JP3514419B2 - FM-CW radar device and method for calculating distance / relative speed in FM-CW radar device - 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-CW radar device and a method for calculating a distance / relative velocity in an FM-CW radar device, and more specifically, to a frequency change amount (frequency sweep velocity) of a frequency-modulated signal per unit time. The frequency change amount per unit time (frequency sweep speed)
The present invention relates to an FM-CW radar device and a method for calculating a distance / relative velocity in an FM-CW radar device, in which the distance / relative velocity of an object is obtained based on the above.

[0002]

2. Description of the Related Art An FM-CW radar device that emits a transmission wave whose frequency changes linearly with time and measures the distance from the difference (beat frequency) between the instantaneous frequencies of the transmission wave and the reception wave is relatively It is suitable for detecting short distances and is used for measuring the distance between automobiles and the distance to obstacles.

FIG. 1 is an explanatory view showing the relationship between the transmitted wave, the received wave and the beat frequency when the object is stationary (when there is no relative velocity). The case where the object is stationary includes the case where the object and the FM-CW radar device are moving in the same direction at the same speed. When the distance to the object is R, the time until the transmitted wave TS is reflected by the object and returns can be obtained by dividing the round-trip distance 2R by the speed of light C, and the time is 2R / C. Is. Since the speed of light C is 3 × 10 8 meters / second, if the distance to the object is 150 meters, the time required for the transmitted wave TS to return as the received wave RS is 1 microsecond.

The lower limit frequency of the transmission wave TS is f1, the transmission wave T
The upper limit frequency of S is f2 and the center frequency of the transmission wave TS is f0.
(F0 = (F1 + f2) / 2), the frequency deviation width of the transmission wave TS is ΔF (ΔF = f2-f1), and the frequency is monotonically increased from the lower limit frequency f1 to the upper limit frequency f2 in the frequency increasing period T / 2. Frequency drop period T / 2
In the case where the frequency is monotonically decreased from the upper limit frequency f2 to the lower limit frequency f1 and a modulation wave whose frequency changes in a triangular wave shape is used as the transmission wave TS, the transmission wave TS and the distance R
The beat frequency fr of the reflected signal (received signal) RS from the target object is: fr = (2R / C) × {ΔF / (T / 2)}. In the above equation, (2R / C) is the time until the transmitted wave TS returns as the received wave RS, and {ΔF /
(T / 2)} is the frequency change amount of the transmission wave TS per unit time.

For example, in an FM-CW radar device using millimeter wave radio waves having a center frequency f0 = 60 GHz, a frequency deviation width ΔF = 400 MHz (lower limit frequency f1 = 59.8 GHz, upper limit frequency f2 = 60). .2
Gigahertz), frequency rising period T / 2 = frequency falling period = 200 microseconds, the distance to the object is 1
If it is 50 meters, the beat frequency fr will be 2 MHz. Since the frequency change amount {ΔF / (T / 2)} of the transmission wave TS per unit time under this condition is 2 MHz / microsecond, there is a time difference of 1 microsecond between the transmission wave TS and the reception wave RS. If so, the beat frequency fb becomes 2 MHz. If the distance to the object is 75 meters, the beat frequency fb is 1 megahertz, and if the distance to the object is 15 meters, the beat frequency fb is 100 kilohertz. As described above, the beat frequency fb is a frequency proportional to the distance R to the object, and therefore the transmitted wave TS
If the frequency change amount {ΔF / (T / 2)} per unit time is known, the distance of the object can be obtained based on the detected beat frequency fb.

Since the frequency change amount per unit time in the frequency rising period and the frequency change amount per unit time in the frequency falling period are set to be equal, when the object is stationary (when there is no relative speed) Includes the beat frequency fbup during the frequency rising period and the beat frequency f during the frequency falling period.
It becomes equal to bdown.

2 and 3 are explanatory views showing the relationship between the transmitted wave, the received wave and the beat frequency when the object is moving (when there is a relative velocity). If the target object is moving, the target object is stationary but FM-C
This also includes the case where the W radar device side is moving. When there is a relative velocity between the object and the FM-CW radar device,
The reflected wave (received wave) receives the Doppler effect. Due to the Doppler effect, the frequency of the reflected wave (received wave) deviates from the frequency of the transmitted wave by the Doppler frequency. The object is FM
-When moving toward the CW radar device side,
The frequency of the reflected wave (received wave) is higher than the frequency of the transmitted wave by the Doppler frequency. When the object is moving away from the FM-CW radar device, the frequency of the reflected wave (received wave) becomes lower than the frequency of the transmitted wave by the amount of the Doppler frequency.

The Doppler frequency fd is fd = 2 · vr · fTS / C, where vr is the relative speed in the direction connecting the FM-CW radar device and the object, fTS is the frequency of the transmitted wave TS, and C is the speed of light. Becomes Since the FM-CW radar device uses a modulation signal as a transmission wave, the Doppler frequency changes according to the instantaneous frequency of the modulation wave. Since the frequency deviation amount ΔF is small with respect to the center frequency f0 and the transmission wave having the frequency deviation around the center frequency f0 is transmitted, it is considered here that the transmission frequency fTS = the center frequency f0. The transmission frequency fTS (center frequency f0) is 60 GHz, and the relative speed vr is 10 m / sec (36 km / sec.
Hour), the Doppler frequency fd becomes 4 kilohertz.

FIG. 2 shows the relationship between the transmitted wave, the received wave and the beat frequency when the object is moving toward the FM-CW radar device. In FIG. 2, the dotted line shows the received wave when the relative velocity is zero. When the relative speed is positive (here, the direction in which the object approaches) is positive, the frequency of the received wave RS is increased by the Doppler frequency fd. Therefore, the beat frequency fbup in the frequency increasing period is a frequency lower than the beat frequency fr corresponding to the distance by the Doppler frequency fd. That is, the beat frequency fbup in the frequency increasing period is fbup = fr-fd. Also, the beat frequency f in the frequency falling period
bdown has a frequency higher by the Doppler frequency fd than the beat frequency fr corresponding to the distance. That is, the beat frequency fbdown in the frequency falling period
Becomes fbdown = fr + fd.

Therefore, when the beat frequency fbdown in the frequency falling period is higher than the beat frequency fbup in the frequency rising period, the relative speed is positive (here, the direction in which the object approaches is positive). Then, by halving the sum of the beat frequency fbup in the frequency rising period and the beat frequency fbdown in the frequency falling period, the beat frequency fr corresponding to the distance can be obtained. fr = (fbup + fbdown) / 2 Further, the Doppler frequency fd can be obtained by halving the difference between the beat frequency fbup in the frequency rising period and the beat frequency fbdown in the frequency falling period. fd = (fbup-fbdown) / 2

If the frequency change amount {ΔF / (T / 2)} of the transmitted wave TS per unit time is known, the distance of the object can be obtained based on the beat frequency fr corresponding to the distance. . Further, the relative speed can be calculated based on the Doppler frequency fd.

FIG. 3 shows the relationship between the transmitted wave, the received wave and the beat frequency when the object is moving in the direction away from the FM-CW radar device side. In FIG. 3, the dotted line shows the received wave when the relative velocity is zero. When the relative speed is negative (here, the direction in which the object approaches is positive), the frequency of the received wave RS is lowered by the Doppler frequency fd. Therefore, the beat frequency fbup in the frequency rising period is higher than the beat frequency fr corresponding to the distance by the Doppler frequency fd. That is, fbup = fr + fd. Also, the beat frequency f in the frequency falling period
bdown is a frequency that is lower than the beat frequency fr corresponding to the distance by the Doppler frequency fd. That is, fbdown = fr−fd.

Therefore, when the beat frequency fbdown in the frequency decreasing period is lower than the beat frequency fbup in the frequency increasing period, the relative speed is negative (here, the direction in which the object approaches is positive). Then, by halving the sum of the beat frequency fbup in the frequency rising period and the beat frequency fbdown in the frequency falling period, the beat frequency fr corresponding to the distance can be obtained. fr = (fbup + fbdown) / 2 Further, the Doppler frequency fd can be obtained by halving the difference between the beat frequency fbup in the frequency rising period and the beat frequency fbdown in the frequency falling period. fd = (fbup-fbdown) / 2

Then, if the frequency change amount {ΔF / (T / 2)} of the transmitted wave TS per unit time is known, the distance of the object can be obtained based on the beat frequency fr corresponding to the distance. . Further, the relative speed can be calculated based on the Doppler frequency fd.

[0015]

As described above, the FM-
In the CW radar device, the frequency change amount (frequency sweep speed) {ΔF / (T / 2)} of the transmitted wave TS per unit time is an important item for obtaining the distance. Further, when the distance and the relative speed are obtained from the beat frequency fbup measured in the frequency rising period and the beat frequency fbdown measured in the frequency falling period, the frequency change amount per unit time in the frequency rising period and the unit in the frequency falling period are calculated. It is necessary that the amount of frequency change per unit time is the same.

However, due to variations in the frequency-designated voltage-oscillation frequency characteristics of the voltage controlled oscillator (VCO) that generates the modulation signal, the amount of frequency change per unit time varies, resulting in a predetermined (designed) frequency per unit time. The amount of change may not be obtained. In addition, the frequency change amount per unit time may change due to changes in the frequency designation voltage-oscillation frequency characteristic over time. Further, the frequency designating voltage signal may fluctuate due to the change with time of the characteristic of the circuit unit that generates the frequency designating voltage signal, and as a result, the frequency change amount per unit time may vary. By generating a staircase-shaped pseudo-triangular waveform signal using a D / A converter or the like, and removing the high-frequency component from this signal through a low-pass filter,
In the case of the configuration for generating the frequency designation voltage signal of the angular waveform, D
The amount of frequency change per unit time may fluctuate as the output cycle of digital data supplied to the A / A converter fluctuates.

FIG. 4 and FIG. 5 are explanatory diagrams showing an example of fluctuations in frequency sweep of a transmission wave. As shown in FIG. 4, when the frequency deviation amount per unit time becomes small as shown by the dotted line with respect to the designed waveform of the transmitted wave TS (shown by the solid line), the shifted transmission wave and reception When the distance to the object is calculated based on the instantaneous frequency difference (beat frequency) with the wave and the designed frequency deviation amount ΔF, a distance shorter than the actual distance is calculated. When the frequency deviation per unit time becomes large as shown by the chain line, the instantaneous frequency difference (beat frequency) between the shifted transmission wave and reception wave
If the distance to the object is calculated based on the designed frequency deviation ΔF, a distance longer than the actual distance will be calculated. Further, as shown by the chain double-dashed line in FIG. 5, when the frequency deviation amount per unit time in the frequency rising period and the frequency deviation amount per unit time in the frequency falling period are different, the distance and the relative speed are I can't get it right.

As described above, if the frequency change amount of the actually transmitted modulated signal per unit time deviates from the designed value, an accurate distance cannot be obtained. Further, if the amount of frequency change per unit time in the frequency rising period and the amount of frequency change per unit time in the frequency falling period are different, the distance of the object having the relative speed and the relative speed cannot be obtained correctly. .

If high precision and long-term operation stability are required (high reliability is required) by the voltage controlled oscillator (VCO) and the circuit section that generates the frequency designation voltage signal, the FM-CW radar device is expensive. Become.

The present invention has been made to solve such a problem, and measures the frequency change amount (frequency sweep speed) of the frequency-modulated signal per unit time, and measures the measured frequency change amount per unit time (frequency Provided is an FM-CW radar device and a distance / relative velocity calculation method for an FM-CW radar device, which can accurately calculate the distance and relative velocity by calculating the distance / relative velocity of an object based on (sweep velocity). The purpose is to do.

[0021]

In order to solve the above problems, an FM-CW radar device according to the present invention is a frequency change amount measuring section for obtaining the frequency change amount of a modulated wave per unit time.
And the unit time measured by the frequency change amount measurement unit
Measured value storage unit that stores the amount of frequency change (measured value) per hit
And each frequency in the frequency rising period and frequency falling period
Number spectrum (beat frequency) and frequency change measurement
Based on the amount of frequency change per unit time supplied from the control unit
And the distance / phase for calculating the distance and relative speed of the object
And a frequency calculation unit, the frequency change amount measuring unit
Frequency change amount per unit time in measured value storage
If (measured value) is stored, the amount of change in each frequency
It is characterized in that the (measured value) is supplied to the distance / relative speed calculation unit .

In order to solve the above problems, the F according to the present invention
The M-CW radar device uses the frequency of the modulated wave per unit time.
The frequency change amount measurement section for obtaining the change amount and the frequency change amount measurement
Unit time in the frequency rising period measured by the constant section
Frequency change amount (measured value) per period, during frequency drop period
Storing frequency change amount (measured value) per unit time
Measured value storage, frequency rising period and frequency falling period
Frequency spectrum (beat frequency) between and
The frequency rise period supplied from the wavenumber change measurement unit and the
The frequency change amount per unit time during the frequency falling period
Distance that calculates the distance and relative speed of the object based on
Equipped with a separation / relative speed calculation unit, the frequency change amount measurement unit is
The measured value storage section stores the cycle per unit time during the frequency rising period.
Wave amount change (measured value), unit time during frequency falling period
When the frequency change amount (measured value) per unit is stored
Shows the amount of each frequency change (measured value) in distance / relative
It is characterized in that it is supplied to the speed calculator. Also unit time
The amount of change in frequency (design value) is registered in advance,
Equipped with a design value storage unit, the frequency change amount measurement unit stores the measured value
Changes in frequency per unit time during frequency rising period
Amount (measured value), per unit time in the frequency falling period
If the frequency change amount (measured value) is not stored, the setting
Frequency change per unit time stored in measured value storage
It is characterized in that the quantity (design value) is supplied to the distance / relative speed calculation unit .

The FM-CW radar device according to the present invention is
Measured by the frequency change amount measurement unit, equipped with a frequency change amount measurement unit that determines the frequency change amount per unit time during the frequency rising period of the modulated wave and the frequency change amount per unit time during the frequency falling period of the modulated wave. When the frequency change amount per unit time in the frequency rising period and the frequency change amount per unit time in the frequency falling period measured by the frequency change amount measuring unit are the same,
The relative velocity was calculated based on the difference between the beat frequency of the frequency rising period and the beat frequency of the frequency falling period, and the beat frequency related to the distance was calculated based on the sum of the beat frequency of the frequency rising period and the frequency falling period. The distance of the object is obtained based on the beat frequency related to the distance and the frequency change amount per unit time measured by the frequency change amount measuring unit, and the distance per unit time in the frequency rising period measured by the frequency change amount measuring unit is calculated. If the frequency change amount and the frequency change amount per unit time in the frequency falling period measured by the frequency change amount measuring unit are different, either or both of the frequency rising period beat frequency and the frequency falling period beat frequency are set. Corrected frequency change per unit time during frequency rising period and per unit time during frequency falling period Obtain a correction beat frequency when the frequency change amount is equal, and obtaining the relative distance and the relative velocity of the object based on the frequency rising period correction beat frequency and the frequency falling period correction beat frequency.

The FM-CW radar device according to the present invention is
The frequency change amount measurement unit is provided, which determines the frequency change amount per unit time during the frequency rising period of the modulated wave and the frequency change amount per unit time during the frequency falling period of the modulated wave. Based on the ratio of the frequency change amount per unit time in the frequency rising period to the preset reference frequency change amount per unit time, the frequency rising period beat frequency is the preset reference frequency change amount per unit time. If there is, it is corrected to the rising frequency beat frequency, and based on the ratio of the frequency change amount per unit time in the frequency decrease period obtained by the frequency change amount measurement unit to the preset reference frequency change amount per unit time. Frequency falling period The beat frequency is compensated to the decreasing period beat frequency when it is the preset amount of frequency change per unit time. And, and obtaining the relative distance and the relative velocity of the object based on the corrected frequency increasing period correcting beat frequency and corrected frequency falling period correction beat frequency.

The frequency change amount measuring unit is characterized in that the frequency change amount per unit time of the modulated wave is obtained based on the beat frequency of the object whose distance is known and whose relative velocity is zero.

The frequency change amount measuring units are first and second objects which are separated by a known distance and have a relative speed of zero, respectively. It is characterized in that the frequency change amount of the modulated wave per unit time is obtained based on the beat frequency.

The frequency change amount measuring unit separates the first beat frequency of the object having a relative velocity of zero detected at the first point and the known distance from the first point toward the object. It is characterized in that the frequency change amount of the modulated wave per unit time is obtained based on the second beat frequency of the object detected at the second point.

The frequency change amount measuring unit obtains the frequency change amount of the modulated wave per unit time based on the beat frequency of the delayed signal and the modulated wave obtained by delaying the modulated wave through the delay means having a known delay time. It is characterized by

The distance / relative velocity calculation method in the FM-CW radar device according to the present invention is such that the frequency change amount per unit time in the frequency rising period of the modulated wave and the frequency per unit time in the frequency falling period of the modulated wave. If the amount of change in frequency measured per unit time during the rising frequency period and the amount of frequency change per unit time measured during the falling frequency period are the same, the The relative speed is calculated based on the difference between the rising frequency beat frequency and the frequency falling period beat frequency, and the beat frequency related to the distance is calculated based on the sum of the frequency rising period beat frequency and the frequency falling period beat frequency. The distance of the object based on the beat frequency and the measured frequency change per unit time. If the amount of frequency change per unit time in the measured frequency rising period and the amount of frequency change per unit time in the measured frequency falling period are different, the beat frequency of the frequency rising period and the beat frequency of the frequency falling period By correcting one or both of the above, and when the frequency change amount per unit time in the frequency rising period and the frequency change amount per unit time in the frequency falling period are equal, the correction beat frequency is calculated, and the frequency rising period correction beat It is characterized in that the relative distance and relative speed of the object are obtained based on the frequency and the frequency falling period correction beat frequency.

The distance / relative velocity calculation method in the FM-CW radar device according to the present invention is such that the frequency change amount per unit time in the frequency rising period of the modulated wave and the frequency per unit time in the frequency falling period of the modulated wave. After determining the amount of change and the amount of change in each frequency, the beat frequency in the frequency rising period is calculated based on the ratio of the frequency change amount per unit time in the measured frequency rising period to the preset reference frequency change amount per unit time. When the frequency change amount per unit time of the preset reference is corrected to the rising frequency beat frequency, the measured frequency change amount per unit time during the falling period of the frequency and the frequency of the preset reference frequency per unit time Frequency fall period based on the ratio to the amount of change Beat frequency is set as a reference frequency change per unit time In the case where the relative frequency and the relative frequency and the relative velocity of the object are calculated based on the corrected frequency rising period correction beat frequency and the corrected frequency falling period correction beat frequency, To do.

The FM-CW radar device according to the present invention is
Since the frequency change amount measuring unit for obtaining the frequency change amount per unit time of the modulated wave is provided, and the distance for the object is obtained using the frequency change amount per unit time obtained by the frequency change amount measuring unit, Due to variations in the frequency-specified voltage-oscillation frequency characteristics of the voltage-controlled oscillator (VCO) that generates the modulation signal and changes over time, the amount of frequency change per unit time of the actually transmitted modulation signal deviates from the designed value. Even in the case, the distance / relative velocity of the object can be calculated based on the actually measured frequency change amount per unit time. Therefore, the distance and the relative speed can be accurately obtained.

A method of calculating a distance / relative velocity in an FM-CW radar device according to the present invention measures an amount of frequency change of a modulated wave per unit time, and based on the measured amount of frequency change per unit time. Since the distance and the relative speed are calculated, the distance and the relative speed can be accurately obtained.

For example, the center frequency f of the modulated wave (transmission wave)
0 is 60 GHz, and the frequency change amount per unit time in the frequency rising period and the frequency change amount per unit time in the frequency falling period are both 300 kilohertz / microseconds (design value). Is 150m, relative speed + 10m /
When an object of second (object approaching at 10 m / s) is detected, reflected wave and modulated wave (transmitted wave) from the object
And the beat frequency (difference in instantaneous frequency) between the beat frequency fbup in the frequency rising period is 296 kHz,
The beat frequency fbdown in the frequency falling period is 3
It becomes 04 kilohertz.

Beat frequency fb in the frequency rising period
up and beat frequency fbdow in the frequency falling period
By halving the sum of n and {(296 + 304) /
2}, the beat frequency fr related to the distance is found to be 300 kilohertz, and the beat frequency fr related to the distance is determined.
(Fr = 300 kilohertz) and the frequency change amount per unit time (300 kilohertz / microsecond), the distance of the object can be obtained (accurately, the time difference between the transmitted wave and the received wave can be obtained, and the time difference and the speed of light C). Distance can be obtained from).

Beat frequency fb in the frequency rising period
up and beat frequency fbdow in the frequency falling period
By halving the difference from n, {(296-304) /
2}, it is found that the Doppler frequency fd is 4 hertz, and the relative speed when the Doppler frequency fd (fd = 4 hertz) is 10 m / sec at the center frequency f0 (f0 = 60 GHz). .

When both the frequency change amount per unit time in the frequency rising period and the frequency change amount per unit time in the frequency falling period of the actually transmitted modulated signal are 330 kilohertz / microsecond, the distance is 1
The beat frequency fbup of a target object of 50 meters and a relative speed of +10 meters / second (a target object approaching at a speed of 10 m / s) in the frequency rising period is 326 kHz, and the beat frequency fbdown in the frequency falling period is 33.
It will be 4 kilohertz.

In this case, the difference between the beat frequency fbup in the frequency rising period and the beat frequency fbdown in the frequency falling period is halved {(326-3
34) / 2}, the Doppler frequency fd is found to be 4 hertz, and the center frequency f0 (f0 = 60 gigahertz)
It is found that the relative speed is 10 meters / second when the Doppler frequency fd (fd = 4 Hertz) is set in.

Beat frequency fb in the frequency rising period
up and beat frequency fbdow in the frequency falling period
By halving the sum of n and {(326 + 334) /
2}, it is found that the beat frequency fr related to the distance is 330 kilohertz. Here, the frequency change amount per design time of 300 kilohertz / microsecond (design value)
When the distance of the target object is obtained by using, the distance becomes 165 meters, which causes an error.

Therefore, if the frequency change amount per unit time of the modulation signal actually transmitted is calculated, the beat frequency fr = 330 kHz related to the distance and the actual frequency change amount per unit time (330 kHz / micro). Second), the distance (150 meters) of the object can be accurately obtained. Further, based on the ratio of the actual frequency change amount per unit time (330 kilohertz / microsecond) and the designed frequency change amount per unit time (300 kilohertz / microsecond), the modulated wave per unit time After converting the beat frequency fr related to the distance when the frequency change amount is 330 kilohertz / microsecond into the beat frequency fr related to the distance when the frequency change amount per design time is 300 kilohertz / microsecond, The distance can be obtained from the converted (corrected) beat frequency fr related to the distance and the designed frequency change amount per unit time.

The frequency change amount per unit time in the frequency rising period of the actually transmitted modulated signal is, for example, 290.
When the frequency change amount per unit time in the frequency falling period of the actually transmitted modulated signal becomes, for example, 330 kilohertz / microsecond in kilohertz / microsecond,
The beat frequency fbup of the object having a distance of 150 meters and a relative speed of +10 meters / second (the object approaching at a speed of 10 m / sec) in the frequency increasing period is 286 kHz, and the beat frequency fbdown in the frequency decreasing period.
Will be 334 kilohertz. Here, the frequency change amount of the modulation signal actually transmitted is the designed value (300 kHz /
Microseconds), the distance is 15
It becomes 5 meters, and an error occurs with the actual distance of 150 meters. Further, the relative speed is 120 meters / second, which is significantly different from the actual relative speed of 10 meters / second.

Therefore, the frequency change amount per unit time during the frequency rising period (290 kHz / microsecond)
The beat frequency fbup (286 kilohertz) detected by the frequency change amount per unit time (290 kilohertz / microsecond) in the frequency rising period, based on the ratio between the design frequency change amount (300 kilohertz / microsecond). The designed frequency change (300 kHz /
The frequency rise period correction beat frequency = 2 by converting (correcting) to the beat frequency in the case of (microsecond).
95.9 kilohertz.

Next, based on the ratio of the frequency change amount (330 kHz / microsecond) per unit time in the frequency decrease period to the designed frequency change amount (300 kHz / microsecond), the unit in the frequency decrease period is set. The beat frequency fbdown (334 kHz) detected by the frequency change amount per hour (330 kHz / microsecond) is converted into the beat frequency when the designed frequency change amount (300 kHz / microsecond) is obtained (correction). By doing so, the frequency falling period correction beat frequency is set to 303.6 kHz.

Based on the frequency rising period correction beat frequency = 295.9 kHz and the frequency falling period correction beat frequency = 303.6 kHz and the designed frequency change amount (300 kHz / microsecond), the distance and relative When the speed is calculated, the distance is 149.9 meters and the relative speed is 9.6 meters / second, and the distance and the relative speed can be calculated with high accuracy.

When the frequency change amount per unit time is different between the frequency rising period and the frequency falling period, the frequency change amount per unit time during the frequency rising period and the frequency change amount per unit time during the frequency falling period. The beat frequency detected in the frequency rising period is converted (corrected) into the beat frequency in the case of the amount of frequency change per unit time in the frequency falling period based on the ratio of The distance and the relative velocity may be obtained based on the beat frequency in the frequency falling period and the frequency change amount per unit time in the frequency falling period.

When the frequency change amount per unit time is different between the frequency rising period and the frequency falling period, the frequency change amount per unit time in the frequency rising period and the frequency change amount per unit time in the frequency falling period. The beat frequency detected in the frequency falling period is converted (corrected) into the beat frequency in the case of the frequency change amount per unit time in the frequency rising period based on the ratio of The distance and the relative velocity may be obtained based on the beat frequency in the frequency rising period and the frequency change amount per unit time in the frequency rising period.

When the relative velocity is zero, the distance can be accurately obtained based on the beat frequency detected in the frequency rising period and the frequency change amount per unit time in the frequency rising period. When the relative velocity is zero, the distance can be accurately obtained based on the beat frequency detected in the frequency falling period and the frequency change amount per unit time in the frequency falling period.

The frequency change amount of the modulated wave (transmitted wave) actually transmitted per unit time can be obtained based on the beat frequency of the object whose distance is known and whose relative velocity is zero. If the distance is known, the time required for the radio wave to travel a distance twice the known distance (time difference between the transmitted wave and the received wave) is obtained, and the amount of frequency change per unit time is calculated from the beat frequency and the time. I want it.

The frequency change amount of the modulated wave (transmission wave) actually transmitted per unit time is the first and second objects separated by a known distance, and the relative speed is zero. It can be obtained based on the first and second beat frequencies of the first and second objects.

The amount of change in frequency of the modulated wave (transmitted wave) actually transmitted per unit time is the first beat frequency relating to the object whose relative velocity detected at the first point is zero, and It can be determined based on the second beat frequency of the object detected at the second point separated from the first point by the known distance toward the object.

The frequency change amount of the modulated wave (transmitted wave) actually transmitted per unit time is the beat frequency between the delayed signal and the modulated wave obtained by delaying the modulated wave through the delay means of which the delay time is known. Can be determined based on.

[0051]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 6 shows an FM- according to the present invention.
It is a block diagram of a CW radar device. FIG. 6 shows an example of an in-vehicle millimeter-wave band FM-CW radar device. An FM-CW radar device 1 according to the present invention includes an FM signal generator 2, a sweep controller 3, a power distributor 4, a circulator 5, a transmitter / receiver antenna 6, a mixer (mixer) 7, and a delay unit. Means 8, switch circuit 9, A / D
A conversion unit 10, a frequency analysis (FFT: fast Fourier transform) unit 11, a distance / relative speed calculation unit 12, a frequency change amount measurement unit 13, a design value storage unit 14, an actual measurement value storage unit 15, and a running. Distance detection unit 16 and measurement condition input unit 17
And a display control unit 18 and an image display device 19.

The FM signal generator 2 generates an FM signal 2a that is frequency-modulated based on the frequency designation voltage signal 3a supplied from the sweep controller 3. The FM signal generator 2
Equipped with a voltage controlled oscillator (VCO) using a Gunn diode, and an F in the millimeter wave band (for example, center frequency 60 GHz)
The M signal 2a is generated. The FM signal generator 2 is a FET
A voltage controlled oscillator (VCO) configured by combining a (field effect transistor) and a variable capacitance diode generates a quasi-millimeter wave band signal and frequency-multiplies it to generate a millimeter wave band FM signal 2a. You may

The sweep control section 3 has a frequency designating voltage signal 3a in which the frequency designating voltage changes in a triangular wave shape in a predetermined cycle.
Is generated and supplied to the FM signal generation unit 2 to generate the FM signal 2a including the frequency rising period and the frequency falling period, and the sweep information 3b indicating whether it is the frequency rising period or the frequency falling period. Is output.

The FM signal 2a output from the FM signal generating section 2 is distributed via the power distributor 4 constituted by using a directional coupler or the like, and one signal 4a is transmitted as a transmission signal via the circulator 5. Is supplied to the transmitting / receiving antenna 6 and is radiated from the transmitting / receiving antenna 6 as a transmission wave TS. The other signal 4b is supplied to the mixing unit 7 as a local signal (local signal). Further, the other signal 4b is supplied to one input terminal of the switch circuit 9 via the delay means 8. The delay means 8 is composed of a delay line having a predetermined delay time (for example, 1 microsecond).

The reception wave RS is received by the transmission / reception antenna 6, converted into a reception signal, and supplied to the mixing section 7 via the circulator 5 and the switch circuit 9. The mixing unit 7 mixes the reception signal and the local signal (a part of the transmission signal), and outputs a difference frequency signal between the frequency of the reception signal and the frequency of the transmission signal as a beat signal 7a. Beat signal 7
a is supplied to the A / D conversion unit 10. A / D converter 10
Outputs the digital beat signal 10a by A / D converting the beat signal 7a. The digital beat signal 10 a is supplied to the frequency analysis (FFT) unit 11.

The frequency analysis (FFT) unit 11 discriminates the frequency rising period and the frequency falling period based on the sweep information 3b, performs frequency analysis for each period, and obtains the frequency spectrum (beat frequency) 11a for each period. It is output with the correspondence with. Frequency spectrum (beat frequency) 11a
Is supplied to the distance / relative speed calculation unit 12 and the frequency change amount measurement unit 13.

The distance / relative velocity calculation unit 12 operates in each frequency spectrum (beat frequency) 11a in the frequency rising period and the frequency falling period, and in the frequency rising period and the frequency falling period supplied from the frequency change amount measuring unit 13. Based on the frequency change amount 13a per unit time, the distance and the relative speed of the object are calculated, and the data 12a relating to the distance and the relative speed of the object obtained by the calculation are output.

The display control unit 18 generates an image representing the position, distance, relative speed, etc. of the object based on the data 12a relating to the distance and relative speed of the object supplied from the distance / relative speed calculation unit 12. Then, the generated image is displayed on the screen of the image display device 19. When the information 13b related to the frequency change amount measurement is supplied from the frequency change amount measurement unit 13, the display control unit 18 performs the image and the measurement for selecting the measurement condition based on the information 13b related to the frequency change amount measurement. Is generated and the generated image is displayed on the screen of the image display device 19. Image display device 19
Is composed of a CRT display device and a liquid crystal display device.

The amount of frequency change per unit time (design value) and the delay time of the delay means 8 (design value) are registered in the design value storage unit 14 in advance. Measured value storage unit 15
Is a frequency change amount per unit time (actually measured value) during the frequency rising period measured by the frequency change amount measuring unit 13, a frequency change amount per unit time (actually measured value) during the frequency falling period, and the delay unit 8 The measurement result of the delay time (measured value of the delay time) is stored. Measured value storage unit 1
5 is RA with EEPROM or battery backup
By using M or the like, each measured value is held even when the power of the FM-CW radar device 1 is cut off.

The traveling distance detector 16 is constructed by using a wheel rotation sensor or the like. The wheel rotation sensor is FM-C
The wheel rotation detection pulse signal 16a is output every time the wheels of the vehicle equipped with the W radar device 1 rotate by a predetermined angle. Then, the frequency change amount measurement unit 13 detects that the vehicle is in a stopped state based on the fact that the wheel rotation detection pulse signal 16a is not supplied for a predetermined time, or the number of pulses of the wheel rotation detection pulse signal 16a. Is calculated to calculate the number of rotations of the wheel, and the traveling distance of the vehicle is calculated based on a preset traveling distance per one rotation of the wheel.

The measurement condition input section 17 is constructed by using a keyboard or the like. The measurement condition input unit 17 includes an operation unit for starting measurement of the frequency change amount, an operation unit for selecting and setting measurement conditions, and the like. The measurement condition input unit 17 may be configured using a transparent touch panel arranged on the screen of the image display device 19.

The frequency change amount measuring section 13 stores the frequency change amount per unit time (measured value) in the frequency rising period and the frequency change amount per unit time (measured value) in the frequency falling period in the measured value storage unit 15. If not,
The frequency change amount per unit time (design value) stored in the design value storage unit 14 is supplied to the distance / relative speed calculation unit 12. The frequency change amount measuring unit 13 stores the frequency change amount (measured value) per unit time in the frequency rising period and the frequency change amount (measured value) per unit time in the frequency falling period in the measured value storage unit 15. In this case, the amount of change in each frequency (measured value) is used to calculate the distance / relative speed calculation unit 1
Supply to 2.

When a measurement request is supplied from the measurement condition input unit 17, the frequency change amount measurement unit 13 displays a menu screen for setting the measurement condition on the screen of the image display device 19 via the display control unit 18. Display it. There are four types of measurement conditions. The first measurement condition is that the amount of frequency change is measured using an object whose distance is known. The second measurement condition is to measure the frequency change amount using the two objects when the distance is known for the two objects. The third measurement condition is that the frequency change amount is measured by moving the vehicle toward the object. The fourth measurement condition is that the amount of frequency change is measured using a delay means.

When the first measurement condition is selected, the frequency change amount measuring unit 13 causes the image display device 19 to display a screen prompting the user to input the distance to the object. When the distance from the measurement condition input unit 17 to the object is input, the frequency change amount measurement unit 13 starts measuring the frequency change amount. If the distance to the target when the frequency change amount is measured under the first measurement condition is predetermined, it is not necessary to input the distance to the target. In this case, it is necessary to store a predetermined distance to the target object in the design value storage unit 14 or the like in advance.

The frequency change amount measuring unit 13 confirms that the vehicle is in a stopped state based on the fact that the wheel rotation detection pulse signal 16a is not supplied from the traveling distance detecting unit 16 for a predetermined time. The frequency change amount measurement unit 13 determines that the beat frequency of the frequency increase period supplied from the frequency analysis (FFT) unit 11 does not change at different times, and that the frequency decrease supplied from the frequency analysis (FFT) unit 11 decreases. Confirm that the object is a stationary object based on the fact that the beat frequency of the period does not change at different times.

As described above, after confirming that there is no relative velocity between the FM-CW radar device 1 and the object, the frequency change amount measuring unit 13 determines the beat frequency in the frequency rising period and the distance to the object. Based on the above, the frequency displacement amount per unit time in the frequency rising period is obtained. Further, the frequency change amount measuring unit 13 obtains the frequency displacement amount per unit time during the frequency falling period based on the beat frequency during the frequency falling period and the distance to the object.

For example, when the distance to the object is 15 meters and the beat frequency of the object is 30 kHz in both the frequency rising period and the frequency falling period,
Since the frequency of the modulated wave changes by 30 kilohertz in the time (0.1 microsecond) that the radio wave travels back and forth over a distance of 15 meters, the frequency displacement of the modulated wave per unit time is 300 kilohertz / microsecond. I want to be there.

Then, the frequency change amount measuring unit 13 stores the obtained frequency displacement amount per unit time in each period in the measured value storage unit 15, respectively. The frequency change amount measuring unit 1
3, the frequency displacement amount per unit time of each period may be stored in the measured value storage unit 15 in association with the measurement condition.

When the second measurement condition is selected, the frequency change amount measuring unit 13 causes the image display device 19 to display a screen prompting the user to input the distance between the two objects. In addition, FM-CW
The radar device and the two objects are arranged on a straight line. When the distance between the two objects is input from the measurement condition input unit 17, the frequency change amount measurement unit 13 starts measuring the frequency change amount. If the distance between the objects when the frequency change amount is measured under the second measurement condition is predetermined,
There is no need to enter the distance between objects. In this case, the predetermined inter-object distance is set to the design value storage unit 14
It is necessary to store them in advance.

The frequency change amount measuring unit 13 confirms that the vehicle is in a stopped state based on the fact that the wheel rotation detection pulse signal 16a is not supplied from the traveling distance detecting unit 16 for a predetermined time. The frequency change amount measuring unit 13 confirms that the beat frequencies of the frequency rising period supplied from the frequency analysis (FFT) unit 11 do not change at different times, and the frequency supplied from the frequency analysis (FFT) unit 11. Based on the fact that each beat frequency in the falling period does not change at different times, it is confirmed that the object is a stationary object.

As described above, after confirming that there is no relative velocity between the FM-CW radar device 1 and the target object, the frequency change amount measuring unit 13 determines that the first target object detected in the frequency rising period. Based on the difference between the first beat frequency and the second beat frequency of the second object and the distance between the objects, the frequency displacement amount per unit time in the frequency rising period is obtained. Further, the frequency change amount measuring unit 13
Is a frequency increase based on the difference between the first beat frequency of the first object and the second beat frequency of the second object detected in the frequency decrease period, and the distance between the objects. The amount of frequency displacement per unit time during the period is calculated.

For example, when the distance between the objects is 30 meters and the difference between the first beat frequency of the first object and the second beat frequency of the second object is 60 kilohertz. , The time difference between the reflected wave from the first object and the reflected wave from the second object is 0.2 microseconds (30 meters × 2 / light speed), and modulation is performed during this 0.2 microsecond. Since the frequency of the wave changes by 60 kilohertz, the frequency displacement of the modulated wave per unit time is 30.
It is required to be 0 kilohertz / microsecond.

Then, the frequency change amount measuring unit 13 stores the obtained frequency displacement amount per unit time in each period in the measured value storage unit 15, respectively. The frequency change amount measuring unit 1
3, the frequency displacement amount per unit time of each period may be stored in the measured value storage unit 15 in association with the measurement condition.

When the third measurement condition is selected, the frequency change amount measuring unit 13 displays a message on the image display device 19 instructing to stop the vehicle at a position several tens meters away from an appropriate object. Display it on the screen. The frequency change amount measurement unit 13 confirms that the vehicle is in a stopped state based on the fact that the wheel rotation detection pulse signal 16a is not supplied from the traveling distance detection unit 16 for a predetermined time. The frequency change amount measurement unit 13 includes a frequency analysis (FFT) unit 11
The beat frequency of the frequency rising period that is supplied from is not changing at different times, and the frequency analysis (F
It is confirmed that the object is a stationary object based on the fact that the beat frequency of the frequency falling period supplied from the FT) unit 11 does not change at different times.

When confirming that the object is a stationary object, the frequency change amount measuring unit 13 determines the beat frequency in the frequency rising period and the beat frequency in the frequency falling period (beat frequency in each period at the first point) as follows. It is temporarily stored in the RAM or the like in the frequency change amount measuring unit 13. When the detection of the beat frequency of each period at the first point is completed, the frequency change amount measurement unit 13 displays a message instructing to move the vehicle toward the object to about half the distance to the object. The image is displayed on the screen of the image display device 19. The frequency change amount measuring unit 13 obtains the number of rotations of the wheel by integrating the number of pulses of the wheel rotation detection pulse signal 16a, and also obtains the traveling distance of the vehicle based on a preset traveling distance per one rotation of the wheel.

The frequency change amount measuring unit 13 confirms that the vehicle has stopped based on the fact that the wheel rotation detection pulse signal 16a is not supplied for a predetermined time. The frequency change amount measurement unit 13 determines that the beat frequency of the frequency rising period supplied from the frequency analysis (FFT) unit 11 does not change at different times, and the frequency analysis (FF
Based on the fact that the beat frequency of the frequency falling period supplied from the (T) unit 11 does not change at different times, it is confirmed again that the target object is a stationary object. ), The beat frequency in the frequency rising period and the beat frequency in the frequency falling period are obtained.

Then, the frequency change amount measuring unit 13
The difference between the beat frequency of the frequency rising period at the point and the beat frequency of the frequency rising period at the second point, and the first
The amount of frequency change per unit time in the frequency rising period is calculated based on the distance between the point and the second point, and the beat frequency of the frequency falling period at the first point and the beat frequency of the frequency falling period at the second point are calculated. And the distance between the first point and the second point, the frequency change amount per unit time in the frequency falling period is obtained.

For example, the beat frequency at the first point is 20
0 kilohertz, the beat frequency at the second point is 100 kilohertz, and the distance between the two points is 50 meters, 1
Since the frequency displacement amount is 100 kilohertz (200 kilohertz-100 kilohertz) with a time difference of / 3 microsecond (50 meters x 2 / light speed), the frequency displacement amount of the modulated wave per unit time is 300 kilohertz / microsecond. Seconds are required.

Then, the frequency change amount measurement unit 13 stores the obtained frequency displacement amount per unit time in each period in the measured value storage unit 15, respectively. The frequency change amount measuring unit 1
3, the frequency displacement amount per unit time of each period may be stored in the measured value storage unit 15 in association with the measurement condition.

When the fourth measurement condition is selected, the frequency change amount measuring section 13 outputs the switch switching control signal 13c, and the switch circuit 9 is provided so that the delay output of the delay means 8 is supplied to the mixing section 7. To switch. As a result, the mixing unit 7 is supplied with the local signal 4b and the delayed signal 8a obtained by delaying the local signal 4b by a predetermined time, and the mixing unit 7 supplies the beat signal which is the difference between the local signal 4b and the delayed signal 8a to the instantaneous frequency. 7a is output. The frequency change amount measurement unit 13 raises the frequency based on the beat frequency supplied from the frequency analysis (FFT) unit 11 and the delay time (design value) of the delay unit 8 stored in the design value storage unit 14. The amount of frequency change per unit time during the period and the frequency falling period is obtained.

For example, when the delay time of the delay means 8 is 1 microsecond and the beat frequency is 300 kilohertz, the frequency displacement amount of the modulated wave per unit time is required to be 300 kilohertz / microsecond.

Then, the frequency change amount measuring unit 13 stores the obtained frequency displacement amount per unit time in each period in the measured value storage unit 15, respectively. The frequency change amount measuring unit 1
3, the frequency displacement amount per unit time of each period may be stored in the measured value storage unit 15 in association with the measurement condition.

When the delay time of the delay means 8 is unknown,
And, the frequency variation per unit time calculated by the first to third measuring methods frequency variation and a fourth measuring method of the unit time per has frequency variation is accurately determined Merare per unit time by If there is an error between the frequency change amount measurement unit 13 and the frequency change amount per unit time obtained by the first to third measurement methods and the beat detected by the fourth measurement method. Based on frequency and
The delay time of the delay unit 8 may be calculated, and the calculated delay time may be stored in the measured value storage unit 15. When the measured value of the delay time of the delay unit 8 is stored in the measured value storage unit 15, the frequency change amount measurement unit 13 stores the measured value in the measured value storage unit 15 when the fourth measurement method is designated. The amount of frequency change per unit time is measured using the actual measured value of the delay time.

In the first measuring method, it is necessary to accurately maintain the distance between the vehicle equipped with the FM-CW radar device and the object. On the other hand, in the second measuring method, the distance between the vehicle and the object may be arbitrary, but two objects whose distances are known are required. In the third measuring method, it is not necessary to know the distance to the target object or the distance between the target objects, but since the vehicle equipped with the FM-CW radar device is moved, it is necessary to measure the moving distance. The fourth measurement method does not require an object and can measure the frequency change amount even when the vehicle is in a traveling state.

In this embodiment, the structure capable of coping with a plurality of measuring methods is shown. However, the frequency variation measuring unit 13
Is sufficient as long as it has a configuration in which the amount of frequency change per unit time can be measured by any one of the measuring methods. When the third measurement method (method that uses the travel distance of the vehicle) is not used, it is not necessary to provide the travel distance detection unit 16. Fourth measurement method (measurement method using delay time of delay means 8)
When using, the frequency change amount measuring unit 13 may measure the frequency change amount per unit time, for example, periodically without providing the measurement condition input unit 17.

The frequency change amount measuring unit 13 calculates the frequency deviation amount per unit time for each period obtained by the measurement as a distance
It is supplied to the relative speed calculator 12. The measured value storage unit 1
When the measurement results are stored in 5 for each of a plurality of measurement methods, the frequency change amount measurement unit 13 calculates the distance / relative velocity of the frequency deviation amount per unit time for each period obtained in the latest measurement. It is supplied to the section 12. Although the measurement conditions are input here, the measurement conditions may be automatically determined and the frequency change amount may be measured based on the determined conditions.

The distance / relative velocity calculation unit 12 receives from each frequency spectrum (beat frequency) 11a in the frequency rising period and the frequency falling period supplied from the frequency analysis (FFT) unit 11 and the frequency change amount measuring unit 13. The distance and the relative speed of the object are calculated based on the frequency change amount 13a per unit time during the supplied frequency rising period and frequency falling period.

When the amount of frequency change per unit time in the frequency rising period and the frequency falling period are the same, the distance / relative speed calculation unit 12 determines that the beat frequency fb in the frequency rising period.
The frequency fr related to the distance is obtained by halving the sum of up and the beat frequency fbdown in the frequency falling period. fr = (fbup + fbdown) / 2 Then, the distance to the object is calculated based on the frequency fr related to the distance and the frequency change amount per unit time. Also,
The distance / relative speed calculation unit 12 determines the beat frequency fbup during the frequency rising period and the beat frequency fbd during the frequency falling period.
Doppler frequency fd
Ask for. fd = (fbup-fbdown) / 2 Then, the relative speed is obtained from the Doppler frequency fd.

For example, the center frequency f of the modulated wave (transmission wave)
0 is 60 GHz, the frequency change amount per unit time in the frequency rising period and the frequency change amount per unit time in the frequency falling period are both 300 kHz / microsecond, and the beat frequency fbup in the frequency rising period is 296 kHz, When the beat frequency fbdown in the frequency decreasing period is 304 kilohertz, the beat frequency fr related to the distance is required to be 300 kilohertz, and the beat frequency f related to this distance is f.
From r (fr = 300 kilohertz) and the amount of frequency change per unit time (300 kilohertz / microsecond), it can be determined that the distance to the object is 150 meters (more precisely, the time difference between the transmitted wave and the received wave can be obtained). , The distance is obtained from the time difference and the speed of light C). Also, the Doppler frequency fd
Is determined to be 4 hertz, and the center frequency f0 (f0
= 60 GHz, the Doppler frequency fd (fd
= 4 Hz), the relative speed is found to be 10 m / sec.

When the frequency change amount per unit time in the frequency rising period and the frequency falling period does not match, the distance / relative speed calculating unit 12 determines the frequency change amount per unit time in the frequency rising period and the frequency falling period in the frequency falling period. Based on the ratio with the frequency change amount per unit time, after converting (correcting) the beat frequency detected in the frequency rising period into the beat frequency when it is the frequency change amount per unit time in the frequency falling period, Frequency rise period correction beat frequency and frequency fall period Beat frequency and distance based on the frequency change amount per unit time in the frequency fall period,
Calculate the relative speed.

When the frequency change amount per unit time in the frequency rising period and the frequency falling period do not match, the distance / relative speed calculation unit 12 determines that the frequency change amount per unit time in the frequency rising period and the frequency falling amount. Based on the ratio with the frequency change amount per unit time in the period, the beat frequency detected in the frequency falling period was converted (corrected) to the beat frequency in the case of the frequency change amount per unit time in the frequency rising period. After that, the distance and the relative speed may be obtained based on the frequency rising period beat frequency, the frequency falling period correction beat frequency, and the frequency change amount per unit time in the frequency rising period.

Furthermore, when the amount of frequency change per unit time in the frequency rising period and the frequency falling period does not match,
The distance / relative velocity calculation unit 12 detects the beat detected in the frequency rising period based on the ratio of the frequency change amount per unit time in the frequency rising period to the designed frequency change amount per unit time (design value). The frequency is converted (corrected) to the beat frequency when the frequency change amount per unit time in the frequency rising period is the design value, and the frequency change amount per unit time in the frequency falling period and the designed unit time Based on the ratio with the frequency change amount (design value), the beat frequency detected in the frequency falling period is converted (corrected) to the beat frequency when the frequency change amount per unit time in the frequency falling period is the design value. After doing
The distance and the relative speed may be obtained based on the frequency rising period correction beat frequency, the frequency falling period correction beat frequency, and the designed frequency change amount per unit time (design value).

For example, while the designed frequency change amount (design value) per unit time is 300 kilohertz / microsecond, the frequency change per unit time in the frequency rising period of the actually transmitted modulated signal is as follows. Amount is 290
When the frequency change amount per unit time in the frequency falling period of the actually transmitted modulated signal becomes, for example, 330 kilohertz / microsecond in kilohertz / microsecond,
The beat frequency fbup of the object having a distance of 150 meters and a relative speed of +10 meters / second (the object approaching at a speed of 10 m / sec) in the frequency increasing period is 286 kHz, and the beat frequency fbdown in the frequency decreasing period.
Will be 334 kilohertz.

Here, when the distance is calculated assuming that the frequency change amount of the actually transmitted modulated signal is the designed value (300 kilohertz / microsecond), the distance becomes 155 meters, and the distance between the actual distance and 150 meters is obtained. There is an error.
Further, the relative speed is 120 meters / second, which is significantly different from the actual relative speed of 10 meters / second. Therefore, based on the ratio of the frequency change amount per unit time (290 kilohertz / microsecond) and the designed frequency change amount (300 kilohertz / microsecond) during the frequency increasing period, the frequency per unit time during the frequency increasing period is calculated. By converting (correcting) the beat frequency fbup (286 kilohertz) detected by the change amount (290 kilohertz / microsecond) into the beat frequency when the designed frequency change amount (300 kilohertz / microsecond) is obtained. , Frequency rising period correction beat frequency = 295.9 kHz.

Next, based on the ratio of the frequency change amount (330 kHz / microsecond) per unit time in the frequency decrease period to the designed frequency change amount (300 kHz / microsecond), the unit in the frequency decrease period is set. The beat frequency fbdown (334 kilohertz) detected by the frequency change amount per hour (330 kilohertz / microsecond) is converted into the beat frequency in the case of the designed frequency change amount (300 kilohertz / microsecond) (correction By doing so, the frequency falling period correction beat frequency is set to 303.6 kHz.

Then, based on the frequency rising period correction beat frequency = 295.9 kHz and the frequency falling period correction beat frequency = 303.6 kHz, and the designed frequency change amount (300 kHz / microsecond), the distance and the relative distance are set. When the speed is calculated, the distance is 149.9 meters and the relative speed is 9.6 meters / second, and the distance and the relative speed can be calculated with high accuracy.

[0097]

As described above, the FM according to the present invention
The CW radar device includes a frequency change amount measurement unit that obtains the frequency change amount of the modulated wave per unit time, and uses the frequency change amount per unit time obtained by the frequency change amount measurement unit to determine the distance to the object. Since the configuration is determined, the frequency change amount per unit time of the modulation signal actually transmitted is designed by the variation in the frequency specification voltage-oscillation frequency characteristic of the voltage controlled oscillator (VCO) that generates the modulation signal and the change over time. Even if the value deviates from the value of, the distance / relative speed of the object can be calculated based on the actually measured frequency change amount per unit time. Therefore, the distance and the relative speed can be accurately obtained.

The distance / relative velocity calculation method in the FM-CW radar device according to the present invention measures the frequency change amount of the modulated wave per unit time, and determines the object based on the measured frequency change amount per unit time. Since the distance and the relative speed are calculated, the distance and the relative speed can be accurately obtained even when the frequency change amount of the modulation signal actually transmitted per unit time fluctuates.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a transmitted wave, a received wave, and a beat frequency when an object is stationary (when there is no relative velocity).

FIG. 2 is an explanatory diagram showing a relationship between a transmission wave, a reception wave and a beat frequency when an object is moving in a direction approaching the FM-CW radar device side.

FIG. 3 is an explanatory diagram showing a relationship between a transmission wave, a reception wave, and a beat frequency when an object is moving in a direction away from the FM-CW radar device side.

FIG. 4 is an explanatory diagram showing a variation example of frequency sweep of a transmission wave.

FIG. 5 is an explanatory diagram showing another variation example of frequency sweep of a transmission wave.

FIG. 6 is a block configuration diagram of an FM-CW radar device according to the present invention.

[Explanation of symbols]

1 ... FM-CW radar device, 2 ... FM signal generator, 3 ...
Sweep control unit, 4 ... Power distributor, 5 ... Circulator, 6
... antenna for both transmission and reception, 7 ... mixing section, 8 ... delay means, 9
... switch circuit, 10 ... A / D conversion section, 11 ... frequency analysis (FFT) section, 12 ... distance / relative speed calculation section, 13 ...
Frequency change amount measuring unit, 14 ... Design value storage unit, 15 ... Actual measurement value storage unit, 16 ... Running distance detection unit, 17 ... Measurement condition input unit.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-2-298882 (JP, A) JP-A-4-242187 (JP, A) JP-A-4-282483 (JP, A) JP-A-7- 146359 (JP, A) JP-A-7-151852 (JP, A) JP-A-9-222474 (JP, A) JP-A-5-188141 (JP, A) JP-A-8-508537 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (11)

(57) [Claims] 1. A modulated wave whose frequency rises and falls repeatedly is transmitted, a reflected wave reflected by an object is received, and the target is based on a beat frequency which is the difference between the frequency of the transmitted wave and the frequency of the received wave. In an FM-CW radar device for obtaining the distance of an object, the frequency change amount measuring unit for obtaining the frequency change amount of the modulated wave per unit time and the frequency change amount measuring unit are used for measurement.
The frequency change amount (measured value) per unit time
The actual measured value storage section and each frequency scan during the frequency rising period and the frequency falling period.
Vector (beat frequency) and frequency change measurement unit
Based on the amount of frequency change per unit time supplied from
Distance / relative to calculate the distance and relative speed of the object
The frequency change amount measuring unit is provided in the measured value storage unit per unit time.
If the frequency change amount (measured value) of is stored,
Provide each frequency change (measured value) to the distance / relative speed calculator
The FM-CW radar device is characterized in that it is supplied . 2. A modulated wave whose frequency repeatedly rises and falls
The transmitted wave is received and the reflected wave reflected by the target object is received.
Based on the beat frequency, which is the difference between the frequency and the frequency of the received wave
In the FM-CW radar device that calculates the distance of the target object based on
And Frequency for obtaining the amount of frequency change of the modulated wave per unit time
A number change amount measuring unit, Measured by frequency change measurement unit
Frequency change per unit time during the specified frequency rise period.
Amount (measured value), per unit time during frequency falling period
A measured value storage unit that stores the frequency change amount (measured value) of Each frequency scan during the frequency rising period and the frequency falling period
Vector (beat frequency) and frequency change measurement unit
Frequency rising period and frequency falling period supplied from
Based on the amount of frequency change per unit time in
Distance / relative speed calculation to calculate the distance and relative speed of an object
Section and The frequency change amount measuring unit stores the frequency rising period in the measured value storage unit.
Frequency change amount per unit time (measured value),
Amount of frequency change per unit time during the wave number falling period (actual
(Measured values) are stored, their respective frequency
Supplying the measured amount (measured value) to the distance / relative speed calculation unit
An FM-CW radar device characterized by: 3. Frequency change per unit time (design value)
Has a design value storage unit that is registered in advance, The frequency change amount measuring unit stores the frequency rising period in the measured value storage unit.
Frequency change amount per unit time (measured value),
Amount of frequency change per unit time during the wave number falling period (actual
If (measured value) is not stored, it is stored in the design value storage unit.
The frequency change amount (design value) per unit time
It supplies to a separation / relative speed calculation unit.
2. The FM-CW radar device according to item 2. 4. A frequency rising which is a difference between a frequency of a transmitted wave and a frequency of a received wave during a frequency rising period is transmitted by transmitting a modulated wave whose frequency repeatedly rises and falls and receives a reflected wave reflected by an object. In the FM-CW radar device, the relative distance and relative velocity of an object are calculated based on a period beat frequency and a frequency falling period beat frequency which is a difference between a frequency of a transmitted wave and a frequency of a received wave in a frequency falling period. A frequency change amount measuring unit for determining the frequency change amount per unit time in the frequency rising period of the wave and the frequency change amount per unit time in the frequency falling period of the modulated wave, respectively, is measured by the frequency change amount measuring unit. Frequency change amount per unit time in the specified frequency rise period and unit in the frequency decrease period measured by the frequency change amount measurement unit When the amount of frequency change per unit is the same, the relative speed is calculated based on the difference between the beat frequency of the frequency rising period and the beat frequency of the frequency falling period, and the beat frequency of the frequency rising period and the beat frequency of the frequency falling period are calculated. The beat frequency relating to the distance is obtained based on the sum of the above, the beat frequency relating to the obtained distance is obtained, and the distance to the object is obtained based on the frequency change amount per unit time measured by the frequency change amount measuring unit. If the frequency change amount per unit time in the frequency rise period measured by the change amount measurement unit and the frequency change amount per unit time in the frequency fall period measured by the frequency change amount measurement unit are different, the frequency rise period Per unit time during frequency rising period by correcting either or both of beat frequency and frequency falling period beat frequency When the amount of frequency change and the amount of frequency change per unit time in the frequency falling period are equal, the corrected beat frequency is obtained, and the relative distance and the relative distance of the object are calculated based on the corrected beat frequency for the rising period and the corrected beat frequency for the falling period An FM-CW radar device characterized by obtaining a velocity. 5. A frequency rising which is a difference between a frequency of a transmitted wave and a frequency of a received wave during a frequency rising period is transmitted by transmitting a modulated wave whose frequency repeatedly rises and falls and receiving a reflected wave reflected by an object. In the FM-CW radar device, the relative distance and relative velocity of an object are calculated based on a period beat frequency and a frequency falling period beat frequency which is a difference between a frequency of a transmitted wave and a frequency of a received wave in a frequency falling period. A frequency change amount per unit time in the frequency rising period of the wave, and a frequency change amount measuring unit for determining the frequency change amount per unit time in the frequency falling period of the modulated wave, respectively, the frequency change amount measuring unit Based on the ratio of the amount of frequency change per unit time obtained during the frequency rise period to the preset amount of frequency change per unit time The frequency rising period beat frequency is corrected to a rising period beat frequency when the frequency change amount is a preset reference frequency unit, and the frequency rising amount beat frequency per unit time is calculated by the frequency change amount measuring unit. Decrease period beat frequency when the frequency falling period beat frequency is the preset reference frequency change amount per unit time based on the ratio of the frequency change amount and the preset reference frequency change amount per unit time F, the relative distance and relative speed of the object are obtained based on the corrected frequency rising period correction beat frequency and the corrected frequency falling period correction beat frequency.
M-CW radar device. 6. The frequency change amount measuring unit obtains a frequency change amount per unit time of the modulated wave based on a beat frequency of an object whose distance is known and relative velocity is zero. Item 6. The FM-CW radar device according to any one of Items 1, 2, 4, and 5 . 7. The frequency change amount measuring unit includes first and second objects which are separated by a known distance and have a relative velocity of zero, respectively. 2. The amount of frequency change of the modulated wave per unit time is calculated based on the second beat frequency.
The FM-CW radar device according to any one of 4 and 5 . 8. The frequency change amount measuring unit is configured to detect a first beat frequency of an object having a relative velocity of zero detected at a first point and a known beat frequency from the first point toward the object. 2. A frequency change amount per unit time of the modulated wave is obtained based on a second beat frequency of the object detected at a second point separated by the distance. , FM-CW according to any one of 4 , 5
Radar equipment. 9. The frequency change amount measuring unit per unit time of the modulated wave based on a beat frequency of a delayed signal obtained by delaying the modulated wave via a delay unit having a known delay time and the modulated wave. 6. The FM- according to any one of claims 1, 2, 4 and 5, wherein the frequency change amount of
CW radar device. 10. A frequency-increasing signal, which is a difference between a frequency of a transmitted wave and a frequency of a received wave during a frequency-increasing period, by transmitting a modulated wave whose frequency repeatedly rises and falls and receives a reflected wave reflected by an object. Distance / velocity in FM-CW radar device for obtaining relative distance and relative velocity of an object based on a period beat frequency and a frequency falling period beat frequency which is a difference between a frequency of a transmitted wave and a frequency of a received wave in a frequency falling period In the calculation method, the frequency change amount per unit time in the frequency rising period of the modulated wave, and the frequency change amount per unit time in the frequency falling period of the modulated wave is obtained by measuring, respectively, the measured frequency Frequency change per unit time during rising period and measured frequency Frequency change per unit time during falling period If and are the same, the relative speed is obtained based on the difference between the beat frequency of the frequency rising period and the beat frequency of the frequency falling period, and the distance is calculated based on the sum of the beat frequency of the frequency rising period and the beat frequency of the frequency falling period. The beat frequency relating to the obtained distance is obtained, the distance of the object is obtained based on the beat frequency relating to the obtained distance and the measured frequency change amount per unit time, and the frequency change per unit time in the measured frequency rising period. If the amount of change and the amount of frequency change per unit time in the measured frequency falling period are different, the unit in the frequency rising period is corrected by correcting either or both of the frequency rising period beat frequency and the frequency falling period beat frequency. When the amount of frequency change per unit time and the amount of frequency change per unit time during the frequency falling period are equal Distance / relative velocity calculation method in FM-CW radar device, characterized in that a corrected beat frequency is obtained, and the relative distance and relative velocity of the object are obtained based on the frequency rising period correction beat frequency and the frequency falling period correction beat frequency. . 11. A frequency-increasing signal, which is a difference between a frequency of a transmitted wave and a frequency of a received wave during a frequency-increasing period, by transmitting a modulated wave whose frequency repeatedly rises and falls and receives a reflected wave reflected by an object. Distance / velocity in FM-CW radar device for obtaining relative distance and relative velocity of an object based on a period beat frequency and a frequency falling period beat frequency which is a difference between a frequency of a transmitted wave and a frequency of a received wave in a frequency falling period In the calculation method, the frequency change amount per unit time in the frequency rising period of the modulated wave, and the frequency change amount per unit time in the frequency falling period of the modulated wave is obtained by measuring, respectively, the measured frequency Based on the ratio of the frequency change amount per unit time during the rising period to the preset reference frequency change amount per unit time. Then, the beat frequency of the frequency rising period is corrected to the beat frequency of the rising period when the reference frequency change amount is a preset reference frequency change amount, and the frequency change amount per unit time in the measured frequency falling period is set in advance. Based on the ratio of the reference frequency change amount per unit time, the frequency falling period beat frequency is corrected to a decreasing period beat frequency when the preset reference frequency change amount per unit time is corrected. F which is characterized in that the relative distance and the relative velocity of the object are obtained based on the frequency rising period correction beat frequency and the corrected frequency falling period correction beat frequency.
Distance / relative velocity calculation method in M-CW radar device.