JP2006300720A - Radar apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably determine a distance by reducing an effect caused by interference in an FMCW radar apparatus. <P>SOLUTION: The radar apparatus allows a window function which can reduce interference-wave components to act on each beat signal Xn in up and down modulation. From the beat signal Xn in the up modulation after the action, a correlation matrix Ru is calculated (S310), and the matrix Ru, a correlation matrix calculated last time Ru1, and a correlation matrix calculated before last Ru2 are integrated to determine a matrix Ra. A plurality of cycles of the beat signals Xn are thereby integrated (S320). The matrix Ra is then subjected to DFT processing (S330) to determine a spectrum Y1 corresponding to the integrated signal of the plurality of cycles of the beat signals in the up modulation. The beat signals in the down modulation are subjected to the similar processing to determine a spectrum Y2 corresponding to the integrated signal of a plurality of cycles of the beat signals in the down modulation. From the spectra Y1, Y2, a beat frequency is specified to determine a distance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radar apparatus that obtains a distance from a target by transmitting and receiving a frequency-modulated radar wave.

  Conventionally, a radar device has been mounted on a vehicle for the purpose of collision prevention and inter-vehicle control. As this type of radar apparatus, there is known an FMCW radar apparatus (hereinafter referred to as “FMCW radar apparatus”) that can simultaneously detect the distance and relative speed with a target and is suitable for downsizing and cost reduction. (For example, refer to Patent Document 1).

  In the FMCW radar apparatus, as shown by a solid line in FIG. 14A, a transmission signal Ss that is frequency-modulated by a triangular wave-like modulation signal and whose frequency gradually increases and decreases linearly with respect to time is transmitted as a radar wave. As shown, the radar wave reflected by the target (hereinafter also referred to as “reflected wave”) is received.

  At this time, the received signal Sr is delayed by the time Tr corresponding to the time required for the radar wave to reciprocate between the targets, that is, the distance to the target, as indicated by the dotted line in FIG. Is shifted by a frequency fd corresponding to the relative speed.

  In the FMCW radar apparatus, the received signal Sr and the transmitted signal Ss are mixed by a mixer, thereby generating a beat signal that is a frequency component of the difference between the two signals Sr and Ss as shown in FIG. Let

  Note that the frequency of the beat signal when the frequency of the transmission signal Ss increases (hereinafter referred to as “beat frequency during upstream modulation”) fb1 and the frequency of the beat signal when the frequency of the transmission signal Ss decreases (hereinafter “ The frequency fr based on the delay time Tr can be calculated from the equation (1) and the Doppler shift frequency fd can be calculated according to the equation (2) from fb2 (expressed as “beat frequency at downstream modulation”).

  Further, the distance D to the target and the relative speed V can be calculated according to the equations (3) and (4) based on these frequencies fr and fd. Where c is the radio wave propagation speed, fm is the modulation frequency of the transmission signal, ΔF is the frequency fluctuation range of the transmission signal, and F0 is the center frequency of the transmission signal.

  Therefore, in the FMCW radar apparatus, the beat frequencies fb1 and fb2 are specified from the beat signal. Signal processing is generally used to specify the beat frequencies fb1 and fb2. Specifically, the beat signal is sampled, and the frequency spectrum of the beat signal is obtained for each modulation time by performing DFT (discrete Fourier transform) processing for each upstream / downstream modulation time. The peak frequency is set as beat frequencies fb1 and fb2.

  As is well known, the beat signal sampling frequency fx needs to be set to at least twice the upper limit frequency of the beat signal. That is, the frequency fluctuation width ΔF of the radar wave so that the frequency component of the beat signal generated based on the reflected wave from the target existing in the preset detection range falls within the signal band below the upper limit frequency. And the modulation period 1 / fm are set.

  By the way, when this type of FMCW radar apparatus is mounted on a vehicle and used, a radar wave output from the FMCW radar apparatus mounted on another vehicle traveling on the opposite lane or the like is output from the own vehicle. In some cases, the distance and relative velocity with respect to the target cannot be accurately obtained due to interference with the reflected wave of the radar wave. That is, in the frequency spectrum calculated based on the beat signal, a peak corresponding to the interference wave component occurs due to the interference wave component, and one or both of the beat frequencies fb1 and fb2 cannot be detected. There is.

In preparation for such a case, the FMCW radar apparatus is equipped with an interpolation function for predicting the distance and relative velocity with respect to the target based on the calculation result of the past distance D, and an interference detection function.
Conventionally, as an interference detection method, a method is known in which the magnitude relationship between the amplitude of a received signal or beat signal and a threshold value is compared, and when the signal amplitude exceeds the threshold value, it is determined that interference has occurred. (For example, refer to Patent Document 2). In addition, as a method for preventing interference, a technique of emitting a spectrum-spread carrier wave from an antenna is known (see, for example, Patent Document 3).
JP-A-8-146126 JP 2002-168947 A JP-A-7-146359

  However, the above-described interference prevention method using spread spectrum cannot be applied to the FMCW radar apparatus, and the conventional technique has a problem that the influence of interference cannot be sufficiently suppressed in the FMCW radar apparatus.

  For example, in the FMCW radar apparatus described in Patent Document 2, when interference is detected for the purpose of suppressing interference, the frequency of the transmission signal is changed or the modulation cycle is changed. The effect of interference could not be sufficiently suppressed. Further, there is a problem that the influence of interference cannot be sufficiently suppressed only by the interpolation function.

  The present invention has been made in view of such a problem, and in various radar apparatuses including an FMCW radar apparatus, it is possible to effectively suppress the influence of interference and to obtain a distance and the like stably. Objective.

  The radar apparatus according to claim 1, which has been made to achieve the above object, includes a transmission signal generation unit, a beat signal generation unit, an acquisition unit, an integration unit, an analysis unit, and a distance calculation unit. The transmission signal generation unit repeatedly generates a frequency-modulated radar wave transmission signal, and the beat signal generation unit generates the transmission signal generated by the transmission signal generation unit and the reflected wave from the target reflecting the radar wave. A beat signal is generated by mixing the received signal.

  The acquisition unit acquires the beat signal generated by the beat signal generation unit from the beat signal generation unit in accordance with the transmission signal generation cycle by the transmission signal generation unit, and the integration unit acquires the beat signal acquired by the acquisition unit. Are integrated for a plurality of predetermined cycles.

  The radar apparatus according to the present invention frequency-analyzes the integrated beat signal obtained by integrating the beat signals for a plurality of cycles by the integrating unit by the analyzing unit, and determines the distance calculating unit based on the analysis result of the analyzing unit. To find the distance to the target.

  In the radar apparatus of the present invention configured as described above, since the beat signals for a plurality of cycles are integrated and frequency analysis is performed, even if an interference wave component is generated in the beat signal of a specific cycle, the same interference wave is generated in other cycles. If no component is present, the effect is suppressed by integration. That is, in the radar apparatus of the present invention, the signal component corresponding to the beat frequency can be selectively emphasized by integrating the beat signals of a plurality of cycles.

Therefore, according to the present invention, it is possible to prevent the beat frequency from becoming undetectable due to the interference wave component, and the distance to the target can be obtained more stably than in the past.
The transmission signal generation means is configured to repeatedly generate a transmission signal that is frequency-modulated by a triangular wave-like modulation signal as a transmission signal and whose frequency gradually increases and decreases linearly with respect to time. be able to. Also, in this case, the radar apparatus is configured so that beat signals for each cycle are acquired every half cycle and integrated, and the beat frequency for upstream modulation and the beat frequency for downstream modulation are obtained individually. Can be configured.

Moreover, it is preferable that the radar apparatus of the present invention is provided with a function of removing interference wave components by a window function.
The radar apparatus according to claim 2 acquires the interference wave component included in the beat signal generated by the beat signal generation means, together with the position of the interference wave component, based on the detection result of the detection means and the detection means. Determining means for determining a window function to be applied to the beat signal acquired by the means; and window function processing means for applying the window function determined by the determining means to the beat signal for each cycle acquired by the acquiring means. Prepare.

  The determination means in the radar apparatus includes a window function capable of selectively attenuating the interference wave component according to a detection position of the interference wave component when the interference wave component is detected by the detection means. The window function to be applied to the beat signal is determined. Further, the integrating means integrates beat signals acquired by the acquiring means and processed by the window function processing means for a plurality of cycles.

  In this radar apparatus, since the interference wave component included in the beat signal can be attenuated by the window function, the distance to the target can be stably obtained even when the beat signal includes the interference wave component. . Therefore, according to the present invention, it is possible to manufacture a radar apparatus that is less susceptible to interference.

  In addition, the analyzing means in the radar apparatus of the present invention can be configured to frequency-analyze the integrated beat signal and generate a frequency spectrum corresponding to the integrated beat signal, and the distance calculating means is generated by the analyzing means. In the obtained frequency spectrum, a peak that is equal to or greater than a predetermined threshold value is detected, and the distance to the target can be obtained based on the frequency (beat frequency) corresponding to the detected peak.

  The radar apparatus further includes a threshold setting unit that sets the threshold value used at the time of peak detection based on a detection result of the detection unit that detects an interference wave component included in the beat signal generated by the beat signal generation unit. Can be provided. The radar apparatus according to claim 3 is configured such that the threshold value setting means sets the threshold value higher than when no interference wave component is detected when the detection means detects an interference wave component. .

  In this radar device, when the interference wave component is detected, the peak threshold value for determining the beat frequency is set higher than normal (when no interference wave component is detected), so that the peak corresponding to the interference wave component is erroneously set. Thus, it is possible to prevent the beat frequency from being determined. As a result, according to this radar apparatus, it is possible to calculate the distance to the target stably and stably without being greatly affected by interference.

  In addition, the radar device according to claim 4 includes the transmission signal generation unit, the beat signal generation unit, and the acquisition unit described above, and performs frequency analysis on the beat signal acquired by the acquisition unit for each cycle, An analysis unit that generates a frequency spectrum corresponding to the beat signal, an integration unit that integrates the frequency spectrum generated by the analysis unit for a plurality of cycles, and an integration in which the frequency spectrum for a plurality of cycles is integrated by the integration unit Distance calculating means for obtaining a distance to the target based on the spectrum.

  In this radar device, the frequency spectrum for a plurality of cycles is integrated to derive the integrated spectrum, and based on this, the distance to the target is obtained, so even if an interference wave component occurs in the beat signal of a specific cycle, If the same interference wave component does not exist in the cycle, the influence of interference can be suppressed by integrating the frequency spectrum. Therefore, according to this radar apparatus, the distance and the like can be obtained stably as in the radar apparatus according to the first aspect.

Moreover, in this radar apparatus, the influence of interference can be further suppressed by using a window function.
The radar apparatus according to claim 5 is a detection unit that detects an interference wave component included in the beat signal generated by the beat signal generation unit together with a position of the interference wave component, and an acquisition unit based on a detection result of the detection unit. Determining means for determining a window function to be applied to the beat signal acquired by the acquisition means, and window function processing means for applying the window function determined by the determination means to the beat signal for each cycle acquired by the acquisition means.

  In the radar apparatus, when the interference wave component is detected by the detection unit, the acquisition unit acquires a beat function by which the acquisition unit acquires a window function that can selectively attenuate the interference wave component according to the detection position of the interference wave component. The window function to be applied to the beat signal including the interference wave component is determined, and the analysis means is the beat signal acquired by the acquisition means, and the beat signal processed by the window function processing means is processed in each cycle. Every time, frequency analysis is performed to generate a frequency spectrum corresponding to the beat signal.

  In this radar apparatus, the interference wave component included in the beat signal can be attenuated by the window function, similarly to the radar apparatus according to claim 2, so that even when the beat signal includes the interference wave component, The distance to the target can be obtained stably, and the influence of interference can be further suppressed.

Further, the concept corresponding to the third aspect of the invention can be applied to a radar apparatus that integrates frequency spectra for a plurality of cycles.
In the radar apparatus according to the sixth aspect, the distance calculating means detects a peak that is equal to or greater than a predetermined threshold in the integrated spectrum, and obtains the distance to the target based on the frequency corresponding to the detected peak. The radar apparatus further includes threshold setting means for setting the threshold used at the time of peak detection based on the detection result of the detecting means for detecting the interference wave component included in the beat signal generated by the beat signal generating means. . When the interference wave component is detected by the detection means, the threshold setting means sets the threshold higher than when the interference wave component is not detected.

  In this radar apparatus, since the threshold value when the interference wave component is detected is set higher than when the interference wave component is not detected, the peak corresponding to the interference wave component is similar to the radar apparatus according to claim 3. It is possible to prevent erroneous determination as a beat frequency. Therefore, according to this radar apparatus, it is possible to calculate the distance to the target stably and stably without being affected by interference.

In addition, the concept corresponding to the inventions of claims 2 and 5 can be applied to a radar apparatus that does not integrate beat signals for a plurality of cycles or frequency spectra for a plurality of cycles.
The radar apparatus according to claim 7 includes the transmission signal generation unit, the beat signal generation unit, and the acquisition unit described above, and converts the interference wave component included in the beat signal generated by the beat signal generation unit into the interference wave. The detection means for detecting together with the position of the component, the determination means for determining the window function to be applied to the beat signal acquired by the acquisition means based on the detection result of the detection means, and the beat signal for each cycle acquired by the acquisition means On the other hand, the window function processing means for applying the window function determined by the determination means, the analysis means for analyzing the frequency of the beat signal acquired by the acquisition means and processed by the window function processing means, and the analysis Distance calculating means for obtaining the distance to the target based on the analysis result of the means.

  In the radar apparatus, when the interference wave component is detected by the detection unit, the acquisition unit acquires a beat function by which the acquisition unit acquires a window function that can selectively attenuate the interference wave component according to the detection position of the interference wave component. In this case, the window function to be applied to the beat signal including the interference wave component is determined.

  According to this radar apparatus, since the interference wave component included in the beat signal is attenuated using the window function, the influence of the interference can be suppressed and stable as in the radar apparatus according to claims 2 and 5. In particular, the distance to the target can be obtained.

In addition, the concept corresponding to the inventions of claims 3 and 6 can be applied to a radar apparatus that does not integrate beat signals for a plurality of cycles and frequency spectra for a plurality of cycles.
The radar apparatus according to claim 8, wherein the analysis unit performs frequency analysis on the beat signal processed by the window function processing unit to generate a frequency spectrum corresponding to the beat signal, and the distance calculation unit includes the analysis In the frequency spectrum generated by the means, a peak equal to or greater than a predetermined threshold is detected, and the distance to the target is obtained based on the frequency corresponding to the detected peak. Further, the radar apparatus includes threshold setting means for setting the threshold used at the time of peak detection based on the detection result of the detection means. The threshold setting means, when the interference wave component is detected by the detection means, The threshold is set higher than when no interference wave component is detected.

  In the radar apparatus configured as described above, similarly to the radar apparatus according to claims 3 and 6, the peak frequency corresponding to the interference wave component can be prevented from being erroneously determined as the beat frequency, The distance to the target can be calculated stably and stably without being affected by interference.

  Further, in the above-described radar apparatus (claims 1 to 8), as described in claims 9 and 10, it is obtained in the past by the distance calculation means during a period in which the distance calculation means cannot be calculated. Generated by an interpolation processing means for predicting a distance to the current target based on at least the distance, a diagnosis output means for outputting diagnosis information when the interpolation processing means operates for a predetermined allowable period, and a beat signal generation means It is preferable to provide an allowable period setting means for setting the allowable period based on the detection result of the detection means for detecting the interference wave component included in the beat signal.

  According to the radar apparatus configured in this manner, the allowable period can be switched depending on whether or not the interference wave component is detected, so that appropriate interpolation processing can be performed when interference occurs and when interference does not occur. It is possible to operate stably while suppressing the influence of interference.

  In other words, if the permissible period at the time of detecting the interference wave component is set longer than that at the time of non-detection, the diagnostic information to the effect of target disappearance due to interference is obtained despite the short period during which the distance due to interference cannot be calculated. It is possible to prevent the warning light from being frequently turned on and the collision prevention function and the inter-vehicle control function from being invalidated. In addition, when the interference wave component is not detected, the interpolation process continues even though the target has actually disappeared, and no diagnostic information indicating that the target has disappeared is output. Can be prevented from malfunctioning.

The inventions according to claims 9 and 10 are not limited to the above-described radar device (claims 1 to 8), and can be applied.
The radar apparatus according to claim 11 includes the transmission signal generation unit, the beat signal generation unit, and the acquisition unit described above, an analysis unit that performs frequency analysis on the beat signal acquired by the acquisition unit, and an analysis result of the analysis unit Based on the above, the distance calculation means for calculating the distance to the target, and the distance to the target can be predicted based on the distance obtained in the past by the distance calculation means for a period during which the distance calculation means cannot be calculated. When the interpolation processing means operates and the interpolation processing means operates for a predetermined allowable period or longer, the interference output component included in the beat signal generated by the diagnosis output means that outputs the diagnosis information and the beat signal generation means is detected. A detection unit; and an allowable period setting unit that sets the allowable period based on a detection result of the detection unit.

  According to this radar apparatus, similarly to the radar apparatus according to claims 9 and 10, the radar apparatus can operate stably without being affected by interference.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an FMCW in-vehicle radar device 2 to which the present invention is applied.
As shown in FIG. 1, the radar apparatus 2 according to the present embodiment includes a D / A converter 10 that generates a triangular wave-shaped modulation signal according to a modulation command, and a modulation signal generated by the D / A converter 10. A voltage controlled oscillator (VCO) 14 that is applied through the buffer 12 and whose oscillation frequency changes according to the modulation signal, a distributor 16 that distributes the output of the VCO 14 to the transmission signal Ss and the local signal L, and the transmission signal Ss The local antenna L is mixed with the received signal Sr supplied from the receiving side antenna unit 20 that receives the radar wave, the receiving side antenna unit 20 that receives the radar wave, and the beat signal B , The amplifier 26 that amplifies the beat signal B generated by the mixer 24, and the beat signal B amplified by the amplifier 26 is sampled according to the timing signal P A / D converter 28 for converting to digital data, timing control unit 30 for generating timing signal P composed of a pulse train having a cycle of 1 / fx, and beat signal taken in via A / D converter 28 A signal processing unit 34 that obtains the distance Ds and the relative velocity Vs from the target that reflected the radar wave by performing signal processing of the sampling data of B;

  The VCO 14 generates a millimeter-wave band high-frequency signal that is modulated so that the frequency gradually increases and decreases linearly with time according to a triangular wave-like modulation signal. In the VCO 14, for example, F0 = 76.5 GHz is set as the center frequency of the high-frequency signal, and ΔF = 100 MHz is set as the frequency fluctuation range.

  In addition, the antenna that configures the reception-side antenna unit 20 is set so that the beam width (angle range in which the gain reduction with respect to the front direction is within 3 dB) includes the entire beam width of the antenna that configures the transmission-side antenna unit 18. ing.

  In addition, the signal processing unit 34 is configured around a known microcomputer including a CPU, a ROM, and a RAM. The signal processing unit 34 has a sweep time T as a time until the modulation frequency reaches from the lowest frequency to the highest frequency (uplink modulation) or as a time from the highest frequency to the lowest frequency (downlink modulation). A process for generating a modulation command such that T = N / fx, where N is the number of samplings, is repeatedly and periodically executed with the uplink modulation command and the downlink modulation command as a pair.

  In addition, the signal processing unit 34 performs frequency analysis on the sampling data of the beat signal B at the time of upstream modulation and the sampling data of the beat signal B at the time of downstream modulation obtained through the A / D converter 28, respectively. A frequency spectrum (also referred to as a power spectrum) Y1 corresponding to the beat signal B at the time of upstream modulation and a frequency spectrum Y2 corresponding to the beat signal B at the time of downstream modulation are obtained, and based on the pair of frequency spectra Y1 and Y2 The beat frequencies fb1 and fb2 are obtained, and the distance D to the target and the relative speed V are obtained.

  In the radar apparatus 2 of this embodiment configured as described above, the distributor 16 distributes the power of the high-frequency signal generated by the VCO 14 according to the modulation signal, so that the transmission signal Ss and the local signal L are generated. The transmission signal Ss is sent out as a radar wave via the transmission-side antenna unit 18. FIG. 2 is an explanatory diagram showing an aspect of the transmission signal Ss that is repeatedly generated.

Further, the radar wave (reflected wave) that has been reflected back to the target is received by the receiving-side antenna unit 20 and supplied to the mixer 24 as the received signal Sr.
In the mixer 24, the received signal Sr and the local signal L from the distributor 16 are mixed to generate a beat signal B, and the beat signal B is amplified by the amplifier 26. The beat signal B amplified by the amplifier 26 is sampled according to the timing signal P in the A / D converter 28.

In the signal processing unit 34, sampling data of the beat signal B is taken from the A / D converter 28 by analysis processing.
Next, analysis processing executed by the signal processing unit 34 will be described with reference to FIGS. FIG. 3 is a flowchart illustrating an analysis process that the signal processing unit 34 repeatedly executes in accordance with a generation cycle of a modulation command (triangular wave-shaped modulation signal). FIG. 4 is a flowchart showing the reading process executed in the analysis process. FIG. 5 is a flowchart (a) representing the first conversion process executed in the analysis process and a flowchart (b) representing the second conversion process.

  When the analysis process is executed, the signal processing unit 34 executes a read process for N data (time-series data) sampled during uplink modulation (during a half cycle) in accordance with the modulation command generation cycle. At the same time (S110), a first conversion process for performing frequency analysis on the data is executed (S120), and a read process for N data sampled during downlink modulation (during a half cycle) is executed. At the same time (S130), a second conversion process for performing frequency analysis on the data is executed (S140). Thereafter, the process proceeds to S150.

  In the reading process executed in S110 and S130, as shown in FIG. 4, N data {X (0), X (1),..., X (t),. , X (N-1)} is taken from a buffer (not shown) of the A / D converter 28 (S210), this is set in the array Xn, and a half-cycle beat signal (uplink modulation or downlink modulation) A matrix Xn representing the beat signal of time), and an N × 1 matrix Xn shown in Expression (5) is generated (S220). For the beat signal set to Xn, it is assumed that the vibration center is set to zero. Moreover, the superscript T in Formula (5) means transposition.

  When the processing in S220 is completed, the signal processing unit 34 determines whether or not an interference wave component exists in the beat signal set in the matrix Xn (S230), and if the interference wave component does not exist in the beat signal. If it is determined (No in S230), the process proceeds to S240, and if it is determined that the interference wave component is present in the beat signal (Yes in S230), the process proceeds to S250.

  Specifically, in this embodiment, it is determined whether or not an interference wave component exists in the beat signal by using a phenomenon that the amplitude of the beat signal increases when the interference wave component is mixed in the beat signal. That is, a component indicating an amplitude greater than or equal to a predetermined threshold Th0 is included in the beat signal {X (0), X (1),..., X (t),. If it exists, it is determined that the interference wave component is present in the beat signal (see FIG. 6).

  If it is determined that no interference wave component exists (No in S230), the window function W to be applied to the matrix Xn is set to the window function Ws for non-interference (S240).

Note that the window function W is expressed by a matrix of N rows and 1 column. In this way, when the processing in S240 is completed, the signal processing unit 34 proceeds to S270.
On the other hand, if it is determined in S230 that an interference wave component is present (Yes in S230), the mixing position t = k0 of the interference wave component in the beat signal is detected, and this detection position t = k0 is set to the variable k (S250). . Specifically, when there are a plurality of elements of the matrix Xn indicating an absolute value equal to or greater than the threshold Th0, the row number of the element having the maximum value can be set as the detection position k0. In addition, an intermediate point between the minimum row number ka of the element indicating the absolute value equal to or greater than the threshold Th0 and the maximum row number kb of the element indicating the absolute value equal to or greater than the threshold Th0 may be set as the detection position k0.

  When the processing in S250 is completed, the signal processing unit 34 proceeds to S260, and sets the window function W to be applied to the matrix Xn to the window function Wc for interference.

  Note that the setting value in S250 is set to the variable k in equation (9). In this way, when the process in S260 is completed, the signal processing unit 34 proceeds to S270, multiplies the matrix Xn by the window function W, and updates the matrix Xn.

  When the window function W is applied to the matrix Xn representing the beat signal according to the equation (10), the interference wave component is removed from the matrix Xn after the action. FIG. 6 is a conceptual diagram of each signal of the beat signal in which no interference wave component exists (the upper stage in FIG. 6) and the beat signal in which the interference wave component exists (the middle stage and the lower stage in FIG. 6). It is explanatory drawing which showed the window function W which acts on each signal.

  When the beat signal in the upper part of FIG. 6 is a processing target in the reading process, since no interference wave component exists in the beat signal, the window function Ws shown in the equation (7) acts on the beat signal as the window function W. (See the upper part of FIG. 7). As a result, in this embodiment, the occurrence of ripples in the frequency spectrum due to the presence of discontinuities at both ends of the sampling data is suppressed.

  On the other hand, for the beat signal in the middle stage of FIG. 6, since an interference wave component exists in the signal component of t = k2, the window function Wc with k = k2 acts on the beat signal (see the middle stage of FIG. 7). Since the window function Wc (t) set to k = k2 takes a zero value at t = k2 (Wc (k2) = 0), when this window function Wc acts on the beat signal in the middle stage of FIG. , T = k2 around the interference wave component is attenuated.

  In addition, since there is an interference wave component in the signal component at t = k3 for the beat signal in the lower part of FIG. 6, the window function Wc with k = k3 acts on the beat signal (see the lower part of FIG. 7). When this window function Wc acts on the lower beat signal of FIG. 6, the interference wave component existing around t = k3 is attenuated.

In this manner, when the interference wave component is removed from the matrix Xn representing the beat signal in S170, the signal processing unit 34 ends the reading process.
Next, the first and second conversion processes shown in FIG. 5 will be described. In the first and second conversion processes shown in FIG. 5, the frequency analysis is basically performed by the same method. Here, in order to clarify the data handled in each conversion process, it is divided into two flowcharts. To do.

  First, the first conversion process executed in S120 will be described with reference to FIG. In the first conversion process, frequency analysis is performed based on the sampling data of the beat signal at the time of uplink modulation acquired in S110.

  When the first conversion process is executed, the signal processing unit 34 calculates a correlation matrix Ru for the sampled beat signal based on the matrix Xn set in the immediately preceding reading process (S110) according to the equation (11). This is stored in the RAM (S310). However, the superscript H means complex conjugate transpose, and the superscript * means complex conjugate. In this embodiment, each element of the matrix Xn is a real number.

  When the processing in S310 is completed, the signal processing unit 34 calculates the correlation matrix Ru calculated in S310 of this time, the correlation matrix Ru1 calculated in the previous S310 and stored in the RAM, and calculated in S310 the previous time. The correlation matrix Ru2 stored in the above is integrated according to the equation (12) to calculate the matrix Ra (S320).

  In S320 after executing S310 three times or more in the past, since the correlation matrices Ru1 and Ru2 are stored in the RAM, the matrix Ra may be calculated according to Equation (12). If it is less than three times, the matrix Ra is obtained according to the equation (12) using the correlation matrix Ru calculated this time instead of the insufficient correlation matrices Ru1 and Ru2.

In addition, when the processing in S320 is completed in this way, the signal processing unit 34 performs DFT processing on the matrix Ra according to the following equation with R = Ra (S330). In addition, i shown in Formula (15) means an imaginary number (i ² = −1). The matrix A is a matrix in which s rows and t columns are expressed by the equation (14) using z in the equation (15) (provided that s = 0, 1,..., N−1, t = 0, 1,..., N−1).

  When the DFT processing in S330 is completed, the signal processing unit 34 extracts a diagonal component for the calculation result G, obtains a frequency spectrum Y as shown in Expression (16), and obtains this as an upstream modulation. The current frequency spectrum Y1 is written in the RAM (S340). Thereafter, the first conversion process is terminated.

  Next, the second conversion process executed in S140 will be described with reference to FIG. In this second conversion process, frequency analysis is performed based on the sampling data of the beat signal at the time of downlink modulation acquired in S130.

  When the second conversion process is executed, the signal processing unit 34 calculates a correlation matrix Rd for the sampled beat signal based on the matrix Xn set in the immediately preceding reading process (S130), and stores this in the RAM. (S410).

  When the processing in S410 is completed, the signal processing unit 34 calculates the correlation matrix Rd calculated in S410 of this time, the correlation matrix Rd1 calculated in the previous S410 and stored in the RAM, and calculated in S410 the previous time. The correlation matrix Rd2 stored in (2) is integrated according to the equation (18) to calculate the matrix Rb (S420).

  In S420 after executing S410 three times or more in the past, since the correlation matrices Rd1 and Rd2 are stored in the RAM, the matrix Rb may be calculated according to Equation (18). If the number is less than 3, the matrix Rb is obtained according to the equation (18) using the correlation matrix Rd calculated this time instead of the insufficient correlation matrices Rd1 and Rd2.

  When the processing in S420 is completed in this way, the signal processing unit 34 performs DFT processing on the matrix Rb according to Expression (13), with R = Rb (S430). Then, when the DFT processing in S430 is completed, a diagonal component for the calculation result G is extracted, and a frequency spectrum Y is obtained as shown in Expression (16), and this is used as a frequency spectrum Y2 at the time of downlink modulation. The data is written into the RAM (S440). Thereafter, the second conversion process is terminated.

  Further, when the second conversion process is completed in this way, the signal processing unit 34 proceeds to S150, and in the readout process in S110 or S130, the interference wave component is added to the beat signal at the time of uplink modulation or downlink modulation. It is determined whether or not the presence of the interference wave component has been confirmed. If the presence of the interference wave component has not been confirmed (No in S150), a threshold Thp for detecting peaks corresponding to the beat frequencies fb1 and fb2 is determined in advance. The obtained normal value Th1 (Thp = Th1) is set (S160). Thereafter, the process proceeds to S165.

  When the process proceeds to S165, the signal processing unit 34 performs a peak search process for searching for a peak equal to or higher than the threshold Thp in the frequency spectrum Y1 obtained in S120 and the frequency spectrum Y2 obtained in S140, and performs a pair match process, A pair of peaks corresponding to the beat frequencies fb1 and fb2 are identified from the peaks detected by the peak search process, and the beat frequencies fb1 and fb2 are derived.

  In addition, in FIG. 8, the conceptual diagram about the synthetic | combination spectrum of the frequency spectrum Y1 and the frequency spectrum Y2 is shown. In this embodiment, since the DFT process is performed using the rotor A of N rows and N columns, in the frequency spectrum Y [s], the relationship between the variable s and the actual frequency f is f = (fx / N) · s. However, in the peak search process, when the variable is in the range of 0 ≦ s ≦ (N / 2), that is, the frequency is in the range of 0 ≦ f ≦ fx / 2, the peak more than the threshold Thp is obtained from the frequency spectra Y1 and Y2. Search for.

  In the pair match processing, a most appropriate peak pair is specified by a well-known algorithm, taking into account the capabilities of the radar device 2 (range of normal measurement and range of relative speed), and the beat frequency fb1, Derives fb2.

  In the pair match processing, when no peak that is a candidate for the beat frequencies fb1 and fb2 is detected in the peak search processing, or within the capability range of the radar device 2 (range of normal measurement and range of relative speed) If an appropriate peak pair does not exist, an error code is output instead of the beat frequencies fb1 and fb2.

  In addition, when no peaks greater than or equal to the threshold value Thp are found in the frequency spectrums Y1 and Y2, an error code “No both peaks” is output, and there are peaks in the frequency spectra Y1 and Y2 that exceed the threshold value Thp. If there is no paired peak, an error code “Detect only one peak” is output.

When the process in S165 is completed in this way, the signal processing unit 34 proceeds to S170, and executes a normal-time interpolation process (described later in detail) shown in FIG. Thereafter, the analysis process ends.
On the other hand, if it is determined in S150 that the presence of the interference wave component has been confirmed (Yes in S150), the signal processing unit 34 determines a threshold Thp for detecting peaks corresponding to the beat frequencies fb1 and fb2. The value Th2 at the time of interference (Thp = Th2) is set (S180). However, the relationship Th1 <Th2 is established between the normal value Th1 and the interference value Th2. That is, the value Th2 is set in advance to a value larger than the normal value Th1.

  When the processing in S180 is completed, the signal processing unit 34 proceeds to S185, and executes peak search processing for searching for a peak equal to or higher than the threshold Thp in the frequency spectrum Y1 obtained in S120 and the frequency spectrum Y2 obtained in S140. At the same time, a pair match process is performed to identify a pair of peaks corresponding to the beat frequencies fb1 and fb2 from the peaks detected by the peak search process, and the beat frequencies fb1 and fb2 are derived. Specifically, in S185, the same processing as S165 is performed to the extent that the value of the threshold Thp is different.

When the process in S185 is completed, the signal processing unit 34 proceeds to S190, and executes an interpolating process (described later in detail) shown in FIG. Thereafter, the analysis process ends.
Next, the normal interpolation process will be described. FIG. 9 is a flowchart showing normal time interpolation processing.

  When the normal time interpolation process is executed, the signal processing unit 34 determines whether or not the pair match is successful based on the result of the previous pair match process (S165) (S510). Specifically, if the beat frequencies fb1 and fb2 are derived in the pair match process, it is determined that the pair match has succeeded (Yes in S510), and if the error code is output in the pair match process, the pair match has failed. Judgment is made (No in S510).

  If it is determined that the pair match is successful (Yes in S510), the number of interpolations E is reset to zero (E = 0) in S523, and then, based on the beat frequencies fb1 and fb2 derived in the pair match process, The measurement distance D and the measurement relative velocity V are obtained according to the equations (1) to (4) (S525). When the process in S525 is completed, the process proceeds to S527, and the distance Ds output to the external apparatus as the detection result of the radar apparatus 2 is calculated according to the equation (19).

  The constant α is a constant that satisfies 0 <α <1. The predicted distance Dnext used when calculating the distance Ds is the predicted distance Dnext held in the RAM in S535 and 575 of the normal time interpolation process or the interpolated process of interference described later. Therefore, in the initial stage, the predicted distance Dnext has never been calculated and the predicted distance Dnext may not be stored in the RAM. However, if the predicted distance Dnext has never been calculated, an exception is made. Then, the predicted distance Dnext is set as the measured distance D obtained this time (Dnext = D), and the distance Ds is obtained.

  When the processing in S527 is completed, the signal processing unit 34 proceeds to S533, and calculates the relative speed Vs output to the external device as the detection result of the radar device 2 according to the equation (20). The calculated relative speed Vs is held in the RAM until the next calculation.

  The predicted distance Dnext is the same value as that used in S527. In addition, since the relative speed Vs calculated in the previous S533 or S633 is used when calculating the relative speed Vs, there may be no previous calculated value in the initial stage. The speed Vs is set to the measurement relative speed V (Vs = V). Note that β is a constant, and the constant T0 is the measurement period of the distance D (the execution period of the pair match process).

  When the processing in S533 is finished, the signal processing unit 34 proceeds to S535 and predicts the next measurement distance. Specifically, the predicted distance Dnext is obtained according to the equation (21). The calculated predicted distance Dnext is held in the RAM until the next predicted distance Dnext is calculated.

  When the predicted distance Dnext is calculated in this way, the signal processing unit 34 proceeds to S537, and outputs the distance Ds calculated in S527 and the relative speed Vs calculated in S533 to the external device. Thereafter, the normal interpolation process is terminated.

  On the other hand, if it is determined in S510 that the pair match has failed (No in S510), the signal processing unit 34 proceeds to S540 and determines whether or not the status value for controlling the number of interpolations E is “normal”. to decide. It is assumed that the status value is set to “normal” when the radar apparatus 2 is turned on.

  If it is determined that the status value is “normal” (Yes in S540), the correction count E is incremented by 1 (S553), and then the process proceeds to S560. On the other hand, if it is determined that the status value is not “normal”, it indicates that the interpolating process at the time of interference (first interpolation process or second interpolation process to be described later) was performed last time, so the status value is set to “normal”. In addition to setting (S555), the number of interpolations E is set to E = 1 (S557). Thereafter, the process proceeds to S560.

  In S560, it is determined whether the correction count E exceeds a predetermined upper limit value Emax0 of normal interpolation count. If it is determined that the correction number E does not exceed the upper limit value Emax0 (No in S560), the process proceeds to S573, and the value of the predicted distance Dnext currently stored in the RAM is used as the distance Ds output to the external device. Set (Ds ← Dnext).

  When the process in S573 is completed in this way, the signal processing unit 34 proceeds to S575 and predicts the next measurement distance. Specifically, the predicted distance Dnext is obtained according to the equation (21). Thereafter, the signal processing unit 34 proceeds to S577, outputs the distance Ds set in S573 and the current relative speed Vs held in the RAM to the external device, and ends the normal-time interpolation processing.

  In addition, if it is determined in S560 that the number of corrections E has exceeded the upper limit Emax0 (Yes in S560), the signal processing unit 34 proceeds to S580 and outputs a diag code indicating the disappearance of the target to the external device. . Thereafter, the normal interpolation process is terminated.

Next, the inter-interference interpolation process executed in S190 will be described. FIG. 10 is a flowchart showing interpolation processing at the time of interference.
When the inter-interference interpolation process is executed, the signal processing unit 34 first determines whether or not the pair match has succeeded by the same method as S510 based on the processing result of the previous pair match process (S185) (S610).

  If it is determined that the pair match has succeeded (Yes in S610), the number of interpolations E is reset to zero (E = 0) in S623, and based on the beat frequencies fb1 and fb2 derived in the pair match process, The measurement distance D and the measurement relative velocity V are obtained according to 1) to Equation (4) (S625). When the process in S625 is completed, the process proceeds to S627, and the distance Ds output to the external apparatus as the detection result of the radar apparatus 2 is calculated according to the equation (19). The process when the predicted distance Dnext has never been calculated is the same as S527.

  When the processing in S627 is completed in this way, the signal processing unit 34 proceeds to S633, and calculates the relative speed Vs output to the external device as the detection result of the radar device 2 according to the equation (20). . The calculated relative speed Vs is held in the RAM until the next calculation. If the previous calculated value does not exist, the measured relative speed V is set as the relative speed Vs (Vs = V) as in S533.

  When the process in S633 is completed, the process proceeds to S635, and the next measurement distance is predicted. Specifically, the predicted distance Dnext is obtained according to the equation (21). The calculated predicted distance Dnext is held in the RAM until the next predicted distance Dnext is calculated.

  When the predicted distance Dnext is calculated in this way, the signal processing unit 34 proceeds to S637, and outputs the distance Ds calculated in S627 and the relative speed Vs calculated in S633 to the external device. Thereafter, the interference interpolation process is terminated.

  On the other hand, if it is determined in S610 that the pair match has failed (No in S610), the signal processing unit 34 proceeds to S640, and the error code output in the immediately previous pair match process (S185) is “no both peaks”. It is determined whether or not it is an error code.

  If it is determined that the error code is not an error code indicating “no both peaks” (that is, an error code indicating “only one peak detected”) (No in S640), in S650, FIG. When the error code is determined to be an error code indicating “no both peaks” (Yes in S640), the second interpolation process shown in FIG. 11B is executed in S660. To do. Then, when the processing of S650 or S660 is finished, the interpolating interpolation processing is finished.

  FIG. 11A is a flowchart showing the first interpolation process executed in S650. When the first interpolation process is executed, the signal processing unit 34 first determines in S710 whether or not the status value is “interference 1” indicating that the previous first interpolation process was performed.

  If it is determined that the status value is not “interference 1” because the status value is “normal” (No in S710), the status value is set to “interference 1” (S723), and the interpolation count E is set. , E = 1 is set (S725). Thereafter, the process proceeds to S730.

On the other hand, if it is determined that the status value is “interference 1”, the interpolation count E is incremented by 1 (S727), and then the process proceeds to S730.
After shifting to S730, the signal processing unit 34 determines whether or not the correction number E exceeds the upper limit value Emax1 of the number of interpolations at the time of predetermined interference (specifically, when only “one peak is detected”). To do. However, the upper limit value Emax1 is set to be larger than the normal upper limit value Emax0 (Emax1> Emax0).

  If it is determined that the correction count E does not exceed the upper limit value Emax1 (No in S730), the signal processing unit 34 proceeds to S743, and the predicted distance currently held in the RAM as the distance Ds output to the external device The value of Dnext is set (Ds ← Dnext).

  When the process in S743 is completed, the next measurement distance is predicted (S745). Specifically, the predicted distance Dnext is obtained according to the equation (21) using the current relative speed Vs held in the RAM and the distance Ds set in S743. Thereafter, the signal processing unit 34 proceeds to S747, outputs the distance Ds set in S743 and the current relative speed Vs held in the RAM to the external device, and ends the first interpolation process.

  In addition, if it is determined in S730 that the number of corrections E has exceeded the upper limit value Emax1 (Yes in S730), the signal processing unit 34 proceeds to S750, and displays a diagnosis code indicating that the target has been lost due to interference as an external device. Output to. Thereafter, the first interpolation process is terminated.

  FIG. 11B is a flowchart showing the second interpolation process executed in S660. When the second interpolation process is executed, the signal processing unit 34 first determines in S810 whether or not the status value is “interference 2” indicating that the second interpolation process was performed last time.

  If it is determined that the status value is not “interference 2” because the status value is “normal” or “interference 1” (No in S810), the status value is set to “interference 2” (S823). The number of interpolations E is set to E = 1 (S825). Thereafter, the process proceeds to S830. On the other hand, if it is determined that the status value is “interference 2”, the interpolation count E is incremented by 1 (S827), and then the process proceeds to S830.

  In S830, the signal processing unit 34 determines whether or not the correction count E exceeds a predetermined upper limit value Emax2 of the interpolation count at the time of interference (specifically, when “both peaks are absent”). . However, it is assumed that the upper limit value Emax2 is set to be larger than the upper limit value Emax0 at the normal time (Emax2> Emax0).

  If it is determined that the correction number E does not exceed the upper limit value Emax2 (No in S830), the process proceeds to S843, and the value of the predicted distance Dnext currently held in the RAM is used as the distance Ds output to the external device. Set (Ds ← Dnext).

  When the process in S843 is completed, the signal processing unit 34 predicts the next measurement distance (S845). Specifically, the predicted distance Dnext is obtained according to the equation (21) using the current relative speed Vs held in the RAM and the distance Ds set in S843. Thereafter, the signal processing unit 34 outputs the distance Ds set in S843 and the current relative speed Vs held in the RAM to the external device (S847), and ends the second interpolation process.

  In addition, if it is determined in S830 that the number of corrections E has exceeded the upper limit Emax2 (Yes in S830), the process proceeds to S850, and a diagnosis code indicating target disappearance is output to the external device due to interference. Thereafter, the second interpolation process is terminated.

  The radar apparatus 2 of the present embodiment has been described above. In the radar apparatus 2 of the present embodiment, the VCO 14 repeatedly generates a high-frequency signal that becomes the frequency-modulated radar wave transmission signal Ss, and the mixer 24 The beat signal B is generated by mixing the high-frequency signal (local signal L) and the reception signal Sr of the reflected wave from the target reflecting the radar wave.

  Further, the signal processing unit 34 acquires sampling data of the beat signal generated by the A / D converter 28 from the A / D converter 28 for each cycle in accordance with the generation cycle of the transmission signal Ss. (S110, S130). Further, by adding the correlation matrices Ru, Ru1, Ru2 and the correlation matrices Rd, Rd1, Rd2 of the beat signal B, the beat signals for a plurality of cycles are integrated (S320, S420).

  Then, matrices Ra and Rb equivalent to signals obtained by integrating beat signals for a plurality of cycles are respectively subjected to DFT processing to obtain frequency spectra Y1 and Y2, and beat frequencies fb1, A peak corresponding to fb2 is detected, and a distance Ds to the target is obtained based on the beat frequencies fb1 and fb2 (S527, S627).

  In the radar apparatus 2 of the present embodiment, the signal components corresponding to the beat frequencies fb1 and fb2 are selectively emphasized by the method described above to derive the frequency spectra Y1 and Y2, and based on this, the beat frequencies fb1 and fb1 are derived. Since fb2 is specified and the distance Ds to the target is obtained, even if an interference wave component occurs in the beat signal of a specific cycle, it is possible to suppress the beat frequency from becoming undetectable due to the interference wave component, Conventionally, the distance Ds to the target can be obtained stably without being affected by interference.

  Particularly, in the radar apparatus 2 of the present embodiment, the interference wave component included in the beat signal B is detected together with the position t = k0 of the interference wave component (S230, S250), and the interference wave component does not exist in the beat signal. In this case, the window function Ws is determined as a window function that acts on the sampling data Xn of the beat signal (S240). When the interference wave component exists in the beat signal, the interference wave component can be selectively attenuated. The window function Wc of k = k0 is determined as a window function that acts on the sampling data Xn of the beat signal (S260). Then, the determined window function W is applied to the sampling data Xn (S270).

  Therefore, in the radar apparatus 2 of the present embodiment, the influence of the interference wave component can be suppressed as compared with the case where the correlation matrix representing the beat signal is simply integrated and the peaks of the beat frequencies fb1 and fb2 are emphasized. The distance to the target can be obtained stably.

  In addition, in the present embodiment, a peak equal to or higher than the threshold Thp in the frequency spectrum Y1, Y2 is detected and the frequency corresponding to this peak is specified as the beat frequency fb1, fb2 (S165, S185), but the interference wave component is detected. If so (Yes in S150), the threshold Thp is set higher than when no interference wave component is detected (S180). Therefore, the radar apparatus 2 can prevent the peak corresponding to the interference wave component from being erroneously specified as the beat frequencies fb1 and fb2.

  Further, in the present embodiment, the beat frequencies fb1 and fb2 cannot be specified, and the distance D cannot be calculated (the period determined as No in S510 or S610), based on the distance D obtained in the past. The calculated predicted distance Dnext is predicted to be the distance Ds to the current target (S573, S743, S843), and if the number of predictions (interpolation) exceeds the upper limit value, the interpolation processing is executed more than the allowable number of times. A diagnosis code indicating the disappearance of the target is output (S580, S750, S850).

  In this case, if the interference wave component is not confirmed in the beat signal ("normal"), if the interference wave component is confirmed in the beat signal ("only one peak detected", "no both peaks" )), Different upper limit values Emax0, Emax1, and Emax2 are set.

  Therefore, according to the radar apparatus 2 of the present embodiment, the interpolation process can be performed for an appropriate period when the interference occurs and when the interference does not occur, and the influence of the interference does not affect the performance so much. Can be operated.

  In this embodiment, the transmission signal generating means of the present invention is realized by the VCO 14 and the beat signal generating means is realized by the mixer 24. The acquisition unit is realized by the A / D converter 28 and an analysis process (reading process) executed by the signal processing unit 34. In addition, the integrating means (claims 1 to 3 and claims 7 to 10) is realized by the processing of S320 and S420, and the analyzing means (claims 1 to 3, claims 7 to 10). 10) is realized in S330 to S340 of the first conversion process and S430 to S440 of the second conversion process shown in FIG. The distance calculation means is realized by S165, S510 to S537, S185, S610 to S637.

  The detection means is realized in S230 and S250, the determination means is realized in S240 and S260, and the window function processing means is realized in S270. In addition, the threshold setting means is realized in S160 and S180. Further, the interpolation processing means is realized in S535, S573, S635, S743, and S843, the diagnosis output means is realized in S580, S750, and S850, and the allowable period setting means depends on whether or not the interference wave component is detected. Thus, it is realized by an operation of switching and setting the upper limit values Emax0, Emax1, Emax2.

(Modification)
By the way, in the above embodiment, the matrix Xn representing the beat signal is integrated for a plurality of cycles, and this is subjected to DFT processing to emphasize the peak of the signal component corresponding to the beat frequencies fb1 and fb2, thereby Although the influence is suppressed, the present invention is not limited to this method, and the same effect can be obtained by performing DFT processing on the beat signal for each cycle and integrating the frequency spectrum obtained thereby for a plurality of cycles. be able to.

  Accordingly, hereinafter, a modified example in which a method of integrating frequency spectra is employed will be described. FIG. 12 is a flowchart (a) representing the first conversion process and a flowchart (b) representing the second conversion process of the modification.

  The radar apparatus according to the modified example executes the first conversion process shown in FIG. 12A at S120 and the second conversion process shown in FIG. 12B at S140. Although it is different from the example, the other points are basically the same as the above embodiment, and therefore the first conversion process of the modification executed in S120 and the modification executed in S140 will be described below. Only the second conversion process will be described with reference to FIG.

  When the first conversion process shown in FIG. 12A is executed in S120, the signal processing unit 34 correlates the sampled beat signal based on the matrix Xn set in the immediately preceding reading process (S110). The matrix Ru is calculated according to the equation (11) (S910).

  When the processing in S910 is completed, the signal processing unit 34 performs DFT processing on the matrix Ru according to Expression (13) with R = Ru (S920). When this DFT processing is completed, the signal processing unit 34 extracts the diagonal component for the calculation result G, obtains the frequency spectrum Y according to the equation (16), and uses this as the frequency spectrum Yu at the time of upstream modulation. Write to the RAM (S930).

  When the processing in S930 is completed, the signal processing unit 34 calculates the frequency spectrum Yu obtained in S930 of this time, the frequency spectrum Yu1 calculated in the previous S930 and stored in the RAM, and calculates in the previous S930 and stores it in the RAM. The accumulated frequency spectrum Ya is calculated using the stored frequency spectrum Yu2 (S940).

  In S940 after the process of S930 has been executed three or more times in the past, the frequency spectrums Yu1 and Yu2 are stored in the RAM. Therefore, the integrated frequency spectrum Ya may be calculated according to Equation (22). When the number of executions is less than 3, the integrated frequency spectrum Ya is obtained according to the equation (22) using the frequency spectrum Yu calculated this time instead of the insufficient frequency spectra Yu1 and Yu2.

  Then, this is written in the RAM as the frequency spectrum Y1 during upstream modulation used in the peak search process and the pair match process (Y1 = Ya) (S940). Thereafter, the first conversion process ends.

  Next, the modified second conversion process executed in S140 will be described with reference to FIG. When the second conversion process is executed, the signal processing unit 34 calculates a correlation matrix Rd for the sampled beat signal based on the matrix Xn set in the immediately preceding reading process (S130) according to Expression (17). (S1010).

  When the processing in S1010 is completed, the signal processing unit 34 performs DFT processing on the matrix Rd using Equation (13), with R = Rd (S1020). When this DFT processing is completed, the signal processing unit 34 extracts the diagonal component for the calculation result G, obtains the frequency spectrum Y according to the equation (16), and uses this as the frequency spectrum Yd at the time of downlink modulation. Write to the RAM (S1030).

  When the processing in S1030 is completed, the signal processing unit 34 calculates the frequency spectrum Yd obtained in S1030 this time, the frequency spectrum Yd1 calculated in the previous S1030 and stored in the RAM, and calculated in the previous S1030 and stored in the RAM. The accumulated frequency spectrum Yb is calculated using the stored frequency spectrum Yd2 (S1040).

  In S1040 after the processing of S1030 has been executed three times or more in the past, the frequency spectrum Yd1 and Yd2 are stored in the RAM, so the integrated frequency spectrum Yb may be calculated according to the equation (23). When the number of executions is less than 3, the integrated frequency spectrum Yb is obtained according to the equation (23) using the frequency spectrum Yd calculated this time instead of the insufficient frequency spectra Yd1 and Yd2. Then, this is written in the RAM as the frequency spectrum Y2 during downlink modulation used in the peak search process and the pair match process (Y2 = Yb) (S1040). Thereafter, the second conversion process ends.

  In this way, in the radar apparatus of the modified example that performs the first and second conversion processes, the combined spectrum of the frequency spectra Y1 and Y2 used in the peak search process is as shown in FIG. The composite spectrum of Yd, the previous composite spectrum of frequency spectra Yu1, Yd1, and the previous composite spectrum of frequency spectra Yu2, Yd2 are integrated.

  Therefore, in the frequency spectrums Y1 and Y2, the peaks corresponding to the beat frequencies fb1 and fb2 are emphasized, and the influence of the interference wave component is less likely to occur during the peak search process and the pair match process. Therefore, according to this modification, it is possible to stably detect (measure) the distance D to the target and the relative speed V while suppressing the influence of interference.

  In the present embodiment, the analyzing means (claims 4 to 10) of the present invention is realized in S920 to S930 of the first conversion process and S1020 to S1030 of the second conversion process shown in FIG. Means (claims 4 to 10) are realized by the processing of S940 and S1040.

  In the modification, the integrated frequency spectrum Ya is obtained according to the equation (22), and the accumulated frequency spectrum Yb is obtained according to the equation (23). However, according to the equation (24) shown below, the frequency spectrum is obtained. Yu, Yu1, Yu2 may be integrated to determine the integrated frequency spectrum Ya, and the frequency spectrums Yd, Yd1, Yd2 may be integrated according to Equation (25) to determine the integrated frequency spectrum Yb.

In addition, the radar apparatus of the present invention is not limited to the above-described embodiments, and can take various forms.
For example, in the radar apparatus 2 of the above-described embodiment including the modification, the window function Wc represented by the equation (9) is used as the window function W when detecting the interference wave component. In addition to the window function Wc represented by the equation (9) with the correction term obtained by modifying the window, the window function Wc represented by the equation (26) obtained by adding the correction term obtained by modifying the Hamming window, and the Blackman window A window function Wc represented by Expression (27) to which a modified correction term is added, a window function Wc represented by Expression (28), and the like can be used.

  In addition, in the radar apparatus 2 of the above embodiment including the modification, the window function W is applied to the beat signal Xn as described above, and then the DFT processing is performed. However, the window function Wc is applied to the beat signal Xn. Even if the DFT process is performed without acting, the effect of the integration described above is exhibited, so that the influence of interference can be suppressed. Specifically, as an example in which the window function Wc is not used, a configuration in which the window function W = Ws is set in S260, or a configuration in which the processing from S230 to S270 is not performed in the reading process is given to the radar device 2. An applied example can be considered.

It is a block diagram showing the structure of the vehicle-mounted radar apparatus 2 to which this invention was applied. It is explanatory drawing which shows the aspect of the transmission signal Ss produced | generated repeatedly. It is a flowchart showing the analysis process which the signal processing part 34 performs repeatedly. 4 is a flowchart showing a reading process executed by a signal processing unit 34. It is the flowchart (a) showing the 1st conversion process which the signal processing part 34 performs, and the flowchart (b) showing the 2nd conversion process. It is a conceptual diagram of the beat signal containing an interference wave component. It is explanatory drawing which showed the window function W made to act on each beat signal. It is a conceptual diagram about the synthetic | combination spectrum of frequency spectrum Y1, Y2. It is a flowchart showing the normal time interpolation process which the signal processing part 34 performs. It is a flowchart showing the interpolation process at the time of the interference which the signal processing part 34 performs. It is the flowchart (a) showing the 1st interpolation process which the signal processing part 34 performs, and the flowchart (b) showing the 2nd interpolation process. It is the flowchart (a) showing the 1st conversion process of a modification, and the flowchart (b) showing the 2nd conversion process. It is explanatory drawing regarding the integrating | accumulating method of the spectrum in a modification. It is explanatory drawing showing the basic principle of a FMCW radar apparatus. It is explanatory drawing regarding generation | occurrence | production of interference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Radar apparatus, 10 ... D / A converter, 12 ... Buffer, 14 ... Voltage controlled oscillator (VCO), 16 ... Distributor, 18 ... Transmission side antenna part, 20 ... Reception side antenna part, 24 ... Mixer, 26 ... Amplifier, 28 ... A / D converter, 30 ... Timing controller, 34 ... Signal processor

Claims (11)

Transmission signal generation means for repeatedly generating a frequency-modulated radar wave transmission signal;
Beat signal generating means for generating a beat signal by mixing a transmission signal generated by the transmission signal generating means and a reception signal of a reflected wave from a target that reflects the radar wave;
An acquisition means for acquiring the beat signal generated by the beat signal generation means from the beat signal generation means in accordance with a transmission signal generation cycle by the transmission signal generation means;
Integration means for integrating the beat signal acquired by the acquisition means for a plurality of predetermined cycles;
Analyzing means for frequency analysis of an integrated beat signal obtained by integrating beat signals for a plurality of cycles by the integrating means,
A distance calculating means for obtaining a distance to the target based on the analysis result of the analyzing means;
A radar apparatus comprising: Detecting means for detecting the interference wave component included in the beat signal generated by the beat signal generating means together with the position of the interference wave component;
Determining means for determining a window function to be applied to the beat signal acquired by the acquiring means based on the detection result of the detecting means;
Window function processing means for causing the window function determined by the determining means to act on the beat signal for each cycle acquired by the acquiring means;
With
In the case where an interference wave component is detected by the detection means, the determination means is a beat signal that the acquisition means acquires a window function that can selectively attenuate the interference wave component according to the detection position of the interference wave component. And determining a window function to act on the beat signal including the interference wave component,
The integration means is configured to integrate beat signals acquired by the acquisition means and processed by the window function processing means for a plurality of predetermined cycles. The radar apparatus according to claim 1. The analyzing means is configured to analyze the frequency of the integrated beat signal and generate a frequency spectrum corresponding to the integrated beat signal.
The distance calculation means is configured to detect a peak that is equal to or greater than a predetermined threshold in the frequency spectrum generated by the analysis means, and obtain a distance to the target based on a frequency corresponding to the detected peak. And
The radar device further includes
Detecting means for detecting an interference wave component included in the beat signal generated by the beat signal generating means;
Threshold setting means for setting the threshold used at the time of peak detection based on the detection result of the detection means;
With
The said threshold value setting means is comprised so that the said threshold value may be set higher than the time of non-detection of an interference wave component, when an interference wave component is detected by the said detection means. Radar device. Transmission signal generation means for repeatedly generating a frequency-modulated radar wave transmission signal;
Beat signal generating means for generating a beat signal by mixing a transmission signal generated by the transmission signal generating means and a reception signal of a reflected wave from a target that reflects the radar wave;
An acquisition means for acquiring the beat signal generated by the beat signal generation means from the beat signal generation means in accordance with a transmission signal generation cycle by the transmission signal generation means;
Analyzing means for analyzing the frequency of the beat signal acquired by the acquiring means for each cycle and generating a frequency spectrum corresponding to the beat signal;
Accumulating means for integrating the frequency spectrum generated by the analyzing means for a plurality of cycles;
Based on an integrated spectrum obtained by integrating frequency spectra for a plurality of cycles by the integrating means, distance calculating means for obtaining a distance to the target;
A radar apparatus comprising: Detecting means for detecting the interference wave component included in the beat signal generated by the beat signal generating means together with the position of the interference wave component;
Determining means for determining a window function to be applied to the beat signal acquired by the acquiring means based on the detection result of the detecting means;
Window function processing means for causing the window function determined by the determining means to act on the beat signal for each cycle acquired by the acquiring means;
With
In the case where an interference wave component is detected by the detection means, the determination means is a beat signal that the acquisition means acquires a window function that can selectively attenuate the interference wave component according to the detection position of the interference wave component. And determining a window function to act on the beat signal including the interference wave component,
The analysis unit generates a frequency spectrum corresponding to the beat signal by analyzing the frequency of the beat signal acquired by the acquisition unit and processed by the window function processing unit for each cycle. The radar apparatus according to claim 4, wherein the radar apparatus is configured as described above. The distance calculation means is configured to detect a peak that is equal to or greater than a predetermined threshold in the integrated spectrum, and obtain a distance to the target based on a frequency corresponding to the detected peak.
The radar device further includes
Detecting means for detecting an interference wave component included in the beat signal generated by the beat signal generating means;
Threshold setting means for setting the threshold used at the time of peak detection based on the detection result of the detection means;
With
5. The threshold value setting unit is configured to set the threshold value higher than when no interference wave component is detected when an interference wave component is detected by the detection unit. Radar device. Transmission signal generation means for repeatedly generating a frequency-modulated radar wave transmission signal;
Beat signal generating means for generating a beat signal by mixing a transmission signal generated by the transmission signal generating means and a reception signal of a reflected wave from a target that reflects the radar wave;
An acquisition means for acquiring the beat signal generated by the beat signal generation means from the beat signal generation means in accordance with a transmission signal generation cycle by the transmission signal generation means;
Detecting means for detecting the interference wave component included in the beat signal generated by the beat signal generating means together with the position of the interference wave component;
Determining means for determining a window function to be applied to the beat signal acquired by the acquiring means based on the detection result of the detecting means;
Window function processing means for causing the window function determined by the determining means to act on the beat signal for each cycle acquired by the acquiring means;
The beat signal acquired by the acquisition means, the beat signal after processing by the window function processing means, analysis means for frequency analysis,
A distance calculating means for obtaining a distance to the target based on the analysis result of the analyzing means;
With
In the case where an interference wave component is detected by the detection means, the determination means is a beat signal that the acquisition means acquires a window function that can selectively attenuate the interference wave component according to the detection position of the interference wave component. A radar apparatus comprising: a window function to be applied to a beat signal including the interference wave component. The analysis means is configured to frequency-analyze the beat signal processed by the window function processing means and generate a frequency spectrum corresponding to the beat signal,
The distance calculation means is configured to detect a peak that is equal to or greater than a predetermined threshold in the frequency spectrum generated by the analysis means, and obtain a distance to the target based on a frequency corresponding to the detected peak. And
The radar device further includes
Threshold setting means for setting the threshold used at the time of peak detection based on the detection result of the detection means,
With
The said threshold value setting means is comprised so that the said threshold value may be set higher than the time of non-detection of an interference wave component, when an interference wave component is detected by the said detection means. Radar device. Interpolation processing means for predicting the current distance to the target based on at least the distance obtained in the past by the distance calculation means during a period in which the distance calculation means cannot be calculated;
When the interpolation processing means operates for a predetermined allowable period or longer, a diagnosis output means for outputting diagnosis information;
Detecting means for detecting an interference wave component included in the beat signal generated by the beat signal generating means;
An allowable period setting means for setting the allowable period based on a detection result of the detection means;
The radar apparatus according to claim 1, further comprising: Interpolation processing means for predicting the current distance to the target based on at least the distance obtained in the past by the distance calculation means during a period in which the distance calculation means cannot be calculated;
When the interpolation processing means operates for a predetermined allowable period or longer, a diagnosis output means for outputting diagnosis information;
An allowable period setting means for setting the allowable period based on a detection result of the detection means;
The radar device according to claim 2, wherein the radar device is one of claim 5 and claim 5. Transmission signal generation means for repeatedly generating a frequency-modulated radar wave transmission signal;
Beat signal generating means for generating a beat signal by mixing a transmission signal generated by the transmission signal generating means and a reception signal of a reflected wave from a target that reflects the radar wave;
An acquisition means for acquiring the beat signal generated by the beat signal generation means from the beat signal generation means in accordance with a transmission signal generation cycle by the transmission signal generation means;
Analysis means for analyzing the frequency of the beat signal acquired by the acquisition means;
A distance calculating means for obtaining a distance to the target based on the analysis result of the analyzing means;
Interpolation processing means for predicting the current distance to the target based on at least the distance obtained in the past by the distance calculation means during a period in which the distance calculation means cannot be calculated;
When the interpolation processing means operates for a predetermined allowable period or longer, a diagnosis output means for outputting diagnosis information;
Detecting means for detecting an interference wave component included in the beat signal generated by the beat signal generating means;
An allowable period setting means for setting the allowable period based on a detection result of the detection means;
A radar apparatus comprising: