiving antenna 21 are separate bodies, but they can be shared by using a circulator or the like. Further, the demodulator 32 may be a Costas demodulator or the like.
Furthermore, when modulating the carrier wave at the transmitter 14, the PN
The same effect can be obtained by individually performing the modulation process for each of the code and the ID.

[0029]

As described above, according to the vehicle forward warning radar device of the present invention, the signal modulated by the result of the logical operation using the transmitting PN code and the ID different for each vehicle is transmitted and received. Sometimes demodulated ID and I used for transmission
Since the obstacle detection is performed only when D matches, the malfunction due to the interference from the radar device mounted on the vehicle other than the own vehicle can be eliminated, and only the front obstacle can be correctly detected.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an operation of detecting a distance to an obstacle in this embodiment.

FIG. 3 is a diagram showing an example configuration of an identification code (ID) in this embodiment.

FIG. 4 is a flowchart showing a flow of operation of a control arithmetic unit in this embodiment.

[Explanation of symbols]

11, 33 PN generator 12 Identification code generator 13 Logical operator 14 Transmitter 15 Transmitting antenna 21 Receiver antenna 22 Receiver 31 Product operator 32 Demodulator 34 Phase controller 51 Control operator _te Transmitting PN code Epoch t _d Radio wave propagation time t _d1 Output phase of PN generator 33 ID Identification code unique to each vehicle

Claims (1)

[Claims] 1. A means for generating a pseudo-noise code for transmission, which is a code string having a predetermined length, a means for generating a different identification code for each vehicle mounted, and a pseudo-noise code for transmission and an identification code. The means for generating a modulated signal by the logical operation described above, the means for phase-modulating the carrier wave by the modulated signal and transmitting it in front of the mounted vehicle, the means for receiving the signal from the front of the vehicle, and the pseudo noise code for transmission Means for generating a receiving pseudo-noise code that is the same code string as the transmitting pseudo-noise code while controlling the phase to gradually increase or decrease so that the phase difference falls within a predetermined range, and a received signal and a receiving pseudo-noise code. And a means for demodulating the received signal to detect the identification code, and a correlation for which the correlation exceeds a predetermined value and the detected identification code corresponds to the identification code generated at the time of transmission. If there is an obstacle in front of the vehicle, the detected ID code does not match the ID code generated at the time of transmission. If there is an obstacle, the obstacle exists at the distance corresponding to the phase difference between the pseudo noise code for transmission and the pseudo noise code for reception only when it is determined that an obstacle exists in front of the vehicle. And a means for outputting information indicating that the distance and / or information indicating the distance are included, and a forward warning radar device for an automobile, comprising: