JP2759576B2 - FM radar equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Recently, in accordance with a growing demand for safety in running a vehicle, an FM radar device is mounted on an automobile.
Developed to detect obstacles in the direction of travel of the vehicle and detect the distance between the vehicle and the vehicle traveling in front, and notify the driver of the risk of collision with obstacles and vehicles traveling ahead. I have.

[0003] In this type of FM radar device, an FM signal whose fundamental frequency is swept is divided into a transmission signal and a local signal, and a reflected wave from a target when the transmission signal is transmitted as a radio wave is received. The distance to the target is determined from the beat frequency generated by mixing the received signal and the local signal.

[0004] However, when such an FM radar device is mounted on an automobile so as to be able to perform radar monitoring in a region in front of the vehicle, an oncoming vehicle is also equipped with a similar FM radar device and installed in the region in front of the vehicle. If a transmission signal using an FM radio wave with the same or similar fundamental frequency is transmitted, the transmission signal of the oncoming vehicle is received and interferes with the detection of the target. Problems such as the distance to the target being out of order occur.

[0005] Therefore, conventionally, in order to eliminate interference by an external radio wave such as a transmission signal from an oncoming vehicle, transmission is stopped for a certain period, and during that time, when a radio wave having the same frequency as the fundamental frequency of the transmission signal of the own vehicle is received. Assuming that there is interference from an external radio wave, the basic frequency of the transmission signal of the own vehicle at that time is changed (Japanese Patent Laid-Open No. 49-3759).
No. 0).

Conventionally, transmission is stopped for a certain period of time, and a beat frequency generated by the reception of an external radio wave is obtained during that period, and the beat frequency is counted every elapse of a predetermined time to calculate the difference from the previous beat frequency. When the difference exceeds the threshold value, it is assumed that there is interference of extraneous radio waves, the current measurement result is invalidated, and processing such as setting the previous value to the current value is performed. (See JP-A-59-79175).

[0007]

The problem to be solved is that, in order to eliminate the interference of the external radio waves, if the basic frequency of the transmission signal is changed when it is determined that there is interference from the external radio waves, the frequency change If it is necessary to take measures and the equipment will be complicated, and if it is determined that there is interference from external radio waves, invalidating the current measurement result and diverting the previous measurement result will result in a constantly changing target. The measurement accuracy of the relative distance is reduced.

[0008]

SUMMARY OF THE INVENTION According to the present invention, it is possible to accurately measure the distance to a target without complicating the apparatus in order to eliminate the interference of the external radio wave and eliminating the interference of the external radio wave. In order to be able to do so, the FM radar device switches between a transmission mode for transmitting a transmission signal and a reception mode for receiving an external radio wave when not transmitting, so that the reception signal and the local signal can be mixed in the reception mode. be stored in the memory in search of the spectrum of the beat signal obtained by the spectrum of subsequent beat signal obtained in the transmission mode can be corrected on the basis of the spectrum stored previously in the memory < br />

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an FM radar apparatus 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 transmitting the FM signal to a transmission signal T.
S and a local signal LS, a power divider 2, a mode switching switch 3 provided in a circuit of the transmission signal TS,
The transmission signal TS is given to the antenna ANT, and the antenna A
A circulator 4 for providing a received signal RS received by the NT to a mixer 5, the mixer 5 for mixing the received signal RS and a local signal LS to generate a beat signal BS,
An AD converter 6 for converting the beat signal BS output from the mixer 5 into a digital signal; and an FFT for reading the digitized data of the beat signal BS and performing a fast Fourier transform to analyze the spectrum of the beat frequency. The circuit 7 and the reception signal RS and the local signal L in the reception mode when the mode changeover switch 3 is 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 changeover switch 3 is on is read, and the spectrum obtained in the transmission mode is read. Is corrected based on the spectrum obtained in the reception mode stored in the memory 9 to obtain a distance from the corrected spectrum to the target searched in the transmission mode. A display 10 displays information on the distance to the target, and a controller 11 controls on / off of the mode switch 3 and controls the entire apparatus.

In the above configuration, under the control of the controller 11, the mode switching switch 3 is periodically turned off for a certain period of time based on the synchronization signal SS from the FM signal generation circuit 1. In the reception mode, the spectrum of the beat signal due to the external radio wave received at that time is updated and stored in the memory 9, and the spectrum of the beat signal obtained in the transmission mode immediately after that is stored in the memory 9 first. Is subtracted, and the spectrum of the beat signal obtained in the transmission mode at that time is corrected, thereby obtaining the spectrum of the beat signal from which the interference component of the external radio wave is removed.
As a result, a true target is detected, and the distance to the target can be accurately obtained. At that time,
Of internal noise that changes over time in the
The data including the sound components will be stored in the memory 9.
Thus, the effect of internal noise can be removed.

FIG. 2 shows another embodiment of the FM radar apparatus according to the present invention. In this case, a plurality of antennas ANT1 to ANT1 are provided so as to monitor a wide area in front of the vehicle.
ANT4 is arranged side by side, and the antennas ANT1 to ANT1
A switch circuit 12 is provided for each transmitting and receiving system in ANT4.
A multi-channel such that transmission and reception by the antennas ANT1 to ANT4 can be performed in a time-sharing manner by providing switching circuits 13 and 14 by the controller 11 and controlling the switching operations of the switching circuits 12, 13 and 14 by the controller 11. It has a configuration.

Each output side of the switch circuit 12 for switching the transmission signal TS is provided with a multiplier 151-154, and each output side of the switch circuit 13 for switching the local signal LS is provided with a multiplier. 161 to 164 are provided, and each frequency of the transmission signal TS and the local signal LS is multiplied as desired.

Each switch circuit 12 for performing time-division transmission and reception by each of the antennas ANT1 to ANT4,
13 is arranged in front of each of the multipliers 151 to 154 and 161 to 164, so that a frequency to be handled is low and time-division driving with high switching efficiency can be performed.

In the figure, reference numerals 41 to 44 denote circulators provided for the respective channels, and reference numerals 51 to 54 denote mixers provided for the respective channels.

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. ANT4
Are sequentially turned on in a time-division manner, and in the reception mode, all the transmission systems of the antennas ANT1 to ANT4 are simultaneously turned off.

FIG. 3 shows an operation state of each of the switch circuits 12, 13, and 14 in the transmission mode. Also,
FIG. 4 shows each switch circuit 12, 1 in the reception mode.
3 and 14 show operation states.

In the above-described configuration, the spectrum of the beat signal due to the external radio wave received in a time-division manner by each of the antennas ANT1 to ANT4 in the reception mode is stored in the memory 9 for each channel in the same manner as described above. order
Next, the spectrum of the beat signal obtained in a time division manner in the transmission mode immediately after that is stored in the memory 9 first.
The spectrum of the beat signal obtained by subtracting the spectrum of the beat signal obtained in the transmission mode at that time is subtracted by subtracting the spectrum of each corresponding channel stored in the beat signal. Is obtained, whereby a true target is detected, and the distance to the target is accurately obtained.

[0018]

As described above, in the FM radar apparatus according to the present invention, the FM signal is divided into the transmission signal and the local signal,
When receiving the reflected wave from the target when transmitting the transmission signal as a radio wave, and calculating the distance to the target from the spectrum of the beat signal obtained by mixing the received signal and the local signal, the transmission signal is A means for switching between a transmission mode for transmitting and a reception mode for receiving an external radio wave when not transmitting, and obtaining a spectrum of a beat signal obtained by mixing a reception signal and a local signal in the reception mode into a memory. To take the means to remember
In which the, the spectrum of the beat signal obtained in the transmission mode, can be corrected on the basis of the spectrum stored in the memory, with a simple configuration,
Interference of extraneous radio waves and aging in radar equipment
There is an advantage that a true target from which the influence is removed is detected by obtaining the influence of the changing internal noise, and the distance to the target can be accurately obtained.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing another embodiment of the FM radar apparatus 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. 2;

FIG. 4 is a time chart showing an operation state of each switch circuit in a reception mode in the embodiment of FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 FM signal generating circuit 2 power distributor 3 mode switching switch 4, 41 to 44 circulator 5, 51 to 54 mixer 6 AD converter 7 FFT circuit 8 signal processing circuit 9 memory 10 display 11 controller 12 to 14 switch circuit 151 to 151 154 multiplier 161 to 164 multiplier ANT, ANT1 to ANT4 Antenna

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-19588 (JP, A) JP-A-50-34187 (JP, A) JP-A-2-42376 (JP, A) JP-A 56-34 18772 (JP, A) JP-A-61-165676 (JP, A) JP-A-51-126857 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 13/34 G01S 7 / 36 G01S 7/40

Claims (3)

(57) [Claims] 1. A method of distributing 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. 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, in an FM radar apparatus for obtaining a distance from a spectrum of an obtained beat signal to a target; The spectrum of the beat signal obtained by mixing the received signal and the local signal at the time is obtained and stored in the memory.
FM radar apparatus characterized by taking means to perform. 2. An FM signal is distributed to a transmission signal and a local signal.
The target signal when transmitting the transmission signal as radio waves
Receives reflected waves and mixes the received signal with local signals
From the spectrum of the beat signal
In an FM radar device that determines the distance to a target,
Transmission mode for transmitting signals and extraneous radio waves when not transmitting
Means for switching to a reception mode for receiving
Signal obtained by mixing the received signal and the local signal in the transmission mode.
To find the spectrum of the beat signal to be stored in memory
And the specifications of the beat signal obtained in the transmission mode.
The tram to the spectrum stored in the memory
It is characterized by taking the means to correct based on
FM radar apparatus according to. 3. A plurality of antennas are provided side by side, and each antenna
A switch circuit is provided for the transmission and reception systems in
Control the transmission and reception at each antenna
In the receiving mode, each antenna
Spec of beat signal due to extraneous radio waves received separately
Tram is stored in the memory sequentially and time division is performed in the transmission mode.
The beat signal spectrum obtained in memory first
Correcting sequentially based on the stored spectrum
Item 2 is characterized in that
FM radar system that.