JP2023182088A - Signal processing device and radar system - Google Patents

Abstract

To provide a technique capable of removing an interference component in a wider frequency domain when removing the interference component included in a beat signal in the frequency domain.SOLUTION: A signal processing device 200 performs Fourier transformation of a beat signal Bw of a time domain to a first signal Bwf1 of a frequency domain in which a frequency component is expressed for each frequency bin, executes adaptive processing of outputting an output signal based on a main input signal and a reference input signal by using each positive frequency component of a first signal sequentially as the main input signal of an adaptive filter 221 and using each corresponding negative frequency component sequentially as the reference input signal of the adaptive filter, executes FIR filter processing of processing the reference input signal by an FIR filter 222 in the adaptive processing, output processing of outputting a residual between the main input signal and the reference input signal processed by the FIR processing as the output signal, and update processing of updating a tap coefficient on the basis of the residual, and changes a step size parameter for updating the tap coefficient on the basis of the bin number.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a signal processing device and a radar system.

In a radar system that measures a target based on a beat signal obtained by mixing a transmitted signal sent as an electromagnetic wave to the target and a received signal obtained by receiving the electromagnetic waves reflected by the target, the beat signal is combined with other signals. Interference signals may occur due to interference of the radar system's transmitted signals. Non-Patent Document 1 discloses that an interference signal contained in a beat signal expressed as a complex signal is removed in the frequency domain by an adaptive filter using the correlation between the positive frequency component and the negative frequency component of the interference signal. The technology to do so is described.

Feng Jin, Siyang Cao “Automotive Radar Interference Mitigation Using Adaptive Noise Canceller”, IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 68, NO. 4, APRIL 2019.

With the technique of Non-Patent Document 1, interference components can be effectively removed in a frequency range corresponding to a nearby region, but interference components cannot be sufficiently removed in a frequency region corresponding to a closer ultra-nearby region or a far region. There are cases. Therefore, there is room for further improvement in removing interference components in a wider frequency range.

The present disclosure can be realized as the following forms.

According to a first aspect of the present disclosure, a signal processing device (200) is provided. In this signal processing device, a received signal (Dw) obtained by receiving a reflected wave from an object (OB) that reflected a transmitted wave and a transmitted signal (Tw) for transmitting the transmitted wave are orthogonal to each other. Transformation in which a beat signal (Bw) representing a time-domain signal generated by mixing in a mixer (105) is Fourier-transformed into a frequency-domain first signal (Bwf1) in which frequency components are expressed for each frequency bin. (210) and an adaptive filter (221) including an FIR filter (222), and a processing unit (210) that generates an interference-cancelled signal (Ts) in which the interference signal component (IFIf) is removed from the first signal. 220). The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. Adaptive processing is performed to output an output signal based on the main input signal and the reference input signal as a reference input signal of the filter. In the adaptive processing, the processing unit performs FIR filter processing in which the reference input signal is processed by the FIR filter, and as the output signal, the main input signal and the reference input signal processed by the FIR filter processing. , and an update process of updating the tap coefficients of the FIR filter based on the residuals, and the step size parameter for updating the tap coefficients is set to the step size parameter for updating the tap coefficients of the FIR filter. It is changed based on the bin number of the frequency bin of one signal.

According to such a configuration, it is possible to reduce the residual error in a frequency range corresponding to a far distance. Therefore, it is more likely that the interference signal component can be effectively removed from the first signal in a frequency range corresponding to a far distance.

According to a second aspect of the present disclosure, a signal processing device (200) is provided. In this signal processing device, a received signal (Dw) obtained by receiving a reflected wave from an object (OB) that reflected a transmitted wave and a transmitted signal (Tw) for transmitting the transmitted wave are orthogonal to each other. Transformation in which a beat signal (Bw) representing a time-domain signal generated by mixing in a mixer (105) is Fourier-transformed into a frequency-domain first signal (Bwf1) in which frequency components are expressed for each frequency bin. (210) and an adaptive filter (221) including an FIR filter (222), and a processing unit (210) that generates an interference-cancelled signal (Ts) in which the interference signal component (IFIf) is removed from the first signal. 220). The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. Adaptive processing is performed to output an output signal based on the main input signal and the reference input signal as a reference input signal of the filter. In the adaptive processing, the processing unit performs FIR filter processing in which the reference input signal is processed by the FIR filter, and as the output signal, the main input signal and the reference input signal processed by the FIR filter processing. , an output process for outputting the residual of , and an update process for updating the tap coefficient of the FIR filter based on the residual, and outputting the positive frequency component of the next frequency bin of the first signal. Before using the main input signal, a recalculation process of performing the FIR filter process, the output process, and the update process using the updated tap coefficient with respect to the current frequency bin of the first signal; Executes a predetermined number of times.

According to this embodiment, the number of times the tap coefficients are updated can be increased compared to the case where the recalculation process is not performed. Therefore, it is more likely that the interference signal component can be effectively removed from the first signal in a frequency range corresponding to a far distance.

According to a third aspect of the present disclosure, a signal processing device (200) is provided. In this signal processing device, a received signal (Dw) obtained by receiving a reflected wave from an object (OB) that reflected a transmitted wave and a transmitted signal (Tw) for transmitting the transmitted wave are orthogonal to each other. Transformation in which a beat signal (Bw) representing a time-domain signal generated by mixing in a mixer (105) is Fourier-transformed into a frequency-domain first signal (Bwf1) in which frequency components are expressed for each frequency bin. (210) and an adaptive filter (221) including an FIR filter (222), and a processing unit (210) that generates an interference-cancelled signal (Ts) in which the interference signal component (IFIf) is removed from the first signal. 220). The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. Adaptive processing is performed to output an output signal based on the main input signal and the reference input signal as a reference input signal of the filter. In the adaptive processing, the processing unit performs FIR filter processing in which the reference input signal is processed by the FIR filter, and as the output signal, the main input signal and the reference input signal processed by the FIR filter processing. , and an update process that updates the tap coefficients of the FIR filter based on the residual, and as the adaptive processing, the frequency bin corresponding to a short distance is changed to a frequency bin corresponding to a long distance. a first adaptive process in which positive frequency components of the first signal are inputted as the main input signal in order toward a frequency bin corresponding to the intermediate distance, and a frequency bin corresponding to the short distance from a frequency bin corresponding to the intermediate distance; a second adaptive process in which the positive frequency component of the first signal is input as the main input signal in order toward The signal outputted by the output processing of the second adaptive processing and the signal outputted by the output processing of the second adaptive processing are combined and output as the interference-removed signal.

According to this embodiment, it is possible to suppress the influence of the residual convergence process on the interference-removed signal. Therefore, for example, compared to the case where the frequency components of the first signal are simply processed by adaptive processing in order from the frequency bin corresponding to a short distance to the frequency bin corresponding to a long distance, the frequency corresponding to the ultra-nearby In this range, the possibility that the interference signal component can be effectively removed from the first signal increases.

FIG. 1 is an explanatory diagram showing a schematic configuration of a radar device in a first embodiment. FIG. 3 is an explanatory diagram showing an example of a high frequency signal before mixing and a beat signal after mixing. 5 is a flowchart of interference signal processing in the first embodiment. An explanatory diagram showing an example of a first signal. The first explanatory diagram showing how the beat signal is multiplied by the window function. The second explanatory diagram showing how the beat signal is multiplied by the window function. Flowchart of adaptive processing. An explanatory diagram of an adaptive filter. An explanatory diagram of an FIR filter. FIG. 3 is an explanatory diagram showing the relationship between step size parameters and bin numbers. FIG. 3 is a diagram illustrating joining of output signals. The figure which shows the simulation result of adaptive processing. 5 is a flowchart of interference signal processing in the second embodiment. FIG. 6 is an explanatory diagram showing an example in which an interference signal occurs at the end of a beat signal. 7 is a flowchart of interference signal processing in the third embodiment.

A. First embodiment:
The radar system 100 shown in FIG. 1 is mounted on, for example, a vehicle such as a car or a motorcycle, and measures a target object OB. The target object OB refers to, for example, a pedestrian, another vehicle, or an obstacle on the road. "Measuring the target object OB" means, for example, measuring the distance and angle between the own vehicle equipped with the radar system 100 and the target object OB, and the relative speed of the target object OB with respect to the own vehicle. Point. The radar system 100 in this embodiment is configured with a millimeter wave radar that measures a target object OB using an FCM (Fast-Chirp Modulation) method.

As shown in FIG. 1, the radar system 100 includes a signal generating section 101, a transmitting section 102, a receiving section 103, a beat signal generating section 104 having a quadrature mixer 105, and a signal processing device 200.

The signal generation unit 101 is configured by, for example, a PLL (Phase Locked Loop) circuit, and generates a transmission signal Tw. The signal generation unit 101 in this embodiment continuously generates a chirp signal whose frequency is linear with respect to time as the transmission signal Tw.

The transmitter 102 is configured as an antenna that radiates the transmission signal Tw into space as an electromagnetic wave Ew, and radiates the transmission signal Tw amplified by the power amplifier PA as the electromagnetic wave Ew. The receiving unit 103 is configured as an antenna that receives the electromagnetic wave Ew reflected by the target object OB as a received signal Dw. Hereinafter, the electromagnetic wave Ew transmitted by the transmission signal Tw will also be referred to as a transmission wave. Further, the electromagnetic wave Ew reflected by the target object OB is also called a reflected wave.

Beat signal generation section 104 generates beat signal Bw. The beat signal Bw represents a time domain complex signal generated by mixing the received signal Dw and the transmitted signal Tw by the orthogonal mixer 105. In addition to the orthogonal mixer 105, the beat signal generation section 104 includes a filter section 106 composed of a low-pass filter, and an analog-to-digital converter 107 composed of an analog-to-digital converter (ADC). are doing.

In this embodiment, the beat signal generation unit 104 generates a signal BwI and a signal BwQ. The signal BwI is a signal based on a signal obtained by mixing a local oscillation signal LO having the same phase as the transmission signal Tw and a reception signal Dw amplified by the low noise amplifier LNA. The signal BwQ is a signal based on a signal obtained by mixing a local oscillation signal LO whose phase is delayed by 90 degrees with respect to the transmission signal Tw and a similarly amplified reception signal Dw. Filter section 106 attenuates high frequency components from the output signal of quadrature mixer 105 and suppresses aliasing in analog-to-digital conversion section 107 . The analog-to-digital conversion section 107 converts the signal processed by the filter section 106 into a time domain digital signal and outputs the signal. The signal BwI output by the beat signal generating section 104 thus corresponds to the real part of the beat signal Bw, and the signal BwQ corresponds to the imaginary part of the beat signal Bw.

FIG. 2 is a schematic graph in which the horizontal axis is time and the vertical axis is frequency. FIG. 2 shows an example of a beat signal Bw, and examples of a local oscillation signal LO and a received signal Dw used to generate the beat signal Bw. In FIG. 2, the received signal Dw is schematically represented by a desired signal Dwp and a mixed signal Iw. The mixed signal Iw is generated when an electromagnetic wave transmitted from a radar system or the like mounted on another vehicle enters the received signal Dw. Furthermore, in FIG. 2, the beat signal Bw is schematically represented by a desired signal IFO originating from the target object OB and an interference signal IFI originating from the mixed signal Iw. As shown in FIG. 2, the desired signal IFO is a signal having only positive frequencies. More specifically, the desired signal IFO has only a certain positive frequency depending on the target object OB. In contrast, the interference signal IFI is a signal having both positive and negative frequencies. The interference signal IFI has symmetry with respect to the time Tc at which the local oscillation signal LO and the mixed signal Iw intersect, and the time waveform of the interference signal IFI in the positive frequency range and the time waveform in the negative frequency range It is almost symmetrical.

The signal processing device 200 is configured as a computer including a CPU, a storage section, and an input/output interface that inputs and outputs signals to and from the outside.

The signal processing device 200 includes a converting section 210, a processing section 220, and a measuring section 230. The converting unit 210, the processing unit 220, and the measuring unit 230 in this embodiment are functional units that are realized by the CPU executing a program stored in the storage unit of the signal processing device 200. In other embodiments, the conversion unit 210, the processing unit 220, and the measurement unit 230 may be configured as a separate device from the signal processing device 200, which operates according to instructions from the CPU, for example. Furthermore, some or all of the functions of the signal processing device 200 may be realized by, for example, a hardware circuit.

The converter 210 performs Fourier transform on the beat signal Bw, which is the complex time waveform described above, into a first signal Bwf1. More specifically, the converter 210 performs fast Fourier transform on the beat signal Bw into the first signal Bwf1. The first signal Bwf1 refers to a frequency domain signal in which frequency components of the beat signal Bw are expressed for each frequency bin. In this embodiment, the number of frequency bins of the beat signal Bw is 1024.

The processing unit 220 generates, from the first signal Bwf1, an interference-cancelled signal Ts in which the interference signal component IFIf included in the first signal Bwf1 is removed. The processing unit 220 has an adaptive filter 221 including an FIR (Finite Impulse Response) filter 222 . Details of the adaptive filter 221 and the FIR filter 222 will be described later.

The measuring unit 230 measures the target object OB based on the generated interference-cancelled signal Ts, as described later.

The signal processing device 200 in this embodiment generates the above-mentioned interference-cancelled signal Ts by executing the interference signal processing shown in FIG. In this embodiment, interference signal processing is executed every time the beat signal Bw is input to the signal processing device 200. More specifically, in the present embodiment, the transmission unit 102 transmits a series of transmission signals Tw as one set of chirp signals, and generates a plurality of beat signals Bw corresponding to these transmission signals Tw. The signal is input to the signal processing device 200. The chirp signal group is usually composed of a number of chirp signals that are a power of 2, for example, 512 chirp signals.

In step S110, the converter 210 performs Fourier transform on the beat signal Bw into a first signal Bwf1. In step S110, the converting unit 210 multiplies the beat signal Bw by a window function (for example, Hanning window, Hamming window, Blackman window), and then performs fast Fourier transform on the signal multiplied by the window function. A first signal Bwf1 is generated.

FIG. 4 is a schematic graph in which the horizontal axis represents frequency and the vertical axis represents amplitude. FIG. 4 shows an example of the first signal Bwf1. FIG. 4 shows a signal derived from the beat signal Bw described in FIG. 2 as an example of the first signal Bwf1. In FIG. 4, the first signal Bwf1 is represented by a desired signal component IFOf originating from the target object OB and an interference signal component IFIf. As shown in FIG. 4, the first signal Bwf1 includes a positive frequency component representing a frequency component at a positive frequency and a negative frequency component representing a frequency component at a negative frequency. Note that in order to facilitate understanding of the technology, only the amplitude is shown as the frequency component of the first signal Bwf1 in FIG. 4, but since the first signal Bwf1 is a complex signal, in reality, as a frequency component, It has phase in addition to amplitude.

The frequency bin number in the first signal Bwf1 is also referred to as the bin number n. In the first signal Bwf1, the same bin number n is assigned to mutually corresponding positive frequency bins and negative frequency bins. The term "frequency bins that correspond to each other" refers to a positive frequency bin and a negative frequency bin that have the same absolute value of frequency. FIG. 4 schematically shows the bin number n. As shown in FIG. 4, the positive frequency bins and the negative frequency bins are each given a serial number that increases by 1 from the frequency bin with the smallest absolute value of frequency to the frequency bin with the largest absolute value. In the following, positive frequency components and negative frequency components that have "frequency bins that correspond to each other" are simply referred to as "positive frequency components that correspond to negative frequency components" and "positive frequency components that correspond to positive frequency components." Also called "negative frequency component".

As described above, since the positive frequency range and the negative frequency range of the interference signal IFI included in the beat signal Bw, which is a complex time waveform, are substantially symmetrical and correlated, the first signal Bwf1 obtained by Fourier transforming the beat signal Bw It also correlates with the positive and negative frequency components of the interference signal component IFIf contained in . More specifically, the positive frequency component and the negative frequency component of the interference signal component IFIf are approximately symmetrical with respect to the zero frequency position. Although not shown in FIG. 4, the difference between the mutually corresponding positive frequency component and negative frequency component of the interference signal component IFIf actually becomes larger in a higher frequency range. Therefore, the positive frequency component and the negative frequency component of the interference signal component IFIf are generally symmetrical with respect to the zero position of the frequency, but the symmetry becomes slightly lower in the higher frequency range.

5 and 6 are schematic graphs in which the horizontal axis is time and the vertical axis is amplitude. FIG. 5 shows how the beat signal Bw is multiplied by the Hanning window when the interference signal IFI occurs earlier than the time Tc of the beat signal Bw. FIG. 6 shows how the beat signal Bw is multiplied by the Hanning window when the interference signal IFI occurs at time Tc. As shown in FIGS. 5 and 6, by multiplying the beat signal Bw by the window function, the signal strength of the beat signal Bw decreases as the time position of the beat signal Bw approaches the edge. More specifically, FIG. 5 shows how the intensity of the earlier side of the interference signal IFI included in the beat signal Bw is reduced by the multiplication of the window function than the intensity of the slower side. That is, in FIG. 5, the strength of the positive frequency range of the interference signal IFI is lower than the strength of the negative frequency range. Moreover, contrary to the example of FIG. 5, if the interference signal IFI occurs on the side later than the time Tc of the beat signal Bw, for example, by multiplying the beat signal Bw by a window function such as a Hanning window, The strength of the negative frequency range of the interference signal IFI is reduced compared to the strength of the positive frequency range. Therefore, if the interference signal IFI occurs earlier or later than the time Tc of the beat signal Bw, the interference signal component IFIf in the first signal Bwf1 generated from the beat signal Bw has a positive value in the higher frequency range. The difference between the frequency component and the negative frequency component becomes larger.

In step S120 of FIG. 3, the processing unit 220 determines whether the intensity of the interference signal component IFIf of the first signal Bwf1 is equal to or greater than a predetermined intensity. In this embodiment, the processing unit 220 determines in step S120 whether the integrated value of the power in the negative frequency range of the first signal Bwf1 is equal to or greater than a predetermined reference power value. Note that in other embodiments, the processing unit 220 determines in step S120, for example, whether the integrated value of the amplitude in the negative frequency range of the first signal Bwf1 is equal to or greater than a predetermined reference amplitude. It's okay.

If it is determined in step S120 that the integrated power value is equal to or greater than the reference power value, that is, if it is determined that the intensity of the interference signal component IFIf is equal to or greater than the predetermined intensity, in step S130, the processing unit 220 , performs adaptive processing. Adaptive processing means that each positive frequency component of the first signal Bwf1 is sequentially used as a main input signal of the adaptive filter 221, and each positive frequency component and the corresponding negative frequency component are sequentially used as a reference input signal of the adaptive filter 221. , refers to the process of outputting an output signal based on a main input signal and a reference input signal. The main input signal of the adaptive filter 221 is also called an observation signal, main signal, or main input, and is input to the P terminal of the adaptive filter 221. The reference input signal of the adaptive filter 221 is also called a reference signal or reference input, and is input to the N terminal of the adaptive filter 221. Examples of adaptive algorithms for adaptive processing include a least mean square (LMS) algorithm, a normalized least mean square (NLMS) algorithm, and a recursive least square (RLS) algorithm. is used.

As shown in FIG. 3, in this embodiment, the processing unit 220 executes a first adaptive process and a second adaptive process as adaptive processes. The order in which frequency bins are processed differs between the first adaptive process and the second adaptive process. More specifically, in the first adaptive processing, the processing unit 220 sequentially selects positive frequency components as the main input signal of the adaptive filter 221 from frequency bins corresponding to short distances to frequency bins corresponding to long distances. do. In the second adaptive processing, the processing unit 220 uses negative frequency components as the main input signal of the adaptive filter 221 in order from frequency bins corresponding to intermediate distances to frequency bins corresponding to short distances. Medium distance refers to a distance that is farther than short distance and closer than long distance. Long distance refers to a distance that is further than short distance and medium distance. A frequency bin with a smaller bin number n is a frequency bin corresponding to a closer distance, and a frequency bin with a larger bin number n is a frequency bin corresponding to a farther distance. Below, when the first adaptive processing and the second adaptive processing are not particularly distinguished, they are also simply referred to as adaptive processing.

In the present embodiment, in the first adaptive process, the processing unit 220 processes positive frequency components in order from the frequency bin corresponding to the closest distance to the frequency bin corresponding to the farthest distance. That is, for example, when the number of frequency bins is 1024, the processing unit 220 sequentially performs the following steps in the first adaptive process, starting from the frequency bin with the bin number 1 and proceeding to the frequency bin with the bin number 1024. Process positive frequency components.

The processing unit 220 executes each step shown in FIG. 7 in the adaptive processing. In this embodiment, the processing unit 220 repeatedly executes steps S131 to S135 shown in FIG. 10 multiple times for one frequency bin.

As shown in FIG. 7, in the adaptive processing, first, in step S131, the processing unit 220 executes FIR filter processing. FIR filter processing means that the FIR filter 222
Refers to processing of the reference input signal of the adaptive filter 221.

As shown in FIG. 8, by inputting the negative frequency component N(n) of bin number n to the FIR filter 222, an output component y(n) is output. It can also be said that the output component y(n) is a reference input signal processed by FIR filter processing. The output component y(n) is expressed by the following equation (1).
y(n)=w(n) ^TX ...(1)
X in the above formula (1) represents an input vector. w(n) represents the tap coefficient of the FIR filter 222. The subscript T represents the transposition of the vector. The tap coefficient w(n) is also called the FIR filter coefficient.

As shown in FIG. 9, the FIR filter 222 is configured as a direct filter with L taps. The input vector X described above is an L-order vector having negative frequency components N(n) to N(n-(L-1)) as components. The tap coefficient w(n) is an L-order vector having w ₁ (n) to w _L (n) as components. As shown in FIG. 9, the FIR filter 222 convolves the input vector X with the tap coefficient w(n). As a result, the sum of the products of the input vector X component and the tap coefficient w(n) component at each tap of the FIR filter 222 is output as the output component y(n) of the FIR filter 222. Note that in other embodiments, the FIR filter 222 may be configured as a transposed type, cascaded type, or lattice type filter.

Next, in step S132 of FIG. 7, the processing unit 220 executes output processing. Output processing is processing for outputting the residual ε(n) between the main input signal of the adaptive filter 221 and the reference input signal processed by the FIR filter processing as the output signal of the adaptive filter 221 shown in FIG. refers to something. That is, in the output process, the residual between the positive frequency component P(n) in the frequency bin of bin number n and the output component y(n) is output as the residual ε(n). Hereinafter, the residual ε(n) will also be referred to as the output signal ε(n). The output signal ε(n) is generated by the subtracter 223 as shown in FIG. The output signal (n) is expressed by the following equation (2).
ε(n)=P(n)−y(n)…(2)

Next, in step S133 of FIG. 7, the processing unit 220 executes update processing. The update process refers to the process of updating the tap coefficient w(n) based on the residual ε(n) using the above-mentioned adaptive algorithm. The tap coefficient w(n) is updated using equation (3) below.
w _R (n)=w(n)+με(n)X ^* …(3)
w _R in the above equation (3) represents the updated tap coefficient. μ represents a step size parameter for updating the tap coefficient w(n). X ^* represents the complex conjugate of the input vector X.

In this embodiment, the processing unit 220 changes the step size parameter μ based on the bin number n. More specifically, the processing unit 220 increases the step size parameter μ as a whole for the bin number n. More specifically, in this embodiment, the processing unit 220 monotonically increases the step size parameter μ with respect to the bin number n. As shown in FIG. 10, the step size parameter μ in this embodiment is defined as a linear function having a positive slope with respect to the bin number n. Note that, in this specification, monotonically increasing refers to a certain variable increasing without decreasing relative to other variables. Therefore, in other embodiments, when the step size parameter μ is monotonically increased with respect to the bin number n, the step size parameter μ is defined as, for example, a quadratic function, an exponential function, etc. that monotonically increases with respect to the bin number n. or may be defined as a function having a step-like part that takes a constant value for the bin number n.

As mentioned above, the difference between the positive frequency component and the negative frequency component of the interference signal component IFIf becomes larger in the higher frequency range, so for example, the step size parameter μ is set constant regardless of the bin number n. In this case, even if the tap coefficient w(n) can be updated appropriately in the lower frequency range, the update width of the tap coefficient w(n) is insufficient in the higher frequency range, and the tap coefficient w(n) cannot be updated appropriately. There are cases. As a result, even if the residual error ε(n) is relatively small in a lower frequency range, the residual error ε(n) may become large in a higher frequency range. In this embodiment, since the step size parameter μ is changed based on the bin number n as described above, the tap coefficient w(n) is This increases the possibility that the information can be updated appropriately. Therefore, the possibility that the residual error ε(n) can be made small in the frequency range corresponding to the far region increases.

Next, in step S134 of FIG. 7, the processing unit 220 determines whether the number of recalculations is equal to or greater than a predetermined number of times. The number of recalculations refers to the number of times that recalculation processing, which will be described later, has been executed. The number of recalculations is counted for each frequency bin. When step S134 is executed for the first time with respect to a certain frequency bin, the number of times of recalculation is zero. In this embodiment, the processing unit 220 determines whether the number of recalculations is two or more in step S134.

If it is determined in step S134 that the number of recalculations is less than two, the processing unit 220 returns the process to step S131. In steps S131 to S133, which are executed again, the processing unit 220 uses the tap coefficients updated immediately before to execute the FIR filter process, output process, and update process again.

For example, in step S131 executed for the second time regarding a certain frequency bin, the processing unit 220 uses the tap coefficient w updated in step S133 executed the first time as the tap coefficient w(n) in the above equation (1). Use _R (n). Similarly, in step S132 executed for the second time, the processing unit 220 calculates the output component calculated using the updated tap coefficient w _R (n) as the output component y(n) in the above equation (2). Using y(n), an output signal ε(n) is output. Similarly, in step S133 executed for the second time, the processing unit 220 uses the updated tap coefficient w _R (n) as the tap coefficient w(n) in the above equation (3) to further increase the tap coefficient. Update.

In this manner, in the present embodiment, before processing the frequency component of the next frequency bin of the first signal Bwf1 by adaptive processing, the processing unit 220, more specifically, processes the positive frequency component of the next frequency bin. Before using the updated tap coefficients as the main input signal of the adaptive filter 221, a recalculation process is performed, which is a process of re-executing the FIR filter process, update process, and output process on the current frequency bin. Execute. Note that when the bin number of the current frequency bin in the first adaptive process is n, the "next frequency bin" is the n+1-th frequency bin. When the bin number of the current frequency bin in the second adaptive process is n, the "next frequency bin" is the frequency bin with the bin number n-1.

If it is determined in step S134 that the number of recalculations is two or more, the processing unit 220 advances the process to step S135. That is, in this embodiment, the processing unit 220 executes the recalculation process a predetermined number of times, more specifically, only twice. In this embodiment, it can be said that steps S131 to S133 are executed a total of three times for a certain frequency bin. In other embodiments, the number of recalculations may be, for example, one time or three or more times. However, the number of recalculations is preferably 1 to 3 times.

Note that, unlike this embodiment, for example, when a time domain signal is processed in real time by an adaptive filter, a process similar to the recalculation process described above is executed, that is, an FIR filter is applied to one time component. Generally, it is difficult to perform processing such as multiple times due to time constraints. In contrast, in the present embodiment, the first signal Bwf1, which is a frequency domain signal, is processed in the adaptive processing, so that the recalculation processing can be easily executed.

In step S135, the processing unit 220 determines whether the current frequency bin is the last frequency bin in the adaptive process. If the processing unit 220 determines that it is not the last frequency bin, it returns the process to step S131. Thereafter, steps S131 to S134 are similarly executed for the next frequency bin. If the processing unit 220 determines in step S135 that it is the last frequency bin, it ends the adaptation process.

In step S140 of FIG. 3, the processing unit 220 splices the output signal of the first adaptive process and the output signal of the second adaptive process, and uses the spliced and generated signal as the interference-cancelled signal Ts. It is output to the measuring section 230.

In the upper part of FIG. 11, a signal Op1 as an example of the output signal of the first adaptive process and a signal Op2 as an example of the output signal of the second adaptive process are shown. Further, in the upper part of FIG. 11, a signal Bwf1a is shown as an example of the first signal Bwf1 processed by the first adaptive processing and the second adaptive processing. The lower part of FIG. 11 shows a signal Oj that is a combination of the signal Op1 and the signal Op2. FIG. 11 shows a frequency bin St1 that is processed first in the first adaptive processing, a frequency bin St2 that is processed first in the second adaptive processing, and a frequency bin E where the signal Op1 and the signal Op2 are joined. It is shown. Note that in FIG. 11, the signal Op1, the signal Op2, the signal Bwf1a, and the signal Oj are all represented by only the interference signal component IFIf, but in reality, at least one of the signal Op1 and the signal Op2, and , signal Bwf1a, and signal Oj include signals originating from target object OB. The bin number of frequency bin E is larger than the bin number of frequency bin St1 and smaller than the bin number of frequency bin St2. More specifically, in the example of FIG. 11, the frequency position corresponding to the bin number of frequency bin E corresponds to the minimum point of the signal Op2, and corresponds to the point at which the convergence process described below ends. Signal Oj has the same frequency components as signal Op2 in the frequency range below the bin number of frequency bin E, and has the same frequency components as signal Op1 in the frequency range greater than the bin number of frequency bin E. is being generated.

Generally, it takes a certain amount of time for residuals to converge in adaptive processing. Note that when processing a discrete signal in the frequency domain as in the adaptive processing in this embodiment, "a certain amount of time" refers to "a certain number of frequency bins." For example, in the example of FIG. 11, a region in which the residual error ε(n) is relatively high exists in a frequency region near frequency bin St1 of signal Op1 and a frequency region near frequency bin St2 of signal Op2. This region corresponds to the convergence process until the residual ε(n) converges. In this embodiment, the signal Op1 and the signal Op2 are combined to generate the signal Oj, and this signal Oj is output as the interference-cancelled signal Ts. Compared to the case of outputting as Ts, it is possible to suppress the influence of such a convergence process from occurring on the interference-cancelled signal Ts. For example, instead of the second adaptive processing, adaptive processing is performed in which positive frequency components are used as the main input signal of the adaptive filter 221 in order from frequency bins corresponding to long distances to frequency bins corresponding to short distances. In this case, as described above, since the difference between the positive frequency component and the negative frequency component is large in the higher frequency range, the residual error ε(n) may not converge but may diverge. In the second adaptive processing in this embodiment, since negative frequency components are processed from the frequency bin corresponding to the middle distance, such divergence of the residual error ε(n) can be suppressed.

FIG. 12 is a graph in which the horizontal axis represents frequency bins and the vertical axis represents power. In FIG. 12, the bin number of the frequency bin of the negative frequency component is given a negative sign. FIG. 12 shows the simulation results when the signal Bwf1b obtained by Fourier transforming the beat signal Bw including the interference signal IFI at the above-described time Tc is processed by adaptive processing. FIG. 12 shows a simulation result of a signal Tsa generated by processing the signal Bwf1b by the above-described adaptive processing as the interference-cancelled signal Ts. Further, FIG. 12 shows a simulation result of a signal Tsb generated by processing a similar signal Bwf1a by an adaptive process different from the above-described adaptive process. This other adaptive processing involves recalculating each frequency component of the signal Bwf1a in order from the frequency bin with bin number 1 to the frequency bin with bin number 1024, while keeping the step size parameter μ constant. This is an adaptive process that is processed without execution. The signal Bw1fb, like the first signal Bwf1 described in FIG. 4, includes a desired signal component IFOf originating from the target object OB and an interference signal component IFIf. In the example of FIG. 12, the desired signal component IFOf is included near the position of the frequency bin with bin number n of 180. The interference signal component IFIf of the signal Bwf1b is included over the entire frequency range.

As shown in FIG. 12, since the interference signal component IFIf is reduced by processing the signal Bwf1b in interference signal processing, the S/N ratio of the desired signal component IFOf to the interference signal component IFIf in the signal Tsa is The S/N ratio increases compared to the S/N ratio at . Furthermore, as shown in FIG. 12, in the signal Tsa, compared to the signal Tsb, the interference signal component IFIf is particularly effectively removed in the frequency range corresponding to the very near region and the frequency region corresponding to the far region. I understand that. More specifically, in the signal Tsa, compared to the signal Tsb, the interference signal component IFIf is effectively reduced at the frequency positions with bin numbers 1 to 20 and at the frequency positions with bin numbers 600 or more. Recognize. In this embodiment, the frequency positions with bin numbers 1 to 20 are frequency positions corresponding to positions at a distance of about 0 m to 6 m from the receiving unit 103, and the frequency positions with bin numbers 600 or more are the frequency positions corresponding to the distances from the receiving unit 103. This is a frequency position corresponding to a position at a distance of about 180 m or more from

The processing unit 220 ends the interference signal processing after step S140. Further, the processing unit 220 also ends the interference signal processing when it is determined in step S120 described above that the intensity of the interference signal component IFIf is less than the predetermined intensity. In this case, the first signal Bwf1 is output to the measuring section 230. If the intensity of the interference signal component IFIf is determined to be less than the predetermined intensity, the intensity of the interference signal component IFIf in the first signal Bwf1 is relatively small compared to the desired signal component IFOf. Therefore, in this case, even if the first signal Bwf1 is used to measure the target object OB, the influence of the interference signal component IFIf on the measurement results of the target object OB is suppressed.

The measurement unit 230 measures the target object OB based on the interference-cancelled signal Ts generated by the interference signal processing described above. In the present embodiment, the measurement unit 230 includes all the interference-cancelled signals Ts generated by processing the beat signal Bw based on each signal constituting the chirp signal group described above through interference signal processing, and the interference signal The target object OB is measured based on all the first signals Bwf1 for which the intensity of the component IFIf is determined to be less than a predetermined intensity. In this case, the measurement unit 230 may, for example, measure the target object OB by analyzing these signals individually, or measure the target object OB based on the results of further Fourier transform of these signals. Good too.

According to the signal processing device 200 in this embodiment described above, the processing unit 220 sequentially uses each positive frequency component of the first signal Bwf1 as a main input signal of the adaptive filter 221, and corresponds to each positive frequency component. In the adaptive processing of sequentially using each negative frequency component as a reference input signal of the adaptive filter 221 and outputting an output signal based on the main input signal, the FIR filter processing in which the reference input signal is processed by the FIR filter 222, and the adaptive filter 221 Output processing that outputs the residual ε(n) between the main input signal of the adaptive filter 221 and the reference input signal processed by the FIR filter 222 as an output signal, and tap coefficient w based on the residual ε(n). (n) An update process for updating the file is executed. Then, the processing unit 220 changes the step size parameter μ for updating the tap coefficient w(n) based on the bin number n. This increases the possibility that the residual error ε(n) can be made small in the frequency range corresponding to the far region. Therefore, the possibility that the interference signal component IFIf can be effectively removed from the first signal Bwf1 increases in the frequency range corresponding to the far region.

Furthermore, in the present embodiment, the processing unit 220 monotonically increases the step size parameter μ with respect to the bin number n. Thereby, the step size parameter μ can be increased in response to the fact that the difference between the positive frequency component and the negative frequency component of the interference signal component IFIf becomes larger in a higher frequency range. Therefore, the possibility that the tap coefficient w(n) can be updated more appropriately increases, so the possibility that the interference signal component IFIf can be effectively removed from the first signal Bwf1 increases in the frequency range corresponding to the far region.

Furthermore, in the present embodiment, the processing unit 220 uses the updated tap coefficient w _R (n) to input the current Regarding the frequency bin, recalculation processing that performs FIR filter processing, output processing, and update processing is performed a predetermined number of times. Thereby, the number of times the tap coefficient w(n) is updated can be increased compared to the case where the recalculation process is not executed. Therefore, the possibility that the interference signal component IFIf can be effectively removed from the first signal Bwf1 increases in the frequency range corresponding to the far region.

Further, in the present embodiment, as an adaptive process, the processing unit 220 sequentially converts positive frequency components into the main input signal of the adaptive filter 221 from frequency bins corresponding to a short distance to frequency bins corresponding to a long distance. and a second adaptive process in which the positive frequency component is used as the main input signal of the adaptive filter 221 in order from the frequency bin corresponding to the middle distance to the frequency bin corresponding to the short distance. . The processing unit 220 outputs a signal Oj, which is a combination of the signal Op1 output by the output process of the first adaptive process and the signal Op2 output by the output process of the second adaptive process, as the interference-cancelled signal Ts. . Thereby, it is possible to suppress the influence of the convergence process of the residual ε(n) on the interference-removed signal Ts. Therefore, for example, compared to the case where the frequency components of the first signal are simply processed by adaptive processing in order from the frequency bin corresponding to a short distance to the frequency bin corresponding to a long distance, In the frequency domain, the possibility that the interference signal component IFIf can be effectively removed from the first signal Bwf1 increases.

B. Second embodiment:
The signal processing device 200 in the second embodiment executes the interference signal processing shown in FIG. 13. In FIG. 13, the same steps as in FIG. 3 described in the first embodiment are given the same reference numerals as in FIG. In interference signal processing, the signal processing device 200 in this embodiment, unlike the first embodiment, executes a determination process, which will be described later, before executing adaptive processing. Of the configurations of the radar system 100 and the signal processing device 200 in the second embodiment, points not particularly described are the same as those in the first embodiment.

The determination process is to determine whether the signal strength difference between the positive frequency component in the high frequency range and the negative frequency component in the high frequency range of the second signal Bwf2 shown at the bottom of FIG. 14 is less than or equal to a predetermined reference value. Refers to the process of determining whether or not the The second signal Bwf2 is generated by Fourier transforming the beat signal Bw into a frequency domain signal in which frequency components are expressed for each frequency bin. In this specification, a "high frequency range" refers to a frequency range in which the absolute value of the frequency is higher than a predetermined frequency.

In step S102 of FIG. 13, the converter 210 performs Fourier transform on the beat signal Bw into a second signal Bwf2. In step S102, the converter 210 performs Fourier transform on the beat signal Bw into a second signal Bwf2 so as not to change the symmetry of the interference signal IFI derived from the mixed signal Iw in the beat signal Bw. More specifically, in step S102, the converting unit 210 performs Fourier transform on the beat signal Bw as it is without integrating the window function on the beat signal Bw.

In step S104, the processing unit 220 executes determination processing. In the present embodiment, in step S104, the processing unit 220 determines that the difference between the integrated value of power of positive frequency components in the high frequency range and the integrated value of power of negative frequency components in the corresponding frequency range is equal to It is determined whether the integrated value of the component power is 10% or less. If the processing unit 220 determines in step S104 that the difference in the integrated power values is 10% or less, that is, if it determines that the signal strength difference is equal to or less than the reference value, the processing unit 220 performs the same processing as described in FIG. , execute step S110 and subsequent steps.

If it is determined in step S104 that the difference in the integrated power values exceeds 10%, that is, if it is determined that the signal strength difference is greater than the reference value, in step S142, the processing unit 220 converts the beat signal Bw into Fourier transform is applied to the first signal Bwf1. After that, the processing unit 220 ends the interference signal processing. In this case, this first signal Bwf1 is output to the measuring section 230. Note that the beat signal Bw converted into the first signal Bwf1 in step S110 and step S142 in this embodiment is a signal similar to the beat signal Bw converted into the second signal Bwf2 in step S102.

The upper part of FIG. 14 shows a schematic graph in which the horizontal axis is time and the vertical axis is amplitude, and the lower part of FIG. 14 shows a schematic graph in which the horizontal axis is frequency and the vertical axis is amplitude. It is shown. The upper part of FIG. 14 shows an example in which the interference signal IFI occurs at the left end of the beat signal Bw in terms of time position, that is, at the earlier end of the beat signal Bw. In the lower part of FIG. 14, an example of the second signal Bwf2 generated by Fourier transforming the beat signal Bw is shown. In FIG. 14, the second signal Bwf2 is represented by a desired signal component IFOf and an interference signal component IFIf, similar to the first signal Bwf1 described in FIG.

As shown in FIG. 14, when the interference signal IFI occurs at the end of the beat signal Bw, all or part of the interference signal IFI may be missing. More specifically, in the example of FIG. 14, as shown in the upper part of FIG. 14, a part of the signal in the positive frequency range of the interference signal IFI is missing. Furthermore, as a result, as shown in the lower part of FIG. 14, a part of the positive frequency component of the interference signal component IFIf included in the second signal Bwf2 is missing. In this way, when the interference signal IFI occurs at the end of the beat signal Bw, the symmetry between the positive frequency component and the negative frequency component of the interference signal component IFIf included in the first signal Bwf1 and the second signal Bwf2 decreases. do. Therefore, in this case, if the adaptive processing is performed on the first signal Bwf1, the residual error ε(n) may diverge and not converge. In this embodiment, the above-described determination process allows the symmetry between the positive frequency component and the negative frequency component to be determined based on the signal strength difference between the positive frequency component and the negative frequency component. Then, if the signal strength difference is determined to be less than the reference value, that is, if the symmetry between the positive frequency component and the negative frequency component is high, then the adaptive process is executed, and in the opposite case, the adaptive process is not executed. Therefore, the divergence of the residual error ε(n) in the above adaptive processing can be suppressed. It is preferable that the above-mentioned range of the high frequency region and the magnitude of the reference value are determined such that, for example, the symmetry between the positive frequency component and the negative frequency component can be appropriately determined.

Further, although not shown, the same applies to the case where the interference signal IFI occurs at the right end of the beat signal Bw, that is, at the slower end of the beat signal Bw. In this case, some or all of the signals in the negative frequency range of the interference signal IFI are missing, so that some or all of the negative frequency components of the interference signal component IFIf included in the first signal Bwf1 and the second signal Bwf2 are missing. Missing.

As mentioned above, by multiplying the beat signal Bw by a window function, the signal strength at the edge of the beat signal Bw decreases, so if the interference signal IFI occurs at the edge of the time position of the beat signal Bw, the beat By multiplying the signal Bw by a window function such as a Hanning window, the amplitude of the interference signal IFI can be further reduced compared to the case where the interference signal IFI occurs at the time Tc of the beat signal Bw. Thereafter, the beat signal Bw multiplied by this window function is Fourier-transformed to generate the first signal Bwf1, thereby making it possible to reduce the signal strength of the interference signal component IFIf in the first signal Bwf1. That is, when the interference signal IFI occurs at the end of the beat signal Bw, the signal strength of the interference signal component IFIf in the first signal Bwf1 can be effectively reduced by executing step S142 described above. Therefore, in this case, for example, even if the first signal Bwf1 generated in step S142 is used to measure the target object OB, the influence of the interference signal component IFIf on the measurement results of the target object OB is suppressed.

According to the second embodiment described above, the processing unit 220 determines whether the signal strength difference between the positive frequency component and the negative frequency component in the high frequency decay period of the second signal Bwf2 is equal to or less than the reference value. A determination process is executed, and when the signal strength difference is less than or equal to a reference value, an adaptive process is executed. Therefore, it is possible to suppress the divergence of the residual error ε(n) in the adaptive processing.

C. Third embodiment:
The signal processing device 200 in the third embodiment executes the interference signal processing shown in FIG. 15. In FIG. 15, the same steps as in FIG. 13 described in the second embodiment are given the same reference numerals as in FIG. 13. The signal processing device 200 in this embodiment executes determination processing similarly to the second embodiment. On the other hand, in the present embodiment, unlike the second embodiment, the signal processing device 200 determines the mode of the power of the positive frequency component and the power of the negative frequency component in the high frequency range of the second signal Bwf2 in the determination process. Compare with the mode value of power. Of the configurations of the radar system 100 and the signal processing device 200 in the third embodiment, points not particularly described are the same as those in the second embodiment.

In step S104b of FIG. 15, the processing unit 220 executes determination processing. In the present embodiment, in step S104b, the processing unit 220 determines whether the difference in the mode of power in the above-mentioned high frequency range is 10% or less with respect to the mode of power in the positive frequency component. judge. If the processing unit 220 determines in step S104b that the difference in the mode of power is 10% or less, that is, if it determines that the signal strength difference is equal to or less than the reference value, the processing unit 220 performs the same process as described in FIG. 13. Then, steps S110 and subsequent steps are executed. Furthermore, if it is determined that the signal strength difference is greater than the reference value, step S142 is executed in the same manner as described with reference to FIG.

Similarly to the second embodiment, the third embodiment described above can suppress the divergence of the residual ε(n) in the adaptive processing. Note that in the second and third embodiments, the integrated value and the mode of power of each component are compared in the determination process, but when performing the determination process in other embodiments, for example, each component The integrated value or mode of the amplitudes of the components may be compared.

D. Other embodiments:
(D-1) In the above embodiment, the processing unit 220 (a) changes the step size parameter μ based on the bin number n in the adaptive process, and (b) performs a recalculation process in the adaptive process based on a predetermined value. (c) executing the first adaptive process and the second adaptive process as the adaptive process. On the other hand, the processing unit 220 may execute only one or two of the above (a) to (c).

(D-2) In the above embodiment, the processing unit 220 monotonically increases the step size parameter μ with respect to the bin number n in the adaptive processing. On the other hand, the processing unit 220 does not need to monotonically increase the step size parameter μ with respect to the bin number n in the adaptive processing. In this case, the step size parameter μ may be defined, for example, as a function that partially decreases with respect to the bin number n and increases as a whole with respect to the bin number n.

(D-3) In the above embodiment, the processing unit 220 determines whether the intensity of the interference signal component IFIf of the first signal Bwf1 is equal to or higher than a predetermined intensity in step S120 of FIG. 3, FIG. 13, or FIG. Although this determination is made, it is not necessary to perform this determination.

E. Other forms:
The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments may be replaced or combined as appropriate in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. is possible. Further, unless the technical feature is described as essential in this specification, it can be deleted as appropriate.

<Form 1> A signal processing device (200) receives a received signal (Dw) obtained by receiving a reflected wave from an object (OB) that reflected a transmitted wave, and a transmitted signal (Dw) for transmitting the transmitted wave. A beat signal (Bw) representing a time-domain signal generated by mixing Tw) and Tw with an orthogonal mixer (105) is converted into a frequency-domain first signal (Bwf1) in which frequency components are expressed for each frequency bin. ), and an adaptive filter (221) including an FIR filter (222), and an interference-cancelled signal (Ts) in which an interference signal component (IFIf) is removed from the first signal. and a processing unit (220) that generates. The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. Adaptive processing is performed to output an output signal based on the main input signal and the reference input signal as a reference input signal of the filter. In the adaptive processing, the processing unit performs FIR filter processing in which the reference input signal is processed by the FIR filter, and as the output signal, the main input signal and the reference input signal processed by the FIR filter processing. , and an update process of updating the tap coefficients of the FIR filter based on the residuals, and the step size parameter for updating the tap coefficients is set to the step size parameter for updating the tap coefficients of the FIR filter. It is changed based on the bin number of the frequency bin of one signal.

<Form 2> In the signal processing device of the above-mentioned Form 1, the processing unit may monotonically increase the step size parameter with respect to the bin number.

<Form 3> A signal processing device (200) receives a received signal (Dw) obtained by receiving a reflected wave from an object (OB) that reflected a transmitted wave, and a transmitted signal (Dw) for transmitting the transmitted wave. A beat signal (Bw) representing a time-domain signal generated by mixing Tw) and Tw with an orthogonal mixer (105) is converted into a frequency-domain first signal (Bwf1) in which frequency components are expressed for each frequency bin. ), and an adaptive filter (221) including an FIR filter (222), and an interference-cancelled signal (Ts) in which an interference signal component (IFIf) is removed from the first signal. and a processing unit (220) that generates. The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. Adaptive processing is performed to output an output signal based on the main input signal and the reference input signal as a reference input signal of the filter. In the adaptive processing, the processing unit performs FIR filter processing in which the reference input signal is processed by the FIR filter, and as the output signal, the main input signal and the reference input signal processed by the FIR filter processing. , an output process for outputting the residual of , and an update process for updating the tap coefficient of the FIR filter based on the residual, and outputting the positive frequency component of the next frequency bin of the first signal. Before using the main input signal, a recalculation process of performing the FIR filter process, the output process, and the update process using the updated tap coefficient with respect to the current frequency bin of the first signal; Executes a predetermined number of times.

<Form 4> A signal processing device (200) receives a received signal (Dw) obtained by receiving a reflected wave from an object (OB) that reflected a transmitted wave, and a transmitted signal (Dw) for transmitting the transmitted wave. A beat signal (Bw) representing a time-domain signal generated by mixing Tw) and Tw with an orthogonal mixer (105) is converted into a frequency-domain first signal (Bwf1) in which frequency components are expressed for each frequency bin. ), and an adaptive filter (221) including an FIR filter (222), and an interference-cancelled signal (Ts) in which an interference signal component (IFIf) is removed from the first signal. and a processing unit (220) that generates. The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. Adaptive processing is performed to output an output signal based on the main input signal and the reference input signal as a reference input signal of the filter. In the adaptive processing, the processing unit includes FIR filter processing in which the main input signal is processed by the FIR filter, and the main input signal and the reference input signal processed by the FIR filter processing as the output signals. , and an update process that updates the tap coefficients of the FIR filter based on the residual, and as the adaptive processing, the frequency bin corresponding to a short distance is changed to a frequency bin corresponding to a long distance. a first adaptive process in which the positive frequency component of the first signal is used as the main input signal in order from a frequency bin corresponding to a medium distance to a frequency bin corresponding to a short distance; and a second adaptive process in which the positive frequency component of the first signal is used as the main input signal, and the signal output by the output process of the first adaptive process and the second adaptive process are A signal output by the output processing of and a signal obtained by splicing are output as the interference-removed signal.

<Embodiment 5> In the radar device according to any one of Embodiments 1 to 4 above, the converter converts the beat signal into a second signal (Bwf2) in a frequency domain in which frequency components are expressed for each frequency bin. Fourier transform is performed, and the processing unit calculates a signal strength difference between a positive frequency component and a negative frequency component in a high frequency range representing a frequency range higher than a predetermined frequency of the second signal based on a predetermined standard. A determination process may be executed to determine whether the signal strength difference is equal to or less than the reference value, and when the signal strength difference is equal to or less than the reference value, the adaptive process may be executed.

<Embodiment 6> A radar system (100) includes a signal processing device according to any one of embodiments 1 to 5 above, and a transmitter (102) that transmits the transmission wave to the target object based on the transmission signal. , a receiving section (103) that receives the received signal, the orthogonal mixer, and a measuring section that measures the target based on the output signal.

DESCRIPTION OF SYMBOLS 100... Radar system, 101... Signal generation part, 102... Transmission part, 103... Receiving part, 105... Orthogonal mixer, 106... Filter part, 107... Analog-to-digital conversion part, 200... Signal processing device, 210... Conversion part, 220 ...processing unit, 221...adaptive filter, 222...FIR filter, 230...measuring unit, Bw...beat signal, Bwf1...first signal, Bwf2...second signal, Dw...received signal, Ew...electromagnetic wave, IFIf...interference signal component , OB...target, Ts...signal after interference removal

Claims (7)

A signal processing device (200),
A received signal (Dw) obtained by receiving the reflected wave from the target object (OB) that reflected the transmitted wave and a transmitted signal (Tw) for transmitting the transmitted wave are mixed by an orthogonal mixer (105). a transformer (210) that performs Fourier transform on a beat signal (Bw) representing a time-domain signal generated by
a processing unit (220) having an adaptive filter (221) including an FIR filter (222) and generating an interference-cancelled signal (Ts) in which an interference signal component (IFIf) is removed from the first signal; ,
The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. performing adaptive processing to output an output signal based on the main input signal and the reference input signal as a reference input signal of a filter;
In the adaptive processing, the processing unit includes:
FIR filter processing of processing the reference input signal by the FIR filter;
Output processing that outputs, as the output signal, a residual difference between the main input signal and the reference input signal processed by the FIR filter processing;
performing an update process of updating tap coefficients of the FIR filter based on the residual;
changing a step size parameter for updating the tap coefficients based on a bin number of frequency bins of the first signal;
Signal processing device. The signal processing device according to claim 1,
The processing unit is a signal processing device, wherein the processing unit monotonically increases the step size parameter with respect to the bin number. A signal processing device (200),
A received signal (Dw) obtained by receiving the reflected wave from the target object (OB) that reflected the transmitted wave and a transmitted signal (Tw) for transmitting the transmitted wave are mixed by an orthogonal mixer (105). a transformer (210) that performs Fourier transform on a beat signal (Bw) representing a time-domain signal generated by
a processing unit (220) having an adaptive filter (221) including an FIR filter (222) and generating an interference-cancelled signal (Ts) in which an interference signal component (IFIf) is removed from the first signal; ,
The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. performing adaptive processing to output an output signal based on the main input signal and the reference input signal as a reference input signal of a filter;
In the adaptive processing, the processing unit includes:
FIR filter processing of processing the reference input signal by the FIR filter;
Output processing that outputs, as the output signal, a residual difference between the main input signal and the reference input signal processed by the FIR filter processing;
performing an update process of updating tap coefficients of the FIR filter based on the residual;
Before taking the positive frequency component of the next frequency bin of the first signal as the main input signal, the FIR filter processing and the A signal processing device that executes a recalculation process that performs an output process and the update process a predetermined number of times. A signal processing device (200),
A received signal (Dw) obtained by receiving the reflected wave from the target object (OB) that reflected the transmitted wave and a transmitted signal (Tw) for transmitting the transmitted wave are mixed by an orthogonal mixer (105). a transformer (210) that performs Fourier transform on a beat signal (Bw) representing a time-domain signal generated by
a processing unit (220) having an adaptive filter (221) including an FIR filter (222) and generating an interference-cancelled signal (Ts) in which an interference signal component (IFIf) is removed from the first signal; ,
The processing unit sequentially uses each positive frequency component of the first signal as a main input signal of the adaptive filter, and sequentially uses each negative frequency component of the first signal corresponding to each positive frequency component as the main input signal of the adaptive filter. performing adaptive processing to output an output signal based on the main input signal and the reference input signal as a reference input signal of a filter;
In the adaptive processing, the processing unit includes:
FIR filter processing of processing the reference input signal by the FIR filter;
Output processing that outputs, as the output signal, a residual difference between the main input signal and the reference input signal processed by the FIR filter processing;
performing an update process of updating tap coefficients of the FIR filter based on the residual;
The adaptive processing includes a first adaptive processing in which the positive frequency component of the first signal is used as the main input signal in order from a frequency bin corresponding to a short distance to a frequency bin corresponding to a long distance; performing a second adaptive process in which the positive frequency component of the first signal is used as the main input signal in order from a frequency bin corresponding to the short distance to a frequency bin corresponding to the short distance;
outputting a signal obtained by splicing the signal output by the output process of the first adaptive process and the signal output by the output process of the second adaptive process as the interference-removed signal;
Signal processing device. The signal processing device according to any one of claims 1 to 4,
The transform unit performs Fourier transform on the beat signal into a second signal (Bwf2) in the frequency domain in which frequency components are expressed for each frequency bin,
The processing unit is configured such that a signal strength difference between a positive frequency component and a negative frequency component in a high frequency range representing a frequency range higher than a predetermined frequency of the second signal is less than or equal to a predetermined reference value. Execute a determination process to determine whether or not,
A signal processing device that performs the adaptive processing when the signal strength difference is less than or equal to the reference value. A radar system (100),
The signal processing device according to any one of claims 1 to 4,
a transmitter (102) that transmits the transmission wave to the target object based on the transmission signal;
a receiving section (103) that receives the received signal;
the orthogonal mixer;
A radar system comprising: a measurement unit that measures the target based on the output signal. A radar system (100),
The signal processing device according to claim 5;
a transmitter (102) that transmits the transmission wave to the target object based on the transmission signal;
a receiving section (103) that receives the received signal;
the orthogonal mixer;
A radar system comprising: a measurement unit that measures the target based on the output signal.

Images