Signal processing device and radar device

Abstract

The signal processing device (2) is configured to include: an amplitude reduction unit (22) which, when a phase shift control signal indicating that a frequency-modulated transmission wave is phase shifted is output, reduces the amplitude of a beat signal having a difference frequency between a transmission wave and a reception wave, the amplitude of the timing at which the transmission wave is phase shifted according to the phase shift control signal; and a signal conversion unit (25) which converts the beat signal after the amplitude is reduced by the amplitude reduction unit (22) at the timing at which the transmission wave is phase shifted, into a frequency domain signal.

Description

Technical Field

[0001] The present invention relates to a signal processing device and a radar device for converting a beat signal having a difference frequency between a transmission wave and a reception wave into a frequency domain signal. Background Art

[0002] As one of the radar methods, there is the FMCW (Frequency Modulated Continuous Waves) method. The FMCW radar device radiates a frequency modulated signal with a modulated frequency as a transmission wave, and receives the transmission wave reflected by the object to be measured as a reflection wave. The FMCW radar device generates a beat signal having a difference frequency between the radiated transmission wave and the received reflection wave, and detects the distance to the object to be measured or the relative speed to the object to be measured based on the frequency contained in the beat signal.

[0003] FMCW radar devices can detect the distance to an object to be measured and the relative speed to the object to be measured with a relatively simple structure, and therefore are often used as, for example, vehicle-mounted millimeter-wave radar devices.

[0004] Radio interference may occur between multiple FMCW radar devices of the same type. That is, a certain FMCW radar device (hereinafter referred to as the "first radar device") may receive a transmission wave emitted by another FMCW radar device of the same type as the first radar device (hereinafter referred to as the "second radar device") in addition to receiving a reflected wave after the transmission wave emitted by the first radar device is reflected by the object to be measured. In this case, the transmission wave emitted from the second radar device and received by the first radar device becomes an interference wave that interferes with the above-mentioned reflected wave received by the first radar device. The interference wave may hinder the first radar device from detecting the object to be measured.

[0005] Patent Document 1 below discloses a radar device that is less susceptible to radio wave interference between a plurality of radar devices of the same type.

[0006] In the radar device disclosed in Patent Document 1, a phase modulator performs two-phase phase modulation on a transmission carrier signal as a frequency modulation signal by using a phase modulation code based on a random code output from a code generator, thereby generating a transmission wave, and a transmission antenna radiates the transmission wave into space. In the radar device, a delay circuit delays the phase modulation code output from the code generator, and a phase demodulator performs two-phase phase demodulation on a reception signal output from a reception antenna by using the delayed phase modulation code, thereby generating a beat signal.

[0007] In the radar device disclosed in Patent Document 1, even if the amplitude of the reflected wave received by the receiving antenna is the same as the amplitude of the interference wave, the amplitude of the beat signal related to the reflected wave is relatively larger than the amplitude of the beat signal related to the interference wave. The amplitude of the beat signal related to the reflected wave is relatively larger than the amplitude of the beat signal related to the interference wave, thereby making it easy to distinguish the beat signal related to the reflected wave from the beat signal related to the interference wave.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2002-014159 Summary of the invention

[0011] Problems to be solved by the invention

[0012] In the radar device disclosed in Patent Document 1, the phase modulator performs two-phase phase modulation on the transmission carrier signal in the middle of frequency modulation of the transmission carrier signal, and the transmission carrier signal shifts the phase in the middle of frequency modulation. The time required for the reflected wave to return to the receiving antenna after the transmission wave is radiated from the transmission antenna is very short, so the timing of the phase shift in the transmission wave and the timing of the phase shift in the reflected wave are roughly the same. Therefore, the phase of the beat signal having the difference frequency of the transmission wave and the reflected wave is roughly continuous.

[0013] On the other hand, since the interference wave is not subjected to two-phase phase modulation by the same phase shift modulation code based on the random code as the transmission wave, the phase of the beat signal having the difference frequency between the transmission wave and the interference wave is discontinuous.

[0014] Here, for example, the beat signal is multiplied by a window function, and the beat signal multiplied by the window function is subjected to fast Fourier transform (FFT), thereby determining the frequency of the beat signal.

[0015] However, when a beat signal having a difference frequency between a transmission wave and an interference wave is multiplied by a window function and FFT is performed on the beat signal multiplied by the window function, the amplitude at a phase discontinuity point increases, and thus noise included in the beat signal increases.

[0016] Therefore, the phase modulator performs two-phase phase modulation on the transmission carrier signal in the middle of frequency modulating the transmission carrier signal, and thus the noise included in the beat signal having the difference frequency between the transmission wave and the interference wave may increase.

[0017] When the noise included in the beat signal having the difference frequency between the transmission wave and the interference wave increases, when the signal strength of the reflected wave component from the object to be measured included in the beat signal having the difference frequency between the transmission wave and the interference wave is small, the reflected wave component from the object to be measured may be buried by the noise included in the beat signal having the difference frequency between the transmission wave and the interference wave. When the reflected wave component from the object to be measured is buried by the noise included in the beat signal having the difference frequency between the transmission wave and the interference wave, there is a problem that the object to be measured may not be detected.

[0018] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a signal processing device and a radar device capable of reducing noise included in a beat signal having a difference frequency between a transmission wave and an interference wave included in a reception wave.

[0019] Means for solving problems

[0020] The signal processing device of the present invention comprises: an amplitude reducing unit which, when a phase shift control signal indicating that a frequency-modulated transmission wave is phase-shifted is output at a timing of discontinuously shifting the phase in the middle of continuously changing the frequency of the transmission wave, reduces the amplitude of a beat signal having a frequency difference between a transmission wave and a reception wave, the amplitude of the timing at which the transmission wave is phase-shifted according to the phase shift control signal; and a signal conversion unit which converts the beat signal after the amplitude is reduced by the amplitude reducing unit at the timing at which the transmission wave is phase-shifted, into a frequency domain signal.

[0021] Effects of the Invention

[0022] According to the present invention, the signal processing device is configured such that, when a phase shift control signal for instructing a frequency-modulated transmission wave to shift its phase is output, the amplitude reduction unit reduces the amplitude of the beat signal having a difference frequency between the transmission wave and the reception wave at the timing when the transmission wave is phase-shifted according to the phase shift control signal. Therefore, the signal processing device of the present invention can reduce the noise included in the beat signal having a difference frequency between the transmission wave and the reception wave. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram showing the configuration of a radar device according to Embodiment 1.

[0024] Figure 2 1 is a hardware configuration diagram showing the hardware of the signal processing device 2 included in the radar device according to the first embodiment.

[0025] Figure 3 This is a hardware configuration diagram of a computer when the signal processing device 2 is implemented by software, firmware, or the like.

[0026] Figure 4 It is a flowchart showing the processing procedure of the signal processing device 2.

[0027] Figure 5 1 is an explanatory diagram showing an example of the window function generated by the window function generation unit 23 and the first beat signal data multiplied by the window function.

[0028] Figure 6 It is an explanatory diagram showing an example of the first spectrum data and the second spectrum data.

[0029] Figure 7 It is an explanatory diagram showing the first spectrum data calculated by the signal conversion unit 25 and the spectrum data calculated by performing FFT on the first beat signal data multiplied by the window function of the Hanning window.

[0030] Figure 8 This is a diagram showing the structure of a radar device according to the second embodiment.

[0031] Fig. 9 1 is a hardware configuration diagram showing the hardware of the signal processing device 2 included in the radar device according to the second embodiment.

[0032] Fig.10 This is an explanatory diagram showing an example in which spectrum data is deformed to generate a plurality of peaks.

[0033] Fig.11 It is an explanatory diagram showing an example of the second window function generated by the second window function generation unit 53 and the second beat signal data multiplied by the second window function.

[0034] Fig.12 It is an explanatory diagram showing an example of the first spectrum data, the second spectrum data, and the third spectrum data. DETAILED DESCRIPTION

[0035] Hereinafter, in order to explain the present invention in more detail, a mode for carrying out the present invention will be described with reference to the accompanying drawings.

[0036] Implementation Method 1

[0037] Figure 1 This is a diagram showing the configuration of a radar device according to Embodiment 1.

[0038] Figure 2 1 is a hardware configuration diagram showing the hardware of the signal processing device 2 included in the radar device according to the first embodiment.

[0039] like Figure 1 As shown, the radar device according to the first embodiment includes a signal transmitting and receiving unit 1 , a signal processing device 2 , and a measurement object detecting unit 3 .

[0040] The signal transmission and reception unit 1 includes a beat signal generation unit 11 , a transmission antenna 12 , and a reception antenna 13 .

[0041] The radar device of Embodiment 1 is an FMCW radar device. The radar device of Embodiment 1 can selectively perform either a transmission process of shifting the phase of the transmission wave during frequency modulation of the transmission wave or a transmission process of not shifting the phase of the transmission wave during frequency modulation of the transmission wave.

[0042] Next, a period during which the radar apparatus of embodiment 1 performs a transmission process of shifting the phase of the transmission wave in the middle of modulating the frequency of the transmission wave is set as a period of the first transmission process, and a period during which the radar apparatus of embodiment 1 performs a transmission process of not shifting the phase of the transmission wave in the middle of modulating the frequency of the transmission wave is set as a period of the second transmission process.

[0043] Therefore, during the first transmission process, a phase shift control signal is output from a phase shift control signal generating unit 21 described later to a signal transmitting and receiving unit 1 described later.

[0044] On the other hand, during the second transmission process, the phase shift control signal is not output from the phase shift control signal generating unit 21 to the signal transmitting and receiving unit 1 .

[0045] When the radiation control signal is output from the phase shift control signal generating unit 21 at the start of the first transmission process period, the signal transmitting and receiving unit 1 starts generating a transmission wave whose frequency changes with the passage of time.

[0046] The signal transmission and reception unit 1 starts radiating the generated transmission wave from the transmission antenna 12 , and starts receiving the reflected wave from the object to be measured as a reception wave by the reception antenna 13 .

[0047] During the first transmission process, the signal transmission and reception unit 1 shifts the phase of the generated transmission wave according to the phase shift control signal output from the phase shift control signal generation unit 21. The phase shift of the frequency modulated signal as the transmission wave will be described later.

[0048] The signal transmitting and receiving unit 1 radiates the phase-shifted transmission wave and receives the reflected wave from the object to be measured as a reception wave.

[0049] The signal transmission and reception unit 1 generates a first beat signal which is a beat signal having a difference frequency between a transmitted wave to be radiated and a received wave to be received.

[0050] The signal transmitting and receiving unit 1 converts the generated first beat signal from an analog signal into a digital signal (hereinafter referred to as a "first digital signal"), and outputs the first digital signal as first beat signal data to a window function multiplication unit 24 of an amplitude reduction unit 22 described later.

[0051] When the second transmission process period starts, the signal transmission and reception unit 1 starts generating a transmission wave whose frequency changes with the passage of time when the radiation control signal is output from the phase shift control signal generation unit 21 .

[0052] The signal transmitting and receiving unit 1 radiates the generated transmission wave and then receives the reflected wave from the object to be measured as a reception wave.

[0053] The signal transmission and reception unit 1 generates a second beat signal which is a beat signal having a difference frequency between the radiated transmission wave and the received reception wave.

[0054] The signal transmitting and receiving unit 1 converts the generated second beat signal from an analog signal into a digital signal (hereinafter referred to as “second digital signal”), and outputs the second digital signal as second beat signal data to the window function multiplication unit 24 of the amplitude reduction unit 22 .

[0055] The beat signal generating unit 11 is implemented by a phase-locked loop circuit, a phase shifter, a frequency converter, an analog-to-digital converter, and the like implemented by a silicon IC (Integrated Circuit) or the like.

[0056] When the first transmission process period starts and the radiation control signal is output from the phase shift control signal generator 21 , the beat signal generator 11 generates a frequency modulation signal whose frequency changes with time and outputs the frequency modulation signal to the transmission antenna 12 .

[0057] During the first transmission process, when the phase shift control signal is output from the phase shift control signal generating unit 21 , the beat signal generating unit 11 phase-shifts the generated frequency modulation signal according to the phase shift control signal and outputs the phase-shifted frequency modulation signal to the transmission antenna 12 .

[0058] The technology for performing phase shifting of a frequency modulated signal is a well-known technology which is also described in Patent Document 1. Figure 1 In the radar device shown, the phase shifter provided in the beat signal generating unit 11 changes the phase of the generated frequency modulation signal when the radiation control signal is output from the phase shift control signal generating unit 21. In order to easily distinguish the reflected wave and the interference wave from the object to be measured, it is preferable that the phase shift amount of the frequency modulation signal is about 180 degrees, but as long as it is greater than 0, it is easier to distinguish the reflected wave and the interference wave than when there is no phase shift at all.

[0059] In addition, the phase shift amount of the frequency modulation signal can be stored in the internal memory of the beat signal generating unit 11, or can be obtained from Figure 1 The radar device shown is provided externally.

[0060] When the second transmission process period starts, the beat signal generating unit 11 generates a frequency modulation signal when the radiation control signal is output from the phase shift control signal generating unit 21 , and outputs the frequency modulation signal to the transmission antenna 12 .

[0061] The transmission antenna 12 radiates the frequency modulation signal output from the beat signal generation unit 11 into space as a transmission wave.

[0062] The receiving antenna 13 receives a reflected wave from the object to be measured as a received wave after the transmission wave is radiated into space from the transmission antenna 12 .

[0063] During the first transmission process, the beat signal generating unit 11 generates a first beat signal having a difference frequency between the radiated transmission wave and the reception wave, and converts the first beat signal from an analog signal into a first digital signal.

[0064] The beat signal generating section 11 outputs the first digital signal as first beat signal data to the window function multiplying section 24 of the amplitude reducing section 22 .

[0065] During the second transmission process, the beat signal generating unit 11 generates a second beat signal having a difference frequency between the radiated transmission wave and the reception wave, and converts the second beat signal from an analog signal into a second digital signal.

[0066] The beat signal generating section 11 outputs the second digital signal as second beat signal data to the window function multiplying section 24 of the amplitude reducing section 22 .

[0067] The signal processing device 2 includes a phase shift control signal generating section 21 , an amplitude reducing section 22 , a signal converting section 25 , and a reflected wave frequency determining section 26 .

[0068] The signal processing device 2 outputs a radiation control signal for instructing radiation of a transmission wave and a phase shift control signal for instructing phase shifting of the transmission wave to the signal transmission and reception unit 1 .

[0069] The signal processing device 2 compares the first beat signal data output from the signal transmitting and receiving section 1 with the second beat signal data output from the signal transmitting and receiving section 1 .

[0070] The signal processing device 2 specifies the frequencies of the reflected waves in the received waves and the reflected waves in the interference waves based on the comparison result of the first beat signal data and the second beat signal data.

[0071] The phase shift control signal generating unit 21 is composed of, for example, Figure 2 The phase shift control signal generating circuit 31 shown is implemented.

[0072] The phase shift control signal generating unit 21 outputs a radiation control signal for instructing radiation of a transmission wave to each of a window function generating unit 23 (described later) of the amplitude reducing unit 22 and the beat signal generating unit 11 .

[0073] The phase shift control signal generating section 21 outputs a phase shift control signal for instructing to shift the phase of the transmission wave to each of the window function generating section 23 of the amplitude reducing section 22 , the signal converting section 25 , and the beat signal generating section 11 .

[0074] The amplitude reduction unit 22 includes a window function generation unit 23 and a window function multiplication unit 24 .

[0075] When the phase shift control signal is output from the phase shift control signal generating section 21 , the amplitude reducing section 22 reduces the amplitude of the first beat signal data output from the signal transmitting and receiving section 1 at the timing when the transmission wave is phase-shifted according to the phase shift control signal.

[0076] The amplitude reduction unit 22 outputs the beat signal obtained by reducing the amplitude at the timing at which the transmission wave is phase-shifted to the signal conversion unit 25 .

[0077] The window function generating unit 23 is composed of, for example, Figure 2 The window function generating circuit 32 shown is implemented.

[0078] When the radiation control signal is output from the phase shift control signal generating unit 21 , the window function generating unit 23 starts generating the window function.

[0079] When a phase shift control signal is output from the phase shift control signal generating unit 21, the window function generating unit 23 generates a window function for reducing the amplitude of the first beat signal data output from the beat signal generating unit 11 at the timing when the transmission wave is phase shifted according to the phase shift control signal.

[0080] The window function generation unit 23 outputs the generated window function to the window function multiplication unit 24 .

[0081] The window function multiplication unit 24 is composed of, for example, Figure 2 The window function multiplication circuit 33 shown is implemented.

[0082] The window function multiplication unit 24 multiplies the first beat signal data output from the beat signal generation unit 11 by the window function generated by the window function generation unit 23 during the first transmission process.

[0083] The window function multiplication unit 24 outputs the first beat signal data multiplied by the window function to the signal conversion unit 25 .

[0084] The window function multiplication unit 24 multiplies the second beat signal data output from the beat signal generation unit 11 by the window function generated by the window function generation unit 23 during the second transmission process.

[0085] The window function multiplication unit 24 outputs the second beat signal data multiplied by the window function to the signal conversion unit 25 .

[0086] The signal conversion unit 25 is composed of, for example, Figure 2 The signal conversion circuit 34 shown is implemented.

[0087] During the first transmission process, the signal conversion unit 25 converts the first beat signal data multiplied by the window function by the window function multiplication unit 24 into a frequency domain signal as first spectrum data.

[0088] The signal conversion unit 25 outputs the first spectrum data to an interference wave identification processing unit 27 described later in the reflected wave frequency identification unit 26 .

[0089] During the second transmission process, the signal conversion unit 25 converts the second beat signal data multiplied by the window function by the window function multiplication unit 24 into a frequency domain signal as second spectrum data.

[0090] The signal conversion unit 25 outputs the second spectrum data to each of the interference wave identification processing unit 27 of the reflected wave frequency identification unit 26 and the reflected wave identification processing unit 28 described later of the reflected wave frequency identification unit 26 .

[0091] The reflected wave frequency identification unit 26 includes an interference wave identification processing unit 27 and a reflected wave identification processing unit 28 .

[0092] The reflected wave frequency identification unit 26 obtains the first spectrum data and the second spectrum data output from the signal conversion unit 25 .

[0093] The reflected wave frequency identification unit 26 compares the first spectrum data and the second spectrum data, and identifies the frequency of the reflected wave based on the comparison result between the first spectrum data and the second spectrum data.

[0094] The interference wave identification processing unit 27 is composed of, for example, Figure 2 The interference wave determination processing circuit 35 shown is implemented.

[0095] The interference wave identification processing unit 27 identifies a peak that does not coincide with any peak included in the first spectrum data, among the one or more peaks included in the second spectrum data.

[0096] The interference wave identification processing unit 27 outputs frequency information indicating the frequency of the identified peak to the reflected wave identification processing unit 28 .

[0097] The reflected wave identification processing unit 28 is composed of, for example, Figure 2 The reflected wave determination processing circuit 36 ​​shown is implemented.

[0098] The reflected wave identification processing unit 28 identifies, among the frequencies of one or more peaks included in the second spectrum data, frequencies other than the frequencies indicated by the frequency information output from the interference wave identification processing unit 27 as frequencies of reflected waves.

[0099] The reflected wave identification processing unit 28 outputs the identified frequency of the reflected wave to the object detection unit 3 .

[0100] The object detection unit 3 calculates one or more of the distance to the object to be measured and the relative speed to the object to be measured based on the frequency of the reflected wave determined by the reflected wave determination processing unit 28 of the signal processing device 2 .

[0101] exist Figure 1 In the above, it is assumed that the phase shift control signal generating unit 21, the window function generating unit 23, the window function multiplying unit 24, the signal converting unit 25, the interference wave determining unit 27 and the reflected wave determining unit 28 as the structural elements of the signal processing device 2 are respectively Figure 2 That is, it is assumed that the signal processing device 2 is implemented by a phase shift control signal generating circuit 31, a window function generating circuit 32, a window function multiplying circuit 33, a signal conversion circuit 34, an interference wave determination processing circuit 35 and a reflected wave determination processing circuit 36.

[0102] Here, the phase shift control signal generating circuit 31, the window function generating circuit 32, the window function multiplication circuit 33, the signal conversion circuit 34, the interference wave determination processing circuit 35 and the reflected wave determination processing circuit 36 ​​are, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array) or a combination thereof.

[0103] The structural elements of the signal processing device 2 are not limited to those implemented by dedicated hardware, and the signal processing device 2 may also be implemented by software, firmware, or a combination of software and firmware.

[0104] Software or firmware is stored as a program in a computer's memory. Computer refers to hardware that executes programs, such as CPU (Central Processing Unit), central processing unit, processing unit, computing unit, microprocessor, microcomputer, processor or DSP (Digital Signal Processor).

[0105] Figure 3This is a hardware configuration diagram of a computer when the signal processing device 2 is implemented by software, firmware, or the like.

[0106] When the signal processing device 2 is implemented by software or firmware, a program for causing a computer to execute the processing sequence of the phase shift control signal generating unit 21, the window function generating unit 23, the window function multiplying unit 24, the signal converting unit 25, the interference wave determining unit 27, and the reflected wave determining unit 28 is stored in the memory 41. Then, the processor 42 of the computer executes the program stored in the memory 41.

[0107] In addition, Figure 2 In FIG. 1 , an example is shown in which the components of the signal processing device 2 are each implemented by dedicated hardware. Figure 3 , an example in which the signal processing device 2 is implemented by software or firmware is shown. However, this is just an example, and some components of the signal processing device 2 may be implemented by dedicated hardware, and the remaining components may be implemented by software or firmware.

[0108] Next, Figure 1 The operation of the radar device shown will be described.

[0109] Figure 4 It is a flowchart showing the processing procedure of the signal processing device 2.

[0110] First, the operation of the radar device during the first transmission process will be described.

[0111] First, the phase shift control signal generating unit 21 outputs a radiation control signal for instructing to radiate a transmission wave to each of the window function generating unit 23 and the beat signal generating unit 11 .

[0112] When the radiation control signal is output from the phase shift control signal generating unit 21 , the beat signal generating unit 11 generates a frequency modulation signal whose frequency changes with the passage of time, and outputs the frequency modulation signal to the transmission antenna 12 .

[0113] When a certain time has passed since the emission control signal was output, the phase shift control signal generating unit 21 outputs a phase shift control signal for instructing the transmission wave to shift the phase to the window function generating unit 23, the signal converting unit 25 and the beat signal generating unit 11 respectively. Figure 4 Step ST1).

[0114] The certain time may be stored in, for example, an internal memory of the phase shift control signal generating unit 21 , or may be provided from outside the signal processing device 2 .

[0115] Furthermore, the certain time may be any time as long as it is a time during which the phase shift control signal is output between the start time and the end time of the period of the first transmission process.

[0116] During the first transmission process, when the phase shift control signal is output from the phase shift control signal generating unit 21 , the beat signal generating unit 11 phase-shifts the generated frequency modulation signal according to the phase shift control signal and outputs the phase-shifted frequency modulation signal to the transmission antenna 12 .

[0117] The transmission antenna 12 radiates the frequency modulation signal output from the beat signal generation unit 11 into space as a transmission wave.

[0118] The transmission wave radiated into space is reflected by the object to be measured, and the transmission wave reflected by the object to be measured is received by the receiving antenna 13 as a reflected wave.

[0119] exist Figure 1 In the radar device shown in the figure, it is assumed that Figure 1 The radar device shown in the figure emits a frequency modulated transmission wave. Figure 1 The transmission waves emitted by radar devices different from the radar devices shown do not shift in phase during frequency modulation.

[0120] From Figure 1 The transmission waves radiated by the radar devices different from the radar devices shown are received by the receiving antenna 13 as interference waves.

[0121] Therefore, the receiving antenna 13 receives the reflected wave and the interference wave from the object to be measured as received waves.

[0122] The beat signal generating unit 11 generates a first beat signal having a difference frequency between a transmission wave radiated from the transmission antenna 12 and a reception wave received by the reception antenna 13 .

[0123] During the first transmission process, the beat signal generating unit 11 phase-shifts the frequency modulated signal at the timing when the phase shift control signal is output from the phase shift control signal generating unit 21. The transmission and reception time required from the time when the transmission wave is radiated from the transmission antenna 12 to the time when the reflected wave reflected by the object to be measured returns to the receiving antenna 13 is extremely short, so the timing of the phase shift in the transmission wave and the timing of the phase shift in the reflected wave are roughly the same. The timing of the phase shift in the transmission wave and the timing of the phase shift in the reflected wave will be described later. Therefore, the phase of the first beat signal having the difference frequency of the transmission wave and the reflected wave is roughly continuous.

[0124] On the other hand, even through Figure 1 The radar device different from the radar device shown modulates the frequency, and the interference wave does not shift its phase during the frequency modulation. Therefore, the phase of the beat signal having the difference frequency between the transmission wave and the interference wave is discontinuous.

[0125] The beat signal generating unit 11 converts the generated first beat signal from an analog signal into a first digital signal.

[0126] The beat signal generation unit 11 outputs the first digital signal to the window function multiplication unit 24 as first beat signal data.

[0127] When the radiation control signal is output from the phase shift control signal generating unit 21 , the window function generating unit 23 starts generating the window function.

[0128] When the phase shift control signal is output from the phase shift control signal generating unit 21, the window function generating unit 23 generates a window function for reducing the amplitude of the first beat signal data output from the beat signal generating unit 11 at the timing at which the transmission wave is phase shifted according to the phase shift control signal ( Figure 4 Step ST2).

[0129] Next, the window function generation process performed by the window function generation unit 23 will be described in detail.

[0130] exist Figure 1 In the radar device shown, for example, the internal memory of the window function generating unit 23 stores the processing time t1 required for phase shifting of the frequency modulated signal in the beat signal generating unit 11, the processing time t2 from the acquisition of the received wave by the beat signal generating unit 11 to the generation of the first beat signal data, and the time t3 during the first sending processing.

[0131] The window function generating unit 23 calculates the starting point time t of the window function based on the processing times t1 and t2 stored in the internal memory and the time t0 at which the radiation control signal is output from the phase shift control signal generating unit 21, as shown in the following equation (1): start .

[0132] t start =t0+t1+t2 (1)

[0133] The window function generating unit 23 calculates the time t4 at which the transmission wave is phase-shifted according to the phase-shift control signal, based on the processing times t1 and t2 stored in the internal memory and the time t4 at which the phase-shift control signal is output, as shown in the following equation (2). phase The time required for the transmission and reception after the transmission wave is radiated from the transmission antenna 12 and the reflected wave after being reflected by the object to be measured returns to the receiving antenna 13 is very short. Therefore, the time t after the transmission wave is phase-shifted is set to phase They correspond to the timing of phase shift in the transmitted wave and the timing of phase shift in the reflected wave, respectively.

[0134] t phase =t4+t1+t2 (2)

[0135] The window function generating unit 23 calculates the time t of the end point of the window function based on the processing times t1 and t2 stored in the internal memory, the time t0 when the radiation control signal is output from the phase shift control signal generating unit 21, and the time t3 during the first transmission processing, as shown in the following formula (3): end .

[0136] t end =t0+t1+t2+t3 (3)

[0137] The transmission and reception time required after the transmission wave is radiated from the transmission antenna 12 and until the reflected wave reflected by the object to be measured returns to the receiving antenna 13 is extremely short. Therefore, the window function generation unit 23 calculates the time t without considering the transmission and reception time. start , time t phase and time t end However, this is just an example, and the window function generation unit 23 may also calculate the time t by taking the transmission and reception time into consideration. start , time t phase and time t end .

[0138] like Figure 5 As shown, the window function generation unit 23 generates the starting point time t start and the end point time t end The amplitude of each first beat signal data is zero, and the transmission wave is phase-shifted according to the phase shift control signal, that is, time t phase A window function is used to make the amplitude of the first beat signal data zero.

[0139] Figure 5 1 is an explanatory diagram showing an example of the window function generated by the window function generation unit 23 and the first beat signal data multiplied by the window function.

[0140] Figure 5 The window function shown is a window function in which the amplitude of the first beat signal data at each of the start point and the end point is zero, and the amplitude of the first beat signal data at the time point when the transmission wave is phase-shifted according to the phase shift control signal is also zero.

[0141] However, the window function only needs to reduce the amplitude of the first beat signal data at the start point and the end point and the amplitude of the first beat signal data at the time when the transmission wave is phase shifted according to the phase shift control signal, and is not limited to the case where the amplitude of the first beat signal data at each point is zero.

[0142] The window function generation unit 23 outputs the generated window function to the window function multiplication unit 24 .

[0143] When receiving the first beat signal data from the beat signal generating unit 11, the window function multiplication unit 24 multiplies the first beat signal data by the window function ( Figure 4 Step ST3).

[0144] The window function multiplication unit 24 converts Figure 5 The first beat signal data after being multiplied by the window function is output to the signal conversion unit 25 .

[0145] When the signal conversion unit 25 receives the first beat signal data multiplied by the window function from the window function multiplication unit 24, it performs FFT on the first beat signal data multiplied by the window function, thereby calculating the first spectrum data ( Figure 4 Step ST4).

[0146] The signal conversion unit 25 outputs the first spectrum data to the interference wave identification processing unit 27 .

[0147] Next, the operation of the radar device during the second transmission process will be described. The second transmission process period is, for example, a transmission process period next to the first transmission process period.

[0148] The phase shift control signal generating unit 21 outputs a radiation control signal for instructing to radiate a transmission wave to each of the window function generating unit 23 and the beat signal generating unit 11 .

[0149] During the second transmission process, the phase shift control signal generating unit 21 stops outputting the phase shift control signal to the signal converting unit 25 and the beat signal generating unit 11, respectively. Figure 4 Step ST5).

[0150] When the radiation control signal is output from the phase shift control signal generating unit 21 , the beat signal generating unit 11 generates a frequency modulation signal and outputs the frequency modulation signal to the transmission antenna 12 .

[0151] During the second transmission process, the phase shift control signal is not output from the phase shift control signal generating unit 21 , and therefore the beat signal generating unit 11 does not shift the phase of the frequency modulation signal during the second transmission process.

[0152] When receiving the frequency modulation signal from the beat signal generating unit 11 , the transmitting antenna 12 radiates the frequency modulation signal as a transmission wave into space.

[0153] The transmission wave radiated into space is reflected by the object to be measured, and the transmission wave reflected by the object to be measured is received by the receiving antenna 13 as a reflected wave.

[0154] From Figure 1 The transmission waves radiated by the radar devices different from the radar devices shown are received by the receiving antenna 13 as interference waves.

[0155] Therefore, the receiving antenna 13 receives the reflected wave and the interference wave from the object to be measured as received waves.

[0156] The beat signal generation unit 11 generates a second beat signal having a difference frequency between a transmission wave radiated from the transmission antenna 12 and a reception wave received by the reception antenna 13 .

[0157] During the second transmission process, the beat signal generator 11 does not shift the phase of the frequency modulation signal. Therefore, the phase of the second beat signal having the difference frequency between the transmission wave and the reflected wave is substantially continuous, and the phase of the second beat signal having the difference frequency between the transmission wave and the interference wave is also substantially continuous.

[0158] The beat signal generating unit 11 converts the generated second beat signal from an analog signal into a second digital signal.

[0159] The beat signal generating unit 11 outputs the second digital signal to the window function multiplying unit 24 as second beat signal data.

[0160] When the radiation control signal is output from the phase shift control signal generating unit 21 , the window function generating unit 23 starts generating the window function.

[0161] The window function generating unit 23 generates the same window function as the window function generated during the first transmission process, and outputs the generated window function to the window function multiplying unit 24 ( Figure 4 Step ST6).

[0162] When receiving the second beat signal data from the beat signal generating unit 11, the window function multiplying unit 24 multiplies the second beat signal data by the window function ( Figure 4 Step ST7).

[0163] The window function multiplication unit 24 outputs the second beat signal data multiplied by the window function to the signal conversion unit 25 .

[0164] When the signal conversion unit 25 receives the second beat signal data multiplied by the window function from the window function multiplication unit 24, it performs FFT on the second beat signal data multiplied by the window function, thereby calculating the second spectrum data ( Figure 4 Step ST8).

[0165] The signal conversion unit 25 outputs the second spectrum data to each of the interference wave identification processing unit 27 and the reflected wave identification processing unit 28 .

[0166] Figure 6 It is an explanatory diagram showing an example of the first spectrum data and the second spectrum data.

[0167] During the first transmission process, the phase of the beat signal having the difference frequency between the transmission wave and the interference wave is discontinuous. Figure 6 As shown in the first spectrum data, a plurality of peaks appear at frequencies shifted from the frequency of the interference wave component.

[0168] During the second transmission process, the phase of the beat signal having the difference frequency between the transmission wave and the interference wave is substantially continuous, so Figure 6 As shown in the second spectrum data, one peak appears in the frequency of the interference wave component. Therefore, the peak of the interference wave component included in the first spectrum data and the peak of the interference wave component included in the second spectrum data do not match.

[0169] The phase of the beat signal having the difference frequency between the transmission wave and the reflected wave is substantially continuous during any period of the first transmission process and the second transmission process. Figure 6 As shown in the first spectrum data and the second spectrum data, one peak appears in the frequency of the reflected wave component. Therefore, the peak of the reflected wave component included in the first spectrum data and the peak of the reflected wave component included in the second spectrum data coincide with each other.

[0170] Figure 7 It is an explanatory diagram showing the first spectrum data calculated by the signal conversion unit 25 and spectrum data calculated by performing FFT on the first beat signal data multiplied by the window function of the Hanning window (hereinafter referred to as “spectrum data to be compared”).

[0171] The window function of the Hanning window is a window function that makes the amplitude of the first beat signal data at each of the start point and the end point zero, but is a window function that makes the amplitude of the first beat signal data at the time when the transmission wave is phase shifted according to the phase shift control signal neither zero nor reduced.

[0172] Regarding the spectrum data of the comparison object, the amplitude at the time point when the transmission wave is phase-shifted according to the phase shift control signal is not zero, so the amplitude at the phase discontinuity point becomes larger, and the noise at the phase discontinuity point in the noise included in the first beat signal data becomes larger. The noise at the phase discontinuity point becomes larger, and thus the signal intensity at the bottom of the spectrum data of the comparison object is larger than the signal intensity at the bottom of the first spectrum data.

[0173] When the signal intensity of the reflection component from the object to be measured is small, the reflection component from the object to be measured may be buried by the noise included in the first beat signal data in the spectrum data of the comparison object. In the first spectrum data, the signal intensity of the bottom is smaller than that of the spectrum data of the comparison object, so the possibility of the reflection component from the object to be measured being buried by the noise included in the first beat signal data is reduced.

[0174] Similar to the first spectrum data, the second spectrum data also has a smaller signal intensity at the bottom than the spectrum data to be compared, so the possibility that the reflection component from the object to be measured is buried by the noise included in the second beat signal data is reduced.

[0175] The interference wave identification processing unit 27 compares the first spectrum data output from the signal conversion unit 25 with the second spectrum data output from the signal conversion unit 25 .

[0176] The interference wave identification processing unit 27 identifies a peak value that does not coincide with any peak value included in the first spectrum data among one or more peak values ​​included in the second spectrum data based on the comparison result between the first spectrum data and the second spectrum data ( Figure 4 In step ST9), among the one or more peaks included in the second spectrum data, the peak that does not coincide with any peak included in the first spectrum data is a peak related to the interference wave component.

[0177] The interference wave identification processing unit 27 outputs frequency information indicating the frequency of the identified peak to the reflected wave identification processing unit 28 .

[0178] The reflected wave identification processing unit 28 identifies, among the frequencies of one or more peaks included in the second spectrum data, frequencies other than the frequencies indicated by the frequency information output from the interference wave identification processing unit 27 as frequencies of reflected waves ( Figure 4 Step ST10).

[0179] The reflected wave identification processing unit 28 outputs the identified frequency of the reflected wave to the object detection unit 3 .

[0180] When receiving the frequency of the reflected wave from the reflected wave identification processing unit 28 , the object detection unit 3 calculates at least one of the distance to the object or the relative speed to the object based on the frequency of the reflected wave.

[0181] The process of calculating the distance to the object to be measured or the relative speed to the object to be measured based on the frequency of the reflected wave is a well-known technique, and thus a detailed description thereof is omitted.

[0182] In the above-mentioned first embodiment, the signal processing device 2 is configured such that when the phase shift control signal for instructing the frequency-modulated transmission wave to shift the phase is output, the amplitude reduction unit 22 reduces the amplitude of the beat signal having the difference frequency between the transmission wave and the reception wave at the timing when the transmission wave is phase-shifted according to the phase shift control signal. Therefore, the signal processing device 2 can reduce the noise included in the beat signal having the difference frequency between the transmission wave and the reception wave.

[0183] exist Figure 1In the radar apparatus shown, the phase shift control signal generating unit 21 outputs the phase shift control signal only once in one transmission process, and the beat signal generating unit 11 shifts the phase of the frequency modulation signal only once in one transmission process.

[0184] However, this is just an example, and the phase shift control signal generating unit 21 may output the phase shift control signal a plurality of times in one transmission process, and the beat signal generating unit 11 may shift the phase of the frequency modulation signal a plurality of times in one transmission process.

[0185] exist Figure 1 In the radar device shown, it is assumed that the second transmission process period is the next transmission process period after the first transmission process period, and the calculation timings of the first spectrum data and the second spectrum data calculated by the signal conversion unit 25 are continuous.

[0186] However, this is just an example, and the calculation timing of the first spectrum data and the second spectrum data may not be continuous. Therefore, the signal conversion unit 25 may calculate the first spectrum data during the first transmission process, for example, calculate the second spectrum data during the next transmission period after the first transmission process.

[0187] Implementation Method 2

[0188] In the second embodiment, a radar device in which the signal conversion unit 56 includes the first signal conversion processing unit 57 and the second signal conversion processing unit 58 will be described.

[0189] Figure 8 This is a diagram showing the structure of a radar device according to the second embodiment.

[0190] Fig. 9 1 is a hardware configuration diagram showing the hardware of the signal processing device 2 included in the radar device according to the second embodiment.

[0191] exist Figure 8 and Fig. 9 In, with Figure 1 and Figure 2 The same reference numerals denote the same or corresponding parts, and thus their descriptions are omitted.

[0192] The amplitude reduction unit 51 includes a first window function generation unit 52 , a second window function generation unit 53 , a first window function multiplication unit 54 , and a second window function multiplication unit 55 .

[0193] The first window function generating unit 52 is, for example, Fig. 9 The first window function generating circuit 71 shown is implemented.

[0194] When the radiation control signal is output from the phase shift control signal generating unit 21 , the first window function generating unit 52 starts generating the first window function.

[0195] The first window function generating unit 52 generates a first window function for reducing the amplitude of the first beat signal data at the timing when the transmission wave is phase-shifted according to the phase shift control signal output from the phase shift control signal generating unit 21 .

[0196] The first window function generation unit 52 outputs the generated first window function to the first window function multiplication unit 54 .

[0197] The second window function generating unit 53 is, for example, Fig. 9 The second window function generating circuit 72 shown is implemented.

[0198] When the radiation control signal is output from the phase shift control signal generating unit 21 , the second window function generating unit 53 starts generating the second window function.

[0199] The second window function generating unit 53 generates a second window function that does not reduce the amplitude of the second beat signal data at the timing at which the transmission wave is phase-shifted according to the phase shift control signal.

[0200] The second window function is a window function having a value that does not reduce the amplitude of the second beat signal data at the timing when the transmission wave is phase-shifted according to the phase shift control signal.

[0201] The second window function generation unit 53 outputs the generated second window function to the second window function multiplication unit 55 .

[0202] The first window function multiplication unit 54 is composed of, for example, Fig. 9 The first window function multiplication circuit 73 shown is implemented.

[0203] The first window function multiplication unit 54 multiplies the first beat signal data output from the beat signal generation unit 11 by the first window function generated by the first window function generation unit 52 during the first transmission process.

[0204] The first window function multiplication unit 54 outputs the first beat signal data multiplied by the first window function to the first signal conversion processing unit 57 .

[0205] During the second transmission process, the first window function multiplication unit 54 multiplies the second beat signal data output from the beat signal generation unit 11 by the first window function generated by the first window function generation unit 52 .

[0206] The first window function multiplication unit 54 outputs the second beat signal data multiplied by the first window function to the first signal conversion processing unit 57 .

[0207] The second window function multiplication unit 55 is composed of, for example, Fig. 9 The second window function multiplication circuit 74 shown is implemented.

[0208] The second window function multiplication unit 55 multiplies the second beat signal data output from the beat signal generation unit 11 by the second window function generated by the second window function generation unit 53 .

[0209] The second window function multiplication unit 55 outputs the second beat signal data multiplied by the second window function to the second signal conversion processing unit 58 .

[0210] The signal conversion unit 56 includes a first signal conversion processing unit 57 and a second signal conversion processing unit 58 .

[0211] The first signal conversion processing unit 57 is composed of, for example, Fig. 9 The first signal conversion processing circuit 75 shown is implemented.

[0212] During the first transmission process, the first signal conversion processing unit 57 converts the first beat signal data multiplied by the first window function by the first window function multiplication unit 54 into a frequency domain signal as first spectrum data.

[0213] The first signal conversion processing unit 57 outputs the first spectrum data to an interference wave identification processing unit 60 described later in the reflected wave frequency identification unit 59 .

[0214] During the second transmission process, the first signal conversion processing unit 57 converts the second beat signal data multiplied by the first window function by the first window function multiplication unit 54 into a frequency domain signal as second spectrum data.

[0215] The first signal conversion processing unit 57 outputs the second spectrum data to the interference wave identification processing unit 60 of the reflected wave frequency identification unit 59 .

[0216] The second signal conversion processing unit 58 is composed of, for example, Fig. 9 The second signal conversion processing circuit 76 shown is implemented.

[0217] The second signal conversion processing unit 58 converts the second beat signal data multiplied by the second window function by the second window function multiplication unit 55 into a frequency domain signal as third spectrum data.

[0218] The second signal conversion processing unit 58 outputs the third spectrum data to a reflected wave identification processing unit 61 of the reflected wave frequency identification unit 59 to be described later.

[0219] The reflected wave frequency identification unit 59 includes an interference wave identification processing unit 60 and a reflected wave identification processing unit 61 .

[0220] The interference wave identification processing unit 60 is composed of, for example, Fig. 9 The interference wave determination processing circuit 77 shown is implemented.

[0221] The interference wave identification processing unit 60 obtains the first spectrum data and the second spectrum data output from the first signal conversion processing unit 57 .

[0222] The interference wave identification processing unit 60 identifies a peak that does not coincide with any peak included in the first spectrum data, among the one or more peaks included in the second spectrum data.

[0223] The interference wave identification processing unit 60 outputs frequency information indicating the frequency of the identified peak to the reflected wave identification processing unit 61 .

[0224] The reflected wave identification processing unit 61 is composed of, for example, Fig. 9 The reflected wave determination processing circuit 78 shown is implemented.

[0225] The reflected wave identification processing unit 61 identifies the frequency of the reflected wave from among the frequencies of one or more peaks included in the third spectrum data output from the second signal conversion processing unit 58 , based on the frequency information output from the interference wave identification processing unit 60 .

[0226] The reflected wave identification processing unit 61 outputs the identified frequency of the reflected wave to the object detection unit 3 .

[0227] exist Figure 8 In the above, it is assumed that the phase shift control signal generating unit 21, the first window function generating unit 52, the second window function generating unit 53, the first window function multiplying unit 54, the second window function multiplying unit 55, the first signal conversion processing unit 57, the second signal conversion processing unit 58, the interference wave determination processing unit 60 and the reflected wave determination processing unit 61 as the structural elements of the signal processing device 2 are respectively Fig. 9 That is, it is assumed that the signal processing device 2 is implemented by a first window function generating circuit 71, a second window function generating circuit 72, a first window function multiplying circuit 73, a second window function multiplying circuit 74, a first signal conversion processing circuit 75, a second signal conversion processing circuit 76, an interference wave determination processing circuit 77 and a reflected wave determination processing circuit 78.

[0228] Here, the first window function generating circuit 71, the second window function generating circuit 72, the first window function multiplication circuit 73, the second window function multiplication circuit 74, the first signal conversion processing circuit 75, the second signal conversion processing circuit 76, the interference wave determination processing circuit 77 and the reflected wave determination processing circuit 78 are, for example, respectively a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA or a combination thereof.

[0229] The structural elements of the signal processing device 2 are not limited to those implemented by dedicated hardware, and the signal processing device 2 may also be implemented by software, firmware, or a combination of software and firmware.

[0230] In the case where the signal processing device 2 is implemented by software or firmware, a program for causing a computer to execute the processing sequence of the phase shift control signal generating unit 21, the first window function generating unit 52, the second window function generating unit 53, the first window function multiplying unit 54, the second window function multiplying unit 55, the first signal conversion processing unit 57, the second signal conversion processing unit 58, the interference wave determination processing unit 60, and the reflected wave determination processing unit 61 is stored in Figure 3 The memory 41 shown. Moreover, Figure 3 The illustrated processor 42 executes programs stored in the memory 41 .

[0231] In addition, Fig. 9 In FIG. 1 , an example is shown in which the components of the signal processing device 2 are each implemented by dedicated hardware. Figure 3 , an example in which the signal processing device 2 is implemented by software or firmware is shown. However, this is just an example, and some components of the signal processing device 2 may be implemented by dedicated hardware, and the remaining components may be implemented by software or firmware.

[0232] Next, Figure 8 The operation of the radar device shown will be described.

[0233] exist Figure 1 In the radar device shown, the window function multiplication unit 24 multiplies the first beat signal data and the second beat signal data by the window function, respectively. Furthermore, the signal conversion unit 25 performs FFT on the first beat signal data multiplied by the window function and the second beat signal data multiplied by the window function, respectively, thereby reducing the noise generated at the bottom of the first spectrum data and reducing the noise generated at the bottom of the second spectrum data.

[0234] However, according to the periodicity condition of the window function generated by the window function generating unit 23 or the 1-bit width condition of the FFT, the spectrum data of the beat signal having the difference frequency of the transmission wave and the reflected wave is deformed, such as Fig.10 As shown, multiple peaks are sometimes generated.

[0235] Fig.10 This is an explanatory diagram showing an example in which spectrum data is deformed to generate a plurality of peaks.

[0236] exist Figure 1 In the radar device shown, when the spectrum data of the beat signal having the difference frequency between the transmission wave and the reflected wave has a plurality of peaks, it is difficult for the reflected wave identification processing unit 28 to identify the frequency of the reflected wave.

[0237] When the beat signal data is multiplied by a window function such as a Hanning window having a value that does not reduce the amplitude of the beat signal data at the timing when the transmission wave is phase-shifted according to the phase shift control signal, as shown in FIG. Fig.10As shown, the spectrum data of the beat signal data having the difference frequency between the transmission wave and the reflected wave is not deformed.

[0238] First, the operation of the radar device during the first transmission process will be described.

[0239] First, the phase shift control signal generator 21 outputs a radiation control signal for instructing radiation of a transmission wave to each of the first window function generator 52 , the second window function generator 53 , and the beat signal generator 11 .

[0240] When the radiation control signal is output from the phase shift control signal generating unit 21 , the beat signal generating unit 11 generates a frequency modulation signal and outputs the frequency modulation signal to the transmission antenna 12 .

[0241] When a certain time has passed since the radiation control signal is output, the phase shift control signal generating unit 21 outputs the phase shift control signal indicating the phase shift of the transmission wave to the first window function generating unit 52, the second window function generating unit 53, the first signal conversion processing unit 57, the second signal conversion processing unit 58 and the beat signal generating unit 11 respectively.

[0242] During the first transmission process, when the phase shift control signal is output from the phase shift control signal generating unit 21 , the beat signal generating unit 11 phase-shifts the generated frequency modulation signal according to the phase shift control signal and outputs the phase-shifted frequency modulation signal to the transmission antenna 12 .

[0243] When receiving the frequency modulation signal from the beat signal generating unit 11 , the transmitting antenna 12 radiates the frequency modulation signal as a transmission wave into space.

[0244] The transmission wave radiated into space is reflected by the object to be measured, and the transmission wave reflected by the object to be measured is received by the receiving antenna 13 as a reflected wave.

[0245] exist Figure 8 In the radar device shown in the figure, it is assumed that Figure 8 A radar device different from the one shown radiates a frequency modulated transmission wave. Figure 8 The transmission waves emitted by radar devices different from the radar devices shown do not shift in phase during frequency modulation.

[0246] From Figure 8 The transmission waves emitted by the radar devices different from the radar devices shown are received by the receiving antenna 13 as interference waves.

[0247] Therefore, the receiving antenna 13 receives the reflected wave and the interference wave from the object to be measured as received waves.

[0248] The beat signal generating unit 11 generates a first beat signal having a difference frequency between a transmission wave radiated from the transmission antenna 12 and a reception wave received by the reception antenna 13 .

[0249] The beat signal generating unit 11 converts the generated first beat signal from an analog signal into a first digital signal.

[0250] The beat signal generating unit 11 outputs the first digital signal to the first window function generating unit 52 as first beat signal data.

[0251] When the radiation control signal is output from the phase shift control signal generating unit 21 , the first window function generating unit 52 starts generating the window function.

[0252] The first window function generating unit 52 generates a first window function when a phase shift control signal is output from the phase shift control signal generating unit 21. The first window function is used to reduce the amplitude of the first beat signal data output from the beat signal generating unit 11 at the timing where the transmission wave is phase shifted according to the phase shift control signal.

[0253] The first window function generated by the first window function generating unit 52 is the same as Figure 1 The window function is the same as the window function generated by the window function generation unit 23 shown in FIG.

[0254] The first window function generation unit 52 outputs the generated first window function to the first window function multiplication unit 54 .

[0255] When the radiation control signal is output from the phase shift control signal generating unit 21 , the second window function generating unit 53 starts generating the window function.

[0256] The second window function generating unit 53 generates a second window function that does not reduce the amplitude of the second beat signal data output from the beat signal generating unit 11 at the timing when the transmission wave is phase-shifted according to the phase shift control signal.

[0257] like Fig.11 As shown, the second window function is a window function having a value that does not reduce the amplitude of the second beat signal data at the timing when the transmission wave is phase-shifted according to the phase shift control signal.

[0258] Fig.11 : is an explanatory diagram showing an example of the second window function generated by the second window function generation unit 53 and the second beat signal data multiplied by the second window function. The second window function is, for example, a Hanning window function.

[0259] The second window function generation unit 53 outputs the generated second window function to the second window function multiplication unit 55 .

[0260] Here, the second window function generating unit 53 generates the second window function during the first transmission process. However, this is just an example, and the second window function generating unit 53 may generate the second window function during the second transmission process.

[0261] Upon receiving the first beat signal data from the beat signal generating unit 11 , the first window function multiplication unit 54 multiplies the first beat signal data by the first window function output from the first window function generating unit 52 .

[0262] The first window function multiplication unit 54 outputs the first beat signal data multiplied by the first window function to the first signal conversion processing unit 57 .

[0263] When receiving the first beat signal data multiplied by the first window function from the first window function multiplication unit 54 , the first signal conversion processing unit 57 performs FFT on the first beat signal data multiplied by the first window function, thereby calculating first spectrum data as a frequency domain signal.

[0264] The first signal conversion processing unit 57 outputs the first spectrum data to the interference wave identification processing unit 60 .

[0265] Next, the operation of the radar device during the second transmission process will be described.

[0266] The phase shift control signal generating unit 21 outputs a radiation control signal for instructing to radiate a transmission wave to each of the first window function generating unit 52 , the second window function generating unit 53 , and the beat signal generating unit 11 .

[0267] During the second transmission process, the phase shift control signal generating unit 21 stops outputting the phase shift control signal to the first window function generating unit 52, the second window function generating unit 53, the first signal conversion processing unit 57, the second signal conversion processing unit 58 and the beat signal generating unit 11 respectively.

[0268] When the radiation control signal is output from the phase shift control signal generating unit 21 , the beat signal generating unit 11 generates a frequency modulation signal and outputs the frequency modulation signal to the transmission antenna 12 .

[0269] During the second transmission process, the phase shift control signal is not output from the phase shift control signal generating unit 21 , and therefore the beat signal generating unit 11 does not shift the phase of the generated frequency modulation signal.

[0270] When receiving the frequency modulation signal from the beat signal generating unit 11 , the transmitting antenna 12 radiates the frequency modulation signal as a transmission wave into space.

[0271] The transmission wave radiated into space is reflected by the object to be measured, and the transmission wave reflected by the object to be measured is received by the receiving antenna 13 as a reflected wave.

[0272] From Figure 8 The transmission waves radiated by the radar devices different from the radar devices shown are received by the receiving antenna 13 as interference waves.

[0273] Therefore, the receiving antenna 13 receives the reflected wave and the interference wave from the object to be measured as received waves.

[0274] The beat signal generation unit 11 generates a second beat signal having a difference frequency between a transmission wave radiated from the transmission antenna 12 and a reception wave received by the reception antenna 13 .

[0275] The beat signal generating unit 11 converts the generated second beat signal from an analog signal into a second digital signal.

[0276] The beat signal generating unit 11 outputs the second digital signal as second beat signal data to each of the first window function multiplying unit 54 and the second window function multiplying unit 55 .

[0277] When the radiation control signal is output from the phase shift control signal generating unit 21 , the first window function generating unit 52 starts generating the first window function.

[0278] The first window function generating unit 52 generates the same window function as the first window function generated during the first transmission process, and outputs the generated first window function to the first window function multiplying unit 54 .

[0279] Upon receiving the second beat signal data output from the beat signal generating unit 11 , the first window function multiplication unit 54 multiplies the second beat signal data by the first window function output from the first window function generating unit 52 .

[0280] The first window function multiplication unit 54 outputs the second beat signal data multiplied by the first window function to the first signal conversion processing unit 57 .

[0281] Upon receiving the second beat signal data output from the beat signal generating unit 11 , the second window function multiplication unit 55 multiplies the second beat signal data by the second window function output from the second window function generating unit 53 .

[0282] The second window function multiplication unit 55 outputs the second beat signal data multiplied by the second window function to the second signal conversion processing unit 58 .

[0283] When receiving the second beat signal data multiplied by the first window function from the first window function multiplication unit 54 , the first signal conversion processing unit 57 performs FFT on the second beat signal data multiplied by the first window function, thereby calculating second spectrum data as a frequency domain signal.

[0284] The first signal conversion processing unit 57 outputs the second spectrum data to the interference wave identification processing unit 60 .

[0285] Upon receiving the second beat signal data multiplied by the second window function from the second window function multiplication unit 55 , the second signal conversion processing unit 58 performs FFT on the second beat signal data multiplied by the second window function, thereby calculating third spectrum data as a frequency domain signal.

[0286] The second signal conversion processing unit 58 outputs the third spectrum data to the reflected wave identification processing unit 61 .

[0287] Fig.12 It is an explanatory diagram showing an example of the first spectrum data, the second spectrum data, and the third spectrum data.

[0288] During the first transmission process, the phase of the beat signal having the difference frequency between the transmission wave and the interference wave is discontinuous. Fig.12 As shown in the first spectrum data, a plurality of peaks appear at frequencies shifted from the frequency of the interference wave component.

[0289] During the second transmission process, the second spectrum data is deformed due to the periodicity of the first window function and the like. Fig.12 As shown, a plurality of peaks appear in the second spectrum data as peaks of interference wave components.

[0290] The reason why multiple peaks related to the interference wave component appear in the first spectrum data is different from the reason why multiple peaks related to the interference wave component appear in the second spectrum data. Fig.12 As shown, the peak value related to the interference wave component included in the first spectrum data and the peak value related to the interference wave component included in the second spectrum data do not match.

[0291] During the first transmission process, the first spectrum data is deformed due to the periodicity of the first window function, etc. Therefore, Fig.12 As shown, a plurality of peaks appear in the first spectrum data as peaks of the reflected wave component.

[0292] During the second transmission process, the second spectrum data is deformed due to the periodicity of the first window function and the like. Fig.12 As shown, a plurality of peaks appear in the second spectrum data as peaks of the reflected wave component.

[0293] The reason why multiple peaks related to the reflected wave component appear in the first spectrum data is the same as the reason why multiple peaks related to the reflected wave component appear in the second spectrum data. Fig.12 As shown, the peak value related to the reflected wave component included in the first spectrum data and the peak value related to the reflected wave component included in the second spectrum data coincide with each other.

[0294] The interference wave identification processing unit 60 compares the first spectrum data output from the first signal conversion processing unit 57 and the second spectrum data output from the first signal conversion processing unit 57 .

[0295] The interference wave determination processing unit 60 determines a peak that is inconsistent with any peak included in the first spectrum data among one or more peaks included in the second spectrum data based on the comparison result between the first spectrum data and the second spectrum data. The peak that is inconsistent with any peak included in the first spectrum data among one or more peaks included in the second spectrum data is a peak related to the interference wave component.

[0296] The interference wave identification processing unit 60 outputs frequency information indicating the frequencies of the identified one or more peaks to the reflected wave identification processing unit 61 .

[0297] The reflected wave identification processing unit 61 acquires the third spectrum data output from the second signal conversion processing unit 58 .

[0298] The second window function is a window function that does not deform the spectrum data, and the third spectrum data is obtained by performing FFT on the second beat signal data multiplied by the second window function. Therefore, in the third spectrum data, Fig.12 As shown, one peak appears in the frequency of the interference wave component, and one peak appears in the frequency of the reflected wave component.

[0299] Among the frequencies of one or more peaks included in the third spectrum data, a frequency close to the frequency indicated by the frequency information is highly likely to be the frequency of an interference wave.

[0300] The reflected wave identification processing unit 61 identifies the frequency of the reflected wave from the frequencies of one or more peaks included in the third spectrum data, based on the frequency information output from the interference wave identification processing unit 50 .

[0301] For example, the reflected wave determination processing unit 61 determines that all frequencies of the one or more peaks indicated by the frequency information output from the interference wave determination processing unit 60 are separated by a threshold value or more from the frequencies of the one or more peaks included in the third spectrum data as frequencies of the reflected waves. The threshold value may be stored in the internal memory of the reflected wave determination processing unit 61, or may be provided from outside the signal processing device 2.

[0302] The reflected wave identification processing unit 61 outputs the identified frequency of the reflected wave to the object detection unit 3 .

[0303] When receiving the frequency of the reflected wave from the reflected wave identification processing unit 61 , the object detection unit 3 calculates at least one of the distance to the object or the relative speed to the object based on the frequency of the reflected wave.

[0304] In the above-mentioned embodiment 2, the interference wave determination processing unit 60 determines a peak that is inconsistent with any peak included in the first spectrum data among one or more peaks included in the second spectrum data, and outputs frequency information indicating the frequency of the determined peak to the reflected wave determination processing unit 61. Figure 8 The signal processing device 2 shown is configured such that the reflected wave identification processing unit 61 identifies the frequency of the reflected wave from the frequencies of one or more peaks included in the third spectrum data based on the frequency information output from the interference wave identification processing unit 60. Figure 8 The signal processing device 2 shown is Figure 1 The signal processing device 2 shown can also reduce the noise contained in the beat signal having the difference frequency of the interference wave contained in the transmitted wave and the received wave, and can also determine the frequency of the reflected wave when multiple peaks appear due to the periodicity of the first window function, etc.

[0305] exist Figure 8 In the radar apparatus shown, the phase shift control signal generating unit 21 outputs the phase shift control signal only once in one transmission process, and the beat signal generating unit 11 shifts the phase of the frequency modulation signal only once in one transmission process.

[0306] However, this is just an example, and the phase shift control signal generating unit 21 may output the phase shift control signal a plurality of times in one transmission process, and the beat signal generating unit 11 may shift the phase of the frequency modulation signal a plurality of times in one transmission process.

[0307] exist Figure 8 In the radar device shown, it is assumed that the second transmission processing period is the transmission processing period next to the first transmission processing period, and the calculation timings of the first spectrum data and the second spectrum data calculated by the first signal conversion processing unit 57 are continuous.

[0308] However, this is only an example, and the calculation timing of the first spectrum data and the second spectrum data may not be continuous. Therefore, the first signal conversion processing unit 57 may calculate the first spectrum data during the first transmission processing, for example, calculate the second spectrum data during the next transmission period after the first transmission processing period.

[0309] In addition, the present application can freely combine the various embodiments, modify the arbitrary components of the various embodiments, or omit the arbitrary components of the various embodiments within the scope of the present invention.

[0310] Industrial Applicability

[0311] The present invention is applicable to a signal processing device and a radar device which convert a beat signal having a difference frequency between a transmission wave and a reception wave into a frequency domain signal.

[0312] Description of symbols

[0313] 1: signal transmission and reception unit; 2: signal processing device; 3: object detection unit; 11: beat signal generation unit; 12: transmission antenna; 13: reception antenna; 21: phase shift control signal generation unit; 22: amplitude reduction unit; 23: window function generation unit; 24: window function multiplication unit; 25: signal conversion unit; 26: reflected wave frequency determination unit; 27: interference wave determination processing unit; 28: reflected wave determination processing unit; 31: phase shift control signal generation circuit; 32: window function generation circuit; 33: window function multiplication circuit; 34: signal conversion circuit; 35: interference wave determination processing circuit; 36: reflected wave determination processing circuit; 41: memory; 42: processor; 51 : Amplitude reducing unit; 52: 1st window function generating unit; 53: 2nd window function generating unit; 54: 1st window function multiplying unit; 55: 2nd window function multiplying unit; 56: signal converting unit; 57: 1st signal converting processing unit; 58: 2nd signal converting processing unit; 59: reflected wave frequency determining unit; 60: interference wave determining processing unit; 61: reflected wave determining processing unit; 71: 1st window function generating circuit; 72: 2nd window function generating circuit; 73: 1st window function multiplying circuit; 74: 2nd window function multiplying circuit; 75: 1st signal converting processing circuit; 76: 2nd signal converting processing circuit; 77: interference wave determining processing circuit; 78: reflected wave determining processing circuit.

Claims

1. A signal processing device, the signal processing device comprising: an amplitude reducing section that, when a phase shift control signal that instructs the frequency-modulated transmission wave to shift its phase is outputted at a timing at which the transmission wave is discontinuously phase-shifted while the frequency of the transmission wave is continuously changing, reduces the amplitude of a beat signal having a difference frequency between the transmission wave and the reception wave at a timing at which the transmission wave is phase-shifted according to the phase shift control signal; and a signal conversion unit that converts the beat signal whose amplitude at the timing is reduced by the amplitude reduction unit into a frequency domain signal, The amplitude reducing unit has: a window function generating unit, which generates a window function when the phase shift control signal is output, the window function being used to reduce the amplitude of the beat signal having the difference frequency between the transmission wave and the reception wave at the timing at which the transmission wave is phase shifted according to the phase shift control signal, The window function is also used to reduce the amplitude of the start point and the end point of the beat signal having the difference frequency between the transmission wave and the reception wave.

2. The signal processing device according to claim 1, characterized in that The signal processing device includes a phase shift control signal generating section that outputs a phase shift control signal that instructs a frequency-modulated transmission wave to shift its phase.

3. The signal processing device according to claim 2, characterized in that: The amplitude reduction unit further comprises: a window function multiplication unit that multiplies a beat signal having a difference frequency between the transmission wave and the reception wave by the window function generated by the window function generation unit, The signal conversion unit converts the beat signal multiplied by the window function by the window function multiplication unit into a frequency domain signal.

4. The signal processing device according to claim 3, characterized in that: During the first transmission process, the phase shift control signal is output from the phase shift control signal generating unit, and during the second transmission process, the phase shift control signal is not output from the phase shift control signal generating unit. The window function multiplication unit multiplies the beat signal having the difference frequency between the transmission wave and the reception wave after phase shifting during the first transmission processing, i.e., the first beat signal, by the window function during the first transmission processing, and multiplies the beat signal having the difference frequency between the transmission wave and the reception wave without phase shifting during the second transmission processing, i.e., the second beat signal, by the window function during the second transmission processing. The signal conversion unit converts the first beat signal obtained by multiplying the window function by the window function multiplication unit as first spectrum data into a frequency domain signal during the first transmission process, and converts the second beat signal obtained by multiplying the window function by the window function multiplication unit as second spectrum data into a frequency domain signal during the second transmission process. The signal processing device has a reflected wave frequency determination unit, which compares the first spectrum data with the second spectrum data, and determines the frequency of the reflected wave from the object to be measured and the interference wave contained in the received wave based on the comparison result of the first spectrum data with the second spectrum data.

5. The signal processing device according to claim 4, characterized in that: The reflected wave frequency determination unit comprises: an interference wave identification processing unit that identifies a peak that does not coincide with any peak included in the first spectrum data among the one or more peaks included in the second spectrum data, and outputs frequency information indicating the frequency of the identified peak; as well as A reflected wave identification processing unit identifies, among the frequencies of the one or more peaks included in the second spectrum data, a frequency other than the frequency indicated by the frequency information output from the interference wave identification processing unit as the frequency of the reflected wave.

6. The signal processing device according to claim 2, characterized in that: During the first transmission process, the phase shift control signal is output from the phase shift control signal generating unit, and during the second transmission process, the phase shift control signal is not output from the phase shift control signal generating unit. The amplitude reducing unit has: a first window function generating unit, which generates a first window function during the first transmission process, the first window function being used to reduce the amplitude of a beat signal having a difference frequency between a transmission wave and a reception wave after phase shifting during the first transmission process, i.e., a first beat signal, at a timing at which the transmission wave is phase shifted according to the phase shift control signal; a second window function generating unit which generates a second window function during the second transmission process, the second window function not reducing the amplitude at the timing among the amplitudes of the beat signal having the difference frequency between the transmission wave and the reception wave which are not phase-shifted during the second transmission process, i.e., the second beat signal; a first window function multiplication unit that multiplies the first beat signal by the first window function during the first transmission process, and multiplies the second beat signal by the first window function during the second transmission process; and a second window function multiplication unit, which multiplies the second beat signal by the second window function, The signal conversion unit has: a first signal conversion processing unit that converts the first beat signal obtained by multiplying the first window function by the first window function multiplication unit into a frequency domain signal as first spectrum data during the first transmission processing, and converts the second beat signal obtained by multiplying the first window function by the first window function multiplication unit into a frequency domain signal as second spectrum data during the second transmission processing; and a second signal conversion processing unit that converts the second beat signal multiplied by the second window function by the second window function multiplication unit into a frequency domain signal as third spectrum data, The signal processing device includes a reflected wave frequency determination unit that determines the frequency of the reflected wave from the object to be measured and one of the interference waves based on the first spectrum data, the second spectrum data, and the third spectrum data.

7. The signal processing device according to claim 6, characterized in that: The reflected wave frequency determination unit comprises: an interference wave identification processing unit that identifies a peak that does not coincide with any peak included in the first spectrum data among the one or more peaks included in the second spectrum data, and outputs frequency information indicating the frequency of the identified peak; and A reflected wave identification processing unit identifies the frequency of the reflected wave from frequencies of one or more peaks included in the third spectrum data based on the frequency information output from the interference wave identification processing unit.

8. A radar device, characterized in that: The radar device has: a signal transmitting and receiving section that generates a frequency-modulated transmission wave, that shifts the phase of the generated transmission wave according to the phase shift control signal output from the phase shift control signal generating section during the first transmission process, that receives a reflected wave from the object under test as a received wave after radiating the phase-shifted transmission wave, and generates a first beat signal having a difference frequency between the radiated transmission wave and the received received wave, and that receives a reflected wave from the object under test as a received wave after radiating the generated transmission wave during the second transmission process, and generates a second beat signal having a difference frequency between the radiated transmission wave and the received received wave; The signal processing device according to any one of claims 4 to 7; as well as The object detection unit calculates at least one of a distance to the object and a speed of the object based on the frequency of the reflected wave determined by the reflected wave frequency determination unit.

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