JPH05240947A - Fm radar equipment - Google Patents

Abstract

PURPOSE:To eliminate the interference of an outside electric wave and precisely measure a distance up to a target by finding to store the spectrum of a bead signal in the time of a receiving mode and correcting the spectrum of another bead signal obtained in the time of a transmission mode on the basis of a stored spectrum. CONSTITUTION:With a switch for mode changeover 3 periodically put off for a certain time under the control of a controller 11, a receiving mode is set. At this time the spectrum of a bead signal caused by an outside received electric wave is renewably stored to a memory 9 and thereafter, with the spectrum previously stored to the memory 9 subtracted from the other spectrum of the bead signal in the time of a transmission mode, correction is performed for the purpose of generating the spectrum of the bead signal eliminating the interference of the outside electric wave and finding a distance up to a true target by means of the spectrum of the bead signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM radar device which eliminates the interference of external radio waves.

[0002]

2. Description of the Related Art Recently, in response to an increasing demand for safety in running a vehicle, an FM radar device is mounted on an automobile,
A system has been developed that detects the obstacle in the traveling direction of the vehicle and detects the distance between the vehicle and the vehicle traveling in front, and informs the driver of the risk of collision with the obstacle or vehicle traveling in front. There is.

In this type of FM radar device, an FM signal having a fundamental frequency swept is distributed into a transmission signal and a local signal, and a reflected wave from a target when the transmission signal is transmitted as an electric wave is received, The distance from the beat frequency generated by mixing the received signal and the local signal to the target is calculated.

However, when such an FM radar device is installed in a vehicle so that radar monitoring of the front area of the vehicle can be carried out, a similar FM radar device is also installed in an oncoming vehicle in the front area. When the transmission signal by the FM radio wave having the same or similar basic frequency is transmitted, the transmission signal of the oncoming vehicle is received and it interferes with the detection of the target object, and the target object is erroneously detected or is measured. There is a problem that the distance to the target is wrong.

Therefore, in the past, in order to eliminate interference from external radio waves such as a transmission signal from an oncoming vehicle, transmission is stopped for a certain period of time, and when a radio wave having the same frequency as the fundamental frequency of the transmission signal of the own vehicle is received during that period. Assuming that there is interference from external radio waves, the fundamental frequency of the transmission signal of the vehicle at that time is changed (Japanese Patent Laid-Open No. 49-3759).
No. 0).

Further, conventionally, the transmission is stopped for a certain period of time, the beat frequency generated by the reception of the external radio wave during that period is obtained, and the beat frequency is counted every time a predetermined time elapses and the difference from the previous beat frequency is calculated. When the difference exceeds the threshold value, there is interference from external radio waves, so this measurement result is invalidated, and the previous value is set to this value. (See JP-A-59-79175).

[0007]

The problem to be solved is to change the fundamental frequency of the transmission signal when it is determined that there is interference from external radio waves in order to eliminate the interference of external radio waves. If the device becomes complicated because of the need for means, and if it is determined that there is interference from extraneous radio waves, and the current measurement result is diverted and the previous measurement result is reused, the That is, the measurement accuracy of the relative distance of is reduced.

[0008]

According to the present invention, the distance to a target can be accurately measured without complicating the device to eliminate the interference of external radio waves and eliminating the interference of external radio waves. In order to be able to do so, in the FM radar device, the transmission mode for transmitting the transmission signal and the reception mode for receiving the external radio wave when not transmitting are switched, and the reception signal in the reception mode and the local signal are mixed. The spectrum of the beat signal obtained by the above is obtained and stored in the memory, and the spectrum of the beat signal obtained in the subsequent transmission mode is corrected based on the spectrum previously stored in the memory.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In an FM radar device according to the present invention, as shown in FIG. 1, an FM signal generating circuit 1 for generating an FM signal whose fundamental frequency is swept and a transmission signal T for transmitting the FM signal.
A power distributor 2 for distributing S and the local signal LS, a mode changeover switch 3 provided in the circuit of the transmission signal TS,
The transmission signal TS is given to the antenna ANT, and the antenna A
A circulator 4 for giving the reception signal RS received by NT to the mixer 5, and the mixer 5 for producing the beat signal BS by mixing the reception signal RS and the local signal LS,
An AD converter 6 that converts the beat signal BS output from the mixer 5 into a digital signal, and an FFT that reads the digitized data of the beat signal BS and performs high-speed Fourier transform to perform spectrum analysis of the beat frequency. The reception signal RS and the local signal L in the reception mode in which the circuit 7 and the mode switching switch 3 are in the off state
The spectrum of the beat signal obtained by mixing with S is read and stored in the memory 9, and the spectrum of the beat signal obtained in the transmission mode in which the mode switching switch 3 is in the on state is read and the spectrum obtained in the transmission mode is read. Is calculated based on the spectrum obtained in the reception mode stored in the memory 9, and the distance from the corrected spectrum to the target searched in the transmission mode is calculated. A display 10 that displays information about the distance to the target and a controller 11 that controls ON / OFF of the mode switching switch 3 and that controls the entire apparatus.

With the above-mentioned configuration, the mode switching switch 3 is periodically turned off for a certain period of time under the control of the controller 11 based on the synchronization signal SS from the FM signal generation circuit 1. In the reception mode, the spectrum of the beat signal received by the external radio wave at that time is updated and stored in the memory 9, and the spectrum of the beat signal obtained immediately after that in the transmission mode is stored in the memory 9 in advance. By subtracting and correcting the spectrum of the beat signal obtained in the transmission mode at that time, the spectrum of the beat signal from which the interference component of the external radio wave is removed is obtained,
As a result, the true target is detected, and the distance to the target can be accurately obtained.

FIG. 2 shows another embodiment of the FM radar device according to the present invention. In this case, a plurality of antennas ANT1 to ANT1 are provided so that the front area of the vehicle can be widely monitored.
ANT4 is installed side by side, and its antennas ANT1 to
A switch circuit 12 for each transmission and reception system in ANT4,
By providing 13 and 14 and controlling the switching operation of the respective switch circuits 12, 13 and 14 by the controller 11, a multi-channel that can perform transmission and reception in the antennas ANT1 to ANT4 in a time division manner. It is configured.

Multipliers 151 to 154 are provided on each output side of the switch circuit 12 for switching the transmission signal TS, and a multiplier is provided on each output side of the switch circuit 13 for switching the local signal LS. 161 to 164 are provided to multiply the frequencies of the transmission signal TS and the local signal LS as desired.

Each switch circuit 12 for performing time division transmission and reception by each antenna ANT1 to ANT4,
Since 13 is arranged in the preceding stage of each of the multipliers 151 to 154 and 161 to 164, the frequency to be handled is low, and the time division drive with good switching efficiency can be performed.

In the figure, 41 to 44 are circulators provided for each channel, and 51 to 54 are mixers provided for each channel.

The switch circuit 12 also serves as a mode switching switch circuit (corresponding to the mode switching switch 3 in FIG. 1) for switching between the transmission mode and the reception mode, and each antenna ANT1 to ANT1 in the transmission mode. ANT4
The transmission system is sequentially turned on in a time division manner, and all the transmission systems of the antennas ANT1 to ANT4 are simultaneously turned off in the reception mode.

FIG. 3 shows the operating state of each switch circuit 12, 13, 14 in the transmission mode. Also,
FIG. 4 shows each switch circuit 12, 1 in the reception mode.
The operation states of 3 and 14 are shown.

In the configuration as described above, the spectrum of the beat signal by the external radio wave which is received by the antennas ANT1 to ANT4 in the reception mode in a time division manner is stored in the memory 9 for each channel in the same manner as described above. The spectrum of each corresponding channel previously stored in the memory 9 is subtracted from the spectrum of the beat signal that is stored renewed and obtained in time-division in the transmission mode immediately after that, and in the transmission mode at that time. By correcting the spectrum of the obtained beat signal, the spectrum of the beat signal from which the interference of external radio waves has been removed is obtained, which allows the true target to be detected and the distance to that target to be determined. Accurately required.

[0018]

As described above, in the FM radar device according to the present invention, the transmitting / receiving mode switching means and the spectrum of the beat signal obtained by mixing the received signal and the local signal in the receiving mode are obtained and stored in the memory. Means to store in
The spectrum of the beat signal obtained in the transmission mode,
A means for correcting the spectrum based on the spectrum stored in the memory is used. With a simple structure, interference of external radio waves is eliminated, a true target is detected, and the target can be detected. It has an advantage that the distance can be accurately obtained.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing another embodiment of the FM radar device according to the present invention.

FIG. 3 is a time chart showing an operation state of each switch circuit in a transmission mode in the embodiment of FIG.

FIG. 4 is a time chart showing an operation state of each switch circuit in a reception mode in the embodiment of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 FM signal generation circuit 2 Electric power distributor 3 Mode changeover switch 4,41-44 Circulator 5,51-54 Mixer 6 AD converter 7 FFT circuit 8 Signal processing circuit 9 Memory 10 Display 11 Controller 12-14 Switch circuit 151- 154 multiplier 161 to 164 multiplier ANT, ANT1 to ANT4 antenna

Claims (1)

[Claims] 1. By dividing an FM signal into a transmission signal and a local signal, receiving a reflected wave from a target when the transmission signal is transmitted as a radio wave, and mixing the received signal and the local signal. In an FM radar device for obtaining a distance from a spectrum of a beat signal obtained to a target, a means for switching between a transmission mode for transmitting a transmission signal and a reception mode for receiving an external radio wave when not transmitting, and a reception mode Means for obtaining the spectrum of the beat signal obtained by mixing the received signal and the local signal at the time and storing it in the memory, and correcting the spectrum of the beat signal obtained in the transmission mode based on the spectrum stored in the memory An FM radar device, characterized in that the means for