JPH08146125A - FM-CW radar - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if the ambient temperature changes, the center frequency of the variable frequency oscillator is made constant, and further, the modulation sensitivity Kv is made constant to improve the measurement accuracy of the distance to the target object. [Structure] The FM modulation voltage generator 12 has a predetermined DC component V _T0.
An FM modulation voltage V _T that cyclically changes in a triangular shape with respect to the center of the frequency variable oscillator 11 is generated, and the frequency variable oscillator 11 changes the frequency of the FM modulation voltage V _T in a cyclical triangular shape with the passage of time based on the FM modulation voltage V _T. The modulated signal is output, the transmitting unit 14 emits the FM modulated signal toward the target object, the receiving unit 15 receives the signal reflected and returned by the target object, and the signal processing unit 16 reflects the transmitted signal and the reflected signal. The distance R to the target or the relative velocity vr is calculated and output based on the beat signal frequency fr between the signals. In this case, the DC voltage correction unit 13 changes the voltage value of the DC component V _T0 of the FM modulation voltage according to the ambient temperature, and
The FM modulation voltage amplitude correction unit 12b increases the amplitude of the FM modulation voltage V _T as the ambient temperature rises.

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, and in particular, it emits a transmission signal whose frequency changes periodically in a triangular shape with respect to the passage of time toward a target, and the target transmits the signal. The present invention relates to an FM-CW radar that receives a signal that is reflected and returned, detects a beat signal frequency between a transmission signal and a reflected signal, and measures a distance to a target object, a relative speed with the target object, and the like.

[0002]

2. Description of the Related Art FM-CW radar is a CW radar (Contin
Frequency modulation (FM modulation) to the transmission signal of the continuous wave radar)
Is applied. FIG. 15 is a schematic configuration diagram of the FM-CW radar, in which 1 is a frequency variable oscillator (VCO) that changes the oscillation frequency according to the input voltage, and 2 is a triangle that periodically changes around a predetermined DC component. This is an FM modulation voltage generator that generates an FM modulation voltage and inputs it to the frequency variable oscillator 1. The frequency variable oscillator 1 has a center frequency f ₀ (= 59.
It oscillates at 5 GHz). Reference numeral 3 is a directional coupler for inputting the triangular FM modulation signal output from the variable frequency oscillator 1 to the transmission antenna and the reflection signal reception side, and 4 is a transmission antenna for radiating the FM modulation signal toward the target object. , 6 is a receiving antenna for receiving the reflected signal returned from the target, and 6 is a mixer (mixer) for mixing the reflected signal (received signal) and the transmitted signal and outputting a beat signal between both signals, A signal processing unit 7 detects the beat signal frequency and calculates the distance R to the target object and the relative velocity vr with the target object.

Assuming that the FM is performed by repeating the triangular wave as described above, the relationship between the frequency of the transmission signal and the time is shown in FIG.
6 shows the solid line, and the relationship between the frequency and time of the reflected signal from the target object (which is assumed to be stationary) at the distance R is as shown by the dotted line in the figure. As a result,
The relationship of the beat signal frequency fr between the transmitted signal and the reflected signal is as shown in FIG. 17, and the distance to the target object can be known by measuring this beat frequency. That is, assuming that the FM repetition frequency is fm and the frequency deviation width of the FM is Δf, the beat signal frequency fr between the reflection signal from the target object at the distance R and the transmission signal is expressed by the following equation: fr = 4R · fm · Δf / c (C is the speed of light) ・ ・ ・ (1) The above is the case where the target object is stationary, but when the target object is moving, the frequency vs. time relationship between the transmission signal and the reception signal is as shown in FIG. 18 due to the Doppler effect. That is, the beat signal frequency fr is as shown in FIG.
As shown in FIG. 9, the beat signal frequency fr in the case of a fixed target is superimposed with the Doppler frequency fd. Then, since the direction changes alternately with positive and negative in each modulation cycle, the following equation fb = fr-fd ... Negative (2) fb = fr + fd ... Positive (3) fd = 2vr.f ₀ / c (vr is the relative velocity to the target) (4) Therefore, if fb (positive) and fb (negative) are measured separately for each half cycle of modulation, fr and fd, that is, up to the target The distance R and the relative velocity vr can be obtained separately.

FIG. 20 is a more detailed block diagram of a conventional FM-CW radar, in which the same parts as in FIG. 15 are designated by the same reference numerals. Reference numerals 8a and 8b are high-frequency amplifiers on the transmitting side and the receiving side, respectively, and 9 is a demodulating section. The FM modulation voltage generation unit 2 has an F that periodically changes in a triangular shape around a predetermined DC component V _T0.
The M modulation voltage v _T is generated and input to the variable frequency oscillator 1. The variable frequency oscillator 1 includes a variable capacitance section 1a and an oscillation section 1b.
It has. The variable capacitance section 1a has a coil CL that cuts off high frequency components and a varactor diode (variable capacitance element) VR that changes the capacitance value based on the magnitude of the applied voltage.
The resistance value viewed from the output side has a value corresponding to the FM modulation voltage V _T input from the FM modulation voltage generation unit 2. Oscillator 1b
Is an oscillator that oscillates at a high frequency with a center frequency of 59.5 GHz, and is composed of a resonator, an FET, a strip line, etc., and shifts the frequency based on the output resistance value of the variable resistance portion 1a.
Actually, a signal oscillated at 29.75 GHz is multiplied and a signal with a center frequency of 59.5 GHz is output.

As the variable frequency oscillator 1, it is not possible to use a variable frequency oscillator having a small frequency drift due to the ambient temperature. Therefore, in the variable frequency oscillator 1, the characteristics of the input voltage V _T and the oscillation frequency f change depending on the ambient temperature. FIG. 21 shows the characteristics of the input voltage V _T and the oscillation frequency f,
Characteristics of A at normal temperature (= 25 ⁰ C), B is at a high temperature (= + 7
5 ⁰ C) characteristics, C is characteristics at low temperature (= -30 ⁰ C). When V _T0 = 4.4 V, the variable frequency oscillator 1 oscillates at a normal frequency of 29.75 GHz and a frequency shift Δf corresponding to the amplitude of the FM modulation voltage V _T at room temperature. When the ambient temperature rises in this state, the characteristic becomes B, and the operating point moves from P _A to P _B. Therefore, the center frequency f ₀ fluctuates (see the dotted line in FIG. 22), and the distance R and the relative speed vr cannot be accurately measured. Similarly, when the ambient temperature decreases, the characteristic becomes C
Then, the operating point moves to P _C , and thus the center frequency f ₀ fluctuates (see the alternate long and short dash line in FIG. 22), and the distance R and the relative speed vr cannot be accurately measured.

Therefore, conventionally, a temperature sensor is provided, and the operating point is shifted in the horizontal direction according to the actual ambient temperature to obtain V _T −.
The problem due to the temperature dependence of f is eliminated. FIG. 23 is a diagram for explaining temperature correction of the conventional V _T -f characteristic. When the ambient temperature rises, the characteristic becomes B and the operating point moves from P _A to P _B ′, so the center frequency f ₀ does not change. Similarly, when the ambient temperature decreases, the characteristic becomes C, and the operating point moves to P _C ′, so the center frequency f ₀ does not change.

[0007]

By the way, the slopes of the characteristics A, B and C at the operating points P _A , P _B ′ and P _C ′ are different. Therefore, according to the conventional temperature characteristic correction method, as shown in FIG.
As shown in, the magnitude of the frequency deviation Δf changes depending on the ambient temperature, and the distance R and the relative speed vr cannot be measured accurately. In the experiment by the inventor, it was confirmed that the
5 ⁰ When the modulation sensitivity of the C and 1.0, -30 ⁰ C the modulation sensitivity 1.2～1.6,70 ⁰ C the modulation sensitivity is 0.
It changed from 6 to 0.8. That is, at −30 ⁰ C, the distance R
The measurement error 17% ~38%, 70 ⁰ C at 25% to 6
It will be 7%. The modulation sensitivity is a value (= Δf / ΔV _T ) obtained by dividing the modulation frequency Δf by the FM modulation voltage ΔV _T. As described above, the conventional FM-CW radar has a problem that the measurement error is large.

Therefore, a first object of the present invention is to provide an FM-CW radar capable of accurately measuring the distance to a target and the relative speed. A second object of the present invention is to make the frequency deviation (modulation sensitivity) constant even if the ambient temperature changes,
FM- that can accurately measure the distance to the target and the relative speed
It is to provide a CW radar. A third object of the present invention is to provide various FM-CW radars capable of keeping the modulation sensitivity constant even when the ambient temperature changes. A fourth object of the present invention is to provide an FM-CW radar capable of keeping the modulation sensitivity constant even if the ambient temperature changes with a simple adjustment. A fifth object of the present invention is to provide an FM-CW radar in which the modulation sensitivity at any ambient temperature can be made equal to the modulation sensitivity at room temperature by adjustment at room temperature.

[0009]

FIG. 1 is a diagram illustrating the principle of the present invention. Reference numeral 11 is a frequency variable oscillator that changes the oscillation frequency according to an input voltage, and 12 is an FM modulation voltage V _T that periodically changes in a triangular shape around a predetermined DC component V _T0 and inputs it to the frequency variable oscillator. FM modulation voltage generator, 13
Is a DC voltage correction unit that changes and outputs the voltage value of the DC component V _T0 of the FM modulation voltage V _T according to the ambient temperature. In FM modulation voltage generation unit 12, 12a is variation generating unit for outputting a variation v _T 'of the FM modulation voltage V _T to be changed periodically to triangular, 12b is the variable portion v _T of the FM modulation voltage V _T An FM modulation voltage amplitude correction unit that increases the amplitude as the temperature increases,
Reference numeral 12c is a combining unit that combines the DC component V _T0 and the fluctuation component v _T. 14 is a transmitting means for amplifying the signal output from the frequency variable oscillator 11 and transmitting it toward the target object, 15 is a receiving means for receiving the reflected signal, and 16 is based on the beat signal frequency between the transmitted signal and the reflected signal. It is a signal processing unit that calculates the distance to the target object.

[0010]

The FM modulation voltage generating section 12 has a predetermined DC component V_T0To
FM modulation voltage V that periodically changes in a triangular shape in the center_TDepart
It is input to the variable frequency oscillator 11. Variable frequency
The shaker 11 is based on the input voltage and the frequency
Then, an FM modulation signal that periodically changes in a triangular shape is output,
The transmitting means emits the FM-modulated signal toward the target and receives it.
The receiving unit 15 receives the signal reflected by the target and returned,
The beat signal frequency fr between the transmitted signal and the reflected signal is processed as a signal.
Input to the management unit 16. The signal processing unit 16 uses the beat frequency f
Based on r, the distance R to the target or the relative velocity vr
Calculate and output. In this case, the DC voltage correction unit 13
DC component V of FM modulation voltage according to ambient temperature_T0The voltage value of
In addition, the FM modulation voltage amplitude correction unit 12b corrects the FM modulation voltage.
Pressure V _TThe amplitude of is increased as the ambient temperature rises. this
By doing so, the ambient temperature is higher or lower than room temperature.
Center frequency f of the variable frequency oscillator 11 even if it changes to the side ₀
Can be kept constant, the modulation sensitivity Kv can be kept constant, and
It is possible to improve the measurement accuracy of the separation and the relative speed.

Further, the FM modulation voltage amplitude correction unit 12b is realized by any one of the following configurations (1) to (6). That is, F
The M modulation voltage amplitude correction unit 12b includes (1) a temperature sensor that outputs a voltage signal according to the ambient temperature, and a _first multiplier that multiplies the temperature difference between the ambient temperature and the room temperature by the amplitude adjustment value Y ₁ . A second multiplier that executes multiplication of the output of the first multiplier and the fluctuation component v _T ′ of the FM modulation voltage, and controls and outputs the amplitude of the FM modulation voltage according to the ambient temperature (modulation sensitivity). Configure. Alternatively, the FM modulation voltage amplitude correction unit 12b is set to (2)
A temperature sensor that outputs a voltage signal according to the ambient temperature, an operational amplifier that outputs a signal obtained by multiplying a temperature difference between the ambient temperature and room temperature by a predetermined amplitude adjustment value, and a variation of the operational amplifier output and the FM modulation voltage. It is composed of a multiplier that executes multiplication with the component v _T ′ and controls and outputs the amplitude of the FM modulation voltage according to the ambient temperature. Alternatively, the FM modulation voltage amplitude correction unit includes (3) a temperature sensor that outputs a voltage signal according to the ambient temperature, and a voltage signal generation unit that outputs a voltage signal having an amplitude according to the temperature difference between the ambient temperature and the room temperature. When the voltage signal output from the voltage signal generating means is positive, the voltage signal is multiplied by the first adjustment value, and when the voltage signal is negative, the voltage signal is multiplied by the second adjustment value. It is composed of an amplitude adjusting means for outputting and a multiplier for executing the multiplication of the output of the amplitude adjusting means and the variation of the FM modulation voltage to control and output the amplitude of the FM modulation voltage according to the ambient temperature.

Alternatively, the FM modulation voltage amplitude correction unit is
(4) A temperature sensor that outputs a voltage signal according to the ambient temperature, an AD converter that AD-converts the temperature sensor output,
A memory that stores the correspondence between the ambient temperature and the amplitude value of the FM modulation voltage, a DA converter that reads the amplitude value according to the ambient temperature from the memory and converts it to analog, and a fluctuation amount v _{T of the} DA converter output and the FM modulation voltage. ′ And a multiplier for controlling and outputting the amplitude of the FM modulation voltage according to the ambient temperature. Alternatively, the FM modulation voltage amplitude correction unit includes (5) a temperature sensor that outputs a voltage signal according to the ambient temperature, an AD converter that performs AD conversion of the temperature sensor output, and an FM modulation voltage that has an amplitude according to each ambient temperature. Are sampled at a predetermined time interval and stored therein, and an FM modulation voltage corresponding to a predetermined ambient temperature is read from the memory at the time interval and converted into an analog signal.
It is composed of a DA converter that outputs as an M modulation voltage.
Alternatively, the FM modulation voltage amplitude correction unit includes (6) a temperature sensor that outputs a voltage signal according to the ambient temperature, an AD converter that performs AD conversion of the temperature sensor output, and an FM modulation voltage that has an amplitude value according to the ambient temperature. And a digital F output from the signal processing unit.
It is composed of a DA converter that converts the M-modulated voltage to analog and outputs it. As described above, since the FM modulation voltage amplitude correction unit can be realized with various configurations, the optimum one should be selected.
An M-CW radar can be provided.

Further, the volume is adjusted only once at a predetermined temperature of high temperature or low temperature so that the frequency deviation (modulation sensitivity) becomes equal to that at room temperature. Since there is a substantially proportional relationship between the frequency deviation and the temperature, the frequency deviation (modulation sensitivity) at all temperatures can be adjusted by adjusting only once.
It can be equal to (modulation sensitivity) and can measure distance and relative velocity with high accuracy at all temperatures. Further, the DC component of the FM modulation voltage at normal temperature is made equal to the DC component of the FM modulation voltage at any ambient temperature. In this state, the volume is adjusted to adjust the amplitude of the FM modulation voltage so that the frequency deviation becomes equal to the frequency deviation at room temperature. By doing so, the modulation sensitivity in the entire temperature range at room temperature can be made equal to the modulation sensitivity at room temperature without using a constant temperature bath, and highly accurate distance and relative velocity measurement can be performed.

[0014]

【Example】

(a) Overall configuration of FM-CW radar FIG. 2 is an overall configuration diagram of the FM-CW radar of the present invention. In the figure, 11 is a frequency variable oscillator that changes the oscillation frequency according to the input voltage, and 12 is a frequency variable oscillator that generates an FM modulation voltage V _T that periodically changes in a triangular shape around a predetermined DC component V _T0. FM modulation voltage generator input to
Is a DC voltage correction unit that corrects and outputs the voltage value of the DC component V _T0 of the FM modulation voltage V _T according to the ambient temperature, and 14 amplifies the FM modulation signal output from the frequency variable oscillator 11 and outputs it to the target object. A transmitting unit that emits toward the receiver, a receiving unit 15 that receives the reflected signal, and a signal processing unit 16 that calculates the distance R to the target object and the relative speed vr based on the beat signal frequency between the transmitted signal and the reflected signal. .

In the variable frequency oscillator 11, 11a is a variable capacitance section and 11b is an oscillation section. Variable capacitance section 11a
Has a coil CL that cuts off high frequency components and a varactor diode (variable capacitance element) VR that changes the resistance value based on the magnitude of the applied voltage, and the capacitance value viewed from the output side is input from the FM modulation voltage generation unit 12. The value becomes a value corresponding to the FM modulation voltage V _T. As shown in FIG. 3, the oscillating unit 11b multiplies the oscillator 11b-1 which oscillates at a high frequency of 29.75 GHz and the output frequency (29.75 GHz) of the oscillator to obtain a center frequency of 59.5.
It is composed of a multiplication circuit 11b-2 which outputs a GHz signal.
In the oscillator 11b-1, 21 is a resonator, 22 is a FET having a source installed, 23 is a strip line connected to the drain terminal of the FET, and 24 is a strip line 23.
Is a stripline coupled in high frequency, and the oscillation frequency can be adjusted by changing the length of the resonator 21.

Further, the oscillator 11b-1 is a varactor diode V
The oscillation frequency is changed according to the capacitance value of R. Therefore, if the capacitance value of the varactor diode VR is controlled by the FM modulation voltage V _T applied to the varactor diode VR, the oscillation frequency f changes. FIG. 4 is an explanatory diagram of temperature correction of the V _T -f characteristic of the present invention, where A is V _T − at room temperature (= ²⁵⁰ ° C.).
f characteristics, B is at a high temperature ^{(= + 75 0 C) V} T -f characteristic of, C
Is the V _T -f characteristic at low temperature (= −30 ⁰ C). At room temperature, the operating point is on the point P _A on the V _T -f characteristic curve, and the FM modulation voltage V _T (= V _TA + v _T ) that changes in a triangular shape.
Is input to the varactor diode VR, the oscillation frequency f periodically fluctuates in a triangular shape with a frequency deviation Δf. F
In M modulation voltage generator 12, 12a is variation v _T of the FM modulation voltage V _T which changes periodically triangular 'variation generator for outputting a, 12b is variation in the FM modulation voltage V _T v _T'
The FM modulation voltage amplitude correction unit 12c that increases the amplitude of the variable V _t0 as the temperature increases, and the combination unit 12c is a combination unit that combines the direct current component V _T0 and the variation component v _T ′. FIG. 5 is a waveform diagram of the FM modulation voltage V _T , which is composed of a DC component V _T0 and a fluctuation component v _T , and the fluctuation component v _T has a frequency f.
It has a waveform that repeats increasing and decreasing in a triangular shape at m. In the DC voltage correction unit 13, 13a is a temperature sensor that detects an ambient temperature and generates a voltage signal having a magnitude corresponding to the ambient temperature, and 13b is a DC component V of the FM modulation voltage V _T according to the temperature.
A voltage correction unit that corrects and outputs _T0 .

When the ambient temperature rises, the variable frequency oscillator 1
1 of V _T -f characteristic (see FIG. 4) is switched to B from A. In parallel with the switching of the V _T -f characteristic, the DC voltage correction unit 13 corrects the DC voltage value from V _TA to V _TB according to the temperature rise. Therefore, the operating point moves from P _A to P _B , and the center frequency f ₀ of the variable frequency oscillator 11 becomes the same as that at room temperature. By the way, in the V _T -f characteristic, as the DC component V _T0 increases, the slope becomes gentler and the frequency deviation (modulation sensitivity Kv) with respect to the FM modulation voltage decreases. Therefore, in parallel with the above control, the FM modulation voltage amplitude correction unit 12 _calculates the amplitude of the fluctuation component v _T of the FM modulation voltage V _T in accordance with the temperature rise.
Increase as indicated by the dotted line. As a result, even at high temperature, the oscillation frequency periodically changes in a triangular shape with the same center frequency and the same frequency deviation Δf as at room temperature.

Similarly, when the ambient temperature decreases, the V _T -f characteristic of the variable frequency oscillator 11 switches from A to C. In parallel with the switching of the V _T -f characteristic, the DC voltage correction unit 13 changes the DC voltage value from V _TA to V _TC according to the temperature decrease. Therefore, the operating point moves from P _A to P _C , and the center frequency f ₀ of the variable frequency oscillator 11 becomes the same as at room temperature. By the way, in the V _T -f characteristic, as the DC component V _T0 becomes smaller, the slope becomes larger and the frequency deviation (modulation sensitivity Kv) with respect to the FM modulation voltage becomes larger. Therefore, in parallel with the above control, the FM modulation voltage amplitude correction unit 12 reduces the amplitude of the fluctuation component v _T of the FM modulation voltage V _T according to the temperature decrease, as shown by the alternate long and short dash line in FIG. As a result, even at low temperature, the oscillation frequency periodically fluctuates in a triangular shape with the same center frequency and the same frequency deviation Δf as at room temperature. still,
When the operating point is changed so that the center frequency of the frequency variable oscillator 11 becomes the same as that at room temperature regardless of the ambient temperature, the relationship between the ambient temperature and the modulation sensitivity Kv is substantially linear as shown by the solid line in FIG. Become.

Returning to FIG. 2, the transmitter 14 includes the oscillator 11
The high frequency amplifier 14a which amplifies the FM modulation signal output from b and the antenna 14b which radiates a transmission signal toward a target object are provided. The receiving unit 15 includes an antenna 15a for receiving a reflected signal reflected by the target object and returning, a high frequency amplifier 15b for amplifying the received signal, and a reflected signal (received signal) and a transmitted signal for mixing between the two signals. Mixer (mixer) 15c that outputs a beat signal, and beat signal frequency f
It has a demodulation unit 15d that demodulates and outputs b (= fr ± fd). The signal processing unit 16 calculates the distance R to the target object and the relative velocity vr with the target object using the expressions (2) to (4). As described above, the DC voltage correction unit 13 changes the F
The voltage value of the direct current component V _T0 of the M modulation voltage is changed, and the FM modulation voltage amplitude correction unit 12b increases the amplitude of the FM modulation voltage V _T as the ambient temperature rises. The center frequency f ₀ of the variable frequency oscillator 11 can be made constant even if the temperature changes to a higher temperature side or a lower temperature side, the frequency deviation (modulation sensitivity Kv) can be made constant, and the distance can be accurately measured even when the ambient temperature changes. And relative velocity can be measured.

(B) FM modulation voltage amplitude correction unit (b-1) First embodiment of FM modulation voltage amplitude correction unit FIG.
It is a figure, and the same code | symbol is attached | subjected to the same part as FIG.
In the FM modulation voltage amplitude correction unit 12b, 31 is the ambient temperature.
Voltage signal X having a magnitude according to the degree T₁Output temperature
Sensor, voltage signal X₁Is the following formula X₁= F (T) = aT + b. The temperature sensor 31 is, for example, reverse depending on the temperature.
The diode D and the resistor R whose direction voltage changes are connected to the power supply VL.
Connected in series, voltage signal X from the cathode of the diode₁
Is provided. In such a configuration,
Voltage signal X₁  X₁= -2.3 (mV /⁰C) ・ (T-25) (⁰It is given by C) +0.60 (V).

Reference numeral 32 denotes a room temperature correction voltage generator which outputs a room temperature correction voltage X ₂ expressed by the following equation: X ₂ = a · 25 + b. 33 is the first
Of the first and second inputs X ₁ and X ₂ (X ₁ −X ₂ ) and the difference between the third and fourth inputs Y ₁ and Y ₂ (Y ₁
It outputs the signal Z obtained by adding the fifth input Z ₂ to the product of −Y ₂ ). That is, the multiplier 33 outputs a Z given by: _{Z = (X 1 -X 2)} · (Y 1 -Y 2) + Z 2 (5). Therefore, Y ₂ = 0 and Z ₂ = 1
Then, the output Z becomes Z = a (T-25) · Y ₁ +1 (6).

Reference numeral 34 is a second multiplier, which has the same structure as the first multiplier 33. Therefore, the first input X ₁ ′
= Z, second input X ₂ ′ = 0, third input Y ₁ ′ = FM modulation voltage variation v _T ′, fourth input Y ₂ ′ = 0, fifth input Z ₂ ′
= 0, the output Z ′ is given by the following equation: Z ′ = Z · v _T ′ (triangular wave voltage) = {a (T-25) · Y ₁ +1} · v _T ′ (7). In the above formula, Z is the amplitude of the triangular wave voltage v _T, the amplitude becomes larger than the amplitude at the normal temperature is at ambient temperature 25 ⁰ C or more, smaller than the amplitude at the normal temperature amplitude at ambient temperature 25 ⁰ C or less . Therefore, the volume VR (the first multiplier 3
The third input Y ₁ ) of No. 3 is adjusted so that the frequency deviation (modulation sensitivity Kv) at the temperature becomes equal to the frequency deviation (modulation sensitivity Kv) at room temperature. With this adjustment, since there is a proportional relationship between the frequency deviation and the ambient temperature as shown in FIG. 6, the frequency deviation (modulation sensitivity Kv) at all temperatures is the frequency deviation (modulation sensitivity) at room temperature. And can measure distance and relative velocity with high accuracy at all temperatures.

(B-2) Second Embodiment of FM Modulation Voltage Amplitude Correction Unit FIG. 8 is a block diagram of a second embodiment of the FM modulation voltage amplitude correction unit 12b, which is the same as the first embodiment shown in FIG. Are given the same reference numerals. The difference from the first embodiment is that the first multiplier 33
Instead of, an operational amplifier is used to output a voltage signal corresponding to equation (6). In FIG. 8, reference numeral 41 is an operational amplifier that outputs a signal obtained by multiplying the temperature difference between the ambient temperature T and the room temperature (= 25 ⁰ C) by a predetermined amplitude adjustment value,
Has the structure of a summer, the output voltage eout following equation eout = - given by _{(R 2 / R 1) ·} e 1 + (1 + R 2 / R 1) · e 2 (8). Here, assuming that e ₁ = -k (T-25) + e ₀ , the output voltage eout is the following equation eout = (R ₂ / R ₁ ) ・ k (T-25)-(R ₂ / R ₁ ) ・e ₀ + (1 + R ₂ / R ₁ ) ・ e ₂ (9). Therefore, in equation (9), if-(R ₂ / R ₁ ) ・ e ₀ + (1 + R ₂ / R ₁ ) ・ e ₂ = 1 then eout = (R ₂ / R ₁ ) ・ k ( T-25) +1 (10), which is the same form as Eq. (6).

From the above, R ₂ / R ₁ is adjusted only once at a predetermined temperature of high temperature or low temperature, and the frequency deviation (modulation sensitivity Kv) at that temperature is equal to the frequency deviation (modulation sensitivity Kv) at room temperature. To be Since the frequency deviation and the ambient temperature have a proportional relationship as shown in FIG. 6 if they are adjusted only once in this manner, the frequency deviation (modulation sensitivity Kv) at all temperatures is Modulation sensitivity), and can measure distance and relative velocity with high accuracy at all temperatures.

(B-3) Third Embodiment of FM Modulation Voltage Amplitude Correcting Section FIG. 9 is a block diagram of a third embodiment of the FM modulation voltage amplitude correcting section 12b, which is the same as the second embodiment of FIG. Are given the same reference numerals. The difference from the second embodiment is that between the analog adder 41 and the multiplier 34 of the operation amplifier configuration,
The point is that the ideal rectifier circuits 42 and 43 having an operational amplifier configuration are provided. The ideal rectifier circuit 42 is the adder 4
Only the positive side of the output voltage eout of 1 is inverted and amplified and output, and the output becomes 0 when it is negative. The ideal rectifier circuit 43 inverts and amplifies only the negative side of the output voltage eout of the adder 41, and outputs 0 when it is positive.
Becomes The output voltage eout of the adder 41 is a second embodiment similarly to the following equation eout = - given by _{(R 2 / R 1) ·} e 1 + (1 + R 2 / R 1) · e 2. Here, assuming that e ₁ = -k (T-25) + e ₀ , the output voltage eout is the following equation eout = (R ₂ / R ₁ ) ・ k (T-25)-(R ₂ / R ₁ ) ・e ₀ + (1 + R ₂ / R ₁ ) ・ e ₂

[0026] Thus, in the above equation, - if _{(R 2 / R 1) ·} e 0 + (1 + R 2 / R 1) · e 2 = 0, eout = (R 2 / R 1) · k (T-25) It becomes (11). That is, the output voltage eout becomes positive at high temperature,
The output voltage eout becomes negative at low temperatures. Therefore, the ideal rectifier circuit 42 inverts and amplifies the output voltage eout at a high temperature, and the ideal rectifier circuit 43 inverts and amplifies the output voltage eout at a low temperature.
Incidentally, the gain of the ideal rectifier circuits 42 and 43 can be changed by adjusting the resistance R _3, R _4. The combined output signals of the ideal rectifier circuits 42 and 43 are input to the first input terminal of the multiplier 34, and the second input terminal X ₂ ′ = 1 and the third input Y ₁ ′ = F
If the variation V _T ′ of the M modulation voltage, the fourth input Y ₂ ′ = 0, and the fifth input Z ₂ ′ = 0, the output Z ′ is given by the following expression Z ′ = (X ₁ ′ −X ₂ ′) Y ₁ ′ = (1−X ₂ ′) · v _T ′ (triangular wave voltage) (12).

Therefore, the ideal rectifier circuit 4 is provided only once when the temperature is high.
The resistor R ₃ of 2 is adjusted to change X ₂ ′ so that the frequency deviation (modulation sensitivity Kv) at the temperature becomes equal to the frequency deviation (modulation sensitivity Kv) at room temperature. Similarly, when the temperature is low, the resistance R ₄ of the ideal rectifier circuit 43 is adjusted only once to change the output X ₂ ′, and the frequency deviation (modulation sensitivity K
v) should be equal to the frequency deviation (modulation sensitivity Kv) at room temperature. As described above, when the adjustment between the high temperature and the low temperature is performed, the frequency shift and the ambient temperature have a different proportional relationship between the high temperature side and the low temperature side as shown by the dotted line in FIG. Also, the frequency deviation (modulation sensitivity Kv) at all temperatures can be made substantially equal to the frequency deviation (modulation sensitivity) at room temperature, and highly accurate distance and relative velocity measurements can be made at all temperatures.

(B-4) Fourth Embodiment of FM Modulation Voltage Amplitude Correction Section FIG. 10 is a block diagram of a fourth embodiment of the FM modulation voltage amplitude correction section 12b, in which the same parts as in FIG. are doing. In the FM modulation voltage amplitude correction unit 12b, 51 is a temperature sensor that outputs a voltage signal having a magnitude corresponding to the ambient temperature, 52 is an AD converter that AD-converts the temperature sensor output, 53 is the amplitude value of the ambient temperature and the FM modulation voltage. A memory (ROM) for storing the correspondence with the, an address conversion unit 54 for converting the ambient temperature into a ROM address, a read control unit 55 for reading and outputting an amplitude value according to the ambient temperature from the memory, and a digital amplitude 56. DA that converts the value to analog
The converter 57 is a multiplier that executes the multiplication of the DA converter output and the variation v _T ′ of the FM modulation voltage. Operating point P _A of the ambient _{temperature, P B, P C V T} -f characteristic A in (see FIG. 4), B, the slope of C is different. Therefore, the frequency deviation Δ with respect to the FM modulation voltage V _T depends on the ambient temperature.
The magnitude of f (modulation sensitivity Kv) changes. In other words, even if the FM modulation voltage V _T having the same amplitude is input, the frequency deviation Δf differs depending on the ambient temperature. Therefore, the amplitude of the FM modulation voltage V _T that gives the same frequency deviation Δf as that at room temperature at each ambient temperature is obtained in advance and stored in the memory (ROM) 53.

The multiplier 57 is similar to the multiplier of the first embodiment, and has the difference (X ₁ ′ −X ₂ ′) between the first and second inputs X ₁ ′ and X ₂ ′,
The signal Z is obtained by adding the fifth input Z ₂ ′ to the product of the difference (Y ₁ ′ −Y ₂ ′) between the third and fourth inputs Y ₁ and Y ₂ .
Therefore, the first input X ₁ ′ = ROM output, the second input X ₂ ′ =
0, the third input Y ₁ ′ = the variation v _T ′ of the FM modulation voltage, the fourth
If the input Y ₂ ′ = 0 and the fifth input Z ₂ ′ = 0, then the output Z ′
It is represented by the following equation _{Z '= X 1' · v} T '( triangular wave voltage) (13). From the above equation, the ROM output (amplitude) X ₁ ′ has an amplitude corresponding to the fluctuation of the FM modulation voltage. The amplitude stored in the ROM 53 is the amplitude of the FM modulation voltage V _T that gives the same frequency deviation Δf as that at room temperature at each ambient temperature.
If the embodiment is used as the FM modulation voltage amplitude correction unit 12b in FIG. 2, the center frequency and frequency deviation can be made constant at each ambient temperature, and accurate distance and relative velocity measurements can be made at all temperatures.

(B-5) Fifth Embodiment of FM Modulation Voltage Amplitude Correction Unit FIG. 11 is a block diagram of a fifth embodiment of the FM modulation voltage amplitude correction unit 12b. In the FM modulation voltage amplitude correction unit 12b,
Reference numeral 61 is a temperature sensor that outputs a voltage signal having a magnitude according to the ambient temperature, 62 is an AD converter that performs AD conversion of the temperature sensor output, and 63 has an amplitude according to the ambient temperature, and
Signal processing unit for outputting a repetitive triangular waveform voltage signal digitally at predetermined intervals fm (DSP), 64 is a DA converter for converting the digital data output from the signal processing unit into an analog voltage signal v _T. Signal processing unit (DSP)
63 is an amplitude value of the FM modulation voltage V _T at each ambient temperature which gives the same frequency deviation Δf as that at room temperature in advance,
The period fm of the FM modulation voltage V _T is set. The amplitude value of is stored in the memory (ROM) corresponding to the temperature as in the fourth embodiment. In this state, when the ambient temperature is input from the temperature sensor 61, the signal processing unit 63
Calculates an amplitude value according to the ambient temperature and digitally outputs a triangular wave voltage of frequency fm having the amplitude. The DA converter 64 outputs the digital data output from the signal processing unit 63 as an analog stepwise voltage signal v _T.

From the above, the frequency deviation at each ambient temperature
The (modulation sensitivity Kv) can be made equal to the frequency deviation (modulation sensitivity Kv) at room temperature. As a result, it is possible to measure the distance and relative velocity with high accuracy at all temperatures. In the above, DSP6
Although the triangular wave-shaped voltage signal v _T was generated by the signal processing of No. 3, the voltage signal v _T was similarly generated by the program control by the microcomputer.
It can also generate _T. Also, 1/4 for each ambient temperature
The triangular wave voltage signal v _T for one cycle is sampled at a predetermined sampling period and stored in the memory, and the stored data corresponding to the ambient temperature is read out and DA converted to generate the triangular wave voltage signal v _T. It can also be configured to do so.

(C) Adjustment method It is necessary to adjust the frequency deviation (modulation sensitivity Kv) at each ambient temperature to be equal to the frequency deviation (modulation sensitivity Kv) at room temperature. (c-1) Adjustment Method Using Constant Temperature Tank FIG. 12 is an explanatory view of the adjustment method of the volume VR in the first embodiment. The FM-CW radar 10 is placed in a constant temperature bath 35, the frequency variable oscillator 11 is connected to a spectrum analyzer 36 provided outside the constant temperature bath 35, and the frequency characteristic of the frequency variable oscillator 11 (FIG. 2) in the FM-CW radar 10 is connected. Can be displayed on the spectrum display unit 37. In this state, the temperature inside the constant temperature bath 35 is set to +75 ⁰ C, for example. Next, if the frequency deviation Δf at room temperature is set to 75 MHz, the adjustment volume VR (see FIG. 7) of the third input Y ₁ of the first multiplier 33 is adjusted, and the spectrum display unit 3
The bandwidth of the spectrum displayed in 7 should be 75 MHz. The adjustment ends when the bandwidth becomes 75 MHz. With the above arrangement, the frequency deviation and the ambient temperature have a proportional relationship, so that the frequency deviation (modulation sensitivity Kv) at all temperatures can be converted to the frequency deviation (modulation sensitivity) at room temperature with only one adjustment.
And can measure distance and relative velocity with high accuracy at all temperatures. It should be noted that adjustment of the volume R ₂ of the second embodiment, adjustment of the volumes R ₃ , R ₄ of the third embodiment, and determination of the amplitude value in the fourth and fifth embodiments can be performed with the same configuration as that of FIG. .

(C-2) Adjustment method not using constant temperature bath As shown in FIG. 13, the v _T -f characteristics A, B and C at room temperature, high temperature and low temperature have similar shapes so that they are overlapped if they move in parallel. Is equipped with. Therefore, v modulation sensitivity of the operating point P _B 'on v _T -f characteristic A in modulator sensitivity and room temperature _T -f characteristic B operating point on P _B at high temperatures are substantially equal. Similarly, at low temperature, v _T
-F upon modulation sensitivity and normal temperature characteristic C operating point on the P _C of v _T -f
The modulation sensitivities of the operating points P _C ′ on the characteristic A are substantially equal. From the above, without adjustment of the volume in a thermostatic chamber as in the first adjustment method, the operation point moves from P _A to P _B 'or P _C', said operating point P _B 'or P _C' The volume can be adjusted so that the frequency deviation becomes equal to the frequency deviation at the normal temperature (at the operating point P _A ).

FIG. 14 is a block diagram showing a case in which such an adjusting method is applied to the first embodiment, and the same parts as those in FIG. 7 are designated by the same reference numerals. Reference numeral 71a denotes a first adjustment voltage generator that outputs the same voltage signal as the output of the temperature sensor 31 at any ambient temperature, and 71b outputs the same voltage signal as the output of the DC voltage corrector 13 at any ambient temperature. Second to output
Is a regulated voltage generator. Reference numeral 72 denotes a first switch that selects one of the output of the temperature sensor 31 and the output of the adjustment voltage generation unit 71a and inputs it to the multiplier 33. At the time of adjustment, the voltage signal output from the adjustment voltage generation unit 71a is used as the multiplication unit. 33
To the multiplying unit 33. In other cases, the voltage signal output from the temperature sensor 31 is input to the multiplying unit 33. Reference numeral 73 denotes a second switch for selecting one of the output of the DC voltage correction unit 13 and the output of the adjustment voltage generation unit 71b and inputting it to the synthesis unit 12c. During the adjustment, the voltage signal output from the adjustment voltage generation unit 71b is output. The voltage signal input to the synthesizing unit 12c and otherwise output from the DC voltage correcting unit 13 is input to the synthesizing unit 12c.
To enter.

At the time of adjustment, the variable frequency oscillator 11 is connected to the spectrum analyzer 36 so that the frequency characteristic of the variable frequency oscillator 11 is displayed on the spectrum display section 37. Then, the first and second switches 72, 7
3 is switched to the illustrated solid line state. Thereafter, the first adjustment voltage generator 71a is adjusted to output a voltage signal having the same magnitude as the voltage signal output from the temperature sensor 31 at +75 ⁰ C, for example. Similarly, the second adjustment voltage generation unit 71b is adjusted to output a voltage signal having the same magnitude as the voltage signal output from the DC voltage correction unit 13b at +75 ⁰ C, for example. In this state, the volume VR for adjusting the third input Y ₁ of the first multiplier 33 is adjusted. Then, the bandwidth of the spectrum displayed on the spectrum display unit 37 is set to 75 MHz, and when the bandwidth becomes 75 MHz, the adjustment ends. The frequency deviation Δf at room temperature is 75 MHz.

By doing so, there is an advantage that the volume (Y ₁ ) can be adjusted at room temperature without using a thermostat, and the adjustment work can be simplified. Also, since there is a proportional relationship between the frequency deviation and the ambient temperature, even in the second adjustment method, the frequency deviation (modulation sensitivity Kv) of all temperatures can be converted to the frequency deviation (modulation sensitivity at normal temperature) by one adjustment operation. Sensitivity) and can measure distance and relative velocity with high accuracy at all temperatures. It should be noted that adjustment of the volume R ₂ of the second embodiment, adjustment of the volumes R ₃ , R ₄ of the third embodiment, and determination of the amplitude value in the fourth and fifth embodiments can be performed with the same configuration as that of FIG. . Although the present invention has been described above with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0037]

As described above, according to the present invention, since the DC voltage correction unit changes the voltage value of the DC component V _T0 of the FM modulation voltage according to the ambient temperature, the ambient temperature changes from the normal temperature to the high temperature side or the low temperature side. However, the center frequency of the variable frequency oscillator can be made constant. In addition, the FM modulation voltage amplitude correction unit uses the FM modulation voltage V
The amplitude of _T is increased as the ambient temperature rises so that the frequency shift (modulation sensitivity) is the same regardless of the ambient temperature. Therefore, since the center frequency and the modulation sensitivity can be made constant regardless of the temperature, it is possible to improve the measurement accuracy of the distance to the target object and the relative speed. Further, according to the present invention, F
Since the M modulation voltage amplitude correction unit can be realized with various configurations,
The FM-CW radar can be configured by appropriately selecting the optimum one. Further, according to the present invention, since the frequency deviation (modulation sensitivity) can be independently adjusted to be equal to the frequency deviation (modulation sensitivity) at room temperature at two points on the high temperature side and the low temperature side, The frequency deviation can be made equal to the frequency deviation at room temperature, and the distance to the target and the relative speed can be measured with high accuracy at all temperatures.

Further, according to the present invention, if the frequency deviation (modulation sensitivity) is made equal to the frequency deviation (modulation sensitivity) at room temperature by adjusting the volume only once at a predetermined temperature of high temperature or low temperature. Since there is a proportional relationship between the frequency deviation and the temperature, the frequency deviation (modulation sensitivity) can be made equal to the frequency deviation (modulation sensitivity) at normal temperature at all temperatures, and the distance and relative speed with high accuracy can be obtained at all temperatures. Can be measured. Further, according to the present invention, since the volume can be adjusted at room temperature without using a thermostat, the adjustment work can be simplified, and the frequency deviation of all temperatures ( The modulation sensitivity Kv) can be made equal to the frequency deviation (modulation sensitivity) at room temperature, and accurate distance and relative velocity measurements can be performed at all temperatures.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an overall configuration diagram of an FM-CW radar of the present invention.

FIG. 3 is a configuration diagram of an oscillator.

FIG. 4 is an explanatory diagram of the operation of the present invention.

FIG. 5 is an FM modulation voltage waveform diagram.

FIG. 6 is a T-Kv (temperature-modulation sensitivity) characteristic diagram.

FIG. 7 is a first embodiment of an FM modulation voltage amplitude correction unit.

FIG. 8 is a second example of the FM modulation voltage amplitude correction unit.

FIG. 9 is a third example of the FM modulation voltage amplitude correction unit.

FIG. 10 is a fourth example of the FM modulation voltage amplitude correction unit.

FIG. 11 is a fifth embodiment of the FM modulation voltage amplitude correction unit.

FIG. 12 is a configuration diagram for adjusting a volume VR (Y ₁ ).

FIG. 13 is an explanatory diagram of a volume VR (Y ₁ ) adjustment method.

FIG. 14 is a configuration diagram of volume VR (Y ₁ ) adjustment.

FIG. 15 is a schematic configuration diagram of an FM-CW radar.

FIG. 16 is an explanatory diagram of a frequency change of a signal.

FIG. 17 is an explanatory diagram of a beat frequency change.

FIG. 18 is an explanatory diagram of a transmission / reception signal when there is a relative speed.

FIG. 19 is an explanatory diagram of a beat frequency.

FIG. 20 is a detailed configuration diagram of a conventional FM-CW radar.

FIG. 21 is a V _T -f characteristic diagram.

FIG. 22 is a diagram illustrating a problem due to temperature dependence of V _T -f characteristic.

FIG. 23 is an explanatory diagram of temperature correction of a conventional V _T -f characteristic.

[Explanation of symbols]

 11. Variable frequency oscillator 12. FM modulation voltage generator 12a. Fluctuation generator 12b. FM modulation voltage amplitude corrector 12c. Synthesizer 13. DC voltage corrector 14. Transmitting means 15 .. Receiving means 16 ... Signal processing unit

Claims (9)

[Claims] 1. A transmission signal whose frequency periodically changes in a triangular shape with the lapse of time is emitted toward a target object, and a signal reflected and returned by the target object is received to obtain a transmission signal. In an FM-CW radar that detects the beat signal frequency between reflected signals and measures the distance to the target or the relative speed to the target, a frequency variable oscillator that changes the oscillation frequency according to the input voltage, centering on a predetermined DC component An FM that generates an FM modulation voltage that periodically changes in a triangular shape and that is input to the frequency variable oscillator.
Modulation voltage generation unit, DC voltage correction unit that corrects the DC component of the FM modulation voltage according to ambient temperature, and F that corrects the amplitude of the FM modulation voltage according to ambient temperature
M modulation voltage amplitude correction unit, means for emitting a signal output from the variable frequency oscillator toward a target, distance to the target or relative speed to the target based on the beat signal frequency between the transmission signal and the reflected signal FM-CW radar with means for calculating. 2. The FM modulation voltage amplitude correction section includes: a temperature sensor that outputs a voltage signal according to ambient temperature; and a _first multiplier that multiplies the temperature difference between ambient temperature and room temperature by an amplitude adjustment value Y ₁ . And a second multiplier that executes a multiplication of the output of the first multiplier and the variation of the FM modulation voltage, and controls and outputs the amplitude of the FM modulation voltage according to the ambient temperature. The described FM-CW radar. 3. The FM modulation voltage amplitude correction unit outputs a signal obtained by multiplying a temperature sensor that outputs a voltage signal according to the ambient temperature and a temperature difference between the ambient temperature and room temperature by a predetermined amplitude adjustment value. The FM- according to claim 1, further comprising: an amplifier; and a multiplier that executes a multiplication of the output of the operational amplifier and a variation of the FM modulation voltage, and controls and outputs the amplitude of the FM modulation voltage according to ambient temperature.
CW radar. 4. The FM modulation voltage amplitude correction unit includes: a temperature sensor that outputs a voltage signal according to ambient temperature; and a voltage signal generator that outputs a voltage signal having an amplitude according to a temperature difference between ambient temperature and room temperature. And the voltage signal output from the voltage signal generating means is positive, the voltage signal is multiplied by the first adjustment value, and when the voltage signal is negative,
An amplitude adjusting unit that multiplies the voltage signal by a second adjustment value and outputs the result is multiplied by the output of the amplitude adjusting unit and the fluctuation amount of the FM modulation voltage, and the FM modulation voltage is changed according to the ambient temperature. The FM according to claim 1, further comprising a multiplier for controlling and outputting the amplitude.
-CW radar. 5. The FM modulation voltage amplitude correction unit includes: a temperature sensor that outputs a voltage signal according to ambient temperature; an AD converter that AD-converts the temperature sensor output; and an ambient temperature and an amplitude value of the FM modulation voltage. A memory that stores the correspondence, a DA converter that reads the amplitude value according to the ambient temperature from the memory and converts it to analog, and a multiplication of the DA converter output and the fluctuation amount of the FM modulation voltage is performed. The FM-C according to claim 1, further comprising a multiplier that controls and outputs the amplitude of the modulation voltage.
W radar. 6. The FM modulation voltage amplitude correction unit includes: a temperature sensor that outputs a voltage signal according to ambient temperature; an AD converter that performs AD conversion of the temperature sensor output; and an FM modulation that has an amplitude according to each ambient temperature. A memory for sampling and storing each voltage at a predetermined time interval, and a DA for reading out an FM modulation voltage corresponding to a predetermined ambient temperature from the memory at the above time interval, converting it into an analog signal, and outputting it.
The FM-CW radar according to claim 1, further comprising a converter. 7. The FM modulation voltage amplitude correction unit includes: a temperature sensor that outputs a voltage signal according to ambient temperature; an AD converter that AD-converts the output of the temperature sensor; and an FM modulation that has an amplitude value according to ambient temperature. The FM-CW radar according to claim 1, further comprising a signal processing unit that outputs a voltage at predetermined time intervals, and a DA converter that converts the FM modulation voltage output from the signal processing unit into an analog signal and outputs the analog signal. 8. The FM modulation voltage amplitude correction unit includes a volume adjusting the amplitude value of the FM modulation voltage, and adjusts the volume at high or low temperature to adjust the volume so that the frequency deviation becomes equal to that at room temperature. The FM-CW radar according to claim 1. 9. The FM modulation voltage amplitude correction section is characterized by:
The FM-C according to claim 1, further comprising means for adjusting the amplitude of the FM modulation voltage at an arbitrary ambient temperature so that the frequency shift at the ambient temperature becomes equal to the frequency shift at room temperature.
W radar.