WO2018154747A1 - Frequency calculation device and radar apparatus - Google Patents

Frequency calculation device and radar apparatus Download PDF

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Publication number
WO2018154747A1
WO2018154747A1 PCT/JP2017/007331 JP2017007331W WO2018154747A1 WO 2018154747 A1 WO2018154747 A1 WO 2018154747A1 JP 2017007331 W JP2017007331 W JP 2017007331W WO 2018154747 A1 WO2018154747 A1 WO 2018154747A1
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Prior art keywords
frequency
signal
circuit
beat
harmonics
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PCT/JP2017/007331
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French (fr)
Japanese (ja)
Inventor
潤 下川床
浩之 水谷
田島　賢一
大塚　浩志
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三菱電機株式会社
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Application filed by 三菱電機株式会社 filed Critical 三菱電機株式会社
Priority to JP2017537520A priority Critical patent/JP6217887B1/en
Priority to PCT/JP2017/007331 priority patent/WO2018154747A1/en
Publication of WO2018154747A1 publication Critical patent/WO2018154747A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G01R23/165—Spectrum analysis; Fourier analysis using filters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal

Definitions

  • the present invention relates to a frequency calculation device and a radar device using the same.
  • an FMCW radar device as a radar device for detecting the distance and relative velocity with respect to a target.
  • the radar uses a chirp signal whose frequency is linearly modulated as a transmission signal, calculates the beat frequency, which is the difference between the frequency of the transmission signal and the frequency of the reception signal, and calculates the distance and relative velocity from the target. .
  • the FMCW radar apparatus disclosed in Patent Document 1 first shortens the chirp period, performs the separation and extraction of the beat frequency spectrum in a state where the frequency shift due to the relative velocity with the target is small, and then the chirp period.
  • the beat frequency is accurately detected in a state where the frequency shift due to the relative speed with respect to the target is prominent.
  • the FMCW radar device disclosed in Patent Document 1 has a modulation signal frequency switching signal and a triangular wave signal generator controlled thereby as a configuration for changing the chirp period. Even when the chirp period is changed, the sampling frequency is also changed by the signal waveform thinning circuit in order to keep the target detection distance range constant.
  • the frequency calculation device of the present invention includes a harmonic generation circuit that generates harmonics of an input signal, a filter that passes the harmonics among signals output from the harmonic generation circuit, and a signal that is output by the filter An A / D converter that converts the signal into a digital signal, a frequency detection circuit that detects a frequency of the digital signal output from the A / D converter, and a frequency of the harmonic detected by the frequency detection circuit And a frequency calculation circuit for calculating the frequency of the input signal.
  • the distance and relative speed accuracy can be improved without changing the period of the chirp signal.
  • FIG. 1 is a block diagram showing a configuration example of a radar apparatus according to Embodiment 1 of the present invention.
  • the radar apparatus includes an oscillator 1, a directional coupler 2, a transmission antenna 3, a reception antenna 4, a mixer 5, a frequency calculation device 6, and a distance / speed calculation circuit 7.
  • the oscillator 1 is an oscillator that generates a chirp signal as a transmission signal and outputs the generated chirp signal to the directional coupler 2.
  • the voltage controlled oscillator (VCO) is used for the oscillator 1.
  • a method for generating a chirp signal there is a method in which a triangular wave or a sawtooth wave having a period T is input from a D / A converter to a control terminal of a VCO.
  • the directional coupler 2 is a directional coupler that distributes the transmission signal output from the oscillator 1 and outputs it to the transmission antenna 3 and the mixer 5.
  • the directional coupler 2 is a coupled line coupler, a Wilkinson coupler, or the like.
  • the transmission antenna 3 is an antenna that converts a transmission signal output from the directional coupler 2 into a transmission radio wave and radiates it into space.
  • the transmission antenna 3 is a patch antenna, a horn antenna, or the like.
  • the receiving antenna 4 is an antenna that receives a reflected radio wave from a target, converts it into a received signal, and outputs it to the mixer 5.
  • the receiving antenna 4 is a patch antenna, a horn antenna, or the like.
  • the mixer 5 mixes the transmission signal input from the directional coupler 2 and the reception signal input from the reception antenna 4 to generate a beat signal (mixed wave fundamental wave) and outputs the beat signal to the harmonic generation circuit 61.
  • a beat signal is a difference frequency between the transmission signal and the reception signal.
  • the mixer 5 is a diode mixer, an FET mixer, or the like.
  • the frequency calculation device 6 is a frequency calculation device that calculates the frequency of the beat signal input from the mixer 5 and outputs it to the distance / speed calculation circuit 7.
  • the frequency calculation device 6 includes a harmonic generation circuit 61, a filter 62, an A / D converter (Analog to Digital Converter) 63, an FFT (Fast Fourier Transform) circuit 64, a frequency detection circuit 65, and a frequency calculation circuit 66.
  • the harmonic generation circuit 61 is a harmonic generation circuit that generates a harmonic of the beat signal output from the mixer 5 and outputs the beat signal and an analog signal including the harmonic to the filter 62.
  • a discrete diode, an inverting amplifier circuit, or the like is used for the harmonic generation circuit 61.
  • the filter 62 is a filter that passes a beat signal and a plurality of signals including the harmonics from the analog signal output from the harmonic generation circuit 61 and outputs the signals to the A / D converter 63.
  • a discrete filter, a low-pass filter, a band-pass filter, or the like is used as the filter 62.
  • the A / D converter 63 is an A / D converter that samples the analog signal output from the filter 62 and converts it into a digital signal, and outputs the converted digital signal to the FFT circuit 64.
  • a / D converter 63 a successive approximation type A / D conversion IC (Integral Circuit), a pipeline type A / D conversion IC, or the like is used.
  • the FFT circuit 64 is an FFT circuit that performs FFT (Fast Fourier Transform) on the digital signal input from the A / D converter 63, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65.
  • FFT Fast Fourier Transform
  • an FPGA Field-Programmable Gate Array
  • the FFT circuit 64 may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
  • the frequency detection circuit 65 is a frequency detection circuit that detects the frequency of the beat signal and its harmonics from the spectrum data output from the FFT circuit 64 and outputs the detection result of the frequency to the frequency calculation circuit 66.
  • an FPGA is used for the frequency detection circuit 65.
  • the frequency detection circuit 65 may replace the arithmetic circuit in the FPGA with an arithmetic operation based on signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
  • the frequency calculation circuit 66 is a frequency calculation circuit that calculates a beat frequency from the frequency detection result output by the frequency detection circuit 65 and outputs the calculated beat frequency to the distance / speed calculation circuit 7.
  • the frequency calculation circuit 66 uses an FPGA.
  • the frequency calculation circuit 66 may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
  • the distance / speed calculation circuit 7 is a circuit that calculates the distance and relative speed from the target from the input beat frequency.
  • an FPGA is used for the distance / speed calculation circuit 7.
  • the distance / speed calculation circuit 7 may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
  • the oscillator 1 generates a chirp signal having a frequency f TX (t) represented by the following expression as a transmission signal.
  • B is the modulation bandwidth
  • T is the chirp period
  • fa is the frequency at the start of modulation.
  • the directional coupler 2 distributes the transmission signal output from the oscillator 1 and outputs it to the transmission antenna 3 and the mixer 5.
  • the transmission antenna 3 converts the input transmission signal into a transmission radio wave and radiates it in the target direction.
  • the receiving antenna 4 receives the reflected radio wave from the target, converts it to a received signal, and outputs it to the mixer 5.
  • the frequency of the received signal can be expressed as follows using the distance x to the target.
  • c indicates the speed of light.
  • f 0 indicates the center frequency of the transmission signal.
  • the mixer 5 mixes the transmission signal output from the directional coupler 2 and the reception signal output from the reception antenna 4 to generate a beat signal.
  • the frequency f beat of the beat signal is the sum of the distance shift df x due to the distance x and the Doppler shift df v due to the relative velocity v with respect to the target.
  • the frequency calculation device 6 detects the beat signal output from the mixer 5 and the harmonic frequency thereof, and calculates the beat frequency using the detection result.
  • the harmonic generation circuit 61 generates harmonics of the beat signal output from the mixer 5.
  • FIG. 2 is a configuration diagram showing a configuration example of the harmonic generation circuit 61 according to Embodiment 1 of the present invention.
  • the input terminal is connected to the inductor 611
  • the inductor output terminal is connected to the output terminal and the anode of the diode 612
  • the cathode of the diode 612 is grounded.
  • a circuit using a diode is shown here, a transistor or a FET (Field Effect Transistor) may be used instead of the diode.
  • a logic IC may be used to generate a rectangular wave and generate only odd-order harmonics.
  • the mixer 5 ideally outputs only the beat signal, it actually includes the harmonics of the beat signal, so that the harmonic generation circuit can be actively extracted to substitute for the harmonic generation circuit. You can also.
  • the filter 62 passes the beat signal and its harmonics from the beat signal output by the harmonic generation circuit 61, its harmonics, and spurious signals, suppresses other signals, and beat signals and their harmonics. Is output to the A / D converter 63.
  • FIG. 3 is an explanatory diagram showing an example of the characteristics of the filter 62 according to Embodiment 1 of the present invention.
  • the filter 62 is passed through the beat signal f beat and harmonics f m of the m-fold, cut off the unnecessary wave mixer 5 outputs, also the Nyquist frequency (f s / 2) above To block noise.
  • fs indicates a sampling frequency of the A / D converter 63 described later.
  • FIG. 4 is an explanatory diagram showing another example of the characteristics of the filter 62 according to the first embodiment of the present invention.
  • the filter 62 may have a plurality of passbands and have a characteristic of taking out harmonics of an arbitrary order.
  • FIG. 5 is an explanatory diagram showing another example of the characteristics of the filter 62 according to the first embodiment of the present invention. As shown in FIG. 5, the pass band of the filter 62 may exist above the Nyquist frequency.
  • a / D converter 63 samples the input analog signal at a sampling frequency f s, and converts an analog signal into a digital signal.
  • the sampling frequency is set to at least twice the maximum frequency of the signal to be sampled.
  • the sampling frequency is not necessarily twice or more. Use the undersampled aliasing frequency.
  • FIG. 6 is an explanatory diagram showing an example of the spectrum of the beat signal after sampling according to Embodiment 1 of the present invention. As shown in FIG. 6, harmonics having a frequency equal to or higher than the Nyquist frequency are undersampled by the A / D converter 63 and observed as a folded wave in the digital domain.
  • the FFT circuit 64 performs FFT processing on the input digital signal, and calculates the beat frequency and the spectrum of its harmonics. In general, in FFT, a frequency resolution ⁇ f corresponding to a sampling frequency and the number of samples is obtained.
  • the frequency detection circuit 65 first detects the beat frequency, and then uses this result to detect the harmonic frequency of the beat signal.
  • a method for detecting each frequency for example, a frequency at which power is maximized is obtained from the input spectrum, and this is used as a beat frequency detection result f beat_DET .
  • an arbitrary threshold power may be provided, and a peak having the lowest frequency among a plurality of peaks exceeding the threshold power may be set as f beat_DET .
  • the obtained f beat_DET is multiplied by m, and a frequency having a power peak in the range of mf beat_DET ⁇ BW search is detected as a frequency of the harmonic of m times.
  • BW search is a power search range, and is at least ⁇ f / 2 or more.
  • FIG. 7 is an explanatory diagram showing an example of a spectrum when undersampling the harmonics of the beat signal according to Embodiment 1 of the present invention.
  • f m represents a frequency of a harmonic wave m times the beat signal at the input of the A / D converter 63
  • f m ′ represents a folding frequency undersampled by the A / D converter 63. If f m is present in the n-th Nyquist region, the relationship between the two is as the following equation.
  • Expression (6) is a case where n is an even number
  • Expression (7) is a case where n is an odd number.
  • n using the detection result and the sampling frequency of the beat frequency is determined from the integer portion of mf beat_DET / f s.
  • a frequency having a power peak in a range of nf s / 2 ⁇ mf beat_DET ⁇ BW search is defined as f m_DET
  • mf beat_DET ⁇ (n ⁇ 1) f s / 2 Let f m_DET be a frequency having a power peak in the range of ⁇ BW search .
  • a method using FFT and peak detection has been described as a method for detecting the beat frequency, but the frequency may be detected by a method such as digital signal processing using a discrete Fourier transform or a Hilbert transform circuit.
  • the frequency calculation circuit 66 is a circuit that more accurately calculates the beat frequency from the input frequency detection result.
  • the beat frequency calculation result f beat_CALC is obtained by dividing the detected sum of the plurality of frequencies by the sum of the orders of the plurality of signals.
  • FIG. 8 is an explanatory diagram showing an example of a spectrum of a digital signal output from the A / D converter 63 according to Embodiment 1 of the present invention. If the true value of the beat frequency is f beat_ID and the error resulting from the FFT resolution is ⁇ 1 , f beat_DET can be expressed by the following equation.
  • the beat frequency can be calculated by dividing f m_DET by m, and the beat frequency calculation result f beat_CALC can be expressed by the following equation.
  • the beat frequency can be calculated by dividing the sum of the detected frequencies by the sum of the orders.
  • a beat frequency calculation result f beat_CALC can be expressed by the following equation. As can be seen from the second term of Equation 13, it can be seen that the accuracy can be improved as compared with the case where the frequency is calculated using only the beat signal.
  • the beat frequency is calculated from the detection result of the beat signal and the frequency of the harmonics 2 to m times higher than it, but any of these signals (k 1 th harmonic, k 2 th harmonic,..., K
  • the beat frequency calculation result f beat_CALC can be expressed by the following equation.
  • FIG. 9 shows the calculation result of the beat frequency according to the first embodiment of the present invention.
  • the vertical axis indicates the frequency error between the true value of the beat frequency and the calculation result of the beat frequency
  • the horizontal axis indicates the order of the harmonic used for the calculation.
  • Beat frequency detection result, beat frequency calculation result (when m times higher harmonics of the beat signal are used), and beat frequency calculation result (when beat signals and 2 to m times higher harmonics are used) Is plotted.
  • the beat frequency was 100.2 kHz
  • the sampling frequency was 1 MHz
  • the chirp period was 2 msec.
  • the beat frequency calculation result shows an error as the harmonic order m increases.
  • beat frequency calculation results (when using beat signals and 2 to m times higher harmonics) converge at a lower order than when using m times higher harmonics than beat signals.
  • the error is 1 / m as shown in the equation (12).
  • the equation (14) is used. ). The accuracy is further improved.
  • Equation (15) becomes Equation (17)
  • Equation (16) becomes Equation (18).
  • a bandpass filter including a desired m-th harmonic can be used instead of the anti-aliasing filter. If the lower limit frequency of the bandwidth is (n ⁇ 1) f S / 2 and the upper limit frequency is nf S / 2, the noise band can be limited in the same manner as oversampling.
  • the distance / speed calculation circuit 7 calculates the distance and relative speed from the target by using the equations (3) to (5) from the input beat frequency.
  • the beat signal output from the harmonic generation circuit and a plurality of signals including the harmonic are taken out by the filter and calculated by the frequency calculation circuit.
  • the frequency can be calculated with high accuracy, and the distance from the target and the relative speed can be calculated with high accuracy without changing the chirp period.
  • the radar apparatus according to Embodiment 1 has a greater effect of improving the accuracy of distance and relative speed as the distance from the target is shorter. This is because the shorter the distance from the target is, the lower the beat frequency is, so that the order of the harmonics that can be extracted by the filter increases, and the higher order harmonics can be used. As a result, the accuracy of distance and relative speed can be improved.
  • Embodiment 2 In the first embodiment, the beat frequency and the harmonic frequency are detected by the same circuit. In the second embodiment, a configuration in which the beat frequency is separated is shown.
  • FIG. 10 is a block diagram showing an example of the configuration of a radar apparatus according to Embodiment 2 of the present invention.
  • the same reference numerals as those in FIG. 10 are identical reference numerals as those in FIG. 10.
  • the frequency calculation device 6 a is a frequency calculation device that calculates the frequency of the beat signal input from the mixer 5 and outputs it to the distance / speed calculation circuit 7.
  • the frequency calculation device 6a includes a harmonic generation circuit 61, a fundamental wave filter 62a, a harmonic filter 62b, an A / D converter 63a, an A / D converter 63b, an FFT circuit 64a, an FFT circuit 64b, and a frequency detection circuit 65a.
  • a frequency detection circuit 65 b and a frequency calculation circuit 66 is a frequency calculation device that calculates the frequency of the beat signal input from the mixer 5 and outputs it to the distance / speed calculation circuit 7.
  • the frequency calculation device 6a includes a harmonic generation circuit 61, a fundamental wave filter 62a, a harmonic filter 62b, an A / D converter 63a, an A / D converter 63b, an FFT circuit 64a, an FFT circuit 64b, and a frequency detection circuit 65a.
  • the fundamental wave filter 62a is a filter that extracts the beat signal output from the mixer 5 and outputs the beat signal to the A / D converter 63a.
  • a low-pass filter, a band-pass filter, or the like is used as the fundamental wave filter 62a.
  • the harmonic filter 62b is a harmonic filter 62b that extracts the harmonics of the beat signal from the analog signal output from the harmonic generation circuit 61 and outputs the harmonics to the A / D converter 63b.
  • a low-pass filter, a band-pass filter, or the like is used for the harmonic filter 62b.
  • the A / D converter 63a is an A / D converter that samples the analog signal input from the fundamental wave filter 62a, converts the analog signal into a digital signal, and outputs the converted digital signal to the FFT circuit 64a.
  • a successive approximation A / D conversion IC, a pipeline A / D conversion IC, or the like is used for the A / D converter 63a.
  • the A / D converter 63b is an A / D converter that samples the analog signal output from the harmonic filter 62b, converts the analog signal into a digital signal, and outputs the obtained digital signal to the FFT circuit 64b.
  • a successive approximation A / D conversion IC and a pipeline A / D conversion IC are used for the A / D converter 63b.
  • the FFT circuit 64a is a circuit that performs FFT on the digital signal output from the A / D converter 63a, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65a.
  • an FPGA is used for the FFT circuit 64a.
  • the FFT circuit 64a may replace an arithmetic circuit in the FPGA with an arithmetic operation based on signal processing, and a program for performing the arithmetic operation may be stored in a memory and executed by the CPU.
  • the FFT circuit 64b performs FFT on the digital signal input from the A / D converter 63b to calculate a spectrum. This circuit outputs the calculated spectrum data to the frequency detection circuit 65b.
  • an FPGA is used for the FFT circuit 64b.
  • the FFT circuit 64b may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
  • the frequency detection circuit 65 a is a circuit that detects the beat frequency from the spectrum data input from the FFT circuit 64 a and outputs the frequency detection result to the frequency calculation circuit 66.
  • an FPGA is used for the frequency detection circuit 65a.
  • the frequency detection circuit 65a may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
  • the frequency detection circuit 65 b is a circuit that detects the harmonic frequency of the beat signal from the spectrum data input from the FFT circuit 64 b and outputs the frequency detection result to the frequency calculation circuit 66.
  • An FPGA is used for the frequency detection circuit 65b.
  • the frequency detection circuit 65b may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
  • the oscillator 1 generates a chirp signal having a frequency f TX (t) shown in Expression (1) as a transmission signal.
  • the directional coupler 2 distributes the power of the transmission signal output from the oscillator 1 and outputs it to the transmission antenna 3 and the mixer 5.
  • the transmission antenna 3 converts the transmission signal output from the directional coupler 2 into a transmission radio wave and radiates it in the target direction.
  • the receiving antenna 4 receives the reflected radio wave from the target, converts it into a received signal, and outputs it to the mixer 5.
  • the mixer 5 mixes the transmission signal and the reception signal to generate a beat signal, and outputs an analog signal including the beat signal to the fundamental wave filter 62a.
  • the fundamental wave filter 62a extracts a beat signal from the analog signal output from the mixer 5.
  • FIG. 11 is an explanatory diagram showing an example of the characteristic of the fundamental wave filter 62a according to the second embodiment of the present invention.
  • the fundamental wave filter 62a is a low-pass filter that passes a beat signal, cuts off an unnecessary wave output from the mixer 5, and cuts off noise at a Nyquist frequency (fs / 2) or higher. .
  • the A / D converter 63a samples the input analog signal at the sampling frequency fs, converts it to a digital signal, and outputs the converted digital signal to the FFT circuit 64a.
  • the A / D converter 63b samples the input analog signal at the sampling frequency fs, converts it to a digital signal, and outputs the converted digital signal to the FFT circuit 64b.
  • the FFT circuit 64a performs FFT processing on the digital signal output from the A / D converter 63a, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65a.
  • the frequency detection circuit 65a detects the frequency of the beat signal by the same method as in the first embodiment.
  • the harmonic generation circuit 61 generates a harmonic of the beat signal output from the mixer 5 and outputs the beat signal and its harmonic to the harmonic filter 62b.
  • the harmonic filter 62b extracts the harmonics of the beat signal from the analog signal output from the harmonic generation circuit 61.
  • FIG. 12 is an explanatory diagram showing an example of the characteristics of the harmonic filter 62b according to the second embodiment of the present invention.
  • the harmonic filter 62b is a low-pass filter that passes harmonics up to m times the beat signal.
  • under-sampling When taking out higher-order harmonics, under-sampling may be used by setting the cutoff frequency higher than the Nyquist frequency, as in the first embodiment.
  • a band pass filter When undersampling is used, a band pass filter may be used as the harmonic filter 62b.
  • FIG. 13 is an explanatory diagram showing another example of the characteristic of the harmonic filter 62b according to Embodiment 2 of the present invention.
  • FIG. 13A shows an input signal of the A / D converter 63b when a low-pass filter is used as the harmonic filter 62b.
  • f m is in the second Nyquist zone
  • sampled signal by the A / D converter 63b generates a folded wave street, with fs / 2 shown in FIG. 13 (B)
  • each Since harmonics overlap each other it causes false detection.
  • FIG. 13C a signal in the first Nyquist region may be blocked using a bandpass filter as the harmonic filter 62b.
  • the signal sampled by the A / D converter 63b is As shown in FIG. 13 (D), overlapping of folded waves can be avoided.
  • the harmonic filter 62b may be a tunable filter or a plurality of switchable filters, and the passband may be changed according to the beat frequency to be detected.
  • the A / D converter 63b samples the input analog signal at the sampling frequency fs, converts it to a digital signal, and outputs the converted digital signal to the FFT circuit 64b.
  • the FFT circuit 64b performs FFT processing on the digital signal output from the A / D converter 63b, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65b.
  • the frequency detection circuit 65b detects the harmonic frequency of the beat signal by the same method as in the first embodiment.
  • the frequency calculation circuit 66 calculates the beat frequency from the frequency detection results output by the frequency detection circuits 65a and 65b using Equation (13).
  • the distance / speed calculation circuit 7 calculates the distance and relative speed from the target by using the equations (3) to (5) from the input beat frequency.
  • FIG. 14 is an explanatory diagram showing an example of a spectrum input to the frequency detection circuit 65a according to Embodiment 2 of the present invention.
  • the frequency detection circuit 65a to handle without generating harmonics of each beat signal, be detected by separating the beat frequency f Beat2 corresponding to the beat frequency f Beat1 and target 2 which corresponds to the target 1 it can.
  • FIG. 15 is an explanatory diagram showing an example of a spectrum input to the frequency detection circuit 65b according to Embodiment 2 of the present invention.
  • the frequency detection circuit 65b because the harmonics of the beat signal is input, for example, when the beat frequency f Beat2 corresponding to the second harmonic 2f Beat1 and target 2 of the beat frequency corresponding to the target 1 is adjacent Are difficult to separate and easy to misdetect. In order to avoid false detection, the frequency of each harmonic is calculated in advance from f beat1 and f beat2 obtained by the frequency detection circuit 65a, the combination of the two adjacent to each other is ignored, and the detection result of the remaining frequency is used. good. Further, not only harmonics but also frequencies of mixed waves and folded waves can be handled in the same manner.
  • the beat signal extracted by the fundamental filter and the harmonics of the beat signal extracted by the harmonic filter are obtained by the frequency calculation circuit.
  • the beat frequency can be calculated with higher accuracy than before, and therefore the distance and speed can also be calculated with higher accuracy.
  • the present embodiment can accurately calculate the distance and the speed even when detecting a plurality of targets.
  • the harmonic generation circuit 61 When detecting a plurality of targets, since a plurality of beat frequencies are output from the mixer 5, when this is input to the harmonic generation circuit 61, the harmonic generation circuit 61 generates a mixed wave other than the harmonics. Therefore, peak detection is complicated.
  • the beat frequency detection path is separated from the harmonic generation circuit 61, the beat frequency can be detected without being affected by the mixed wave, and the beat frequency and its harmonics can be detected. Since the beat frequency is calculated using the result, a plurality of targets can be detected with high accuracy.

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  • Engineering & Computer Science (AREA)
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Abstract

A conventional frequency calculation device has the problem of deterioration in real time performance because, due to change of a chirp signal period, the frequency calculating device takes a certain time to detect the distance from a target and a relative speed. The frequency calculation device according to the present invention is provided with: a harmonic generation circuit that generates harmonics of an input signal; a filter that allows, among signals outputted from the harmonic generation circuit, the harmonics to pass therethrough; an A/D converter that samples a signal outputted from the filter and converts the sampled signal into a digital signal; a frequency detection circuit that detects the frequency of the digital signal outputted from the A/D converter; and a frequency calculation circuit that calculates the frequency of the input signal by using the frequency of the harmonics detected by the frequency detection circuit.

Description

周波数算出装置及びレーダ装置Frequency calculation device and radar device
　本発明は、周波数算出装置及びこれを用いたレーダ装置に関するものである。 The present invention relates to a frequency calculation device and a radar device using the same.
物標との距離及び相対速度を探知するためのレーダ装置としてＦＭＣＷレーダ装置がある。同レーダでは、送信信号として周波数を直線的に変調したチャープ信号用い、送信信号の周波数と受信信号の周波数との差分の周波数であるビート周波数を求め、物標との距離及び相対速度を算出する。 There is an FMCW radar device as a radar device for detecting the distance and relative velocity with respect to a target. The radar uses a chirp signal whose frequency is linearly modulated as a transmission signal, calculates the beat frequency, which is the difference between the frequency of the transmission signal and the frequency of the reception signal, and calculates the distance and relative velocity from the target. .
　特許文献１で開示されているＦＭＣＷレーダ装置は、はじめにチャープの周期を短くし、物標との相対速度による周波数シフトが小さい状態でビート周波数のスペクトルの分離及び抽出を行い、次にチャープの周期を長くして物標との相対速度による周波数シフトを顕著にした状態でビート周波数を精度良く検出する。 The FMCW radar apparatus disclosed in Patent Document 1 first shortens the chirp period, performs the separation and extraction of the beat frequency spectrum in a state where the frequency shift due to the relative velocity with the target is small, and then the chirp period. The beat frequency is accurately detected in a state where the frequency shift due to the relative speed with respect to the target is prominent.
なお、特許文献１で開示されているＦＭＣＷレーダ装置では、チャープの周期を変更するための構成として、変調信号周波数の切替え信号とこれにより制御される三角波信号発生器とをもつ。また、チャープの周期を変更した場合でも、物標の検知距離範囲は一定に保つために、信号波形間引き回路によって、サンプリング周波数も変更する。 The FMCW radar device disclosed in Patent Document 1 has a modulation signal frequency switching signal and a triangular wave signal generator controlled thereby as a configuration for changing the chirp period. Even when the chirp period is changed, the sampling frequency is also changed by the signal waveform thinning circuit in order to keep the target detection distance range constant.
特開平９－１３３７６５号公報JP-A-9-133765
　しかしながら、特許文献１によれば、周期の短いチャープ信号を用いて複数のビート周波数を分離した後に、ビート周波数を精度良く検出するために、周期の長いチャープ信号を用いて各ビート周波数の検出をするため、物標との距離及び相対速度を１回検出するのにかかる時間も長くなり、データ取得率が悪化するという課題がある。 However, according to Patent Document 1, in order to accurately detect beat frequencies after separating a plurality of beat frequencies using a short-cycle chirp signal, each beat frequency is detected using a long-cycle chirp signal. Therefore, it takes a long time to detect the distance to the target and the relative speed once, and there is a problem that the data acquisition rate deteriorates.
　本発明の周波数算出装置は、入力信号の高調波を発生させる高調波発生回路と、前記高調波発生回路が出力した信号のうち前記高調波を通過させるフィルタと、前記フィルタが出力した信号をサンプリングしてデジタル信号に変換するＡ／Ｄ変換器と、前記Ａ／Ｄ変換器が出力した前記デジタル信号の周波数を検出する周波数検出回路と、前記周波数検出回路が検出した前記高調波の周波数を用いて、前記入力信号の周波数を算出する周波数算出回路とを備える。 The frequency calculation device of the present invention includes a harmonic generation circuit that generates harmonics of an input signal, a filter that passes the harmonics among signals output from the harmonic generation circuit, and a signal that is output by the filter An A / D converter that converts the signal into a digital signal, a frequency detection circuit that detects a frequency of the digital signal output from the A / D converter, and a frequency of the harmonic detected by the frequency detection circuit And a frequency calculation circuit for calculating the frequency of the input signal.
　この発明によれば、チャープ信号の周期を変更することなく、距離及び相対速度精度を向上させることができる。 According to the present invention, the distance and relative speed accuracy can be improved without changing the period of the chirp signal.
この発明の実施の形態１に係るレーダ装置の一構成例を示す構成図である。It is a block diagram which shows one structural example of the radar apparatus which concerns on Embodiment 1 of this invention. この発明の実施の形態１に係る高調波発生回路６１の一構成例を示す構成図である。It is a block diagram which shows one structural example of the harmonic generation circuit 61 which concerns on Embodiment 1 of this invention. この発明の実施の形態１に係るフィルタ６２の特性の一例を示す説明図である。It is explanatory drawing which shows an example of the characteristic of the filter 62 which concerns on Embodiment 1 of this invention. この発明の実施の形態１に係るフィルタ６２の特性の他の例を示す説明図である。It is explanatory drawing which shows the other example of the characteristic of the filter 62 which concerns on Embodiment 1 of this invention. この発明の実施の形態１に係るフィルタ６２の特性の他の例を示す説明図である。It is explanatory drawing which shows the other example of the characteristic of the filter 62 which concerns on Embodiment 1 of this invention. この発明の実施の形態１に係るサンプリング後のビート信号のスペクトルの一例を示す説明図である。It is explanatory drawing which shows an example of the spectrum of the beat signal after the sampling which concerns on Embodiment 1 of this invention. この発明の実施の形態１に係るビート信号の高調波をアンダーサンプリングする場合のスペクトルの一例を示す説明図である。It is explanatory drawing which shows an example of the spectrum in the case of undersampling the harmonic of the beat signal which concerns on Embodiment 1 of this invention. この発明の実施の形態１に係るＡ／Ｄ変換器６３が出力するデジタル信号のスペクトルの一例を示す説明図である。It is explanatory drawing which shows an example of the spectrum of the digital signal which the A / D converter 63 which concerns on Embodiment 1 of this invention outputs. この発明の実施の形態１に係るビート周波数の算出結果である。It is a calculation result of the beat frequency concerning Embodiment 1 of this invention. この発明の実施の形態２に係るレーダ装置の一構成例を示す構成図である。It is a block diagram which shows one structural example of the radar apparatus which concerns on Embodiment 2 of this invention. この発明の実施の形態２に係る基本波用フィルタ６２ａの特性の一例を示す説明図である。It is explanatory drawing which shows an example of the characteristic of the filter for fundamental waves 62a which concerns on Embodiment 2 of this invention. この発明の実施の形態２に係る高調波用フィルタ６２ｂの特性の一例を示す説明図である。It is explanatory drawing which shows an example of the characteristic of the filter 62b for harmonics concerning Embodiment 2 of this invention. この発明の実施の形態２に係る高調波用フィルタ６２ｂの特性の他の例を示す説明図である。It is explanatory drawing which shows the other example of the characteristic of the filter 62b for harmonics concerning Embodiment 2 of this invention. この発明の実施の形態２に係る周波数検出回路６５ａに入力されるスペクトルの一例を示す説明図である。It is explanatory drawing which shows an example of the spectrum input into the frequency detection circuit 65a which concerns on Embodiment 2 of this invention. この発明の実施の形態２に係る周波数検出回路６５ｂに入力されるスペクトルの一例を示す説明図である。It is explanatory drawing which shows an example of the spectrum input into the frequency detection circuit 65b which concerns on Embodiment 2 of this invention.
実施の形態１.
　図１は、この発明の実施の形態１に係るレーダ装置の一構成例を示す構成図である。本レーダ装置は、発振器１、方向性結合器２、送信アンテナ３、受信アンテナ４、ミキサ５、周波数算出装置６、及び距離・速度算出回路７を備える。 Embodiment 1.
FIG. 1 is a block diagram showing a configuration example of a radar apparatus according to Embodiment 1 of the present invention. The radar apparatus includes an oscillator 1, a directional coupler 2, a transmission antenna 3, a reception antenna 4, a mixer 5, a frequency calculation device 6, and a distance / speed calculation circuit 7.
発振器１は、送信信号としてチャープ信号を生成し、生成したチャープ信号を方向性結合器２に出力する発振器である。例えば、発振器１には、Ｖｏｌｔａｇｅ　Ｃｏｎｔｒｏｌｌｅｄ　Ｏｓｃｉｌｌａｔｏｒ（ＶＣＯ）が用いられる。また、チャープ信号の生成方法としては、Ｄ／Ａ変換器からＶＣＯの制御端子に周期Ｔの三角波や鋸波を入力する方法がある。 The oscillator 1 is an oscillator that generates a chirp signal as a transmission signal and outputs the generated chirp signal to the directional coupler 2. For example, the voltage controlled oscillator (VCO) is used for the oscillator 1. As a method for generating a chirp signal, there is a method in which a triangular wave or a sawtooth wave having a period T is input from a D / A converter to a control terminal of a VCO.
方向性結合器２は、発振器１が出力する送信信号を分配し、送信アンテナ３とミキサ５とに出力する方向性結合器である。例えば、方向性結合器２は、結合線路型カプラ、ウィルキンソン型カプラなどが用いられる。 The directional coupler 2 is a directional coupler that distributes the transmission signal output from the oscillator 1 and outputs it to the transmission antenna 3 and the mixer 5. For example, the directional coupler 2 is a coupled line coupler, a Wilkinson coupler, or the like.
送信アンテナ３は、方向性結合器２が出力した送信信号を送信電波に変換して空間に放射するアンテナである。例えば、送信アンテナ３は、パッチアンテナ、ホーンアンテナなどが用いられる。 The transmission antenna 3 is an antenna that converts a transmission signal output from the directional coupler 2 into a transmission radio wave and radiates it into space. For example, the transmission antenna 3 is a patch antenna, a horn antenna, or the like.
受信アンテナ４は、物標からの反射電波を受信し、受信信号に変換してミキサ５に出力するアンテナである。例えば、受信アンテナ４は、パッチアンテナ、ホーンアンテナなどが用いられる。 The receiving antenna 4 is an antenna that receives a reflected radio wave from a target, converts it into a received signal, and outputs it to the mixer 5. For example, the receiving antenna 4 is a patch antenna, a horn antenna, or the like.
ミキサ５は、方向性結合器２より入力された送信信号と受信アンテナ４より入力された受信信号を混合し、ビート信号（混合波の基本波）を生成し、高調波発生回路６１に出力するミキサである。ここで、ビート信号とは、送信信号と受信信号との差周波である。例えば、ミキサ５には、ダイオードミキサ、ＦＥＴミキサなどが用いられる。 The mixer 5 mixes the transmission signal input from the directional coupler 2 and the reception signal input from the reception antenna 4 to generate a beat signal (mixed wave fundamental wave) and outputs the beat signal to the harmonic generation circuit 61. It is a mixer. Here, the beat signal is a difference frequency between the transmission signal and the reception signal. For example, the mixer 5 is a diode mixer, an FET mixer, or the like.
周波数算出装置６は、ミキサ５より入力されたビート信号の周波数を算出し、距離・速度算出回路７に出力する周波数算出装置である。周波数算出装置６は、高調波発生回路６１、フィルタ６２、Ａ／Ｄ変換器（Ａｎａｌｏｇ　ｔｏ　Ｄｉｇｉｔａｌ　Ｃｏｎｖｅｒｔｅｒ）６３、ＦＦＴ（Ｆａｓｔ　Ｆｏｕｒｉｅｒ　Ｔｒａｎｓｆｏｒｍ）回路６４、周波数検出回路６５、及び周波数算出回路６６を備える。 The frequency calculation device 6 is a frequency calculation device that calculates the frequency of the beat signal input from the mixer 5 and outputs it to the distance / speed calculation circuit 7. The frequency calculation device 6 includes a harmonic generation circuit 61, a filter 62, an A / D converter (Analog to Digital Converter) 63, an FFT (Fast Fourier Transform) circuit 64, a frequency detection circuit 65, and a frequency calculation circuit 66.
高調波発生回路６１は、ミキサ５が出力したビート信号に対してその高調波を発生させ、ビート信号及びその高調波を含むアナログ信号をフィルタ６２に出力する高調波発生回路である。例えば、高調波発生回路６１には、ディスクリートのダイオード、反転増幅回路などが用いられる。 The harmonic generation circuit 61 is a harmonic generation circuit that generates a harmonic of the beat signal output from the mixer 5 and outputs the beat signal and an analog signal including the harmonic to the filter 62. For example, a discrete diode, an inverting amplifier circuit, or the like is used for the harmonic generation circuit 61.
フィルタ６２は、高調波発生回路６１が出力したアナログ信号から、ビート信号とその高調波を含む複数の信号を通過させ、Ａ／Ｄ変換器６３に出力するフィルタである。例えば、フィルタ６２には、ディスクリートのフィルタ、ローパスフィルタ、バンドパスフィルタなどが用いられる。 The filter 62 is a filter that passes a beat signal and a plurality of signals including the harmonics from the analog signal output from the harmonic generation circuit 61 and outputs the signals to the A / D converter 63. For example, as the filter 62, a discrete filter, a low-pass filter, a band-pass filter, or the like is used.
Ａ／Ｄ変換器６３は、フィルタ６２が出力したアナログ信号をサンプリングしてデジタル信号に変換し、変換したデジタル信号をＦＦＴ回路６４に出力するＡ／Ｄ変換器である。例えば、Ａ／Ｄ変換器６３には、逐次比較型Ａ／Ｄ変換ＩＣ（Ｉｎｔｅｇｒａｌ　Ｃｉｒｃｕｉｔ）、パイプライン型Ａ／Ｄ変換ＩＣなどが用いられる。 The A / D converter 63 is an A / D converter that samples the analog signal output from the filter 62 and converts it into a digital signal, and outputs the converted digital signal to the FFT circuit 64. For example, as the A / D converter 63, a successive approximation type A / D conversion IC (Integral Circuit), a pipeline type A / D conversion IC, or the like is used.
ＦＦＴ回路６４は、Ａ／Ｄ変換器６３より入力されたデジタル信号にＦＦＴ（高速フーリエ変換）を施し、スペクトルを算出し、算出したスペクトルデータを周波数検出回路６５に出力するＦＦＴ回路である。例えば、ＦＦＴ回路６４には、ＦＰＧＡ（Ｆｉｅｌｄ-Ｐｒｏｇｒａｍｍａｂｌｅ　Ｇａｔｅ　Ａｒｒａｙ）が用いられる。また、ＦＦＴ回路６４は、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The FFT circuit 64 is an FFT circuit that performs FFT (Fast Fourier Transform) on the digital signal input from the A / D converter 63, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65. For example, an FPGA (Field-Programmable Gate Array) is used for the FFT circuit 64. Further, the FFT circuit 64 may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
周波数検出回路６５は、ＦＦＴ回路６４が出力したスペクトルデータからビート信号及びその高調波の周波数を検出し、その周波数の検出結果を周波数算出回路６６に出力する周波数検出回路である。例えば、周波数検出回路６５には、ＦＰＧＡが用いられる。また、周波数検出回路６５は、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The frequency detection circuit 65 is a frequency detection circuit that detects the frequency of the beat signal and its harmonics from the spectrum data output from the FFT circuit 64 and outputs the detection result of the frequency to the frequency calculation circuit 66. For example, an FPGA is used for the frequency detection circuit 65. Further, the frequency detection circuit 65 may replace the arithmetic circuit in the FPGA with an arithmetic operation based on signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
周波数算出回路６６は、周波数検出回路６５が出力した周波数の検出結果からビート周波数を算出し、算出したビート周波数を距離・速度算出回路７へ出力する周波数算出回路である。例えば、周波数算出回路６６は、ＦＰＧＡが用いられる。また、周波数算出回路６６は、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The frequency calculation circuit 66 is a frequency calculation circuit that calculates a beat frequency from the frequency detection result output by the frequency detection circuit 65 and outputs the calculated beat frequency to the distance / speed calculation circuit 7. For example, the frequency calculation circuit 66 uses an FPGA. Further, the frequency calculation circuit 66 may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
距離・速度算出回路７は、入力されたビート周波数から物標との距離及び相対速度を算出する回路である。例えば、距離・速度算出回路７には、ＦＰＧＡが用いられる。また、距離・速度算出回路７は、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The distance / speed calculation circuit 7 is a circuit that calculates the distance and relative speed from the target from the input beat frequency. For example, an FPGA is used for the distance / speed calculation circuit 7. Further, the distance / speed calculation circuit 7 may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
次に、この発明の実施の形態１に係るレーダ装置の動作について説明する。
発振器１は、送信信号として下式に示す周波数ｆＴＸ（ｔ）のチャープ信号を生成する。 Next, the operation of the radar apparatus according to Embodiment 1 of the present invention will be described.
The oscillator 1 generates a chirp signal having a frequency f TX (t) represented by the following expression as a transmission signal.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
ここで、Ｂは変調帯域幅、Ｔはチャープの周期、ｆａは変調開始時の周波数を示す。 Here, B is the modulation bandwidth, T is the chirp period, and fa is the frequency at the start of modulation.
方向性結合器２は、発振器１が出力した送信信号を分配し、送信アンテナ３とミキサ５とに出力する。送信アンテナ３は、入力された送信信号を送信電波に変換して物標方向に放射する。受信アンテナ４は、物標からの反射電波を受信し、受信信号に変換してミキサ５に出力する。 The directional coupler 2 distributes the transmission signal output from the oscillator 1 and outputs it to the transmission antenna 3 and the mixer 5. The transmission antenna 3 converts the input transmission signal into a transmission radio wave and radiates it in the target direction. The receiving antenna 4 receives the reflected radio wave from the target, converts it to a received signal, and outputs it to the mixer 5.
受信信号の周波数は物標との距離ｘを用いて、下式のように表すことができる。 The frequency of the received signal can be expressed as follows using the distance x to the target.
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
ここで、ｃは光速を示す。物標がレーダ装置に対して相対速度ｖを持つ場合、物標からの反射電波の周波数はドップラー効果により、下式に示すドップラーシフトｄｆｖを生じる。 Here, c indicates the speed of light. When the target has a relative velocity v with respect to the radar apparatus, the frequency of the reflected radio wave from the target causes the Doppler shift df v shown in the following equation due to the Doppler effect.
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
ここで、ｆ０は送信信号の中心周波数を示す。 Here, f 0 indicates the center frequency of the transmission signal.
ミキサ５は、方向性結合器２が出力した送信信号と受信アンテナ４が出力した受信信号とを混合し、ビート信号を生成する。ビート信号の周波数ｆｂｅａｔは、距離ｘによる距離シフトｄｆｘと、物標との相対速度ｖによるドップラーシフトｄｆｖの和であるため、下式で表される。 The mixer 5 mixes the transmission signal output from the directional coupler 2 and the reception signal output from the reception antenna 4 to generate a beat signal. The frequency f beat of the beat signal is the sum of the distance shift df x due to the distance x and the Doppler shift df v due to the relative velocity v with respect to the target.
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
距離シフトｄｆｘは、式（１）と式（２）との差周波数になるので、下式で表される。 Since the distance shift df x is a difference frequency between the formula (1) and the formula (2), it is expressed by the following formula.
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000005
周波数算出装置６は、ミキサ５が出力したビート信号及びその高調波の周波数を検出し、この検出結果を用いて、ビート周波数の算出を行う。 The frequency calculation device 6 detects the beat signal output from the mixer 5 and the harmonic frequency thereof, and calculates the beat frequency using the detection result.
　高調波発生回路６１は、ミキサ５が出力したビート信号の高調波を発生させる。 The harmonic generation circuit 61 generates harmonics of the beat signal output from the mixer 5.
　図２は、この発明の実施の形態１に係る高調波発生回路６１の一構成例を示す構成図である。入力端子は、インダクタ６１１に接続され、インダクタ出力端子は、出力端子とダイオード６１２のアノードとに接続され、ダイオード６１２のカソードは、グランドに接地される。なお、ここでは、ダイオードを用いた回路を示したが、ダイオードの代わりにトランジスタ、ＦＥＴ（Ｆｉｅｌｄ　Ｅｆｆｅｃｔ　Ｔｒａｎｓｉｓｔｏｒ）を使用しても良い。また、ロジックＩＣを使用し、矩形波を生成し奇数次の高調波のみを発生させても良い。さらに、ミキサ５は、理想的にはビート信号のみを出力するが、実際にはビート信号の高調波を含んでいるので、高調波を積極的に取出すことで、高調波発生回路の代用することもできる。 FIG. 2 is a configuration diagram showing a configuration example of the harmonic generation circuit 61 according to Embodiment 1 of the present invention. The input terminal is connected to the inductor 611, the inductor output terminal is connected to the output terminal and the anode of the diode 612, and the cathode of the diode 612 is grounded. Although a circuit using a diode is shown here, a transistor or a FET (Field Effect Transistor) may be used instead of the diode. Alternatively, a logic IC may be used to generate a rectangular wave and generate only odd-order harmonics. Furthermore, although the mixer 5 ideally outputs only the beat signal, it actually includes the harmonics of the beat signal, so that the harmonic generation circuit can be actively extracted to substitute for the harmonic generation circuit. You can also.
フィルタ６２は、高調波発生回路６１が出力するビート信号、その高調波、及びスプリアスを含むアナログ信号から、ビート信号とその高調波を通過させ、他の信号を抑圧し、ビート信号とその高調波をＡ／Ｄ変換器６３に出力する。 The filter 62 passes the beat signal and its harmonics from the beat signal output by the harmonic generation circuit 61, its harmonics, and spurious signals, suppresses other signals, and beat signals and their harmonics. Is output to the A / D converter 63.
図３は、この発明の実施の形態１に係るフィルタ６２の特性の一例を示す説明図である。図３に示すように、フィルタ６２は、ビート信号ｆｂｅａｔとそのｍ倍の高調波ｆｍを通過させ、ミキサ５が出力する不要波を遮断し、また、ナイキスト周波数（ｆｓ／２）以上の雑音を遮断する。ここで、ｆｓは、後述するＡ／Ｄ変換器６３のサンプリング周波数を示す。 FIG. 3 is an explanatory diagram showing an example of the characteristics of the filter 62 according to Embodiment 1 of the present invention. As shown in FIG. 3, the filter 62 is passed through the beat signal f beat and harmonics f m of the m-fold, cut off the unnecessary wave mixer 5 outputs, also the Nyquist frequency (f s / 2) above To block noise. Here, fs indicates a sampling frequency of the A / D converter 63 described later.
　図４は、この発明の実施の形態１に係るフィルタ６２の特性の他の例を示す説明図である。図４で示すように、フィルタ６２は、複数の通過帯域を持ち、任意の次数の高調波を取出す特性としてもよい。 FIG. 4 is an explanatory diagram showing another example of the characteristics of the filter 62 according to the first embodiment of the present invention. As shown in FIG. 4, the filter 62 may have a plurality of passbands and have a characteristic of taking out harmonics of an arbitrary order.
　図５は、この発明の実施の形態１に係るフィルタ６２の特性の他の例を示す説明図である。図５に示すように、フィルタ６２の通過帯域は、ナイキスト周波数以上に存在してもよい。 FIG. 5 is an explanatory diagram showing another example of the characteristics of the filter 62 according to the first embodiment of the present invention. As shown in FIG. 5, the pass band of the filter 62 may exist above the Nyquist frequency.
Ａ／Ｄ変換器６３は、入力されたアナログ信号をサンプリング周波数ｆｓでサンプリングし、アナログ信号をデジタル信号に変換する。一般的なＡ／Ｄ変換器では、サンプリング周波数は、サンプリングする信号の最大周波数の２倍以上に設定するが、実施の形態１では必ずしも２倍以上でなくともよく、その場合は後述の方法により、アンダーサンプリングされた折り返しの周波数を利用する。 A / D converter 63 samples the input analog signal at a sampling frequency f s, and converts an analog signal into a digital signal. In a general A / D converter, the sampling frequency is set to at least twice the maximum frequency of the signal to be sampled. However, in the first embodiment, the sampling frequency is not necessarily twice or more. Use the undersampled aliasing frequency.
　図６は、この発明の実施の形態１に係るサンプリング後のビート信号のスペクトルの一例を示す説明図である。図６に示すように、ナイキスト周波数以上の周波数の高調波は、Ａ／Ｄ変換器６３によりアンダーサンプリングされ、デジタル領域では折り返し波として観測される。 FIG. 6 is an explanatory diagram showing an example of the spectrum of the beat signal after sampling according to Embodiment 1 of the present invention. As shown in FIG. 6, harmonics having a frequency equal to or higher than the Nyquist frequency are undersampled by the A / D converter 63 and observed as a folded wave in the digital domain.
ＦＦＴ回路６４は、入力されたデジタル信号にＦＦＴ処理を施し、ビート周波数及びその高調波のスペクトルを算出する。一般的に、ＦＦＴではサンプリング周波数及びサンプル数に応じた周波数分解能Δｆが得られる。 The FFT circuit 64 performs FFT processing on the input digital signal, and calculates the beat frequency and the spectrum of its harmonics. In general, in FFT, a frequency resolution Δf corresponding to a sampling frequency and the number of samples is obtained.
周波数検出回路６５は、まず、ビート周波数の検出を行い、次にこの結果を用いてビート信号の高調波の周波数を検出する。各周波数の検出方法としては、例えば、入力されたスペクトルから電力が最大となる周波数を求め、それをビート周波数の検出結果ｆｂｅａｔ＿ＤＥＴとする。 The frequency detection circuit 65 first detects the beat frequency, and then uses this result to detect the harmonic frequency of the beat signal. As a method for detecting each frequency, for example, a frequency at which power is maximized is obtained from the input spectrum, and this is used as a beat frequency detection result f beat_DET .
また、任意の閾値電力を設け、これを超える複数のピークのうち、周波数が最も低いものをｆｂｅａｔ＿ＤＥＴとしても良い。 Further, an arbitrary threshold power may be provided, and a peak having the lowest frequency among a plurality of peaks exceeding the threshold power may be set as f beat_DET .
ｍ倍の高調波の周波数を検出する方法の一例として、得られたｆｂｅａｔ＿ＤＥＴをｍ倍し、ｍｆｂｅａｔ＿ＤＥＴ±ＢＷｓｅａｒｃｈの範囲で電力のピークをもつ周波数をｍ倍の高調波の周波数の検出結果ｆｍ＿ＤＥＴとする方法がある。ここで、ＢＷｓｅａｒｃｈは、電力の検索範囲であり、少なくともΔｆ／２以上とする。 As an example of a method of detecting the frequency of the harmonic of m times, the obtained f beat_DET is multiplied by m, and a frequency having a power peak in the range of mf beat_DET ± BW search is detected as a frequency of the harmonic of m times. There is a method of fm_DET . Here, BW search is a power search range, and is at least Δf / 2 or more.
　次に、アンダーサンプリングされた折り返しの周波数からｆｍ＿ＤＥＴを検出する方法について説明する。 Next, a method for detecting f m_DET from the undersampled aliasing frequency will be described.
　図７は、この発明の実施の形態１に係るビート信号の高調波をアンダーサンプリングする場合のスペクトルの一例を示す説明図である。ｆｍは、Ａ／Ｄ変換器６３の入力においてビート信号のｍ倍の高調波の周波数を示し、ｆｍ’はＡ／Ｄ変換器６３でアンダーサンプリングされた折り返しの周波数を示す。ｆｍが第ｎナイキスト領域に存在する場合、両者の関係は下式の通りとなる。 FIG. 7 is an explanatory diagram showing an example of a spectrum when undersampling the harmonics of the beat signal according to Embodiment 1 of the present invention. f m represents a frequency of a harmonic wave m times the beat signal at the input of the A / D converter 63, and f m ′ represents a folding frequency undersampled by the A / D converter 63. If f m is present in the n-th Nyquist region, the relationship between the two is as the following equation.
Figure JPOXMLDOC01-appb-M000006
Figure JPOXMLDOC01-appb-M000006
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000007
　ここで、式（６）はｎが偶数の場合、式（７）はｎが奇数の場合である。ｎは、ビート周波数の検出結果とサンプリング周波数を用いて、ｍｆｂｅａｔ＿ＤＥＴ／ｆｓの整数部から求める。 Here, Expression (6) is a case where n is an even number, and Expression (7) is a case where n is an odd number. n, using the detection result and the sampling frequency of the beat frequency is determined from the integer portion of mf beat_DET / f s.
　ｎが偶数の場合は、ｎｆｓ／２－ｍｆｂｅａｔ＿ＤＥＴ±ＢＷｓｅａｒｃｈの範囲で電力のピークをもつ周波数をｆｍ＿ＤＥＴとし、ｎが奇数の場合は、ｍｆｂｅａｔ＿ＤＥＴ－（ｎ－１）ｆｓ／２±ＢＷｓｅａｒｃｈの範囲で電力のピークをもつ周波数をｆｍ＿ＤＥＴとする。 When n is an even number, a frequency having a power peak in a range of nf s / 2−mf beat_DET ± BW search is defined as f m_DET , and when n is an odd number, mf beat_DET − (n−1) f s / 2 Let f m_DET be a frequency having a power peak in the range of ± BW search .
　ここでは、ビート周波数を検出する方法として、ＦＦＴとピーク検出を用いる方法について説明したが、離散フーリエ変換やヒルベルト変換回路を用いたデジタル信号処理等の方法で周波数を検出しても良い。 Here, a method using FFT and peak detection has been described as a method for detecting the beat frequency, but the frequency may be detected by a method such as digital signal processing using a discrete Fourier transform or a Hilbert transform circuit.
　周波数算出回路６６は、入力された周波数の検出結果から、ビート周波数をより正確に算出する回路である。算出の方法としては、検出した複数の周波数の総和を複数の信号の次数の総和で除算することで、ビート周波数の算出結果ｆｂｅａｔ＿ＣＡＬＣを求める。 The frequency calculation circuit 66 is a circuit that more accurately calculates the beat frequency from the input frequency detection result. As a calculation method, the beat frequency calculation result f beat_CALC is obtained by dividing the detected sum of the plurality of frequencies by the sum of the orders of the plurality of signals.
周波数算出回路６６における算出方法について説明する。 A calculation method in the frequency calculation circuit 66 will be described.
図８は、この発明の実施の形態１に係るＡ／Ｄ変換器６３が出力するデジタル信号のスペクトルの一例を示す説明図である。ビート周波数の真の値をｆｂｅａｔ＿ＩＤとし、ＦＦＴの分解能に起因する誤差をε１とすればｆｂｅａｔ＿ＤＥＴは、下式で示すことができる。 FIG. 8 is an explanatory diagram showing an example of a spectrum of a digital signal output from the A / D converter 63 according to Embodiment 1 of the present invention. If the true value of the beat frequency is f beat_ID and the error resulting from the FFT resolution is ε 1 , f beat_DET can be expressed by the following equation.
Figure JPOXMLDOC01-appb-M000008
Figure JPOXMLDOC01-appb-M000008
ここで、ε１とΔｆとの関係は、下式に示す通りであり、ε１の最大値はΔｆ／２となる。 Here, the relationship between ε 1 and Δf is as shown in the following equation, and the maximum value of ε 1 is Δf / 2.
Figure JPOXMLDOC01-appb-M000009
Figure JPOXMLDOC01-appb-M000009
同様に、ｍ倍の高調波の周波数の真の値をｆｍ＿ＩＤ、ＦＦＴの分解能に起因する誤差をεｍとすれば、ｆｍ＿ＤＥＴは、下式で示すことができる。 Similarly, the true value of the frequency of m times the harmonics f M_ID, if the error due to the resolution of the FFT and ε m, f m_DET can be shown by the following formula.
Figure JPOXMLDOC01-appb-M000010
Figure JPOXMLDOC01-appb-M000010
ここで、εｍとΔｆとの関係は、下式に示す通りであり、εｍの最大値は、Δｆ／２である。 Here, the relationship between the epsilon m and Delta] f, are as shown in the following formula, the maximum value of epsilon m is Delta] f / 2.
Figure JPOXMLDOC01-appb-M000011
Figure JPOXMLDOC01-appb-M000011
ｆｍ＿ＤＥＴをｍで除算すれば、ビート周波数を算出することができ、ビート周波数の算出結果ｆｂｅａｔ＿ＣＡＬＣは、下式で示すことができる。 The beat frequency can be calculated by dividing f m_DET by m, and the beat frequency calculation result f beat_CALC can be expressed by the following equation.
Figure JPOXMLDOC01-appb-M000012
Figure JPOXMLDOC01-appb-M000012
ビート周波数の検出結果と、ビート周波数の算出結果とを比較すると、後者は、前者よりもＦＦＴの分解能に起因する誤差の最大値はｍ分の１となり、精度がｍ倍改善する。 Comparing the detection result of the beat frequency with the calculation result of the beat frequency, in the latter, the maximum value of the error due to the FFT resolution becomes 1 / m, and the accuracy is improved by a factor of m.
複数の高調波を用いる場合は、検出した周波数の総和を次数の総和で除算すればビート周波数を算出することができる。ビート信号とその２～ｍ倍の高調波の周波数を用いる場合、ビート周波数の算出結果ｆｂｅａｔ＿ＣＡＬＣは、下式で示すことができる。式１３の第２項を見ると分かるように、ビート信号のみで周波数を算出した場合に比べて、精度を改善できることが分かる。 When using a plurality of harmonics, the beat frequency can be calculated by dividing the sum of the detected frequencies by the sum of the orders. When a beat signal and a frequency of harmonics 2 to m times higher are used, a beat frequency calculation result f beat_CALC can be expressed by the following equation. As can be seen from the second term of Equation 13, it can be seen that the accuracy can be improved as compared with the case where the frequency is calculated using only the beat signal.
Figure JPOXMLDOC01-appb-M000013
Figure JPOXMLDOC01-appb-M000013
ここでは、ビート信号及びその２～ｍ倍の高調波の周波数の検出結果からビート周波数を算出したが、このうちの任意の複数信号（ｋ１倍波，ｋ２倍波，・・・，ｋｎ倍波）を使用しても良く、その場合、ビート周波数の算出結果ｆｂｅａｔ＿ＣＡＬＣは、下式で示すことができる。 Here, the beat frequency is calculated from the detection result of the beat signal and the frequency of the harmonics 2 to m times higher than it, but any of these signals (k 1 th harmonic, k 2 th harmonic,..., K In this case, the beat frequency calculation result f beat_CALC can be expressed by the following equation.
Figure JPOXMLDOC01-appb-M000014
Figure JPOXMLDOC01-appb-M000014
図９は、この発明の実施の形態１に係るビート周波数の算出結果である。縦軸は、ビート周波数の真値とビート周波数の算出結果との周波数誤差を示し、横軸は、算出に用いた高調波の次数を示す。ビート周波数の検出結果と、ビート周波数の算出結果（ビート信号のｍ倍の高調波を使用した場合）、及びビート周波数の算出結果（ビート信号とその２～ｍ倍の高調波を使用した場合）がプロットされている。ここで、ビート周波数を１００．２ｋＨｚ、サンプリング周波数を1ＭＨｚ、チャープの周期を２ｍｓｅｃとした。ビート周波数の検出結果の誤差がε１＝２００Ｈｚであるのに対して、ビート周波数の算出結果（ビート信号のｍ倍の高調波を使用した場合）は、高調波の次数ｍが上がるにつれ誤差が収束していく。また、ビート周波数の算出結果（ビート信号とその２～ｍ倍の高調波とを使用した場合）は、ビート信号のｍ倍の高調波を使用した場合に比べて、より低い次数で収束することがわかる。ビート信号のｍ倍波のみを使用した場合は、式（１２）に示す通り、誤差はｍ分の１となるが、ビート周波数と２～ｍ倍の高調波とを使用した場合は式（１４）に示す通りΣｋ分の１となるため、より精度が向上する。 FIG. 9 shows the calculation result of the beat frequency according to the first embodiment of the present invention. The vertical axis indicates the frequency error between the true value of the beat frequency and the calculation result of the beat frequency, and the horizontal axis indicates the order of the harmonic used for the calculation. Beat frequency detection result, beat frequency calculation result (when m times higher harmonics of the beat signal are used), and beat frequency calculation result (when beat signals and 2 to m times higher harmonics are used) Is plotted. Here, the beat frequency was 100.2 kHz, the sampling frequency was 1 MHz, and the chirp period was 2 msec. The error in the beat frequency detection result is ε 1 = 200 Hz, while the beat frequency calculation result (when using harmonics m times the beat signal) shows an error as the harmonic order m increases. Converge. Also, beat frequency calculation results (when using beat signals and 2 to m times higher harmonics) converge at a lower order than when using m times higher harmonics than beat signals. I understand. When only the m-th harmonic wave of the beat signal is used, the error is 1 / m as shown in the equation (12). However, when the beat frequency and the harmonics 2 to m times are used, the equation (14) is used. ), The accuracy is further improved.
さらに、ビート周波数と２～ｍ倍の高調波と式（１４）とを使用した場合は、ビート信号の１～ｍ倍波の検出結果を平均化した場合よりも高精度となる。ビート信号の１～ｍ倍波の検出結果を平均化した場合の誤差を式（１５）に、ビート周波数と２～ｍ倍の高調波と式（１４）とを使用した場合の誤差を式（１６）に示す。 Further, when the beat frequency, 2 to m times higher harmonics and equation (14) are used, the accuracy is higher than when the detection results of 1 to m times harmonics of the beat signal are averaged. The error when averaging the detection results of 1 to m harmonics of the beat signal is expressed by equation (15), and the error when the beat frequency, the harmonic of 2 to m times and equation (14) are used is expressed by equation (15) 16).
Figure JPOXMLDOC01-appb-M000015
Figure JPOXMLDOC01-appb-M000015
Figure JPOXMLDOC01-appb-M000016
Figure JPOXMLDOC01-appb-M000016
ここで、εk　（ｋ＝１，２，・・・，ｍ）＝εとすると、式（１５）は式（１７）となり、式（１６）は式（１８）となる。 Here, if εk (k = 1, 2,..., M) = ε, Equation (15) becomes Equation (17), and Equation (16) becomes Equation (18).
Figure JPOXMLDOC01-appb-M000017
Figure JPOXMLDOC01-appb-M000017
Figure JPOXMLDOC01-appb-M000018
Figure JPOXMLDOC01-appb-M000018
このように、ｍが２以上の場合において、式（１７）に示す誤差よりも、式（１８）に示す誤差は小さくなる。したがって、ビート周波数と２～ｍ倍の高調波と式（１４）とを使用した場合は、ビート信号の１～ｍ倍波の検出結果を平均化した場合よりも高精度となる。 Thus, when m is 2 or more, the error shown in equation (18) is smaller than the error shown in equation (17). Therefore, when the beat frequency, 2 to m times higher harmonics, and Equation (14) are used, the accuracy becomes higher than when the detection results of 1 to m times harmonics of the beat signal are averaged.
式（１２）（１４）に示す通り、検出に用いるビート信号の高調波の次数ｍが高いほど誤差を小さくすることができる。高い周波数を検出する場合は、Ａ／Ｄ変換器６３のサンプリング周波数を上げたうえでオーバーサンプリングする方法と、サンプリング周波数を上げずにアンダーサンプリングする方法とがある。一般的にオーバーサンプリングを行う場合は、Ａ／Ｄ変換器６３の入力にカットオフ周波数がｆＳ／２のローパスフィルタ（アンチエイリアシングフィルタ）を挿入し、入力される雑音の帯域を制限する。一方アンダーサンプリングの場合は、Ａ／Ｄ変換器６３にサンプリング周波数以上の帯域の信号が入力されるため、アンチエイリアシングフィルタに替えて、所望のｍ倍波を含むバンドパスフィルタを用いればよく、通過帯域幅の下限周波数を（ｎ－１）ｆＳ／２、上限周波数をｎｆＳ／２とすれば、オーバーサンプリングと同様に雑音の帯域を制限することができる。 As shown in equations (12) and (14), the higher the order m of the harmonics of the beat signal used for detection, the smaller the error. When detecting a high frequency, there are a method of oversampling after increasing the sampling frequency of the A / D converter 63 and a method of undersampling without increasing the sampling frequency. In general, when oversampling is performed, a low-pass filter (anti-aliasing filter) having a cutoff frequency of f S / 2 is inserted into the input of the A / D converter 63 to limit the band of input noise. On the other hand, in the case of undersampling, since a signal in a band equal to or higher than the sampling frequency is input to the A / D converter 63, a bandpass filter including a desired m-th harmonic can be used instead of the anti-aliasing filter. If the lower limit frequency of the bandwidth is (n−1) f S / 2 and the upper limit frequency is nf S / 2, the noise band can be limited in the same manner as oversampling.
距離・速度算出回路７は、入力されたビート周波数より式（３）～（５）を用いることで物標との距離及び相対速度を算出する。 The distance / speed calculation circuit 7 calculates the distance and relative speed from the target by using the equations (3) to (5) from the input beat frequency.
以上で明らかなように、この発明の実施の形態１のレーダ装置によれば、高調波発生回路より出力されるビート信号及びその高調波を含む複数の信号をフィルタで取出し、周波数算出回路により演算を行うことで、周波数を精度良く算出でき、チャープの周期を変更せずに、物標との距離及び相対速度を精度よく算出することができる。 As is apparent from the above, according to the radar apparatus of the first embodiment of the present invention, the beat signal output from the harmonic generation circuit and a plurality of signals including the harmonic are taken out by the filter and calculated by the frequency calculation circuit. Thus, the frequency can be calculated with high accuracy, and the distance from the target and the relative speed can be calculated with high accuracy without changing the chirp period.
なお、実施の形態１のレーダ装置は、物標との距離が近いほど距離及び相対速度の精度に対する改善効果は大きくなる。これは、物標との距離が近いほど、ビート周波数は低くなるため、フィルタで取出すことのできる高調波の次数が大きくなり、次数の大きい高調波を使うことができるためである。その結果、距離及び相対速度の精度を改善できる。 Note that the radar apparatus according to Embodiment 1 has a greater effect of improving the accuracy of distance and relative speed as the distance from the target is shorter. This is because the shorter the distance from the target is, the lower the beat frequency is, so that the order of the harmonics that can be extracted by the filter increases, and the higher order harmonics can be used. As a result, the accuracy of distance and relative speed can be improved.
実施の形態２.
実施の形態１では、ビート周波数の検出とその高調波の周波数の検出とを同一の回路で行っていたが、実施の形態２では、これを分離した構成を示す。 Embodiment 2.
In the first embodiment, the beat frequency and the harmonic frequency are detected by the same circuit. In the second embodiment, a configuration in which the beat frequency is separated is shown.
図１０は、この発明の実施の形態２に係るレーダ装置の一構成例を示す構成図である。図１０において図１と同一符号は、同一または相当部分を示すので説明を省略する。 FIG. 10 is a block diagram showing an example of the configuration of a radar apparatus according to Embodiment 2 of the present invention. In FIG. 10, the same reference numerals as those in FIG.
周波数算出装置６ａは、ミキサ５より入力されたビート信号の周波数を算出し、距離・速度算出回路７に出力する周波数算出装置である。周波数算出装置６ａは、高調波発生回路６１、基本波用フィルタ６２ａ、高調波用フィルタ６２ｂ、Ａ／Ｄ変換器６３ａ、Ａ／Ｄ変換器６３ｂ、ＦＦＴ回路６４ａ、ＦＦＴ回路６４ｂ、周波数検出回路６５ａ、周波数検出回路６５ｂ、及び周波数算出回路６６を備える。 The frequency calculation device 6 a is a frequency calculation device that calculates the frequency of the beat signal input from the mixer 5 and outputs it to the distance / speed calculation circuit 7. The frequency calculation device 6a includes a harmonic generation circuit 61, a fundamental wave filter 62a, a harmonic filter 62b, an A / D converter 63a, an A / D converter 63b, an FFT circuit 64a, an FFT circuit 64b, and a frequency detection circuit 65a. A frequency detection circuit 65 b and a frequency calculation circuit 66.
基本波用フィルタ６２ａは、ミキサ５が出力したビート信号を取出し、Ａ／Ｄ変換器６３ａに出力するフィルタである。例えば、基本波用フィルタ６２ａには、ローパスフィルタ、バンドパスフィルタなどが用いられる。 The fundamental wave filter 62a is a filter that extracts the beat signal output from the mixer 5 and outputs the beat signal to the A / D converter 63a. For example, a low-pass filter, a band-pass filter, or the like is used as the fundamental wave filter 62a.
高調波用フィルタ６２ｂは、高調波発生回路６１が出力したアナログ信号からビート信号の高調波を取出し、Ａ／Ｄ変換器６３ｂに出力する高調波用フィルタ６２ｂである。例えば、高調波用フィルタ６２ｂには、ローパスフィルタ、バンドパスフィルタなどが用いられる。 The harmonic filter 62b is a harmonic filter 62b that extracts the harmonics of the beat signal from the analog signal output from the harmonic generation circuit 61 and outputs the harmonics to the A / D converter 63b. For example, a low-pass filter, a band-pass filter, or the like is used for the harmonic filter 62b.
Ａ／Ｄ変換器６３ａは、基本波用フィルタ６２ａから入力されるアナログ信号をサンプリングし、デジタル信号に変換し、変換したデジタル信号をＦＦＴ回路６４ａに出力するＡ／Ｄ変換器である。例えば、Ａ／Ｄ変換器６３ａには、逐次比較型Ａ／Ｄ変換ＩＣ、パイプライン型Ａ／Ｄ変換ＩＣなどが用いられる。 The A / D converter 63a is an A / D converter that samples the analog signal input from the fundamental wave filter 62a, converts the analog signal into a digital signal, and outputs the converted digital signal to the FFT circuit 64a. For example, a successive approximation A / D conversion IC, a pipeline A / D conversion IC, or the like is used for the A / D converter 63a.
Ａ／Ｄ変換器６３ｂは、高調波用フィルタ６２ｂが出力したアナログ信号をサンプリングし、デジタル信号に変換し、得られたデジタル信号をＦＦＴ回路６４ｂに出力するＡ／Ｄ変換器である。例えば、Ａ／Ｄ変換器６３ｂには、逐次比較型Ａ／Ｄ変換ＩＣ、パイプライン型Ａ／Ｄ変換ＩＣが用いられる。 The A / D converter 63b is an A / D converter that samples the analog signal output from the harmonic filter 62b, converts the analog signal into a digital signal, and outputs the obtained digital signal to the FFT circuit 64b. For example, a successive approximation A / D conversion IC and a pipeline A / D conversion IC are used for the A / D converter 63b.
ＦＦＴ回路６４ａは、Ａ／Ｄ変換器６３ａが出力したデジタル信号にＦＦＴを施し、スペクトルを算出し、算出したスペクトルデータを周波数検出回路６５ａに出力する回路である。例えば、ＦＦＴ回路６４ａには、ＦＰＧＡが用いられる。また、ＦＦＴ回路６４ａは、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The FFT circuit 64a is a circuit that performs FFT on the digital signal output from the A / D converter 63a, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65a. For example, an FPGA is used for the FFT circuit 64a. In addition, the FFT circuit 64a may replace an arithmetic circuit in the FPGA with an arithmetic operation based on signal processing, and a program for performing the arithmetic operation may be stored in a memory and executed by the CPU.
ＦＦＴ回路６４ｂは、Ａ／Ｄ変換器６３ｂより入力されたデジタル信号にＦＦＴを施し、スペクトルを算出し。算出したスペクトルデータを周波数検出回路６５ｂに出力する回路である。例えば、ＦＦＴ回路６４ｂには、ＦＰＧＡが用いられる。また、ＦＦＴ回路６４ｂは、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The FFT circuit 64b performs FFT on the digital signal input from the A / D converter 63b to calculate a spectrum. This circuit outputs the calculated spectrum data to the frequency detection circuit 65b. For example, an FPGA is used for the FFT circuit 64b. Further, the FFT circuit 64b may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
周波数検出回路６５ａは、ＦＦＴ回路６４ａより入力されたスペクトルデータよりビート周波数の検出を行い、周波数の検出結果を周波数算出回路６６に出力する回路である。例えば、周波数検出回路６５ａには、ＦＰＧＡが用いられる。また、周波数検出回路６５ａは、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The frequency detection circuit 65 a is a circuit that detects the beat frequency from the spectrum data input from the FFT circuit 64 a and outputs the frequency detection result to the frequency calculation circuit 66. For example, an FPGA is used for the frequency detection circuit 65a. Further, the frequency detection circuit 65a may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
周波数検出回路６５ｂは、ＦＦＴ回路６４ｂより入力されたスペクトルデータよりビート信号の高調波の周波数を検出し、周波数の検出結果を周波数算出回路６６に出力する回路である。周波数検出回路６５ｂには、ＦＰＧＡが用いられる。また、周波数検出回路６５ｂは、ＦＰＧＡにおける演算回路を信号処理による演算に置換え、その演算を行うプログラムをメモリに保存し、ＣＰＵで実行しても良い。 The frequency detection circuit 65 b is a circuit that detects the harmonic frequency of the beat signal from the spectrum data input from the FFT circuit 64 b and outputs the frequency detection result to the frequency calculation circuit 66. An FPGA is used for the frequency detection circuit 65b. Further, the frequency detection circuit 65b may replace the arithmetic circuit in the FPGA with an arithmetic operation by signal processing, store a program for performing the arithmetic operation in a memory, and execute it by the CPU.
次に、この発明の実施の形態２に係るレーダ装置の動作について説明する。
発振器１は、送信信号として式（１）に示す周波数ｆＴＸ（ｔ）のチャープ信号を生成する。方向性結合器２は、発振器１が出力した送信信号の電力を分配、送信アンテナ３とミキサ５とに出力する。送信アンテナ３は、方向性結合器２が出力した送信信号を送信電波に変換して物標方向に放射する。受信アンテナ４は、物標からの反射電波を受信し、受信信号に変換して、ミキサ５に出力する。ミキサ５は、送信信号と受信信号とを混合しビート信号を生成し、ビート信号を含むアナログ信号を基本波用フィルタ６２ａに出力する。 Next, the operation of the radar apparatus according to Embodiment 2 of the present invention will be described.
The oscillator 1 generates a chirp signal having a frequency f TX (t) shown in Expression (1) as a transmission signal. The directional coupler 2 distributes the power of the transmission signal output from the oscillator 1 and outputs it to the transmission antenna 3 and the mixer 5. The transmission antenna 3 converts the transmission signal output from the directional coupler 2 into a transmission radio wave and radiates it in the target direction. The receiving antenna 4 receives the reflected radio wave from the target, converts it into a received signal, and outputs it to the mixer 5. The mixer 5 mixes the transmission signal and the reception signal to generate a beat signal, and outputs an analog signal including the beat signal to the fundamental wave filter 62a.
基本波用フィルタ６２ａは、ミキサ５が出力したアナログ信号からビート信号を取出す。 The fundamental wave filter 62a extracts a beat signal from the analog signal output from the mixer 5.
図１１は、この発明の実施の形態２に係る基本波用フィルタ６２ａの特性の一例を示す説明図である。図１１に示すように、基本波用フィルタ６２ａは、ビート信号を通過させ、ミキサ５から出力される不要波を遮断し、またナイキスト周波数（ｆｓ／２）以上の雑音を遮断するローパスフィルタである。 FIG. 11 is an explanatory diagram showing an example of the characteristic of the fundamental wave filter 62a according to the second embodiment of the present invention. As shown in FIG. 11, the fundamental wave filter 62a is a low-pass filter that passes a beat signal, cuts off an unnecessary wave output from the mixer 5, and cuts off noise at a Nyquist frequency (fs / 2) or higher. .
Ａ／Ｄ変換器６３ａは、入力されたアナログ信号をサンプリング周波数ｆｓでサンプリングし、デジタル信号に変換し、変換したデジタル信号をＦＦＴ回路６４ａに出力する。 The A / D converter 63a samples the input analog signal at the sampling frequency fs, converts it to a digital signal, and outputs the converted digital signal to the FFT circuit 64a.
Ａ／Ｄ変換器６３ｂは、入力されたアナログ信号をサンプリング周波数ｆｓでサンプリングし、デジタル信号に変換し、変換したデジタル信号をＦＦＴ回路６４ｂに出力する。 The A / D converter 63b samples the input analog signal at the sampling frequency fs, converts it to a digital signal, and outputs the converted digital signal to the FFT circuit 64b.
ＦＦＴ回路６４ａは、Ａ／Ｄ変換器６３ａが出力したデジタル信号にＦＦＴ処理を施し、スペクトルを算出し、算出したスペクトルデータを周波数検出回路６５ａに出力する。 The FFT circuit 64a performs FFT processing on the digital signal output from the A / D converter 63a, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65a.
周波数検出回路６５ａは、実施の形態１と同様の方法でビート信号の周波数の検出を行う。 The frequency detection circuit 65a detects the frequency of the beat signal by the same method as in the first embodiment.
高調波発生回路６１は、ミキサ５が出力したビート信号の高調波を発生させ、ビート信号及びその高調波を高調波用フィルタ６２ｂに出力する。高調波用フィルタ６２ｂは、高調波発生回路６１が出力したアナログ信号から、ビート信号の高調波を取出す。 The harmonic generation circuit 61 generates a harmonic of the beat signal output from the mixer 5 and outputs the beat signal and its harmonic to the harmonic filter 62b. The harmonic filter 62b extracts the harmonics of the beat signal from the analog signal output from the harmonic generation circuit 61.
図１２は、この発明の実施の形態２に係る高調波用フィルタ６２ｂの特性の一例を示す説明図である。図１２に示すように、高調波用フィルタ６２ｂは、ビート信号のｍ倍までの高調波を通過させるローパスフィルタである。 FIG. 12 is an explanatory diagram showing an example of the characteristics of the harmonic filter 62b according to the second embodiment of the present invention. As shown in FIG. 12, the harmonic filter 62b is a low-pass filter that passes harmonics up to m times the beat signal.
より高い次数の高調波を取出す場合は実施の形態１と同様に、カットオフ周波数をナイキスト周波数より高くし、アンダーサンプリングを用いても良い。また、アンダーサンプリングを用いる場合は、高調波用フィルタ６２ｂとして、バンドパスフィルタを用いても良い。 When taking out higher-order harmonics, under-sampling may be used by setting the cutoff frequency higher than the Nyquist frequency, as in the first embodiment. When undersampling is used, a band pass filter may be used as the harmonic filter 62b.
図１３は、この発明の実施の形態２に係る高調波用フィルタ６２ｂの特性の他の例を示す説明図である。図１３（Ａ）は、高調波用フィルタ６２ｂとしてローパスフィルタを用いた場合のＡ／Ｄ変換器６３ｂの入力信号である。例として、ｆｍが第二ナイキスト領域にある場合を考えると、Ａ／Ｄ変換器６３ｂでサンプリングされた信号は、図１３（Ｂ）に示す通り、ｆｓ／２で折返し波を発生し、各高調波同士が重なるため、誤検出の原因となる。この場合は、図１３（Ｃ）に示すとおり高調波用フィルタ６２ｂとしてバンドパスフィルタを用いて第一ナイキスト領域の信号を遮断すればよく、Ａ／Ｄ変換器６３ｂでサンプリングされた信号は、図１３（Ｄ）に示す通り、折返し波の重なりを避けることができる。なお、高調波用フィルタ６２ｂはチューナブルフィルタもしくは、複数の切替え式フィルタを用い、検出したいビート周波数に合わせて通過帯域を変更できるようにしてもよい。 FIG. 13 is an explanatory diagram showing another example of the characteristic of the harmonic filter 62b according to Embodiment 2 of the present invention. FIG. 13A shows an input signal of the A / D converter 63b when a low-pass filter is used as the harmonic filter 62b. As an example, consider the case where f m is in the second Nyquist zone, sampled signal by the A / D converter 63b generates a folded wave street, with fs / 2 shown in FIG. 13 (B), each Since harmonics overlap each other, it causes false detection. In this case, as shown in FIG. 13C, a signal in the first Nyquist region may be blocked using a bandpass filter as the harmonic filter 62b. The signal sampled by the A / D converter 63b is As shown in FIG. 13 (D), overlapping of folded waves can be avoided. The harmonic filter 62b may be a tunable filter or a plurality of switchable filters, and the passband may be changed according to the beat frequency to be detected.
Ａ／Ｄ変換器６３ｂは、入力されたアナログ信号をサンプリング周波数ｆｓでサンプリングし、デジタル信号に変換し、変換したデジタル信号をＦＦＴ回路６４ｂに出力する。 The A / D converter 63b samples the input analog signal at the sampling frequency fs, converts it to a digital signal, and outputs the converted digital signal to the FFT circuit 64b.
ＦＦＴ回路６４ｂは、Ａ／Ｄ変換器６３ｂが出力したデジタル信号にＦＦＴ処理を施し、スペクトルを算出し、算出したスペクトルデータを周波数検出回路６５ｂに出力する。 The FFT circuit 64b performs FFT processing on the digital signal output from the A / D converter 63b, calculates a spectrum, and outputs the calculated spectrum data to the frequency detection circuit 65b.
周波数検出回路６５ｂは、実施の形態１と同様の方法でビート信号の高調波の周波数の検出を行う。 The frequency detection circuit 65b detects the harmonic frequency of the beat signal by the same method as in the first embodiment.
周波数算出回路６６は、周波数検出回路６５ａ及び６５ｂが出力した周波数の検出結果から、式（１３）によりビート周波数を算出する。 The frequency calculation circuit 66 calculates the beat frequency from the frequency detection results output by the frequency detection circuits 65a and 65b using Equation (13).
距離・速度算出回路７は、入力されたビート周波数より式（３）～（５）を用いることで物標との距離及び相対速度を算出する。 The distance / speed calculation circuit 7 calculates the distance and relative speed from the target by using the equations (3) to (5) from the input beat frequency.
次に、物標が複数個ある場合の本レーダ装置の動作について説明する。例として、物標１と物標２の検出を行う場合を考える。 Next, the operation of this radar apparatus when there are a plurality of targets will be described. As an example, let us consider a case where target 1 and target 2 are detected.
図１４は、この発明の実施の形態２に係る周波数検出回路６５ａに入力されるスペクトルの一例を示す説明図である。周波数検出回路６５ａでは、各ビート信号の高調波を発生させずに扱うため、物標１に対応するビート周波数ｆｂｅａｔ１と物標２に対応するビート周波数ｆｂｅａｔ２とを分離して検出することができる。 FIG. 14 is an explanatory diagram showing an example of a spectrum input to the frequency detection circuit 65a according to Embodiment 2 of the present invention. The frequency detection circuit 65a, to handle without generating harmonics of each beat signal, be detected by separating the beat frequency f Beat2 corresponding to the beat frequency f Beat1 and target 2 which corresponds to the target 1 it can.
図１５は、この発明の実施の形態２に係る周波数検出回路６５ｂに入力されるスペクトルの一例を示す説明図である。周波数検出回路６５ｂでは、各ビート信号の高調波が入力されるため、例えば、物標１に対応するビート周波数の２倍波２ｆｂｅａｔ１と物標２に対応するビート周波数ｆｂｅａｔ２とが隣接する場合は、両者の分離が難しく誤検出しやすい。誤検出を避けるためには、周波数検出回路６５ａで求めたｆｂｅａｔ１及びｆｂｅａｔ２から各高調波の周波数を予め計算し、両者が隣接する組合せを無視し、残りの周波数の検出結果を使用すれば良い。また、高調波だけでなく、混合波や折返し波の周波数についても、同様に扱うことができる。 FIG. 15 is an explanatory diagram showing an example of a spectrum input to the frequency detection circuit 65b according to Embodiment 2 of the present invention. The frequency detection circuit 65b, because the harmonics of the beat signal is input, for example, when the beat frequency f Beat2 corresponding to the second harmonic 2f Beat1 and target 2 of the beat frequency corresponding to the target 1 is adjacent Are difficult to separate and easy to misdetect. In order to avoid false detection, the frequency of each harmonic is calculated in advance from f beat1 and f beat2 obtained by the frequency detection circuit 65a, the combination of the two adjacent to each other is ignored, and the detection result of the remaining frequency is used. good. Further, not only harmonics but also frequencies of mixed waves and folded waves can be handled in the same manner.
以上で明らかなように、この発明の実施の形態２のレーダ装置によれば、基本波用フィルタで取り出したビート信号と、高調波用フィルタで取り出したビート信号の高調波とを周波数算出回路で演算することで、従来よりもビート周波数を精度良く算出することができるため、距離及び速度についても精度良く算出することができる。 As is apparent from the above, according to the radar device of the second embodiment of the present invention, the beat signal extracted by the fundamental filter and the harmonics of the beat signal extracted by the harmonic filter are obtained by the frequency calculation circuit. By calculating, the beat frequency can be calculated with higher accuracy than before, and therefore the distance and speed can also be calculated with higher accuracy.
さらに、本実施の形態は、複数の物標を探知する場合でも、距離及び速度を精度良く算出できる。複数の物標を探知する場合、ミキサ５から複数のビート周波数が出力されるため、これが高調波発生回路６１に入力されると、高調波発生回路６１は、高調波以外の混合波を発生させるので、ピークの検出が複雑になる。本実施の形態では、ビート周波数の検出経路が高調波発生回路６１から分離されているため、混合波の影響を受けることなく、ビート周波数を検出することができ、ビート周波数及びその高調波の検出結果を用いてビート周波数を算出するので、複数の物標に対して精度良く探知することができる。 Furthermore, the present embodiment can accurately calculate the distance and the speed even when detecting a plurality of targets. When detecting a plurality of targets, since a plurality of beat frequencies are output from the mixer 5, when this is input to the harmonic generation circuit 61, the harmonic generation circuit 61 generates a mixed wave other than the harmonics. Therefore, peak detection is complicated. In this embodiment, since the beat frequency detection path is separated from the harmonic generation circuit 61, the beat frequency can be detected without being affected by the mixed wave, and the beat frequency and its harmonics can be detected. Since the beat frequency is calculated using the result, a plurality of targets can be detected with high accuracy.
　１　発振器、２　方向性結合器、３　送信アンテナ、４　受信アンテナ、５　ミキサ、６　６ａ　周波数算出装置、６１　高調波発生回路、６２　６２ａ　６２ｂ　フィルタ、６３　６３ａ　６３ｂ　Ａ／Ｄ変換器、６４　６４ａ　６４ｂ　ＦＦＴ回路、６５　６５ａ　６５ｂ　周波数検出回路、６６　周波数算出回路、７　距離・速度算出回路。 1 oscillator, 2 directional coupler, 3 transmit antenna, 4 receive antenna, 5 mixer, 6 6a frequency calculation device, 61 harmonic generation circuit, 62 62a 62b filter, 63 63a 63b A / D converter, 64 64a 64b FFT Circuit, 65 65a 65b frequency detection circuit, 66 frequency calculation circuit, 7 distance / speed calculation circuit.

Claims (8)

  1. 　入力信号の高調波を発生させる高調波発生回路と、
    　前記高調波発生回路が出力した信号のうち前記高調波を通過させるフィルタと、
    　前記フィルタが出力した信号をサンプリングしてデジタル信号に変換するＡ／Ｄ変換器と、
    　前記Ａ／Ｄ変換器が出力した前記デジタル信号の周波数を検出する周波数検出回路と、
    　前記周波数検出回路が検出した前記高調波の周波数を用いて、前記入力信号の周波数を算出する周波数算出回路と、
    　を備えることを特徴とする周波数算出装置。     A harmonic generation circuit for generating harmonics of the input signal;
    A filter that passes the harmonics out of the signal output by the harmonic generation circuit;
    An A / D converter that samples and converts the signal output by the filter into a digital signal;
    A frequency detection circuit for detecting a frequency of the digital signal output by the A / D converter;
    A frequency calculation circuit that calculates the frequency of the input signal using the harmonic frequency detected by the frequency detection circuit;
    A frequency calculation apparatus comprising:
  2. 　前記フィルタは、前記入力信号及び前記高調波を通過させ、
    　前記周波数算出回路は、前記周波数検出回路が検出した前記入力信号の周波数及び前記高調波の周波数を用いて前記入力信号の周波数を算出することを特徴とする請求項１に記載の周波数算出装置。     The filter passes the input signal and the harmonics;
    The frequency calculation device according to claim 1, wherein the frequency calculation circuit calculates the frequency of the input signal using the frequency of the input signal and the harmonic frequency detected by the frequency detection circuit.
  3. 　前記周波数算出回路は、前記周波数検出回路が検出した複数の前記高調波の周波数の和を、複数の前記高調波の次数の和で除算することで、前記入力信号の周波数を算出することを特徴とする請求項１に記載の周波数算出装置。 The frequency calculation circuit calculates the frequency of the input signal by dividing the sum of the frequencies of the plurality of harmonics detected by the frequency detection circuit by the sum of the orders of the plurality of harmonics. The frequency calculation apparatus according to claim 1.
  4. 　前記Ａ／Ｄ変換器に入力される前記高調波の周波数が、前記Ａ／Ｄ変換器のサンプリング周波数よりも高く、
    　前記周波数検出回路は、前記Ａ／Ｄ変換器が出力した前記デジタル信号のうちアンダーサンプリングされた前記高調波の折り返しの周波数を検出し、
    　前記周波数算出回路は、前記周波数検出回路が検出した前記高調波の折り返しの周波数を用いて、前記入力信号の周波数を算出することを特徴とする請求項１の周波数算出装置。     The harmonic frequency input to the A / D converter is higher than the sampling frequency of the A / D converter;
    The frequency detection circuit detects the frequency of aliasing of the harmonics undersampled in the digital signal output from the A / D converter,
    The frequency calculation apparatus according to claim 1, wherein the frequency calculation circuit calculates a frequency of the input signal using a frequency of aliasing of the harmonics detected by the frequency detection circuit.
  5. 　前記高調波発生回路に並列に配置され、前記入力信号を通過させる第２のフィルタと、
    　前記第２のフィルタが出力した信号をサンプリングしてデジタル信号に変換する第２のＡ／Ｄ変換器と、
    　前記第２のＡ／Ｄ変換器が出力した前記デジタル信号の周波数を検出する第２の周波数検出回路とを備え、
    　前記周波数算出回路は、前記周波数検出回路が検出した前記入力信号の周波数と前記第２の周波数検出回路が検出した前記高調波の周波数とを用いて、前記入力信号の周波数を算出するとを特徴とする請求項１の周波数算出装置。     A second filter disposed in parallel with the harmonic generation circuit and passing the input signal;
    A second A / D converter that samples the signal output from the second filter and converts it into a digital signal;
    A second frequency detection circuit for detecting a frequency of the digital signal output by the second A / D converter;
    The frequency calculation circuit calculates the frequency of the input signal using the frequency of the input signal detected by the frequency detection circuit and the harmonic frequency detected by the second frequency detection circuit. The frequency calculation apparatus according to claim 1.
  6. 　前記周波数算出回路は、前記周波数検出回路が検出した前記入力信号の周波数と前記高調波の周波数との和を、前記入力信号の次数と前記高調波の次数との和で除算することで、前記入力信号の周波数を算出することを特徴とする請求項２に記載の周波数算出装置。 The frequency calculation circuit divides the sum of the frequency of the input signal and the harmonic frequency detected by the frequency detection circuit by the sum of the order of the input signal and the harmonic order, The frequency calculation apparatus according to claim 2, wherein the frequency of the input signal is calculated.
  7. 発振信号を出力する発振器と、
    前記発振器が出力した前記発振信号を送信信号として送信する送信アンテナと、
    前記送信信号の反射電波を受信信号として受信する受信アンテナと、
    前記送信信号と前記受信信号とを混合してビート信号を生成するミキサと、
    前記ミキサが生成したビート信号の周波数を算出する請求項１の周波数算出装置と、
    前記周波数算出装置が算出したビート信号の周波数から物標との距離及び相対速度を算出する距離・速度算出回路と、
    を備えることを特徴とするレーダ装置。     An oscillator that outputs an oscillation signal;
    A transmission antenna that transmits the oscillation signal output from the oscillator as a transmission signal;
    A receiving antenna that receives a reflected radio wave of the transmission signal as a received signal;
    A mixer that generates a beat signal by mixing the transmission signal and the reception signal;
    The frequency calculation apparatus according to claim 1, wherein the frequency of the beat signal generated by the mixer is calculated.
    A distance / speed calculation circuit for calculating the distance and relative speed with the target from the frequency of the beat signal calculated by the frequency calculation device;
    A radar apparatus comprising:
  8. 　前記ミキサは、前記ビート信号及び前記ビート信号の高調波を発生させ、発生させた前記ビート信号及び前記ビート信号の高調波を前記周波数算出装置に出力し、
    　前記周波数算出装置から前記高調波発生回路を削除したことを特徴とする請求項７に記載のレーダ装置。     The mixer generates the beat signal and harmonics of the beat signal, and outputs the generated beat signal and harmonics of the beat signal to the frequency calculation device,
    The radar apparatus according to claim 7, wherein the harmonic generation circuit is deleted from the frequency calculation apparatus.
PCT/JP2017/007331 2017-02-27 2017-02-27 Frequency calculation device and radar apparatus WO2018154747A1 (en)

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