JP5029045B2 - Radar system and transmitter and receiver used therefor - Google Patents

Description

  The present invention relates to a radar system and a transmitter and a receiver used therefor, and more particularly to a radar system having a relative distance and relative speed measuring function and a wireless communication function, and a transmitter and a receiver used therefor.

Safe driving system in recent years, in order to increase traffic safety, which performs a relative distance and the measurement of the relative velocity between the vehicle and the front and rear, right and left of the vehicle by the radar mounted on a vehicle, to support the driver on the basis of the information Development is underway. Furthermore, using the communication between the vehicles, information on the driver and the state of the vehicle, and information on the surrounding situation located in the blind spot from the own vehicle is communicated, so that the movement of the surrounding vehicles can be controlled. Support systems are being developed to predict and show the next action to the driver.

  In order to realize such a system, it is important that measurement of relative distance and relative speed (hereinafter simply referred to as distance measurement) and wireless communication can be performed at the same time. Vehicle-to-vehicle UWB (Ultra WideBand) wireless communication system. In this system, not only high-speed data communication is performed using ultra-fine pulses, but also the distance between vehicles is measured by taking advantage of high time resolution, which is one of the features of ultra-fine pulses. Since this system is intended for high-speed data communication between vehicles, it is used for communication and distance measurement between the host vehicle and a vehicle located at a short distance.

  On the other hand, for measurement of the relative distance between the host vehicle and a vehicle located at a long distance, millimeter waves with small attenuation and excellent straightness are used even in bad weather such as rain and fog. In the ranging system, a frequency-modulated signal is used. The signal transmitted from the host vehicle is reflected by the other vehicle and received by the host vehicle. The received reflected signal and the transmitted signal are compared, and the relative distance and relative speed are determined from the frequency displacement and the phase difference. It has come to be measured.

  Furthermore, the millimeter wave band has a feature that a usable bandwidth is wide, and is a frequency band in which high-speed data communication is possible. In the wireless communication system using the millimeter wave band, unlike the case of using the UWB wireless communication system, high-speed data communication between vehicles located at a long distance is possible. For example, application of the millimeter wave radio communication system described in Patent Document 2 to inter-vehicle communication has been proposed. Further, as related techniques, there are also techniques described in Patent Documents 3 and 4.

JP 2004-258209 A JP 2002-246922 A JP 2002-267743 A Japanese Patent Laying-Open No. 2005-092415

  However, when the distance measuring system and the wireless communication system using the above-described millimeter wave are constructed, a wireless device is required for each system. In addition to an increase in the size of the system, there are a plurality of expensive millimeter wave oscillators. This will cause the vehicle price to rise. Furthermore, since the distance measurement signal and the wireless communication signal are transmitted uncorrelated, there is a possibility that the communication quality may be deteriorated due to signal interference or interference, and the relative distance and relative speed may be erroneously measured. .

  Patent Documents 3 and 4 disclose a technique for wirelessly transmitting a radar wave and a communication wave at the same time, but it is necessary to establish synchronization between the transmitter and the receiver. Therefore, the configuration becomes complicated and the vehicle price increases.

  Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a radar system capable of suppressing deterioration in communication quality and reducing the size, and a transmitter and a receiver used therefor. Is to provide.

A radar system according to the present invention comprises:
A radar system for measuring relative distance and relative velocity,
The frequency-modulated measurement signal and the transmission information signal for measuring the relative distance and the relative speed are converted into a radio frequency band communication signal using the frequency-modulated measurement signal as a local signal. A transmitter for transmitting the communication signal in the radio frequency band and the measurement signal so that the frequency difference between these signals is constant regardless of time ;
A receiving unit that receives the communication signal and the measurement signal transmitted from a counterpart transmission unit, and detects the transmission information signal by square detection of the received communication signal and the measurement signal;
A distance measurement unit that compares the measurement signal received by reflection from a reflection object and the measurement signal transmitted from the transmission unit, and measures a relative distance and a relative speed with the reflection object,
It is characterized by including.

The transmitter according to the present invention comprises:
A transmitter in a radar system that measures relative distance and relative velocity,
The frequency-modulated measurement signal and the transmission information signal for measuring the relative distance and the relative speed are converted into a radio frequency band communication signal using the frequency-modulated measurement signal as a local signal. And a transmitter that transmits the communication signal in the radio frequency band and the measurement signal so that the frequency difference between the two signals is constant regardless of time .

A receiver according to the present invention comprises:
A frequency-modulated measurement signal and a transmission information signal for measuring relative distance and relative speed are converted into a communication signal in a radio frequency band using the frequency-modulated measurement signal as a local signal, A receiver in a radar system having a transmitter for transmitting the communication signal in the radio frequency band and the measurement signal so that the frequency difference between the two signals is constant regardless of time ,
Detecting means for receiving the communication signal and the measurement signal transmitted from a partner transmitter and detecting the transmission information signal by square detection of the received communication signal and the measurement signal; It is characterized by that.

  According to the present invention, a ranging signal obtained by frequency up-converting a transmission information signal and a radio communication signal generated by this up-conversion are simultaneously transmitted, and the receiving vehicle performs square detection from these two received signals. Since the transmission information signal is demodulated, it is possible to prevent degradation of the wireless communication quality due to interference and interference between the distance measurement signal and the wireless communication signal, and one transmission of the distance measurement signal and the communication signal. Since it can be sent out from the machine, the system can be downsized.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a system to which an embodiment of the present invention is applied. The system according to the embodiment of the present invention includes a transmission-side radio 2 mounted on the vehicle 1 and a reception-side radio 4 mounted on the vehicle 3. In the following description, it is assumed that communication is performed from the vehicle 1 to the vehicle 3, and the vehicle 1 measures the relative distance d and the relative speed v with the vehicle 3.

<First embodiment>
FIG. 2 is a block diagram of the first embodiment, and shows the configuration of the transmitter-side radio 2 mounted on the vehicle 1. The transmission-side radio 2 includes a transmission unit 5, a distance measurement unit 6, and a control unit 7. The transmission unit 5 includes a transmission information signal generation unit 8, a frequency modulation pulse signal generator 9, a voltage controlled oscillator 10, a mixer 11, a transmission amplifier 12, and a transmission antenna 13.

The transmission information signal generation unit 8 is detected by sensors installed in various places of the vehicle 1 according to the control signal from the control unit 7, for example, the vehicle 1 or the vehicle 1 is accelerating or the driver is likely to fall asleep. A transmission information signal (f _IF ) to be transmitted to the vehicle 3 is generated and output to the mixer 11 based on the information on the driver and the information on the surrounding situation of the vehicle 1 such that the motorcycle is approaching from behind the vehicle 1. .

The frequency modulation pulse signal generator 9 generates a periodic pulse signal for generating a ranging signal in accordance with a control signal from the control unit 7 and outputs it to the voltage controlled oscillator 10. The voltage-controlled oscillator 10 outputs the ranging signals (f _a , f _b ) that periodically change to the mixer 11 in response to the pulse signal from the frequency modulation pulse generator 9. The mixer 11 up-converts the transmission signal generated by the transmission information signal generation unit 8 to a radio frequency band using a ranging signal input from the voltage controlled oscillator 10 and generates a radio communication signal (f _a + f _IF , f _b + f _IF ). The mixer 11 also outputs the ranging signals (f _a , f _b ) used when up-converting the radio communication signal and the transmission information signal to the transmission amplifier 12 at the same time.

The transmission amplifier 12 amplifies the ranging signal and the wireless communication signal input from the mixer 11 to transmission power and outputs the amplified signal to the transmission antenna 13. The transmission antenna 13 radiates the distance measurement signal and the radio communication signal input from the transmission amplifier 12 toward the vehicle 3. FIG. 3 shows the time change of the signal radiated from the transmission antenna 13. Ranging signals (f _a, f _b) is accompanied to change its frequency periodically, wireless communication signals _{(f a + f IF, f} b + f IF) has a frequency also changes periodically in I understand that. Furthermore, the frequency difference between the ranging signal and the wireless communication signal is constant at f _IF regardless of time.

The distance measuring unit 6 includes a signal processing unit 14, a mixer 15, a delay time measuring unit 16, a frequency discriminator 17, a band pass filter (BPF) 18, a low noise amplifier 19, and a receiving antenna 20. is doing. Ranging signals reflected by the vehicles _{3 (f a '', f} b '', hereinafter these referred to as a reflected distance measuring signal) and a radio communication signal _{(f a '' + f IF} , f b '' + F _IF (hereinafter referred to as “reflection radio communication signals”) is received by the receiving antenna 20, amplified by the low noise amplifier 19, and then input to the BPF 18. At this time, the reflected distance measurement signal and the reflected wireless communication signal are changed to signals having different frequencies from the transmitted distance measurement signal and the wireless communication signal by Doppler shift.

The amount of frequency change (f _a ″ −f _a ) is
f _a ″ −f _a = f _a × (2 v / c) (1)
It is represented by Here, it is assumed that the vehicle 3 is traveling toward the vehicle 1 at a relative speed v. c is the speed of light.

The BPF 18 is designed so as to obtain the frequency characteristics shown in FIG. 4, and the reflected wireless communication signal is cut off and only the reflected distance measuring signal is allowed to pass. The reflected distance measurement signal that has passed through the BPF 18 is divided into two and input to the mixer 15 and the frequency discriminator 17. The mixer 15 mixes the reflection distance measurement signal input from the BPF 18 and the transmission distance measurement signal input from the voltage controlled oscillator 10 constituting the transmission unit 5, and these difference frequency signals (f _a ″). -F _a ) is output to the signal processing unit 14. In the signal processing unit 14, the frequency difference and
v = (c / f _a ) × (f _a ″ −f _a ) (2)
From this equation, the relative speed is obtained and output.

  On the other hand, the frequency discriminator 17 generates a pulse signal from the reflection distance measurement signal input from the BPF 18 and supplies the pulse signal to the delay time measurement unit 16. The delay time measuring unit 16 measures the pulse signal from the frequency modulation pulse signal generator 9 and the delay time between the pulse signals input from the frequency discriminator 17 and supplies the measured signal to the signal processing unit 14. The signal processing unit 14 obtains the relative distance based on the delay time.

FIG. 5 is a diagram in which the pulse signal input to the delay time measuring unit 16 is plotted with respect to time. Since the reflected distance measurement signal is reflected from the vehicle 3 and returned, it can be seen that it is delayed from the signal of the frequency modulation pulse signal generator 9. If this delay time is t, the relative distance d is
d = c × t / 2 (3)
Is required.

FIG. 6 is a functional block diagram of the reception-side radio device 4 mounted on the vehicle 3. The reception-side radio device 4 includes a reception unit 21 and a control unit 22. The receiving unit 21 includes a receiving antenna 23, a low noise amplifier 24, a square detector 25, and a received signal processing unit 26. The received ranging signal by the receiving antenna _{23 (f a ', f b} ', hereinafter these call received ranging signal) and a radio communication signal _{(f a '+ f IF,} f b' + f IF These are hereinafter referred to as reception radio communication signals) and are amplified by the low noise amplifier 24 and then input to the square detector 25.

  The square detector 25 detects a transmission information signal from the received ranging signal and the received wireless communication signal and supplies the transmission information signal to the received signal processing unit 26. The reception signal processing unit 26 converts the transmission information signal supplied from the square detector 25 into information on the vehicle 1 and notifies the driver.

FIG. 7 is a diagram in which the received ranging signal, the received radio communication signal, and the output of the square detector 25 are plotted with respect to time. The frequency of the reception ranging signal and the reception radio signal communication signal is periodically changed, but since the frequency difference is constant with f _IF , the transmission information signal can be reproduced by square detection. .

  As described above, the transmission side radiates the correlation between the ranging signal and the wireless communication signal at the same time, and the reception side detects the transmission signal from these two signals. In addition to suppressing deterioration in communication quality due to interference with communication signals, and the like, these signals can be radiated from one transmitter, so that the apparatus can be downsized.

<Second embodiment>
Next, a second embodiment of the present invention will be described. FIG. 8 is a functional block diagram of the transmitting-side radio device 2 mounted on the vehicle 1, and the same parts as those in FIG. 2 are denoted by the same reference numerals. The transmission-side radio device 2 includes a transmission unit 5, a distance measurement unit 6, and a control unit 7. The transmission unit 5 includes a transmission information signal generation unit 8, a frequency modulation sawtooth wave generation unit 27, a voltage controlled oscillator 10, a mixer 11, a transmission amplifier 12, a directional coupler 28, and a transmission antenna 13. Have

The transmission information signal generation unit 8 generates a signal to be transmitted to the vehicle 3 and outputs it to the mixer 11 as in the first embodiment. The frequency modulation sawtooth generator 27 generates a sawtooth signal (see FIG. 9) having a period T for generating a distance measurement signal in accordance with a control signal from the control unit 7 and outputs the sawtooth signal to the voltage controlled oscillator 10. . The voltage controlled oscillator 10 outputs a ranging signal (LO) that periodically changes to the mixer 11 in response to a signal from the frequency modulation sawtooth generator 27. At this time, the frequency of the ranging signal changes linearly with respect to time from f _{LO1 to} f _LO2 .

  The mixer 11 up-converts the transmission signal generated by the transmission information signal generation unit 8 to a radio frequency band using a ranging signal input from the voltage controlled oscillator 10 to generate radio communication (RF). The mixer 11 also outputs the ranging signal used when up-converting the radio communication signal and the transmission information signal to the transmission amplifier 12 at the same time. The transmission amplifier 12 amplifies the ranging signal and the wireless communication signal input from the mixer 11 to a predetermined power and outputs the amplified signal to the directional coupler 28.

  The directional coupler 28 distributes the power of the ranging signal and the wireless communication signal input from the transmission amplifier 12, outputs most of the power to the transmission antenna 13, and part of the power to the ranging unit 6. Output. For example, the power distribution ratio is set to 9: 1. Here, the gain of the transmission amplifier 12 is determined so that the power of the signal output from the directional coupler 28 to the transmission antenna 13 becomes the transmission power. The transmission antenna 13 radiates the distance measurement signal and the wireless communication signal input from the directional coupler 28 toward the vehicle 3.

FIG. 9 is a diagram illustrating a time change of a signal radiated from the transmission antenna 13. It can be seen that, as the distance measurement signal periodically changes its frequency, the wireless communication signal also changes periodically. Furthermore, the frequency difference between the distance measurement signal and the radio communication signal is constant at f _IF regardless of time.

  The distance measuring unit 6 includes a signal processing unit 14, a BPF 29, a power / phase comparator 30, a BPF 18, a low noise amplifier 19, and a receiving antenna 20. The BPF 29 passes only the ranging signal among the transmission signals distributed by the directional coupler 28 of the transmission unit 5 and supplies it to the power / phase comparator 30. On the other hand, the reflected distance measurement signal (LO ′) and the reflected wireless communication signal (RF ′) reflected by the vehicle 2 are received by the receiving antenna 20, amplified by the low noise amplifier 19, and then supplied to the BPF 18. The The BPF 18 passes only the reflection distance measurement signal and supplies it to the power / phase comparator 30 as in the first embodiment.

The power / phase comparator 30 compares the transmission distance measurement signal input from the BPF 29 with the reflection distance measurement signal input from the band pass filter 18, and reflects the distance measurement signal with respect to the transmission distance signal power. The ratio of power (reflection distance signal power / transmission distance signal power: S21) and the phase change from the transmission distance measurement signal to the reflection distance measurement signal are measured for each period and output to the signal processing unit 14. To do. FIG. 10 shows S21 (reflection distance signal power / transmission distance signal power) measured by the power / phase comparator 30 and the phase change. The measured frequency range is a range f _LO1 ~f _LO2 distance measurement signal output from the voltage controlled oscillator 10.

  The signal processing unit 14 performs inverse Fourier transform on the measurement data input from the power / phase comparator 30 to calculate the reflected power with respect to the time axis. FIG. 11 is a diagram illustrating the reflected power calculated by the signal processing unit 14. The earliest reflected wave (hereinafter referred to as the first reflected wave) is the reflection from the vehicle 3, and the subsequent reflected wave is from another vehicle or another reflector. Therefore, by measuring the arrival time t of the first reflected wave, the relative distance can be obtained from Equation (3).

Moreover, since the calculation data of FIG. 11 is obtained for every sawtooth wave (every T time), the time passage of the first reflected wave can be observed. If the arrival time of the first reflected wave observed after T time is t + Δt, the relative velocity at this time is
v = (c / 4) × (Δt / T) (4)
Is required.

  The configuration of the reception-side radio device 4 mounted on the vehicle 3 according to the second embodiment is the same as that of the first embodiment.

  As described above, by using the distance measuring system and the wireless communication system, the reflected waves from the vehicle 3 and other reflecting objects can be separated, and more accurate relative distance and relative velocity can be measured. Is.

1 is a schematic system diagram to which an embodiment of the present invention is applied. It is a block diagram of the transmission side radio | wireless machine of 1st embodiment of this invention. It is a figure which shows the radiation signal radiated | emitted from the transmission side radio | wireless machine of FIG. FIG. 3 is a frequency characteristic diagram of a BPF 18 mounted on the transmission-side radio in FIG. 2. It is a figure which shows the input signal of the delay time measurement part 16 mounted in the transmission side radio | wireless machine of FIG. The block diagram of the receiving side radio | wireless machine of 1st embodiment of this invention. It is a figure which shows the received signal of the receiving side radio | wireless machine of FIG. 6, and the output signal of the square detector 25. FIG. It is a block diagram of the transmission side radio | wireless machine of 2nd embodiment of this invention. It is a figure which shows the radiation signal radiated | emitted from the transmission side radio | wireless machine of FIG. It is a figure which shows the frequency characteristic measured with the electric power and phase comparator 30 of FIG. It is a figure which shows the reflected wave measured by the signal processing part 14 of FIG.

Explanation of symbols

1,3 Vehicle
2 Transmitter radio
4 Receiver radio
5 Transmitter
6 Distance measuring unit 7,22 Control unit
8 Transmission information signal generator
9 Frequency Modulated Pulse Signal Generator 10 Voltage Controlled Oscillator 11, 15 Mixer 12 Transmitting Amplifier 13 Transmitting Antenna 14 Signal Processing Unit 16 Delay Time Measuring Unit 17 Frequency Discriminator 18, 29 BPF
19, 24 Low noise amplifier 20, 23 Receiving antenna 21 Receiving unit 25 Square detector 26 Received signal processing unit 27 Frequency modulation sawtooth wave generator 28 Directional coupler 30 Power / phase comparator

Claims (9)

A radar system for measuring relative distance and relative velocity,
The frequency-modulated measurement signal and the transmission information signal for measuring the relative distance and the relative speed are converted into a radio frequency band communication signal using the frequency-modulated measurement signal as a local signal. A transmitter for transmitting the communication signal in the radio frequency band and the measurement signal so that the frequency difference between these signals is constant regardless of time ;
A receiving unit that receives the communication signal and the measurement signal transmitted from a counterpart transmission unit, and detects the transmission information signal by square detection of the received communication signal and the measurement signal;
A distance measurement unit that compares the measurement signal received by reflection from a reflection object and the measurement signal transmitted from the transmission unit, and measures a relative distance and a relative speed with the reflection object,
A radar system comprising:   The radar system according to claim 1, wherein the measurement signal is a signal frequency-modulated by a periodic pulse signal.   2. The radar system according to claim 1, wherein the measurement signal is a signal frequency-modulated by a periodic sawtooth signal.   The distance measuring unit includes a band pass filter that allows only the received measurement signal to pass therethrough, and compares the output of the band pass filter with the measurement signal transmitted from the transmission unit, and the reflector The radar system according to claim 1, wherein a relative distance and a relative speed are measured. A transmitter in a radar system that measures relative distance and relative velocity,
The frequency-modulated measurement signal and the transmission information signal for measuring the relative distance and the relative speed are converted into a radio frequency band communication signal using the frequency-modulated measurement signal as a local signal. A transmitter comprising: a transmitter that transmits the communication signal in the radio frequency band and the measurement signal so that the frequency difference between the two signals is constant regardless of time .   6. The transmitter according to claim 5, wherein the measurement signal is a signal frequency-modulated by a periodic pulse signal.   6. The transmitter according to claim 5, wherein the measurement signal is a signal frequency-modulated by a periodic sawtooth signal.   The transmitter compares the measurement signal received by reflection from a reflector and the measurement signal transmitted from the transmitter, and measures a relative distance and a relative speed with respect to the reflector. The transmitter according to claim 5, further comprising a unit. A frequency-modulated measurement signal and a transmission information signal for measuring relative distance and relative speed are converted into a communication signal in a radio frequency band using the frequency-modulated measurement signal as a local signal, A receiver in a radar system having a transmitter for transmitting the communication signal in the radio frequency band and the measurement signal so that the frequency difference between the two signals is constant regardless of time ,
Detecting means for receiving the communication signal and the measurement signal transmitted from a partner transmitter and detecting the transmission information signal by square detection of the received communication signal and the measurement signal; A receiver characterized by that.

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