JP2009008451A - Wide band radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent decline of target recognition accuracy by performing band width synthesis in consideration of a phase error resulting from a circuit delay generated by sub-band division, concerning a wide band radar device. <P>SOLUTION: In this wide band radar device, a reflected wave of a transmitted wide band signal is received, and the received reflected wave is divided into a plurality of sub-band signals having each mutually different frequency band, and band width synthesis of the plurality of sub-band signals is performed, and the target is recognized based on a result of the band width synthesis. In the device, a calibration signal inputted into a sub-band dividing circuit is generated, and it is determined whether target recognition is unnecessary or not, and when discriminated that the target recognition is unnecessary, a signal outputted from a transmission signal is switched from a wide band signal to a calibration signal. Then, a circuit delay error between sub-bands is detected, while the calibration signal is inputted into the sub-band dividing circuit instead of the reflected wave of the wide band signal, and phase correction necessary for the band width synthesis is performed based on the circuit delay error. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a broadband radar device, and in particular, transmits a broadband signal, receives a reflected wave of the transmitted broadband signal, and divides the reflected wave into subband signals of each frequency band, thereby hand width. The present invention relates to a broadband radar device that recognizes a target by synthesizing.

  Conventionally, a radar apparatus that recognizes a target such as an object is known (see, for example, Patent Document 1). In this radar device, radio waves are transmitted and the reflected waves are received. Then, the target is recognized based on the relationship between the transmission signal and the reception signal. For example, the distance from the target and the speed of the target are detected based on the time from transmission of the transmission signal to reception of the reception signal.

The distance resolution in such a radar apparatus is proportional to the bandwidth of the transmission pulse. Therefore, in order to increase the distance resolution, it is necessary to widen the transmission radio wave. In the radar device in which the transmission radio wave is widened, when the reflected wave is received, the reflected wave is divided into a plurality of subband signals having different frequency bands in a dividing circuit, and each subband signal is A / D conversion is performed to synthesize the bandwidth.
JP-A-6-138217

  However, when a plurality of subband signals having different frequency bands are generated from the received wideband signal in the dividing circuit, a circuit delay error occurs between the subbands. Since this circuit delay error becomes a phase error at the time of sub-band synthesis, if the generated sub-band signal is subjected to bandwidth synthesis as it is, the target recognition accuracy will be reduced.

  The present invention has been made in view of the above points, and prevents a reduction in recognition accuracy of a target by performing bandwidth synthesis in consideration of a phase error due to a circuit delay caused by subband division. It is an object of the present invention to provide a broadband radar apparatus capable of performing

  The object is to transmit a wideband signal, a receiving means for receiving a reflected wave of the wideband signal transmitted from the transmitting means, and a plurality of reflected waves received by the receiving means with different frequency bands. A sub-band dividing circuit that divides the sub-band signal, a sub-band synthesizing circuit that synthesizes the plurality of sub-band signals divided by the sub-band dividing circuit, and a result of bandwidth synthesis by the sub-band synthesizing circuit A broadband recognition apparatus comprising: a target recognition means for recognizing a target based on the calibration signal generation means for generating a predetermined calibration signal input to the subband dividing circuit; and a reflected wave of the broadband signal Instead, the predetermined calibration signal generated by the calibration signal generating means is input to the sub-band dividing circuit, so that A circuit delay error detecting means for detecting a delay error, a phase correcting means for performing a phase correction necessary for bandwidth synthesis by the subband synthesizing circuit based on the circuit delay error detected by the circuit delay error detecting means, This is achieved by a broadband radar device comprising:

  In this aspect of the invention, a circuit delay error between subbands is detected in a situation where a predetermined calibration signal generated by the calibration signal generating means is input to the subband dividing circuit instead of the reflected wave of the wideband signal. . Then, based on the detected circuit delay error, phase correction necessary for bandwidth synthesis is performed. If such phase correction is performed, then the phase error is eliminated when the reflected wave of the wideband signal is divided into subband signals and combined with the hand width, thereby preventing a reduction in target recognition accuracy. It will be.

  In the above-described broadband radar apparatus, the calibration signal generating means is a circuit provided on the transmitting means side, and the signal transmitted by the transmitting means is generated by the broadband signal and the calibration signal generating means. If the signal switching means for switching to any one of the predetermined calibration signals is provided, it is not necessary to use a dedicated circuit as the circuit that generates the calibration signal. Since both can be selectively generated, it is possible to simplify the circuit configuration of the radar apparatus that realizes the elimination of the phase error due to the circuit delay caused by the subband division.

  The broadband radar apparatus further includes target recognition necessity determining means for determining whether or not the target recognition is unnecessary, and the signal switching means is configured to detect the target by the target recognition necessity determination means. When it is determined that recognition is unnecessary, the signal transmitted by the transmission unit is switched from a wideband signal to the predetermined calibration signal generated by the calibration signal generation unit. Calibration signals can be input to the sub-band division circuit at unnecessary timing, and circuit delay errors between sub-bands can be detected when performing phase correction necessary for bandwidth synthesis. Even if the delay changes over time, it is possible to perform appropriate bandwidth synthesis in consideration of the phase error, and as a result, it is possible to reliably prevent a reduction in target recognition accuracy. It can be can be, to ensure the accuracy reliability.

  Further, in the broadband radar apparatus described above, if the calibration signal generating means generates a pulse signal at equal time intervals as the predetermined calibration signal, it is possible to detect a circuit delay error between subbands.

  According to the present invention, it is possible to prevent a reduction in recognition accuracy of a target by performing bandwidth synthesis in consideration of a phase error accompanying a circuit delay caused by subband division.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of a broadband radar apparatus 10 according to an embodiment of the present invention. FIG. 2 is a diagram showing a wideband signal (FIG. (A)) and a subband signal (FIG. (B)) obtained by dividing the wideband signal used in the wideband radar apparatus 10 of the present embodiment. Show. FIG. 3 shows the time waveform of the transmission signal in the transmission mode (FIG. 3A) and the time waveform of the calibration signal in the calibration mode (FIG. 3B) in the radar apparatus 10 of the present embodiment. FIG.

  The broadband radar apparatus 10 according to the present embodiment is mounted on a moving object such as a vehicle or a fixed object around which the moving object moves, and an object (target) existing around the moving object or the fixed object. It is a radar device to recognize.

  As shown in FIG. 1, the broadband radar apparatus 10 includes a recognition necessity determination circuit 12. The recognition necessity determination circuit 12 is a circuit that determines whether or not the target is to be recognized, that is, whether or not the radar function is to be performed (hereinafter referred to as a transmission mode). The determination in the recognition necessity determination circuit 12 is performed immediately after the power is turned on, whether the moving body is stopped, whether the target to be recognized does not actually exist, or moved. This is performed based on whether the body traveling direction is opposite to the radar detection direction (for example, forward).

  The broadband radar apparatus 10 also includes a signal generator 14. The signal generator 14 is connected to the recognition necessity determination circuit 12 described above. The determination result in the recognition necessity determination circuit 12 is supplied to the signal generator 14. The signal generator 14 generates an impulse-like pulse signal whose pulse width on the time axis is sufficiently narrow with respect to a broadband signal. The signal generator 14 changes the time waveform of the generated signal in accordance with the mode determination result of whether or not the target recognition is required, supplied from the recognition necessity determination circuit 12.

  Specifically, the time waveform of the signal generated by the signal generator 14 is, for example, a wideband signal having a bandwidth of 0 to 2 GHz on the frequency axis when the target is in the transmission mode in which the target is to be recognized (see FIG. 2 (A)) is to be generated, an impulse-like pulse signal is generated at unequal time intervals (FIG. 3A). In this case, the above broadband signal is generated. On the other hand, when the target is not in the transmission mode for recognizing the target, it is assumed that a calibration signal should be generated, and an impulse-like pulse signal is generated at equal time intervals (FIG. 3B); Is called calibration mode). In this case, a calibration signal that is a pulse signal at equal time intervals is generated.

  A transmission circuit 16 is connected to the signal generator 14. The signal generated by the signal generator 14 is supplied to the transmission circuit 16. The transmission circuit 16 is a circuit that mixes a predetermined carrier wave (for example, 26 GHz) with the signal supplied from the signal generator 14 and up-converts the signal to a high-frequency signal (for example, 24 GHz to 28 GHz).

  A transmission antenna 20 is connected to the transmission circuit 16 via a mode switching circuit 18. The mode switching circuit 18 is connected to the recognition necessity determination circuit 12 described above. The determination result in the recognition necessity determination circuit 12 is supplied to the mode switching circuit 18. The mode switching circuit 18 determines the connection destination of the transmission circuit 16, that is, the supply destination of the signal output from the transmission circuit 16, according to the mode determination result of the necessity of target recognition supplied from the recognition necessity determination circuit 12. And a receiving side (specifically, a mixer 24 described later).

  When the mode switching circuit 18 connects the transmission circuit 16 to the transmission antenna 20, the output of the transmission circuit 16 is supplied to the transmission antenna 20. The transmission antenna 20 radiates an RF band wideband signal toward the direction in which the target is to be recognized (for example, in the case of an in-vehicle radar, in front of or behind the vehicle).

  In addition, the broadband radar apparatus 10 includes a receiving antenna 22. The reception antenna 22 receives a wideband signal transmitted from the transmission side as a reflected wave after being reflected by an object. A reception circuit 26 is connected to the reception antenna 22 via a mixer 24. The reception signal received by the reception antenna 22 is supplied to the reception circuit 26. The reception circuit 26 is a circuit that down-converts the reception signal supplied from the reception antenna 22 into a signal having a predetermined intermediate frequency IF.

  A subband dividing circuit 28 is connected to the receiving circuit 26. The IF signal output from the receiving circuit 26 is supplied to the subband dividing circuit 28. The subband division circuit 28 divides the reception signal supplied from the reception circuit 26 into a plurality of subband signals having different center frequencies and different frequency bands. For example, when the received broadband signal is a signal of 24 GHz to 28 GHz, the broadband signal is divided into subband signals having a bandwidth of several tens to several hundreds of MHz. Then, the subband dividing circuit 28 frequency-converts all the subband signals obtained by the division into signals having a band of, for example, 0 to several hundred MHz. Each subband signal is frequency converted to the same baseband.

Specifically, the subband division circuit 28 has a power distributor and the same number of bandpass filters as the number n of subband signals to be divided. The subband dividing circuit 27 distributes the IF signal to a desired number n in the power distributor, and extracts subband signals in different bands in each bandpass filter. For example, the bandwidth of each subband signal is 85 MHz, and its center frequency fk (k = 1 to n) is set to 42 MHz, 125 MHz, 375 MHz, 875 MHz, 1375 MHz, 1542 MHz, 1792 MHz, and 1959 MHz, respectively. Here, the k-th subband signal is defined as y _k (t).

The subband splitting circuit 28 also has n mixers, n local oscillators, and n bandpass filters. The subband dividing circuit 28 mixes a subband signal in a different band with a signal from a corresponding local oscillator in each mixer, and a subband signal y _k ^v (t) in a baseband of 0 to fb (Hz). Frequency conversion. For example, the signal frequency from each local oscillator is set to 42 MHz, 125 MHz, 375 MHz, 875 MHz, 1375 MHz, 1542 MHz, 1792 MHz, and 1959 MHz in accordance with the center frequency of the corresponding subband signal. At this time, the relationship of the following equation (1) is established between the subband signals in different bands and the subband signals in the baseband band.

y _k (t) = y _k ^v (t) · e ^{i2π (fk−0.5fb) t} (1)
Then, the sub-band division circuit 28 removes noise by allowing a signal in the band of 0 to fb to pass through the band-pass filter.

  An AD conversion circuit 30 is connected to the subband dividing circuit 28 corresponding to each of the plurality of subband signals. The AD conversion circuits 30 are provided in the same number as the number of subband signals to be obtained by dividing the wideband signal. Each of the plurality of subband signals generated by the subband dividing circuit 28 is supplied to a separate AD conversion circuit 30. Each AD conversion circuit 30 converts the baseband subband signal supplied from the subband division circuit 28 into digital data.

Since the signal converted into digital data by the AD conversion circuit 30 is a subband signal y _k ^v (t) in the baseband band 0 to fb, the sampling frequency necessary for the AD conversion circuit 30 is 2 · fb (Hz). That's it. For example, 170 MHz is used as the sampling frequency. In this respect, if the baseband subband signal is digitally converted, the sampling frequency of the AD conversion circuit 30 can be reduced.

  A subband synthesis circuit 32 is connected to the AD conversion circuit 30. All of the digital data generated by each AD conversion circuit 30 is supplied to a single subband synthesis circuit 32. The subband synthesis circuit 32 includes n correlators and a single bandwidth synthesis circuit. The subband synthesizing circuit 32 may be stored in digital data of each subband signal supplied from the AD conversion circuit 30 in each correlator and digital data of a wideband signal transmitted on the transmitter side (memory or the like). )) To obtain a correlation for each subband signal. Further, in the bandwidth synthesis circuit, for each subband signal output from each correlator, reception of the transmission signal is performed based on the difference in order to compensate for the difference in the phase of the spectrum for each different frequency in one subband signal. The signal delay time is corrected, the correlation of the whole (all channels) obtained by integrating a plurality of subband signals is obtained, and the corrected delay time Δτ ′ is obtained.

  Specifically, the subband synthesis circuit 32 performs a rough search for obtaining a correlation between each subband signal and a corresponding transmission signal, and a plurality of subband signals as a correlation operation for obtaining a delay time of the received signal with respect to the transmission signal. Perform both the search and the fine search that considers the integrated correlation.

<Coarse search>
First, the rough search will be described. In the subband synthesizing circuit 32, each correlator performs a correlation operation between the reception side subband signal supplied from the corresponding AD conversion circuit 30 and the corresponding transmission side subband signal, so that the reception signal with respect to the transmission signal is converted. Find the delay time. Here, the reception side subband signal is y _k (t _j ), the transmission side subband signal corresponding to the reception side subband signal is x _k (t _j ), and these baseband signals are x _k. ^{Assuming v} (t _j ) and y _k ^v (t _j ), each correlator obtains a correlation between x _k (t _j ) and y _k (t _j ). Here, x _k ^v _{(t j)} is a spectrum obtained by Fourier transform of _X ^k v a ^{_{(f j), y k v}} (t j) is a spectrum obtained by Fourier transform of _Y ^k v cross-spectral and ^{_{(f j) S k v (}} f _j ). Note that * represents a complex conjugate.

S _k ^v (f _j ) = X _k ^v (f _j ) · Y _k ^{v *} (f _j ) (2)
Information of the mutual spectrum S _k ^v (f _j ) corresponding to the subband signal of each channel is supplied to the bandwidth synthesis circuit. First, the bandwidth synthesis circuit obtains a correlation function F _k (Δτ) for each channel's mutual spectrum S _k ^v (f _j ) by the following equation (3). Note that j = 1 to J. J is the number of subband signals, and fjv is the frequency for the baseband band index j.

F _k (Δτ) = (1 / (J−1)) Σ {S _k ^v (f _j ) · e ^{−i2πfjvΔτ} } (3)
Then, the bandwidth synthesis circuit obtains a rough decision search function F (Δτ) obtained by summing up the correlation functions of the respective channels by the following equation (4), and then obtains Δτ that maximizes the F (Δτ). Note that the value of Δτ obtained is Δτ _s .

F (Δτ) = Σ {F _k (Δτ)} (k = 1 to n) (4)
Here, since the received signal is reflected and returned to the target such as the object or oncoming vehicle, if the transmission signal is delayed by the delay time, the correlation between the transmission signal and the received signal is the largest. Become. Hereinafter, a case where the mutual spectrum X (f) · Y ^* (f) between the transmission signal and the reception signal is obtained while giving a predetermined delay time τ to the transmission signal will be considered. If τ is changed, the delay time τ that maximizes the overall correlation between the transmission signal and the reception signal can be obtained.

When the Fourier transform of the transmission signal x (t) is X (f), the Fourier transform of x (t + Δτ) shifted by Δτ with respect to x (t) is X ′ (f) = X (f) · e ^−iφ . However, φ = 2πfΔτ, and f is a frequency.

The delay of Δτ on the time axis appears as a phase shift proportional to the frequency after Fourier transform. That is, if the transmission signal is delayed by Δτ on the time axis, the phase of the component is rotated more greatly as the frequency is higher on the frequency axis after Fourier transform. Accordingly, X (f) · Y ^* (f) · e ⁻ is obtained by correcting the phase by Δτ with respect to the mutual spectrum X (f) · Y ^* (f) of x (t) and y (t). it can be expressed as ^i2πfΔτ.

In this regard, changing Δτ corresponds to rotating the phase of Y ^* (f), and it is possible to obtain a plausible delay time Δτ by searching for a delay time that maximizes the correlation. The delay time Δτ can be obtained by performing independent and independent correlation operations for each subband signal. Therefore, by obtaining Δτ that maximizes the sum of correlations F (Δτ) for all subband signals, it is possible to obtain the search result Δτ _s of the coarse search.

<Fine search>
Next, the bandwidth synthesis circuit obtains a fine-decision search function D (Δτ ′) that is a correlation function obtained by synthesizing all channels according to the following equation (5), and the correlation is maximized using the function D (Δτ ′). A delay time Δτ ′ is obtained. Note that k = 1 to N. F0k is the center frequency of the RF frequency band of the kth subband channel, Δφk is the value of the phase shift in the transmission / reception circuit of the kth subband signal, and N is the number of subband signals. It is.

D (Δτ ′) = (1 / N) Σ {F _k (Δτ _s ) · e− ^{i (2πf0kΔτ ′ + Δφk} } (5)
Then, Δτ ′ that maximizes D (Δτ ′) is obtained. The obtained Δτ ′ becomes the delay time of the radar pulse, and based on this, the relative distance R to the target is obtained.

  Here, the coarse search is a correlation operation for obtaining a delay time by compensating the phase of each subband signal. For this reason, if the entire band of the wideband signal is viewed, there is a possibility that the phase is rotated for the mutual spectrum of the other subband signal even when the phase is not rotated for the mutual spectrum of one subband signal. . Therefore, if the delay time is changed slightly and the maximum value is obtained for the correlation obtained by integrating the subband signals of all channels, the phase based on the difference in frequency for each subband signal can be compensated. This is to obtain Δτ ′ that maximizes the aforementioned D (Δτ ′).

  In the present embodiment, each subband signal is a signal having a center frequency separated from each other. For this reason, a phase shift exceeding 360 ° cannot be determined. That is, a phase shift of 0.1 rotation cannot be distinguished from a phase shift of 1.1 rotation or 2.1 rotation. On the other hand, in the present embodiment, the coarse search is performed before the fine search is performed. Since Δτ obtained by the coarse search does not cause an error phase shift exceeding 360 °, therefore, according to the fine search, Δτ ′ having high accuracy can be selected by Δτ obtained by the coarse search.

  In such a configuration, in order to detect the arrival delay time of the reception signal with respect to the transmission signal, the subband synthesis circuit 32 side grasps the timing (transmission timing) at which the broadband signal is generated from the transmitter side. There is a need. The delay of the transmission side subband signal can be realized by shifting the timing of reading from the memory from the generation timing of the wideband signal.

  A signal processing circuit 34 is connected to the subband synthesis circuit 32. The result of the delay time Δτ ′ obtained by the subband synthesis circuit 32 is supplied to the signal processing circuit 34. Based on the delay time Δτ ′ supplied from the subband synthesizing circuit 32, the signal processing circuit 34 determines the relative distance R (= c · Δτ ′ / 2) between itself (for example, the host vehicle) and the target; Light speed). Note that the signal processing circuit 34 may calculate a relative speed or a relative acceleration with the target together with or instead of the relative distance R with the target.

  As described above, according to the wideband radar apparatus 10 of the present embodiment, a wideband signal is transmitted, and a reflected wave of the transmitted wideband signal is divided into a plurality of subband signals, and then the bandwidth is synthesized. The delay time of the received signal with respect to the signal can be obtained, and the relative distance R to the target can be calculated based on the delay time, whereby the target existing in the vicinity can be recognized.

  In the present embodiment, the transmission circuit 16 is connected to the mixer 24 on the reception side via the mode switching circuit 18 described above. When the mode switching circuit 18 connects the transmission circuit 16 to the mixer 24, the output of the transmission circuit 16 is supplied to the reception circuit 26 via the mixer 24. That is, when the mode switching circuit 18 connects the transmission circuit 16 and the transmission antenna 20 to the mixer 24, the reception signal received by the reception antenna 22 is input. However, the mode switching circuit 18 is connected to the transmission circuit. 16 and the mixer 24 are connected, the output of the transmission circuit 16 is input.

  Further, an error detection circuit 36 is also connected to the AD conversion circuit 30. All of the digital data generated by each AD conversion circuit 30 is supplied to a single error detection circuit 36. The above-described recognition necessity determination circuit 12 is also connected to the error detection circuit 36. The determination result in the recognition necessity determination circuit 12 is supplied to the error detection circuit 36. The error detection circuit 36 determines between the subbands based on the data from each AD conversion circuit 30 as will be described in detail later according to the mode determination result of the necessity of target recognition supplied from the recognition necessity determination circuit 12. A circuit delay error is calculated.

  By the way, in this embodiment, the wideband signal (reflected wave) received on the receiver side is divided into a plurality of subband signals having different frequency bands in the subband dividing circuit 28. A circuit delay error caused by the division process occurs between the subbands. The circuit delay error between the subbands appears as a phase error during the bandwidth synthesis in the subband synthesis circuit 32. For this reason, if the sub-band signal generated by the sub-band dividing circuit 28 is directly subjected to the bandwidth synthesis without phase correction based on the circuit delay error, the bandwidth synthesis is not performed accurately, and the target is Recognition accuracy will be reduced.

  Therefore, in the wideband radar apparatus 10 of the present embodiment, a reduction in the recognition accuracy of the target is prevented by compensating for the phase error due to the circuit delay due to the subband division and appropriately performing the bandwidth synthesis. . Hereafter, the characteristic part of a present Example is demonstrated with reference to FIG. 4 thru | or FIG.

  FIG. 4 shows waveforms representing one pulse on the time axis and the frequency axis, respectively. FIG. 5 shows waveforms that represent pulse trains at equal time intervals on the time axis and the frequency axis, respectively. FIG. 6 shows a flowchart of an example of a control routine executed on the transmitter side in the broadband radar apparatus 10 of the present embodiment. FIG. 7 shows a flowchart of an example of a control routine executed by the error detection circuit 36 on the receiver side in the broadband radar apparatus 10 of the present embodiment. FIG. 8 is a diagram showing the time change of the input signal of each AD conversion circuit 30.

  One pulse signal having a short time width has a waveform having a wide frequency band on the frequency axis, as shown in FIG. On the other hand, since the same pulse signal is repeated in the pulse train output at equal time intervals, there is no frequency information of one pulse signal itself, and as shown in FIG. The waveform has a frequency.

  Therefore, when pulse trains of equal time intervals are generated and input to the subband division circuit 28, the subband division circuits 28 are in phase with each other unless the circuit delay of the subband division circuit 28 is taken into consideration. A plurality of subband signals will be generated. That is, if a circuit delay of the subband dividing circuit 28 occurs, a phase error associated with the circuit delay becomes obvious between the subband signals generated from the subband dividing circuit 28. Therefore, in this case, it is possible to detect the phase error between the subbands.

  Then, if the phase error accompanying the circuit delay between the subbands is detected and the phase correction necessary for the bandwidth synthesis in the subband synthesis circuit 32 is performed based on the phase error, the subband division circuit 28 It is possible to perform appropriate bandwidth synthesis in consideration of circuit delay.

  In the broadband radar apparatus 10 of this embodiment, after the vehicle is turned on such as when the ignition is turned on, the recognition necessity determination circuit 12 is in a transmission mode in which the target should be recognized or the target is recognized. It is determined whether or not the calibration mode is set to detect the phase error between the subbands by stopping or interrupting (step 100).

  The recognition necessity determination circuit 12 is not immediately after the power is turned on, or the moving body on which the broadband radar apparatus 10 is mounted is moving, the target to be recognized actually exists, or the traveling direction of the moving body is If the direction is the radar detection direction, it is determined that the current state is the transmission mode (negative determination in step 100). When such a negative determination is made, the mode switching circuit 18 is instructed to connect the transmission circuit 16 to the transmission antenna 20 side, and the signal generator 14 is impulsed to generate a wideband signal. Command to generate a pulse signal at unequal time intervals.

  In this case, the mode switching circuit 18 connects the transmission circuit 16 to the transmission antenna 20 (step 102), and the signal generator 14 selects a pulse waveform of unequal time intervals that becomes a wideband signal as a signal generation pattern. (Step 104), a wideband signal is generated (step 106), so that the wideband signal is transmitted from the transmission antenna 20 toward the external radar detection direction.

  In such a situation where a broadband signal is transmitted in the radar detection direction, if a target is present in the radar detection direction, the broadband signal is reflected on the target. When the reflected wave of the broadband signal is received by the reception antenna 22, the received signal is supplied to the reception circuit 26 and down-converted to an IF signal of an intermediate frequency, and then the frequency band in the subband division circuit 28. Are divided into a plurality of subband signals different from each other. Next, each of these subband signals is frequency-converted into a baseband band and converted into digital data, and then the bandwidth is synthesized by the subband synthesis circuit 32. In this case, by calculating the delay time of the reception signal with respect to the transmission signal, the target existing in the vicinity is recognized, and the distance R from the target is calculated.

  On the other hand, in the present embodiment, the recognition necessity determination circuit 12 is immediately after the power is turned on, or the moving body on which the broadband radar apparatus 10 is mounted is not immediately after the power is turned on, and the target to be recognized is If it is not present in the surroundings or the traveling direction of the moving body is opposite to the radar detection direction (for example, the moving body is retreated), it is determined that the current state is the calibration mode (affirmative determination in step 100). If such an affirmative determination is made, the mode switching circuit 18 is instructed that the transmission destination of the transmission circuit 16 should be the receiving mixer 24 side, and a calibration signal is generated for the signal generator 14. Command to generate impulse-like pulse signals at equal time intervals as much as possible.

  In this case, the mode switching circuit 18 connects the transmission circuit 16 to the mixer 24 (step 108), and the signal generator 14 selects a pulse waveform of equal time intervals as a calibration signal as a signal generation pattern ( (Step 110) Since the calibration signal is generated (Step 112), the calibration signal is received by the receiver via the mixer 24 without transmitting the wideband signal from the transmitting antenna 20 to the outside. It will be.

  When the calibration signal is received on the receiver side, the calibration signal is supplied to the reception circuit 26 and down-converted to an intermediate frequency IF signal. After being divided into band signals, each of these subband signals is frequency-converted into a baseband band and converted into digital data. Since the calibration signal is a pulse train at equal time intervals, if the circuit delay of the subband division circuit 28 is not taken into consideration, the subband division circuit 28 outputs a waveform having a frequency for every equal interval, and the phase thereof is They should match each other.

  In this embodiment, an error detection circuit 36 is provided on the receiver side in order to detect a circuit delay error of the subband division circuit 28. If the recognition necessity determination circuit 12 determines that the current state is the calibration mode, the recognition necessity determination circuit 12 supplies the error detection circuit 36 with the mode determination result to instruct that the circuit delay error between each subband should be calculated. To do. When it is determined that the mode determination result supplied from the recognition necessity determination circuit 12 is the calibration mode (when affirmative determination is made in step 150), the error detection circuit 36 calculates a circuit delay error between the subbands. To do.

  Specifically, in the calibration mode, the error detection circuit 36 first inputs each input from the subband division circuit 28 to the AD conversion circuit 30 based on output data (digital data) from each AD conversion circuit 30. Subband signal (signal waveform y (t) as shown in FIG. 8) sin (ωmT + φm); where m is a natural number from 1 to n, and n is the number of subband signals divided from the wideband signal. ) Is measured (step 152). Then, the phase difference Δφm (for example, = φn−φm) between the phase φm of each subband signal and the reference phase (for example, φn) is calculated (step 154).

  When calculating the phase difference φm between the subbands as described above in the calibration mode, the error detection circuit 36 divides the wideband signal into a plurality of subband signals according to the phase difference φm and synthesizes the subband signals. A process of calculating a correction value p of the phase to be corrected at the time of bandwidth synthesis in the transmission mode and supplying information of the correction value p to the subband synthesis circuit 32 is executed (step 156).

  When the subband synthesis circuit 32 receives the information of the phase correction value p from the error detection circuit 36, the subband synthesis circuit 32 performs phase correction necessary for bandwidth synthesis based on the phase correction value p, and after the correction in the subsequent transmission mode. A target recognition process is performed with reference to the phase of, and a distance R from the target is calculated.

  In the calibration mode, the phase difference Δφm for each subband signal should be all zero if the circuit delay of the subband dividing circuit 28 is not taken into account, but if the circuit delay occurs, the delay error is generated. A value corresponding to will appear. According to the configuration described above, the circuit delay error between the subbands in the subband dividing circuit 28 is detected in the calibration mode, the phase correction is performed in consideration of the circuit delay error, and the phase after correction is performed in the subsequent transmission mode. It is possible to synthesize the bandwidth of subband signals based on.

  Therefore, according to the wideband radar apparatus 10 of the present embodiment, it is possible to perform the bandwidth synthesis in consideration of the phase error accompanying the circuit delay caused by the subband division from the wideband signal to the subband signal in the subband division circuit 28. The phase error can be eliminated at the time of the bandwidth synthesis in the subband synthesis circuit 32. For this reason, it is possible to prevent a reduction in the recognition accuracy of the target due to the phase error of the sub-band division circuit 28, and as a result, the maximum distance at which the target can be recognized can be extended. It is possible.

  In this embodiment, in order to detect a circuit delay error between the subbands in the subband dividing circuit 28, a calibration signal which is a pulse signal at equal time intervals is generated. This calibration signal is generated. The circuit is not provided on the receiver side, but is provided on the transmitter side for generating a broadband signal that is a pulse signal with unequal time intervals, and the calibration signal indicates the timing at which the pulse signal is generated. It is realized simply by making it different from that of the wideband signal.

  For this reason, according to the wideband radar apparatus 10 of the present embodiment, it is not necessary to use a circuit dedicated to generating the calibration signal as its own dedicated circuit, and the transmitter side selectively selects the wideband signal and the calibration signal. Therefore, it is possible to simplify the circuit configuration of the radar apparatus that realizes the elimination of the phase error caused by the circuit delay caused by the subband division.

  In this embodiment, the mode switching circuit 18 connects the output of the transmission circuit 18 to the mixer 24 on the receiver side, and the output signal of the transmission circuit 18 is switched from the wideband signal to the calibration signal, that is, the subband. The calibration mode for detecting the circuit delay error between the sub-bands in the dividing circuit 28 is required immediately after the power is turned on to enable the radar function or not but immediately after the power is turned on to recognize the target and activate the radar function. More specifically, when the moving body on which the broadband radar device 10 is mounted is stopped, there is no target to be recognized around, or the moving direction of the moving body is opposite to the radar detection direction This is realized when (for example, the moving body is retracted).

  Therefore, the calibration signal can be supplied to the receiver side and input to the subband dividing circuit 28 instead of the wideband signal immediately before the radar function is started or at the timing when the target recognition is unnecessary. In performing necessary phase correction, it is possible to detect a circuit delay error between subbands.

  For this reason, according to the wideband radar apparatus 10 of the present embodiment, it is possible to finely detect the circuit delay error between the subbands, and the temporal change in the circuit delay due to the subband division is caused by a temperature change or the like. If this occurs, it is possible to perform appropriate subband signal bandwidth synthesis that takes into account the phase error associated with the circuit delay, thereby reliably preventing a reduction in target recognition accuracy. It is possible to ensure accuracy and reliability.

  In the above-described embodiment, the transmitter including the signal generator 14, the transmission circuit 16, and the transmission antenna 20 includes the reception antenna 22, the reception circuit 26, the subband, and the "transmission means" described in the claims. The receiver composed of the dividing circuit 28, the AD conversion circuit 30, the sub-band synthesis circuit 32, and the signal processing circuit 34 is described in the “receiving means” described in the claims, and the signal processing circuit 34 is described in the claims. In the “target recognition means”, the signal generator 14 is in the “calibration signal generation means” described in the claims, and the error detection circuit 36 is in the “circuit delay error detection means” in the claims. The switching circuit 18 corresponds to “signal switching means” recited in the claims. Further, when the subband synthesizing circuit 32 executes the processing of step 156 in the routine shown in FIG. 7, the “phase correction means” described in the claims is recognized by the recognition necessity determining means 12 in the routine shown in FIG. By executing the processing of step 100, the “target recognition necessity determining means” described in the claims is realized.

It is a block diagram of the broadband radar apparatus which is an Example of this invention. It is a figure showing the wideband signal used in a present Example, and the subband signal which divided | segmented the wideband signal, respectively. It is the figure showing the time waveform of the transmission signal in the transmission mode in a present Example, and the time waveform of the calibration signal in calibration mode. It is a figure which shows the waveform which each represented 1 pulse by the time-axis and the frequency axis. It is a figure which shows the waveform which each represented the pulse train of equal time intervals by the time-axis and the frequency axis. It is a flowchart of an example of the control routine performed by the transmitter side in the wideband radar apparatus of a present Example. It is a flowchart of an example of a control routine executed by the error detection circuit on the receiver side in the wideband radar apparatus of the present embodiment. It is a figure showing the time change of the input signal of each AD converter circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Broadband radar apparatus 12 Recognition necessity determination circuit 14 Signal generator 16 Transmission circuit 18 Mode switching circuit 26 Reception circuit 28 Subband division circuit 30 AD conversion circuit 32 Subband synthesis circuit 36 Error detection circuit

Claims (4)

Transmitting means for transmitting a wideband signal, receiving means for receiving a reflected wave of the broadband signal transmitted from the transmitting means, and the reflected wave received by the receiving means into a plurality of subband signals having different frequency bands A subband dividing circuit for dividing, a subband synthesizing circuit for combining a hand width of the plurality of subband signals divided by the subband dividing circuit, and a target based on a result of bandwidth combining by the subband combining circuit. A broadband radar apparatus comprising a target recognition means for recognizing
Calibration signal generating means for generating a predetermined calibration signal input to the subband dividing circuit;
Circuit delay error detecting means for detecting a circuit delay error between subbands in a situation where the predetermined calibration signal generated by the calibration signal generating means instead of a reflected wave of a wideband signal is input to the subband dividing circuit; ,
Phase correction means for performing phase correction necessary for bandwidth synthesis by the subband synthesis circuit based on the circuit delay error detected by the circuit delay error detection means;
A broadband radar apparatus comprising: The calibration signal generating means is a circuit provided on the transmitting means side, and
2. The broadband according to claim 1, further comprising a signal switching unit that switches a signal transmitted by the transmission unit to either a broadband signal or the predetermined calibration signal generated by the calibration signal generation unit. Radar device. A target recognition necessity judging means for judging whether recognition of the target is unnecessary,
The signal switching means generates a signal transmitted by the transmitting means from a wideband signal by the calibration signal generating means when the target recognition necessity determining means determines that the target recognition is unnecessary. 3. The broadband radar apparatus according to claim 2, wherein switching to the predetermined calibration signal is performed.   4. The broadband radar apparatus according to claim 1, wherein the calibration signal generating means generates a pulse signal at regular time intervals as the predetermined calibration signal.

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