JPH0968573A - Monopulse radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monopulse radar system in which the mutual interference of radio waves caused with another communication device generating radio waves is suppressed so that a satisfactory target detecting performance can be regularly provided. SOLUTION: The transmitted signal from an oscillator 22 is supplied to two-terminal feed type antenna cells 2a-2c through 90 deg.-hybrid circuits 28a-28c to emit circularly polarized radio waves from the antenna cells 2a-2c. When a radio wave in a turning direction differed from in transmission (reflected wave from a target) is received by the antenna cells 2a-2c, the received signal is taken through the 90 deg.-hybrid circuits 28a-28c to detect an obstruction from the amplitude and phase of each received signal. Phase shifters 30a-30c the phase change quantity of which are changeable to 0 deg. or 180 deg. are provided in one route extending from the 90 deg.-hybrid circuits 28a-28c to the antenna cells 2a-2c, and the phase change quantity is switched, whereby the turning direction of the transmittable and receivable circularly polarized wave is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with a plurality of antenna elements arranged so that a part of their radiation patterns overlap each other, and a predetermined radio wave is transmitted and received using each antenna element. The present invention relates to a monopulse radar device that detects the orientation of a target existing outside based on the received signal.

[0002]

2. Description of the Related Art Conventionally, it has been expected that an obstacle detection radar using radio waves as a transmission medium will be realized as a means for assisting a driver's vision in order to prevent a vehicle collision. In addition, in this type of radar device,
Determining the horizontal position of an obstacle is a very important technique for predicting the possibility of a collision. Therefore, as such a radar device for an automobile, for example, Japanese Patent Laid-Open No. 61-
The monopulse radar device as disclosed in 167890 is considered to be effective.

That is, the monopulse radar device is generally used as an aircraft tracking radar, but since it is an excellent radar device for discriminating the position in the horizontal or vertical direction, it seems to be the driving environment of an automobile. It is considered to function extremely effectively in the presence of many obstacles.

[0004]

However, when a collision prevention system using such a monopulse radar device becomes widespread and the number of vehicles equipped with such a collision prevention system increases, radio wave interference between transmitted and received radio waves between the systems becomes inevitable. It is expected that the ability to detect targets such as obstacles will decline.

The present invention has been made in view of the above problems, and suppresses mutual interference of radio waves generated with other communication devices that generate radio waves, so that a monopulse radar capable of always obtaining good target detection capability. The purpose is to provide a device.

[0006]

The invention according to claim 1 made in order to achieve the above object, comprises a plurality of antenna elements arranged so that a part of radiation patterns overlap each other,
A signal generating means for generating a transmission signal and a signal for inputting the transmission signal from the signal generating means to each antenna element to radiate a radio wave from each antenna element and for extracting each reception signal received by each antenna element A monopulse radar device comprising: input / output means; and target detection means for detecting an external target based on a received signal from each antenna element obtained via the signal input / output means. Is constituted by an antenna element for circular polarization capable of transmitting and receiving circularly polarized radio waves, and further, a polarization switching means for switching the turning direction of circular polarization transmitted and received by each antenna element is provided.

In the monopulse radar device according to the first aspect of the present invention configured as above, a plurality of signal input / output means are provided so that the transmission signals from the signal generation means are arranged so that a part of their radiation patterns overlap. To each of the antenna elements, to radiate a radio wave from each antenna element, and to take out each of the received signals received by each antenna element,
The target detection means detects an external target based on the extracted received signal. In particular, in this device, a circularly polarized wave antenna element capable of transmitting and receiving circularly polarized radio waves is used for each antenna element, and the polarization switching means is used for the direction of circularly polarized wave rotation of each antenna element. Switch.

That is, the monopulse radar device radiates radio waves from a plurality of antenna elements arranged so that a part of the radiation patterns overlap each other, and the reflected waves reflected by the radiated radio waves hitting an external target are reflected by each antenna. The direction of the target is detected from the difference in the amplitude or phase of the received signal obtained by each antenna element by receiving by the element, but another monopulse radar device of the same standard near the device is detected. Exists or there is a communication device that transmits or receives signals in the same frequency band as the radio waves transmitted or received by the device, radio wave interference occurs with these other devices, and the interference wave causes physical interference. The ability to detect the target is reduced.

Therefore, in the monopulse radar device according to claim 1, a circularly polarized wave antenna element capable of transmitting and receiving circularly polarized radio waves is used for each antenna element, and each antenna element is transmitted and received by the polarization switching means. By changing the turning direction of the circular polarized wave, the deterioration of the detection capability due to the interference wave is prevented by the polarization discrimination of each antenna element.

As a result, according to the monopulse radar device of the first aspect, even if the monopulse radar device is applied to a system mounted on a vehicle to detect an obstacle or the like, it is affected by a radio wave transmitted from another device. Therefore, the target such as an obstacle can be accurately detected, and the target detection capability can be improved to improve the traveling safety of the vehicle.

As the polarization switching means for switching the direction of circularly polarized wave of each antenna element, for example, a target detection operation of transmitting a radio wave from each antenna element to detect a target is performed once or. The direction of circularly polarized wave may be alternately switched every time it is performed a plurality of times, or may be randomly switched based on a random number. Also, for example,
Normally, the target detection operation is performed using circularly polarized waves in an arbitrary direction of rotation, and the direction of circularly polarized waves is switched when the received signal obtained by each antenna element has a signal level that is normally impossible. You may do it.

Next, a second aspect of the present invention is the first aspect.
In the monopulse radar device according to the item 1, each of the antenna elements is a two-terminal feeding type circularly polarized antenna element, and the signal input / output unit is provided for each of the antenna elements, and the transmission signal has a phase difference. The signal is divided into 90-degree transmission signals and output to the two feeding terminals of the antenna element,
Of a pair of reception signals input from each power supply terminal of the antenna element, reception signals having a phase difference of 90 degrees in the opposite direction to the distributed transmission signal are combined and taken into the device.
The polarization switching means is composed of a plurality of 90-degree hybrid circuits, is provided in one of a pair of signal paths connecting the 90-degree hybrid circuit and a power feeding terminal of the antenna element, and has a phase change amount of 0 degrees and 180 degrees. It is characterized by being composed of a phase shifter of variable phase change amount that can be switched to any of the above.

That is, the 90-degree hybrid circuit distributes the signal input to the input terminal into a signal having a phase difference of 90 degrees and outputs the signal from a pair of input / output terminals. When a signal having a phase difference (-90 degrees) is input, the signals are combined and output from the output terminal. Therefore, in the monopulse radar device according to claim 2, each antenna element has a position. A two-terminal feed type circularly polarized antenna element that receives a signal with a phase difference of 90 degrees and transmits circularly polarized waves in a predetermined turning direction is used. A pair of feeding terminals of each antenna element and a pair of 90 degree hybrid circuit input terminals are used. By connecting the output terminals to each other and inputting the transmission signal from the signal generating means to the input terminal of the 90-degree hybrid circuit, the transmission signal with a phase difference of 90 degrees is fed to the pair of feeding terminals of each antenna element. , Each Cause radiate circularly polarized radio wave in a predetermined turning direction from antenna element.

As described above, when each antenna element radiates a circularly polarized radio wave in a predetermined turning direction, and the radiated radio wave strikes an external target and is reflected, the turning direction of the reflected wave is opposite to that at the time of transmission. Then, it enters each antenna element,
When a reflected wave from the target is received by each antenna element, a signal having a phase difference (-90 degrees) opposite to that at the time of transmission is induced at the pair of power supply terminals of each antenna element. In this case, the received signals are combined by the 90-degree hybrid circuit and output from the output terminal to the target detection means. Only the radio waves reflected by the target by the polarization discrimination of each antenna element. Can be received to perform target detection.

Further, a phase shifter capable of switching the amount of phase change to either 0 degree or 180 degrees is provided on one of the pair of signal paths connecting the 90 degree hybrid circuit and the feeding terminal of the antenna element. Therefore, by switching the phase change amount of this phase shifter, the phase difference of the transmission signal input to the feeding terminal of the antenna element is switched to either 90 degrees or −90 degrees, and the radio wave emitted from the antenna element is changed. The turning direction can be switched to either a right turn or a left turn.

Therefore, according to the monopulse radar device of the second aspect, the monopulse radar device of the first aspect can be realized with a relatively simple structure, and the turning direction of the radio wave can be easily switched. be able to. That is, in the monopulse radar device according to claim 1, for example, each antenna element is composed of a waveguide circularly polarized antenna and a polarizer for giving a magnetic field in a predetermined direction to the power supplied to the antenna to rotate the radio wave. Alternatively, the signal input / output means may be constituted by a circulator, and the polarization switching means may be configured to switch the direction of the magnetic field generated by the polarizer to switch the circularly polarized wave turning direction. Since a circuit such as a circulator is used, the device becomes large and the device configuration becomes complicated.

On the other hand, according to the monopulse radar device of the second aspect, the high-frequency circuit section including the antenna element, the signal input / output means, and the polarization switching means is provided with a two-terminal feed type circular polarization antenna element. , A 90-degree hybrid circuit and a variable phase change type phase shifter, these parts can be realized without using a ferrite circuit, and the device configuration can be simplified and downsized. is there.

Next, the invention described in claim 3 is the same as claim 2
In the monopulse radar device according to the item 1, the high-frequency circuit unit for transmission and reception, which includes the antenna element, the 90-degree hybrid circuit, and the phase shifter, is composed of a planar circuit formed by a conductive pattern on a predetermined substrate. To do.

As described above, in the monopulse radar device according to the third aspect of the invention, the high-frequency circuit part is constituted by the planar circuit composed of the conductive pattern (microstrip line) on the predetermined substrate. Can be further miniaturized, and the range of use of the device can be expanded.

In order to configure the high-frequency circuit section with a planar circuit, for example, a 90-degree hybrid circuit can be formed with a hybrid circuit that can be configured with a microstrip line such as a rat race power combining circuit or a Wilkinson power combining circuit. It should be configured.

On the other hand, the invention according to claim 4 is the same as claim 1.
The monopulse radar device according to any one of claims 3 to 4, wherein the signal generating means includes a frequency variable oscillator that generates a frequency modulated signal whose frequency changes in a predetermined cycle as the transmission signal, and further comprises the signal input / output means. Frequency conversion means for mixing the received signal from each antenna element input via the above with the transmission signal, converting each received signal into an intermediate frequency signal, and outputting the intermediate frequency signal to the target detection means is provided. And

That is, a monopulse radar device according to a fourth aspect of the present invention causes a generally-known monopulse radar device to radiate a transmission signal whose frequency continuously rises or falls from an antenna element and causes the antenna element to emit the transmitted signal. The received signal and the currently transmitted transmission signal are mixed by using a frequency conversion means such as a mixer circuit, and the reception signal has a frequency corresponding to the deviation between the frequency of the reception signal and the frequency of the transmission signal. By performing frequency conversion to the intermediate frequency signal of, the time from the frequency of the intermediate frequency signal until the transmission signal radiated from the antenna element hits the target and returns to the antenna element, and further from the antenna element to the target The technology of the FM-CW radar for detecting the distance is applied.

Therefore, according to the monopulse radar device of the fourth aspect, on the side of the target detecting means for receiving the received signals from the respective antenna elements converted into the intermediate frequency signal by the frequency converting means, these receiving signals are received. The azimuth of the target and the distance from the (intermediate frequency signal) to the target can be easily and accurately obtained. Therefore, if it is mounted on a vehicle to detect an obstacle, the direction of the obstacle and the distance to the obstacle are accurately detected, and the risk of collision of the vehicle with the obstacle is detected by the vehicle driver. Promptly to improve the safety when the vehicle is traveling.

Next, in the invention described in claim 5, in the monopulse radar device according to claim 4, the frequency conversion means frequency-converts the reception signal from each antenna element using the transmission signal. It is characterized in that it is provided with a plurality of frequency converters for converting and an output switch means for sequentially selecting the intermediate frequency signals frequency-converted by the plurality of frequency converters and outputting them to the target detecting means.

That is, in the monopulse radar device according to the fifth aspect, in realizing the FM-CW system monopulse radar device according to the fourth aspect, the intermediate frequency signal frequency-converted by the frequency converter is The output switch means sequentially inputs to the target detection means in a time division manner.

Therefore, according to the monopulse radar device according to the fifth aspect, the target detecting means inputs in order to accurately obtain the azimuth and distance of the target from the intermediate frequency signal corresponding to each antenna element. Further, it is not necessary to provide a plurality of signal processing circuits for amplifying and shaping the waveform of the intermediate frequency signal, corresponding to each antenna element, and the device configuration can be simplified.

The invention according to claim 6 is the same as claim 4
In the monopulse radar device according to the item 1, the frequency conversion means uses an input switch means for sequentially selecting and receiving the reception signals from the respective antenna elements, and a reception signal sequentially input from the input switch means using the transmission signal. And a frequency conversion unit that sequentially performs frequency conversion and outputs the frequency to the target detection unit.

That is, in the monopulse radar device according to the sixth aspect, in realizing the FM-CW system monopulse radar device according to the fourth aspect, from each antenna element input through the signal input / output means. The received signal is captured by time division by the input switch means, and the captured received signal is converted into an intermediate frequency signal by the frequency conversion section.

Therefore, according to the monopulse radar device of the sixth aspect, like the device of the fifth aspect, it is not necessary to provide a plurality of signal processing circuits in the target detecting means, and the configuration of the device can be simplified. At the same time, it is not necessary to provide a plurality of frequency conversion units for converting the received signal into the intermediate frequency in the frequency conversion means, so that the device configuration can be further simplified.

Further, in order to convert the received signal into the intermediate frequency signal in the frequency conversion unit, the transmission signal output from the frequency variable oscillator is supplied to the frequency conversion unit as well as the signal input / output unit corresponding to each antenna element. However, in the device according to the sixth aspect, since the frequency conversion unit can be one regardless of the number of antenna elements, the frequency conversion unit corresponds to each antenna element. Compared with the case where a plurality of transmission signals are provided, it is possible to suppress the power reduction of the transmission signal due to the distribution of the transmission signal and reduce the output power of the variable frequency oscillator.

Next, the invention described in claim 7 is the monopulse radar device according to claim 4, wherein at least three antenna elements are provided, and the frequency conversion means corresponds to the antenna element. The frequency converter converts the frequency of the reception signal from each antenna element using the transmission signal, and includes a pair of intermediate frequency signals from the intermediate frequency signals output from the frequency conversion units. A signal selecting means for selecting a frequency signal and outputting the selected frequency signal to the target detecting means is provided, and by changing the intermediate frequency signal selected by the signal selecting means, an interval between antenna elements used for detecting the target can be adjusted. It is characterized by

In other words, the monopulse radar device basically arranges two antenna elements at predetermined intervals so that the radiation patterns partially overlap each other, and the received signal obtained by each antenna element is basically the same. Since the azimuth of the target is detected from the difference in the amplitude or the phase, the monopulse radar device of the present invention can be realized by providing two antenna elements. However, if the azimuth and the distance of the target are simply attempted with only two antenna elements, for example, when the distance between the antenna elements is narrow and the distance to the target is short, the amplitude of the received signal of each antenna element is small. Or, although the position of the target can be satisfactorily detected from the phase difference, if the distance to the target is long, the difference between the amplitude and phase of the received signal obtained by each antenna element becomes extremely small, In some cases, the target position may not be detected well.

Therefore, in the monopulse radar device according to the seventh aspect, at least three or more antenna elements are provided, and a signal is selected from the received signals from each antenna element converted into the intermediate frequency signal by the frequency converter. By adjusting any two using the means, the interval between the antenna elements used for detecting the target is adjusted (switched).
I am able to do it.

As a result, according to the monopulse radar device of the seventh aspect, for example, the intermediate frequency signal selected by the signal selecting means is selected in accordance with the distance from the device to the target and the detection state of the target. By switching, it becomes possible to switch the interval between the antenna elements used for target detection to a value at which the target can be detected best, and the detection accuracy of the target (particularly its direction) is further improved, It is possible to realize a radar device having excellent angle measurement resolution.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION A vehicle obstacle detection device according to an embodiment of the present invention will be described below. (First Embodiment) FIG. 1 is a block diagram showing the structure of a vehicle obstacle detection device according to the first embodiment.

As shown in FIG. 1, the vehicle obstacle detection device of this embodiment includes a plurality (three in this embodiment) of two-terminal feed type circularly polarized antenna elements (hereinafter simply referred to as antenna cells).
A multi-beam dielectric lens antenna (hereinafter simply referred to as an antenna device) 6 including 2a, 2b, 2c and a dielectric lens 4 and circularly polarized radio waves in a predetermined turning direction are radiated from each antenna cell 2a to 2c of the antenna device 6. At the same time, the position of the obstacle existing in front of the dielectric lens 4 is detected based on the received signals from the antenna cells 2a to 2c, and the alarm device 12 is operated when the vehicle may collide with the obstacle. The electronic control unit (hereinafter simply referred to as “ECU”) 10 that notifies the vehicle driver of that fact, and the antenna cells 2a to 2c emit circularly polarized radio waves in accordance with output signals from the ECU 10, and Each antenna cell 2a-2
The transmission / reception circuit 20 processes the received signal obtained in c and inputs it to the ECU 10.

Here, in the antenna device 6, the antenna cells 2a to 2c are horizontally arranged at a predetermined interval, and the radiation pattern (directivity) of each of the antenna cells 2a to 2c is determined by the dielectric lens 4. 2 (a) to (c)
As shown in FIG. 5, the radiation patterns are different in the horizontal direction, and partly overlap each other.

That is, of the three antenna cells 2a to 2c, the central antenna cell 2b is substantially left-right symmetric along the central axis of the dielectric lens 4 shown by the dotted line in the figure, as shown in FIG. 2 (b). As shown in FIGS. 2 (a) and 2 (c), the left and right antenna cells 2a and 2c have radiation patterns that are biased to the right or left with respect to the central axis of the dielectric lens 4 shown by the dotted line in the figure. It is designed to be a pattern.

The radiation pattern (directivity) of the entire antenna device 6 is the radiation pattern shown in FIG. 2 (d), which is a combination of the radiation patterns of these antenna cells 2a to 2c. Next, in the transmission / reception circuit 20, a voltage control type frequency variable oscillator (hereinafter simply referred to as an oscillator) that generates a transmission high frequency signal (transmission signal) of a predetermined frequency according to a voltage-controlled control signal output from the ECU 10. ) 22, and a power supply signal for supplying a transmission signal from the oscillator 22 to each antenna cell 2a to 2c and each antenna cell 2a to 2c.
A first power divider 24 that divides the received signal obtained in step 4 into three local signals for frequency conversion;
A second power distributor 26 is further provided, which further divides the transmission signal distributed by the power distributor 24 as a power supply signal into three as a power supply signal for supplying to each of the antenna cells 2a to 2c.

The transmission signals to the antenna cells 2a to 2c distributed by the second power distributor 26 are input terminals of 90-degree hybrid circuits 28a to 28c provided corresponding to the antenna cells 2a to 2c. Input to B respectively. The 90-degree hybrid circuits 28a to 28c divide the transmission signal input to the input terminal B into halves with a phase difference of 90 degrees and output the output signals from the pair of input / output terminals C and D, and conversely. When a signal having a phase opposite to the transmission signal (a phase difference of −90 degrees) is received by C and D, this signal is synthesized and output from the output terminal A. Among them, one input / output terminal C is directly connected to one feeding terminal H of the corresponding antenna cells 2a to 2c, and the other input / output terminal D is the corresponding antenna cell 2a.
~ 2c to the other power supply terminal V via the phase change amount variable phase shifter (hereinafter simply referred to as a phase shifter) 30a to 30c capable of switching the phase change amount Φ to 0 degree or 180 degrees. .

Therefore, the transmission signals input from the second power distributor 26 to the 90-degree hybrid circuits 28a to 28c are transmitted to the pair of power supply terminals of each antenna cell 2a to 2c as a transmission signal having a phase difference of 90 degrees. The antenna cells 2a to 2c are supplied respectively, and the circularly polarized radio waves in the predetermined turning direction are radiated from the respective antenna cells 2a to 2c.

When the antenna cells 2a to 2c receive circularly polarized radio waves that are in the opposite direction to the radiated radio waves, the antenna cells 2a to 2c are fed to the power supply terminals of the antenna cells 2a to 2c in the direction opposite to the direction of transmission.
Since reception power having a phase difference of -90 degrees is generated, in the 90-degree hybrid circuits 28a to 28c, when the antenna cells 2a to 2c receive a transmission radio wave and a reverse-turning radio wave (in other words, If so, when the transmitted radio wave hits an external target and is reflected, the reflected radio wave is received)
Then, the received signals are combined, and the combined received signal is output from the output terminal A.

In addition, the 90-degree hybrid circuits 28a-2
8c and one of the power supply terminals V of the antenna cells 2a to 2c between the input / output terminal D of 8c and the phase shifters 30a to 3 respectively.
0c is provided, the phase shifters 30a to 30c
Since the phase change amount Φ can be switched to 0 degrees or 180 degrees, the circular polarization that can be transmitted and received via the antenna cells 2a to 2c by switching the phase change amount Φ of the phase shifters 30a to 30c. The turning direction of can be switched. The phase change amount Φ of each of the phase shifters 30a to 30c
Are switched by the ECU 10.

Next, 90-degree hybrid circuits 28a-2
The output terminal A of 8c has mixer circuits 32a to 32c, respectively.
The transmission signals distributed as three local signals by the first power distributor 24 are input to the mixer circuits 32a to 32c, respectively. That is, in this embodiment, the mixer circuits 32a to 32c mix the reception signals output from the output terminals A of the 90-degree hybrid circuits 28a to 28c with the transmission signals from the oscillator 22 to generate the reception signals. The transmission signal is converted into a local signal into an intermediate frequency signal (IF signal) having a frequency that is the difference between the frequencies of these signals.

Then, each of these mixer circuits 32a-32
The output signal (IF signal) from c is the IF circuits 34a to 34a.
4c, each of which is amplified and waveform-shaped in each of the IF circuits 34a to 34c, and then input to each of the ECUs 10. Next, the ECU 10 is composed of a well-known microcomputer mainly including a CPU, a ROM, a RAM, etc., and in the measurement mode for detecting an obstacle, the ECU 10 operates as an FM-CW radar at every predetermined measurement cycle. Control the transmission of. That is, by gradually changing the voltage of the control signal output to the oscillator 22 from the predetermined lower limit voltage to the upper limit voltage in each predetermined measurement cycle, the frequency of the transmission signal output from the oscillator 22 is set to the preset lower limit. The transmission control is executed by gradually changing the frequency to the upper limit frequency.

As a result, from each of the antenna cells 2a to 2c, a transmission signal (frequency modulation signal) whose frequency changes sequentially
Is the phase change amount Φ of the phase shifters 30a to 30c (0 degree or 1
A circularly polarized radio wave corresponding to 80 degrees) is repeatedly radiated every predetermined measurement cycle.

During execution of this transmission control, the ECU 10 takes in output signals (IF signals) from the IF circuits 34a to 34c via an A / D converter (not shown), and outputs the taken in IF signals. By comparing the amplitude, the phase, or both, the position (direction) of an obstacle existing outside the antenna device 6 can be detected, and the I / F
Obstacle detection processing is performed to detect the distance to the obstacle and the relative speed by frequency analysis of the signal.

When the direction of the obstacle, the distance to the obstacle, and the relative speed to the obstacle are detected in the obstacle detection process during the transmission control as described above, the next transmission is performed. Until the control is started, from the detection result, it is determined whether or not the vehicle is in a dangerous situation in which it collides with an obstacle, and when it is determined that the risk of collision is high, the alarm device 12 is operated, Collision warning processing is executed to notify the vehicle driver of that fact.

That is, when the radio waves radiated from the antenna cells 2a to 2c hit an obstacle and are reflected, the turning direction of the radio wave is opposite to that at the time of transmission, and the reflected radio waves from the obstacles are reflected by the antenna cells 2a to 2c. When received, the signal is input to the ECU 10 as an IF signal via the 90-degree hybrid circuits 28a to 28c, the mixer circuits 32a to 32c, and the IF circuits 34a to 34c.
In the CU 10, the presence / absence of an obstacle, the direction of the obstacle, the distance to the obstacle, and the obstacle are detected based on the received signals (IF signals) input from the antenna cells 2a to 2c via these units. When the vehicle is in a dangerous situation where it collides with an obstacle, the vehicle driver is notified of that fact and the safety when the vehicle is traveling is improved.

By the way, in the present embodiment, since the antenna element for circular polarization is used for each antenna cell 2a to 2c, the radio wave transmitted by itself is an obstacle due to the polarization identification by each antenna cell 2a to 2c. It will be possible to relatively well receive only the reflected wave reflected by hitting, and to detect an obstacle, but a vehicle obstacle detection device to which such a monopulse radar device is applied has spread, and this device is When the number of mounted vehicles increases, the interference of the obstacle detection radio waves easily occurs between the vehicles, and the radio wave interference may reduce the accuracy of obstacle detection.

Therefore, in the present embodiment, the ECU 10 executes the polarization switching process as shown in FIG. 3 or FIG. 4 to prevent the detection accuracy of the obstacle from being lowered due to the radio wave interference with other devices. It is supposed to do. That is,
In the polarization switching process shown in FIG. 3, in S100 (S: represents step), it is determined whether or not the measurement mode in which the apparatus performs the obstacle detection operation is completed (measurement completed?), And the measurement is performed. If the mode is finished, the process is finished as it is, and if the measurement mode is not finished, the process proceeds to S110 and waits for the completion of one measurement turn for executing the transmission control and the obstacle detection process. .

When this one measuring turn is completed,
In step S120, a random number Ran # is generated in a random function arithmetic circuit incorporated in the CPU, the value Ran # is read, and in step S130, it is determined whether the random number Ran # is an even number. If Ran # is odd and not even, then S
At 140, the phase change amount Φ of the phase shifters 30a to 30c is set to 0.
If the random number Ran # is an even number, the phase change amount Φ of the phase shifters 30a to 30c is set to 180 degrees, and the process proceeds to S100.

That is, in the polarization switching process shown in FIG. 3, a random number Ran # is generated and the random number is generated after the above-mentioned transmission control and obstacle detection process are executed and before the next control is started. Depending on whether Ran # is even or odd, the phase shifter 30a-
The phase change amount Φ of 30c is randomly switched to 0 degree or 180 degrees.

As a result, for example, when the phase change amount Φ of the phase shifters 30a to 30c is set to 0 degree in S140, the radio waves transmitted from other devices or their reflected radio waves are transmitted to the antenna cells 2a to 2c. The received signal is received at 9
0 degree hybrid circuits 28a to 28c, mixer circuit 32
a through 32c and IF circuits 34a through 34c, and E
Even when the obstacle is no longer detected by the ECU 10 based on each IF signal after being input to the CU 10, when the phase change amount Φ of the phase shifters 30a to 30c is switched to 180 degrees in S150, the relevant Since the turning direction of circularly polarized waves that can be transmitted and received by the device changes from clockwise to counterclockwise (or vice versa), even if radio waves from other devices are received by the antenna cells 2a to 2c, The received signal is 90
Is cut by the hybrid circuit 28a to 28c,
Only the IF signal of the received signal corresponding to the reflected radio waves of the radio waves radiated from the antenna cells 2a to 2c will be input to the CU 10, and the ECU 10 side will detect the obstacle based on each IF signal input at this time. Can be accurately detected.

On the other hand, in the polarization switching processing shown in FIG.
Similar to the processing shown in step S100, in S100, it is determined whether or not the apparatus ends the measurement of the obstacle, and when the measurement is ended, the processing is ended as it is, and when the measurement is continued, In S110, wait for the end of one measurement turn.

When this one measurement turn is completed,
After shifting to S220, based on the amplitude of each IF signal captured during one measurement turn, among the received signals received during that period, there is a received signal having a peak of received power higher than a preset level. If there is a received signal having a peak of received power higher than the set level, it is determined that the received signal is affected by some radio wave interference, and the process proceeds to S230. The phase change amount Φ of the phase shifters 30a to 30c is inverted from the current phase change amount and the process proceeds to S100.
The process proceeds to S100 as it is.

That is, in the polarization switching process shown in FIG. 4, after the transmission control and the obstacle detection process described above are executed, the peak of the received power higher than the set level is obtained based on the IF signal taken in during the execution of this control. By determining whether there is a received signal, it is determined whether the received signal received up to now is affected by the radio waves from other devices. If the received power is abnormally high, what Each of the phase shifters 30a to 30a is considered to be affected by the radio wave interference.
The phase change amount Φ of 0c is the phase change amount (0 degree or 1
The phase change amount is inverted from 80 degrees to 180 degrees (180 degrees or 0 degrees). As a result, similarly to the polarization switching process shown in FIG. 3, the obstacle can be accurately detected without being affected by the radio waves transmitted from other devices.

As described above, according to the vehicle obstacle detection device of the present embodiment, the antenna cells 2a to 2c constituting the antenna device 6 use the two-terminal feed type circularly polarized antenna element. , 90 degree hybrid circuits 28a to 28c are used for the signal input / output circuits for supplying the transmission signals and extracting the reception signals for each of the antenna cells 2a to 2c. Each antenna cell 2a is made to transmit the polarized wave.
2 to 2c, the received signal is taken in only when a radio wave in a turning direction different from that at the time of transmission is received, and moreover, the turning direction of the radio wave at the time of transmitting / receiving the phase shifters 30a to 30c. It is designed to be switched using.

Therefore, according to the present embodiment, even if radio wave interference occurs between a vehicle equipped with the same vehicle obstacle detection device as this device or another communication device different from the device, The obstacle can be detected without being affected by the interference wave, and the obstacle detection accuracy can be improved. Since the accuracy of obstacle detection can be improved in this way, the danger of collision of the vehicle with the obstacle can be predicted very accurately, and the vehicle driver can be alerted to the safety of the vehicle. Can be increased.

The vehicle obstacle detection apparatus of this embodiment applies the FM-CW radar technology to the monopulse radar apparatus to detect the direction of the obstacle, the distance to the obstacle, and the relative distance to the obstacle. Since the speed is detected, the risk of the vehicle colliding with an obstacle can be detected accurately and promptly, which also improves the running safety of the vehicle.

Further, the 90-degree hybrid circuits 28a-2
If 8c is composed of, for example, a rat race power combiner circuit, a Wilkinson power combiner circuit, etc., the 90 degree hybrid circuits 28a to 28c are formed into a predetermined substrate shape together with the antenna cells 2a to 2c and the phase shifters 30a to 30c. Since each of these parts can be realized as a so-called planar antenna by configuring with a microstrip line, it is possible to reduce the size and weight of the device.

In this embodiment, the phase shifters 30a to 30d are connected to the input / output terminal D side of the 90 degree hybrid circuits 28a to 28c.
Although the description has been given assuming that 30 c is provided, this phase shifter 30
a to 30c are 90-degree hybrid circuits 28a to 28c.
The input / output terminals C and D may be provided.

In this embodiment, the antenna device 6 has three
Although the vehicle obstacle detection device provided with the individual antenna cells 2a to 2c has been described, in the monopulse radar device,
An external target can be detected as long as it has at least two antenna elements, and thus an antenna device having two antenna cells may be used. Further, the number of antenna cells is further increased, and the azimuth and distance of each obstacle are detected from the amplitude and phase of the received signal obtained by the adjacent antenna cells, and the position of the obstacle is specified from the detection result. However, in this case, the position of the obstacle can be detected with higher accuracy. (Second Embodiment) Here, in the above embodiment, the mixer circuit 3
Each antenna cell 2a whose frequency is converted by 2a to 32c
To 2c, the intermediate frequency signals (IF signals) of the received signals are subjected to signal processing using the IF circuits 34a to 34c, respectively, and EC
Although it is configured to be input to U10, one of the three types of IF signals output from each of the mixer circuits 32a to 32c, for example, as in the vehicle obstacle detection device of the second embodiment shown in FIG. An output switch circuit 36 that selects and outputs one IF signal may be provided, and the IF signal selected by the output switch circuit 36 may be switched at high speed on the ECU 10 side. That is, the three types of IF signals may be acquired at high speed by time division.

By doing so, the IF circuit 34 for processing the IF signal and the A / D converter for A / D converting the IF signal in the ECU 10 are integrated into one, regardless of the number of antenna cells. As compared with the device according to the first embodiment, the device configuration can be further simplified, and the device can be reduced in size and weight. (Third Embodiment) Further, for example, like the vehicle obstacle detection device of the third embodiment shown in FIG. 6, between the output terminal A of each 90-degree hybrid circuit 28a to 28c and the mixer circuit 32. , An input switch circuit 38 for selecting and receiving one reception signal from the output signals from the 90-degree hybrid circuits 28a to 28c (that is, the reception signals from the antenna cells 2a to 2c) is provided.
The reception signal selected by the ECU 10 may be switched at high speed on the ECU 10 side. That is, each antenna cell 2 obtained via the 90-degree hybrid circuits 28a to 28c
The received signals from a to 2c may be acquired at high speed in a time division manner. Then, in this way, not only the IF circuit 34 and the A / D converter but also the mixer circuit 32 can be made one regardless of the number of antenna cells, which is more than that of the device of the second embodiment. Further, the device configuration can be simplified, and the device can be reduced in size and weight.
Further, in this case, in the first power distributor 24, the oscillator 22
From the second power distributor 26 side and the mixer 32.
It is sufficient to divide the transmission signal into two parts, and the amount of attenuation of each transmission signal passing through the first power distributor 24 can be reduced. Therefore, the output power of the transmission signal from the oscillator 22 can be reduced.

In this case, in the 90-degree hybrid circuit in which the reception signal is not selected (in other words, is not connected to the mixer circuit 32), the reception signal output to the output terminal A is reflected to the input / output terminals C and D side. Therefore, the input switch circuit 38 is provided with terminating resistors Ra to Rc for terminating the output terminals A of the 90-degree hybrid circuits 28a to 28c with a predetermined circuit impedance, and the output terminals A are connected to the mixer circuit 32. The output terminal A of the 90-degree hybrid circuit that is not connected to is required to be terminated by the corresponding termination resistors Ra to Rc. (Fourth Embodiment) Further, in each of the above embodiments, the received signals from the antenna cells 2a to 2c obtained via the 90-degree hybrid circuits 28a to 28c are converted into intermediate frequency signals (I
(F signal) frequency conversion, and this is input to the ECU 10 at the same time or in a time-sharing manner.
The position of the obstacle (direction, distance, etc.) using the seed IF signal
However, for example, the fourth
Like the vehicle obstacle detection device of the embodiment, the mixer circuit 3
A reception signal selection circuit 40 that selects an arbitrary pair of IF signals from the reception signals (IF signals) from the antenna cells 2a to 2c frequency-converted into intermediate frequency signals by 2a to 32c is provided. The pair of IF signals selected by the signal selection circuit 40 are respectively supplied to the pair of IF circuits 34-1 and 34-3.
4-2 is used to perform signal processing and input to the ECU 10, and further, on the ECU 10 side, the reception signal selection circuit 4
The interval of antenna cells used for obstacle detection may be switched by changing the IF signal selected by 0.

That is, since the monopulse radar device basically detects the azimuth of the target from the difference in the amplitude or phase of the reception signals obtained by the pair of antenna elements, it has two antenna elements. However, if the azimuth and distance of the target are simply determined by using only two antenna elements, for example, a pair of antennas as shown in FIG. Elements a and b
If the distance D1 is small, and the distance L to the target X is short, the angle θ1 formed by the straight line connecting the antenna elements a and b and the target X becomes relatively large, and the received signal Although the position of the target can be satisfactorily detected from the difference in the amplitude or the phase of the target X, if the distance L to the target X is long, the angle θ1
Becomes smaller and the difference between the amplitudes and phases of the received signals obtained by the antenna elements a and b (corresponding to ΔL1 shown in the figure) also becomes smaller, so that the position of the target X cannot be detected well. However, for example, as shown in FIG. 8B, if the antenna elements used for detecting the target X are switched from a and b with a narrow interval D1 to a and c with a wide interval D2,
Even when the distance L to the target X is long, the angle θ2 formed by the straight line connecting the respective antenna elements a and c and the target X becomes relatively large and can be obtained by the respective antenna elements a and c. The amplitude and phase difference of the received signal (corresponding to ΔL2 shown in the figure) can be increased, and the position of the target can be detected well.

Therefore, in the present embodiment, the reception signal selection circuit 40 can select an arbitrary pair of IF signals from the three types of IF signals frequency-converted by the mixer circuits 32a to 32c and input them to the ECU 10. And ECU 10
On the side, by switching the IF signal selected by the reception signal selection circuit 40 and by extension the interval between the antenna cells used for obstacle detection, the ECU 10 can always detect the position of the obstacle well. Of.

In the ECU 10, when the IF signal selected by the reception signal selection circuit 40 is actually switched, for example, the reception signal switching process as shown in FIG. 9 may be executed. That is, in the reception signal switching process shown in FIG. 9, similarly to the polarization switching process shown in FIGS. 3 and 4, in S100, it is determined whether or not the device finishes measuring the obstacle, When the measurement is to be ended, the processing is ended as it is, and when the measurement is to be continued, S
At 110, wait for the end of one measurement turn. And
When this one measurement turn ends, the process moves to S320,
The frequency of the IF signal captured during one measurement turn is extremely high, and it is determined whether or not a target (obstacle) exists at a point that is equal to or greater than the preset distance. When it exists at a point (that is, when the distance to the obstacle is long), the process proceeds to S330, and the reception signal selection circuit 4 is used to widen the interval between the antennas that receive the reception signal.
One switch SW1 of 0 is switched to the side of the mixer 32a corresponding to the antenna cell 2a, and the other switch SW2 is switched to the side of the mixer 32c corresponding to the antenna cell 2c, and the process proceeds to S100. Conversely, an obstacle is set. If it does not exist at a point equal to or longer than the distance (that is, if the distance to the obstacle is short or the obstacle cannot be detected), in order to narrow the interval between the antennas that receive the received signal, One switch SW1 is connected to the antenna cell 2a
On the side of the mixer 32a corresponding to, and the other switch SW2 is switched to the side of the mixer 32b corresponding to the antenna cell 2b, and the process proceeds to S100.

As a result, according to this embodiment, the azimuth of the obstacle can always be detected accurately without being affected by the distance from the device to the obstacle, and the obstacle having an excellent angle measurement resolution can be obtained. A detection device can be realized. Although the present invention has been specifically described with reference to the first to fourth examples, the present invention is not limited to these examples and can take various aspects. For example, in each of the above-described embodiments, the vehicle obstacle detection device mounted on the vehicle to detect an obstacle has been described, but the present invention is not limited to such an obstacle detection radar device. It can also be applied to a radar device for guiding an automated guided vehicle that automatically travels following another vehicle or a target object.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a vehicle obstacle detection device according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating directional characteristics of an antenna device.

FIG. 3 is a flowchart showing an example of polarization switching processing executed in an ECU.

FIG. 4 is a flow chart showing another example of polarization switching processing similarly executed in the ECU.

FIG. 5 is a block diagram showing a configuration of a vehicle obstacle detection device according to a second embodiment.

FIG. 6 is a block diagram showing a configuration of a vehicle obstacle detection device according to a third embodiment.

FIG. 7 is a block diagram showing a configuration of a vehicle obstacle detection device according to a fourth embodiment.

FIG. 8 is an explanatory diagram illustrating the relationship between the distance between antenna elements and the detection accuracy of a target.

FIG. 9 is a flowchart showing a received signal switching process executed in the ECU of the fourth embodiment.

[Explanation of symbols]

2a to 2c ... Antenna cell (two-terminal feed type circularly polarized antenna element) 4 ... Dielectric lens 6 ... Antenna device (multi-beam dielectric lens antenna) 10 ... ECU (electronic control device) 12 ... Alarm device 20 ... Transceiver Circuit 22 ... Oscillator 24 ... First power distributor 26 ... Second
Electric power distributor 28a to 28c ... 90 degree hybrid circuit 30a to 30c ... Phase shifter (phase change amount variable type phase shifter) 32, 32a to 30c ... Mixer circuit 34, 34a.
34c ... IF circuit 36 ... Output switch circuit 38 ... Input switch circuit 40 ... Received signal selection circuit

Claims (7)

[Claims] 1. A plurality of antenna elements arranged so that a part of radiation patterns are overlapped with each other, signal generating means for generating a transmission signal, and a transmission signal from the signal generating means is input to each antenna element. A signal input / output unit for emitting a radio wave from each antenna element and for extracting a received signal received by each antenna element, and an external device based on the received signal from each antenna element obtained through the signal input / output unit. In the monopulse radar device including: a target detecting unit that detects the target of the above, each antenna element is configured by a circular polarization antenna element capable of transmitting and receiving a circular polarization radio wave, and further, each antenna element A monopulse radar device characterized by comprising polarization switching means for switching the direction of rotation of circularly polarized waves transmitted and received by. 2. Each antenna element comprises a two-terminal feed type circularly polarized antenna element, and the signal input / output means is provided for each antenna element, and the transmission signal has a phase difference of 90 degrees. A phase difference of 90 degrees in the opposite direction to the distributed transmission signal among the pair of reception signals input from the respective power supply terminals of the antenna element while being distributed to the transmission signal and output to the two power supply terminals of the antenna element. Comprising a plurality of 90-degree hybrid circuits for synthesizing a received signal having the signal and taking it into the device, wherein the polarization switching means is one of a pair of signal paths connecting the 90-degree hybrid circuit and a feeding terminal of an antenna element. The monopulse radar device according to claim 1, wherein the monopulse radar device comprises a phase shifter of a variable phase shift type, which is provided in the phase shifter and is capable of switching the phase shift amount to either 0 degree or 180 degrees. 3. A transmission / reception high-frequency circuit unit comprising the antenna element, a 90-degree hybrid circuit, and a phase shifter,
The monopulse radar device according to claim 2, wherein the monopulse radar device comprises a planar circuit formed of a conductive pattern on a predetermined substrate. 4. The signal generating means comprises a frequency variable oscillator for generating, as the transmission signal, a frequency modulated signal whose frequency changes in a predetermined cycle, and further, each of the antennas input via the signal input / output means. Mixing the received signal from the element with the transmitted signal,
4. The monopulse radar device according to claim 1, further comprising frequency conversion means for converting each received signal into an intermediate frequency signal and outputting it to the target detection means. 5. The frequency conversion means includes a plurality of frequency conversion units that respectively frequency-convert a reception signal from each of the antenna elements using the transmission signal, and an intermediate frequency-converted by the plurality of frequency conversion units. The monopulse radar device according to claim 4, further comprising output switch means for sequentially selecting frequency signals and outputting the selected frequency signals to the target detection means. 6. The frequency conversion means uses an input switch means for sequentially selecting and receiving the reception signals from the respective antenna elements, and a reception signal sequentially input from the input switch means using the transmission signals to sequentially frequency-convert the received signals. The monopulse radar device according to claim 4, further comprising a frequency conversion unit that converts the frequency and outputs the frequency to the target detection unit. 7. At least three or more said antenna elements are provided, and said frequency conversion means frequency-converts the reception signal from each antenna element corresponding to said antenna element using said transmission signal. And a signal selecting means for selecting a pair of intermediate frequency signals from the intermediate frequency signals output from the respective frequency converting sections and outputting the selected intermediate frequency signals to the target detecting means. By changing the intermediate frequency signal selected by the selection means,
The monopulse radar device according to claim 4, wherein the distance between the antenna elements used for detecting the target is adjustable.