JP2010109708A - Triangular wave signal generating circuit, and radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely generate a plurality of rectangular wave signals having different desired amplitudes without changing the number of adjustment widths of a D/A converter. <P>SOLUTION: A triangular signal generation circuit includes: an integration circuit which integrates an input rectangular wave signal to generate a triangular wave signal; and the D/A converter which drops reference voltage with adjustment widths obtained by equally dividing the reference voltage by a predetermined number, generates a rectangular wave signal with the dropped reference voltage as the amplitude, and inputs the rectangular wave signal to the integration circuit. The A/D converter generates, for each of a plurality of reference voltages, the rectangular wave signals having such different amplitudes that cause the integration circuit to generate the triangular wave signals having desired amplitudes respectively. Accordingly, the A/D converter adjusts a small reference voltage with a small adjustment width when generating the rectangular wave signal having small amplitude, and adjusts a large reference voltage with a large adjustment width when generating the rectangular wave signal having large amplitude to precisely generate the plurality of rectangular wave signals having the different desired amplitudes without changing the number of adjustment widths. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a triangular wave signal generation circuit including an integration circuit that integrates an input rectangular wave signal to generate a triangular wave signal and a D / A converter that generates a rectangular wave signal and inputs the rectangular wave signal to the integration circuit. In particular, the present invention relates to a technique for generating a plurality of triangular wave signals having different amplitudes.

  As an obstacle detection means in a vehicle, an FM-CW (Frequency Modulated-Continuous Wave) type radar device using a radar signal frequency-modulated so that the frequency linearly rises and falls with respect to time is known. The FM-CW radar device has a triangular wave signal generation circuit that generates a triangular wave signal that alternately repeats a period in which the voltage rises linearly and a period in which the voltage falls with respect to time, and a voltage-controlled oscillator (VCO) A radar signal frequency-modulated as described above is generated according to the voltage of the triangular wave signal. Then, a beat signal having a frequency corresponding to the frequency difference between the two is generated by multiplying the transmission / reception signal, and the A / D converted beat signal is analyzed by a signal processing device such as a microcomputer, and the target object is calculated based on the frequency. Detect speed and relative distance. Patent Document 1 describes an example of a radar apparatus having such a configuration.

  FIG. 1 is a diagram illustrating a general configuration of a triangular wave signal generation circuit in an FM-CW radar device. The triangular wave signal generation circuit 2a receives a predetermined number of bits of digital data D and a reference voltage Rv from a signal processing device, and uses the reference voltage Rv to generate an analog signal (rectangular wave signal) having a voltage indicated by the digital data D. A D / A converter 22a to be generated, and an integration circuit 24a for generating a triangular wave signal by integrating the difference between a predetermined comparison reference voltage Cv and the voltage value of the rectangular wave signal by charging and discharging. The triangular wave signal output from the integrating circuit 24a is applied to the VCO 4, and the VCO 4 generates a radar signal having a frequency corresponding to the voltage of the triangular wave signal, that is, a frequency-modulated radar signal. Therefore, the frequency modulation width of the radar signal corresponds to the amplitude of the triangular wave signal.

  Here, a method for detecting the relative speed and the relative distance of the target object using the radar signal generated based on the triangular wave signal will be described.

  FIG. 2 is a diagram for explaining the principle of detection of the relative distance and the relative speed by the FM-CW radar device. In FIG. 2, the horizontal axis represents time, and the vertical axis represents frequency. A solid line indicates a frequency change with respect to time of a transmission signal. The frequency of this transmission signal rises and falls linearly with a center frequency f0 and a frequency modulation width ΔF according to a triangular wave signal with a frequency fm. On the other hand, the broken line indicates the frequency change of the received signal that is reflected by the target object and returns. The frequency of the received signal is subjected to a time delay ΔT depending on the relative distance and a deviation corresponding to the Doppler frequency γ according to the relative speed. As a result, the transmission / reception signal has a frequency difference α during the frequency increase period of the transmission signal and a frequency difference β during the frequency decrease period. The frequency differences α and β are detected as beat signal frequencies (beat frequencies). Then, the signal processing device of the radar apparatus calculates the relative distance K and the relative speed S of the target object by the following equations. Here, C is the speed of light.

K = C · (α + β) / (8 · ΔF · fm) (1)
S = C · (β−α) / (4 · f0) (2)
Here, as shown in the above formulas (1) and (2), in order to detect the relative speed and the relative distance with high accuracy, the frequency modulation with a predetermined frequency modulation width ΔF and the center frequency f0 is performed with high accuracy. It is necessary to generate a radar signal. In the case of an on-vehicle radar device, the frequency band of radio waves that can be used in Japan is limited to 76 to 77 GHz according to the regulations of the Radio Law, and ΔF = 100 MHz and f0 = 76.5 GHz are used as examples.

  In order to obtain such a radar signal, it is necessary to accurately generate a triangular wave signal applied to the VCO 4 in consideration of the performance of the VCO 4. For this purpose, it is necessary to input a rectangular wave signal having such an amplitude that a triangular wave signal having a desired amplitude is input to the integrating circuit 24a. However, the integrating circuit 24a has an individual error. Therefore, when the radar apparatus is manufactured, the amplitude of the rectangular wave signal generated by the D / A converter 22a is adjusted so that a triangular wave signal having a desired amplitude is obtained for each individual integration circuit 24a.

Specifically, when n-bit digital data D indicating the amplitude of the rectangular wave signal is input to the D / A converter 22a, the reference voltage Rv with an adjustment width obtained by equally dividing the reference voltage Rv by 2 to the power of n. And a rectangular wave signal having the amplitude of the reduced voltage is generated. Here, digital data D indicating the amplitude of a rectangular wave signal that outputs a triangular wave signal having a desired amplitude when input to the integrating circuit 24a is detected in advance and stored in the memory of the signal processing device. During operation of the apparatus, the D / A converter 22a adjusts the reference voltage Rv based on the digital data to generate a rectangular wave signal having a desired amplitude.
JP 2007-208400 A

  By the way, for example, in the case of a radar apparatus that detects a target object in front of a vehicle, it is required to track a preceding vehicle ahead of several tens of meters during traveling at a certain high speed. On the other hand, during low-speed traveling in a traffic jam, tracking of a preceding vehicle and detection of an interrupting vehicle at a short distance about several meters ahead are required. Alternatively, detection of a pedestrian ahead of about several tens of centimeters to several meters is required during low speed traveling when entering an intersection or traveling in a parking lot. Thus, detection of target objects having different relative distances is required according to the traveling speed of the vehicle.

  Here, as shown by the above equation (1), by increasing the frequency modulation width ΔF of the radar signal, the resolution of the relative distance K can be improved, and the detection accuracy of the target object at a short distance or a close distance is improved. be able to. However, on the other hand, if it is attempted to detect a target object at a long distance with the frequency modulation width ΔF being increased, the beat frequencies α and β are increased accordingly, and a beat signal in a wider frequency band is not processed. It will not be. Then, a bandpass filter that removes high-frequency noise from the beat signal when A / D converting the beat signal needs to use a filter circuit that passes a wider band. Also, when the beat signal is subjected to FFT (Fast Fourier Transform) processing to detect the beat frequency in the signal processing device, the amount of data to be subjected to FFT processing increases, and a signal processing device with higher processing performance is required. This leads to an increase in the cost of the entire radar apparatus, which is not desirable.

  Therefore, it is desirable to dynamically switch the frequency modulation width of the radar signal according to the traveling state of the vehicle. For example, when a radar signal having a frequency modulation width of 2 · ΔF is doubled at high speeds and ΔF at low speeds, a rectangular wave input to the integration circuit 24 is generated so that a triangular wave signal having a different amplitude can be generated by the integration circuit 24a. It is necessary to switch the amplitude of the wave signal between two levels: large (amplitude V1) and small (amplitude V2).

  However, since the amplitude of the rectangular wave generated by the D / A converter 22a is adjusted within the reference voltage Rv, the reference voltage Rv is set in advance to a voltage larger than the larger amplitude V1, and the amplitude within the reference voltage is set. The following problems arise when trying to generate V1 and V2 rectangular wave signals. That is, since the D / A converter 22a adjusts the reference voltage by an adjustment width equally divided by 2 to the power of n (the number of bits of input digital data), if the reference voltage Rv is made larger than V1, Accordingly, the adjustment range is also increased. Then, when adjusting the reference voltage Rv to obtain the amplitude V2, the adjustment range with respect to the amplitude increases, and the adjustment accuracy decreases. Here, in order to prevent a decrease in adjustment accuracy, it is necessary to reduce the adjustment width of the D / A converter 22a. For this purpose, a larger number of bits is used so that the adjustment width can be reduced by increasing the number of adjustment widths. A D / A converter that can handle digital data is required. However, such a D / A converter is undesirable because it leads to an increase in cost.

  Accordingly, an object of the present invention made in view of such a problem is a triangular wave signal that can accurately generate a plurality of rectangular wave signals having different desired amplitudes without changing the number of adjustment widths of the D / A converter. It is to provide a generation circuit.

  In order to achieve the above object, according to the first aspect of the present invention, an integration circuit that integrates an input rectangular wave signal to generate a triangular wave signal, and an adjustment width that equally divides the reference voltage by a predetermined number A triangular wave signal generation circuit including a D / A converter that reduces the reference voltage and generates a rectangular wave signal having an amplitude of the reduced reference voltage and inputs the rectangular wave signal to the integration circuit, The A converter is provided with a triangular wave signal generation circuit that generates rectangular wave signals having different amplitudes for each of a plurality of reference voltages.

  According to the above aspect, the D / A converter generates rectangular wave signals having different amplitudes for each of a plurality of reference voltages. That is, when generating a rectangular wave signal with a small amplitude, a small reference voltage is adjusted with a small adjustment width, and when generating a rectangular wave signal with a large amplitude, the large reference voltage is adjusted with a large adjustment width. It is possible to reduce the adjustment accuracy when a rectangular wave signal having a desired amplitude is generated. Therefore, it is possible to accurately generate a plurality of rectangular wave signals having different amplitudes such that triangular wave signals having different desired amplitudes are generated by the integration circuit without changing the number of adjustment widths of the D / A converter.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

  FIG. 3 is a diagram for explaining a situation when the radar apparatus according to the present invention is used as a radar apparatus for front monitoring of a vehicle. The FM-CW radar device 10 is mounted in the front bumper portion of the vehicle 1 or in the front grille, transmits a radar signal to the front of the vehicle 1 through the decorative plate on the front surface of the bumper or the front grille front, A reflected signal reflected by the object is received. And the beat signal of the frequency corresponding to the frequency difference of a transmission / reception signal is processed with a signal processing apparatus, and the relative speed and relative distance of target objects, such as a preceding vehicle and a pedestrian, are detected. The detected target object information is output to the vehicle control device 100 that controls the behavior of the vehicle 1.

  The vehicle control device 100 performs various vehicle controls based on the target object information. For example, the vehicle 1 is accelerated and decelerated by controlling actuators such as a throttle and a brake of the vehicle 1 to perform follow-up running control that follows the preceding vehicle at a constant inter-vehicle distance. Alternatively, when the distance from other vehicles or pedestrians approaches a certain distance and the probability of collision increases beyond a certain distance, a warning to the driver is output or voice output, or the vehicle 1 is accelerated or decelerated to avoid a collision Perform collision avoidance control. Further, when the probability of collision further increases, collision response control is performed to activate a safety device such as an airbag to protect the occupant.

  FIG. 4 is a diagram for explaining the configuration of the radar apparatus according to the present invention. The radar apparatus 10 generates and transmits / receives a radar signal that is frequency-modulated by the FM-CW method, and controls the operation of the radar transceiver 10a that generates a beat signal from the transmission / reception signal. And a signal processing device 40 for detecting the relative distance and relative speed of the target object.

  The radar transceiver 10a further includes a triangular wave signal generation circuit 2 that generates a triangular wave signal as a frequency modulation signal, a VCO 4 that generates a radar signal frequency-modulated based on the triangular wave signal, and a distributor 6 that distributes the power of the radar signal. And an amplifier 7 for amplifying the power-distributed radar signal and outputting it to the transmitting antenna 8T. The amplified radar signal is transmitted from the transmitting antenna 8T. Further, the radar transceiver 10a multiplies the amplifier 9 for amplifying the reception signal received by the reception antenna 8R, and the amplified reception signal and the power-distributed transmission signal to beat the frequency corresponding to the frequency difference between the two. It has a mixer 30 that generates a signal, a band-pass filter 32 that removes high-frequency noise and DC components from the beat signal, and an A / D converter 34 that A / D converts the beat signal that has passed through the band-pass filter 32.

  The signal processing device 40 includes an arithmetic processing device that performs FFT (Fast Fourier Transform) processing on the A / D converted beat signal and detects a frequency spectrum, and a known microcomputer. The signal processing device 40 detects the beat frequency of the beat signal that forms a peak in the frequency spectrum, detects the relative speed and the relative distance of the target object according to the above-described formulas (1) and (2), and uses the detection result as the vehicle. Output to the control device 100. The signal processing device 40 receives a traveling speed signal of the vehicle 1 from the speed sensor 42 of the vehicle 1, and the signal processing device 40 controls the operation of the radar transceiver 10 a based on the traveling speed of the vehicle 1.

  Specifically, the signal processing device 40 uses a radar when the vehicle 1 travels at a predetermined relatively fast traveling speed (a traveling speed that requires traveling ahead of a preceding vehicle ahead of several tens of meters). The processing load is reduced by reducing the frequency modulation width of the signal (here, ΔF shown in FIG. 2) and narrowing the frequency band of the beat signal to be processed. On the other hand, it is required that the vehicle 1 travels following a predetermined relatively slow traveling speed (several tens of centimeters to several meters ahead), avoids a collision with an interrupting vehicle or a collision with a pedestrian. When the vehicle is traveling at such a speed, the frequency modulation width of the radar signal is increased (in this case, 2 × ΔF), and the distance resolution is increased to improve the detection accuracy of the target object at a short distance. Improve. In addition, when switching the frequency modulation width of the radar signal, the signal processing device 40 inputs the digital data D1 and D2 instructing the triangular wave signal circuit 2 to switch the amplitude of the triangular wave signal, and two different reference voltages Rv1. , Rv2 is supplied from the internal voltage circuit 40a. Next, the triangular wave generation circuit 2 that switches the amplitude of the triangular wave signal based on the digital data D1 and D2 and the reference voltages Rv1 and Rv2 will be described.

  FIG. 5 is a diagram illustrating the configuration of the triangular wave signal generation circuit according to the first embodiment. The triangular wave signal generation circuit 2 includes a D / A converter 22 that generates a rectangular wave signal, and an integration circuit 24 that integrates the rectangular wave signal to generate a triangular wave signal and outputs the triangular wave signal to the VCO 4.

  Here, when a rectangular wave signal having an amplitude V1 is input to the integrating circuit 24, the integrating circuit 24 generates a triangular wave signal having an amplitude E1, and at this time, the VCO 4 outputs a radar signal having a frequency modulation width ΔF. Further, when a rectangular wave signal having an amplitude V2 (> V1) is input to the integrating circuit 24, the integrating circuit 24 generates a triangular wave signal having an amplitude E2 (> E1). At this time, the VCO 4 is a radar having a frequency modulation width 2 · ΔF. A signal shall be output.

  In the above configuration, when a radar signal having a frequency modulation width ΔF is transmitted, n-bit digital data D1 indicating the amplitude V1 of the rectangular wave signal and the reference voltage Rv1 (> V1) are transmitted from the signal processing device 40 to the D / A converter 22. Is entered. Then, the D / A converter 22 reduces the reference voltage Rv1 to the voltage V1 by an adjustment width obtained by equally dividing the reference voltage Rv1 by 2 to the power of n, and outputs a rectangular wave signal whose amplitude is the reduced voltage V1. . Further, when transmitting a radar signal having a frequency modulation width of 2 · ΔF, the signal processing device 40 sends the reference voltage Rv2 (> Rv1 and> V2) and the amplitude V2 of the rectangular wave signal to the D / A converter 22. Data D2 is input. Then, the D / A converter 22 reduces the reference voltage Rv2 to the voltage V2 by an adjustment width obtained by equally dividing the reference voltage Rv2 by the power of 2 and outputs a rectangular wave signal having the amplitude of the reduced voltage V2. .

  Each digital data D1, D2 is detected in advance when the radar apparatus 10 is manufactured. That is, the reference voltage Rv1 is adjusted by an adjustment width equally divided by 2 to the nth power, and the digital data D1 for obtaining the amplitude V1 and the reference voltage Rv2 is adjusted by an adjustment width equally divided by the nth power of 2, Digital data D2 for obtaining the amplitude V2 is detected. The digital data D1 and D2 are respectively stored in the ROM of the signal processing device 40, read during operation of the radar device 10, and input to the D / A converter 22.

  Furthermore, in the first embodiment, voltages V1 and V2 corresponding to the amplitude of the rectangular wave signal are output from the D / A converter 22 to the integrating circuit 24. The detailed configuration of the integrating circuit 24 is shown in FIG. 6. The voltages V 1 and V 2 are divided by resistors 241 and 242, and the respective center voltages are stabilized by the voltage follower circuit 244, and then compared as comparison reference voltages Cv 1 and Cv 2. It is input to a comparator (op-amp) 246. Then, the comparator 246 compares the rectangular wave signal with the comparison reference voltages Cv 1 and Cv 2, and the difference is charged / discharged by the capacitor 248. Then, a triangular wave signal having a slope corresponding to the charge / discharge amount and the charge / discharge time is output.

  By adopting such a configuration, the comparison reference voltage of the integration circuit 24 can be made to coincide with the center voltage in the amplitude of the rectangular wave signal, and it is avoided that the charge / discharge balance is lost and the amplitude of the triangular wave is distorted. Can do. Of course, the resistors 241 and 242 and the voltage follower circuit 244 may be provided outside the integrating circuit 24.

  Here, as an embodiment, a case where the frequency modulation width of a radar signal is switched between 100 MHz and 200 MHz will be described. The VCO 4 outputs a radar signal with a modulation width of 100 MHz when a triangular wave signal with an amplitude of 1 Vp-p is input, and a radar with a modulation width of 200 MHz when a triangular wave signal with an amplitude of 2 Vp-p is input. A signal shall be output. The integration circuit 24 generates a triangular wave signal having an amplitude of 1 Vp-p when a rectangular wave signal having an amplitude of 2 Vp-p is input, and 2 Vp when a rectangular wave signal having an amplitude of 4 Vp-p is input. It is assumed that a triangular wave signal having an amplitude of −p is generated. The D / A converter 22 is a D / A converter having a 10-bit resolution.

  Then, when transmitting a radar signal having a frequency modulation width of 100 MHz, 10-bit digital data D1 indicating the amplitude 2Vp-p of the rectangular wave signal and the reference voltage 3V are input from the signal processing device 40 to the D / A converter 22. . Then, the D / A converter 22 reduces the reference voltage 3V to 2V with an adjustment width obtained by equally dividing the reference voltage 3V by 10 n = 1024, that is, an adjustment width of 2.9 mV / bit. A 2 Vp-p rectangular wave signal having an amplitude between the voltage 2 V and the ground (0 V) is output. At this time, by adjusting with an adjustment width of 2.9 mV / bit, the reference voltage can be adjusted with an error of 1% or less with respect to 2 Vp-p.

  On the other hand, when transmitting a radar signal having a frequency modulation width of 200 MHz, 10-bit digital data D2 indicating the amplitude 4Vp-p of the rectangular wave signal and the reference voltage 5V are input from the signal processing device 40 to the D / A converter 22. Then, the D / A converter 22 reduces the reference voltage 5V to 4V with an adjustment width obtained by equally dividing the reference voltage 5V by 10 n = 1024, that is, an adjustment width of 4.9 mV / bit. A 4 Vp-p rectangular wave signal having an amplitude between the voltage 4 V and the ground (0 V) is output. At this time, by adjusting with an adjustment width of 4.9 mV / bit, the reference voltage can be adjusted with an error of 1% or less with respect to 4 Vp-p.

  In this way, a plurality of rectangular wave signals having different desired amplitudes V1 or V2 are accurately generated without changing the number of adjustment widths (2 to the nth power) of the D / A converter 22, and the integrating circuit 24 Can be entered. Therefore, the integrating circuit 24 can generate triangular signals of different E1 and E2 with high accuracy, and thus the VCO 4 can generate radar signals of different frequency modulation widths ΔF and 2 · ΔF with high accuracy.

  FIG. 7 is a diagram illustrating the configuration of the triangular wave signal generation circuit 2 according to the second embodiment. In the second embodiment, the comparison reference voltage of the integration circuit 24 is fixed to a preset voltage Cv. The comparison reference voltage Cv is supplied from a voltage circuit in the signal processing device 40 as an example. The digital data D11 and D12 input to the D / A converter 22 indicate voltages including an offset such that the center voltage of the rectangular wave signal matches the comparison reference voltage Cv. By doing so, when generating rectangular wave signals with amplitudes V 1 and V 2 from the reference voltages Rv 1 and Rv 2, the center voltage at the amplitude of each rectangular wave signal can be matched with the center voltage Cv of the integrating circuit 24. Other configurations are the same as those of the first embodiment.

  According to such a configuration, a plurality of rectangular wave signals having different desired amplitudes V <b> 1 or V <b> 2 can be accurately generated without changing the number of adjustment widths of the D / A converter 22 and input to the integration circuit 24. it can. Therefore, the integration circuit 24 can generate triangular wave signals having different amplitudes E1 and E2 with high accuracy, and thus the VCO 4 can generate radar signals with different frequency modulation widths ΔF and 2 · ΔF with high accuracy. And it can avoid that the balance of charging / discharging in the integration circuit 24 collapse | crumbles and the amplitude of a triangular wave is distorted as a result.

  The first and second embodiments described above are particularly suitable when the modulation sensitivity of the VCO 4 is high. When a VCO 4 having a low oscillation frequency per 1 V amplitude of a triangular wave signal, that is, low modulation sensitivity is used, even if a triangular wave signal having an amplitude for obtaining a radar signal having a desired frequency modulation width is generated with a certain degree of accuracy. It is not a big problem in practical use. However, when the VCO 4 having a large oscillation frequency per 1 V amplitude of the triangular wave signal, that is, high modulation sensitivity is used, the triangular wave signal having an amplitude for obtaining a radar signal having a desired frequency modulation width is accurately obtained, that is, the amplitude is changed. On the other hand, it is necessary to adjust and generate the reference voltage with a small adjustment width. Therefore, as shown in the first and second embodiments, the D / A converter 22 has such an amplitude that a triangular wave signal having a desired amplitude is generated by the integrating circuit 24 for each of a plurality of reference voltages. By generating different rectangular wave signals, a triangular wave signal can be generated with high accuracy without changing the adjustment accuracy of the D / A converter.

  Note that the number of frequency modulation width switching patterns of the radar signal and the frequency modulation width are not limited to the example described above, and may be switched to, for example, three or more different frequency modulation widths. In that case, three or more sets of digital data and a reference voltage are input to the D / A converter so that radar signals having respective frequency modulation widths are generated. Then, rectangular wave signals having different amplitudes are generated for each case, and integrated by an integrating circuit to generate triangular wave signals having different amplitudes. Further, the number of bits of the digital data input to the D / A converter is not limited to the above example, and an arbitrary number of bits according to the performance of the D / A converter can be used.

  As described above, according to the present invention, it is possible to accurately generate a plurality of rectangular wave signals having different desired amplitudes without changing the number of adjustment widths of the D / A converter.

It is a figure explaining the general structure of the triangular wave signal generation circuit in an FM-CW system radar apparatus. It is a figure explaining the detection principle of the relative distance and the relative velocity by the radar apparatus of FM-CW system. It is a figure explaining the situation when the radar apparatus in this invention is used as a radar apparatus for front monitoring of a vehicle. It is a figure explaining the structure of the radar apparatus in this invention. It is a figure explaining the structure of the triangular wave signal generation circuit in 1st Embodiment. 3 is a diagram illustrating a detailed configuration example of an integration circuit 24. FIG. It is a figure explaining the structure of the triangular wave signal generation circuit 2 in 2nd Embodiment.

Explanation of symbols

2: triangular wave signal generation circuit, 22: D / A converter, 24: integration circuit, 10: radar device

Claims (5)

An integration circuit that integrates an input rectangular wave signal to generate a triangular wave signal, and a rectangular wave that reduces the reference voltage by an adjustment width obtained by equally dividing the reference voltage by a predetermined number, and uses the reduced reference voltage as an amplitude. A triangular wave signal generation circuit having a D / A converter that generates a signal and inputs the signal to the integration circuit,
The D / A converter generates a rectangular wave signal having different amplitudes for each of a plurality of reference voltages. In claim 1,
The integration circuit generates a triangular wave signal by integrating a difference between the rectangular wave signal and the comparison reference voltage using a center voltage at an amplitude of the rectangular wave signal as a comparison reference voltage. circuit. In claim 1,
The integration circuit integrates a difference between the rectangular wave signal and a predetermined comparison reference voltage to generate the triangular wave signal,
The D / A converter generates the rectangular wave signal so that the comparison reference voltage becomes a center voltage of an amplitude. In any one of Claims 1 thru | or 3,
A radar apparatus having the triangular wave signal generation circuit and transmitting / receiving a radar signal frequency-modulated by the triangular wave signal. In claim 4,
A radar apparatus mounted on a vehicle, wherein the amplitude of the triangular wave signal is changed according to the speed of the vehicle.

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