JP2008215842A - Target discrimination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire discrimination information on a plurality of targets efficiently by using a wideband signal. <P>SOLUTION: Concerning a rough determination search function F(Δτ) calculated based on an acquired reception signal, a maximum value searching part 516 extracts the first target having the closest correlation, and detects its delay time τ<SB>s1</SB>. Then, a rough replica generation part 512 generates a first target rough determination search function replica F<SB>rep1</SB>which is a rough determination search function acquired by assuming that only the first target exists based on the delay time τ<SB>s1</SB>. A subtraction part 514 subtracts the first target rough determination search function replica F<SB>rep1</SB>from the rough determination search function F(Δτ). Then, concerning the rough determination search function F<SB>c1</SB>(Δτ) of a subtraction result acquired by the subtraction part 514, the maximum value searching part 516 extracts the second target having the closest correlation from within, and detects its delay time Δτ<SB>s2</SB>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a target identification device that identifies a target using a broadband signal.

  Conventionally, radar devices have been widely used as devices for identifying various targets. This radar device basically transmits a radio wave, receives a reflected wave from the target, and identifies the target based on the difference between the transmitted wave and the reflected wave. For example, a pulse is transmitted, and a distance from the transmission to reception to the target is detected.

  Here, the distance resolution in such a radar apparatus is proportional to the bandwidth of the transmission pulse (Non-Patent Document 1). Therefore, to increase the distance resolution, it is necessary to widen the transmission pulse.

  However, when the transmission pulse is widened, it is necessary to process a high-frequency signal on the receiving side, and the processing becomes difficult. For example, when AD conversion processing is performed on a received signal, there is a problem that the sampling clock becomes very fast.

  Here, a distance measurement technique called a very long baseline interferometer (VLBI) is known (Non-Patent Document 2). Although this VLBI does not transmit radio waves, the distance is obtained by comparing two broadband signals. In this VLBI, the wideband signal is divided into subband signals, and the subband signals are compared with each other, thereby facilitating arithmetic processing with the comparison target as a subband.

  Note that a radar apparatus mounted on a vehicle is described in Patent Document 1 and the like.

JP-A-10-54874 Takashi Yoshida, “Revised Radar Technology”, IEICE, 1996 Fujinobu Takahashi, Tetsuro Kondo, Yukio Takahashi, “VLBI Technology”, Ohmsha, 1997

  Here, a broadband signal is transmitted, and target identification is performed from the received wave. At this time, there is a request to facilitate processing of the received signal, and there is a request to further improve the accuracy of identification of a plurality of targets. .

  The present invention relates to a transmitter that transmits a transmission signal composed of a wideband signal or a plurality of subband signals that can be combined with a wideband signal, a receiver that receives a reflected wave from a target and obtains a reception signal, and a reception signal For a plurality of obtained subband signals, a rough decision search function calculating unit that calculates a rough decision search function indicating a correlation with a corresponding signal in a wideband signal, and a rough decision search function obtained by the coarse decision search function calculating unit Based on the first target obtained by the first coarse search unit that extracts the first target having the highest correlation and detects the delay time of the signal received from the first target. A first coarse search replica that generates a first target coarse search replica that is a coarse decision search function obtained on the assumption that only the first target exists A generation unit, a subtraction unit for subtracting the first target coarse search replica generated by the first coarse search replica generation unit from the rough determination search function, and a rough determination search function of a subtraction result obtained by the subtraction unit, A second coarse search unit that extracts a second target having the highest correlation and detects a delay time of a signal received from the second target, and delays of the first and second coarse search units Information for identifying the first and second targets is obtained based on time.

  The present invention also provides a transmitter that transmits a transmission signal composed of a wideband signal or a plurality of subband signals that can be combined with a wideband signal, a receiver that receives a reflected wave from a target, and obtains a reception signal; A rough decision search function calculation unit for calculating a rough decision search function indicating a correlation with a corresponding signal in a wideband signal for a plurality of subband signals obtained from the signal, and a coarse decision search obtained by the coarse decision search function calculation unit A first rough search unit that extracts a first target having the highest correlation among the functions and detects a delay time of a signal received from the first target; and reception of the delay time obtained by the first coarse search unit Based on the phase difference between the correlation functions for a plurality of subband signals in the signal, the first fine decision is performed by combining the bands of the correlation functions and calculating the fine decision search function. A first function search unit for obtaining a delay time of a signal received from the first target having the highest correlation among the fine determination search functions obtained by the fine determination search function calculation unit; A first coarse search replica generation unit that generates a first target coarse search replica that is a coarse decision search function obtained on the basis of the first target obtained by the fine search unit, assuming that only the first target exists; A subtraction unit for subtracting the first target coarse search replica generated by the first coarse search replica generation unit from the coarse determination search function for the received signal, and a coarse determination search function of the subtraction result obtained by the subtraction unit , A second coarse search unit for extracting a second target having the highest correlation and detecting a delay time of a signal received from the second target Based on the phase difference between the correlation functions for the plurality of subband signals in the received signal having the delay time obtained by the second coarse search unit, the second bandwidth is calculated by synthesizing the bands of the correlation functions. Based on the first target obtained by the refinement search function calculation unit and the first refinement search unit, a first target refinement search replica that is a refinement search function obtained on the assumption that only the first target exists A first fine search replica generating unit to be generated; and a subtracting unit for subtracting the first target fine search replica generated by the fine search replica generating unit from the fine search function obtained by the second fine search function calculating unit. A second refinement search unit that obtains a delay time of the signal received from the second target from the refinement search function of the subtraction result obtained by the subtraction unit. The information for identifying the first and second targets is obtained based on the delay times of the first and second fine search units.

  The present invention also provides a transmitter that transmits a transmission signal composed of a wideband signal or a plurality of subband signals that can be combined with a wideband signal, a receiver that receives a reflected wave from a target, and obtains a reception signal; For a plurality of sub-band signals obtained from a signal, a coarse-decision search function calculation unit that calculates a coarse-decision search function that indicates a correlation with a corresponding signal in a wideband signal; A rough search replica generation unit that generates a previous detection target rough search replica that is a rough determination search function obtained on the assumption that only the previous detection target exists, and the rough search replica generation from the rough determination search function The subtraction unit that sequentially subtracts the previously detected target rough search replica generated by the unit, and the subtraction unit For the coarsely-decision search function of the subtraction result, the current detection target with the highest correlation among them is extracted, and the coarse search unit for detecting the delay time of the signal received from the current detection target, and the current detection obtained in this coarse search unit Based on the phase difference between the correlation functions for the plurality of subband signals in the received signal of the target delay time, a precise search function calculation unit that calculates the precise search function by combining the bands of the correlation functions and the previous detection When there is a target, a fine search replica is generated based on the previous detection target, and the previous detection target fine search replica, which is a refined search function obtained assuming that only the previous detection target exists, is accumulated. Based on the precise determination search function obtained by the integration unit and the precise determination search function calculation unit, A subtraction unit that subtracts the integration of the detected target refinement search replica generated by the torch replica generation integration unit and a refinement search that obtains the delay time of the signal received from the current detection target from the subtraction result search function obtained by the subtraction unit And information for identifying a plurality of targets are sequentially obtained based on delay times of the fine search unit.

  Moreover, it is preferable that the received signal is divided into a plurality of sections in which the transmission cycle of the transmission signal is divided and is a received signal in each section, and information for identifying a target is received for the received signal in each section.

  According to the present invention, processing for each subband is performed also in processing on the receiving side. Accordingly, the bandwidth to be processed is reduced and the processing becomes easy. Then, when there are multiple targets, the coarse search or fine search target replica obtained by assuming that only the target detected earlier from the coarse decision search function or the fine decision search function to be processed this time exists is subtracted. A target is detected based on the decision search function. Therefore, it is possible to identify the remaining targets by reducing the adverse effects of the side lobe of the target detected earlier.

  Hereinafter, embodiments of a target identification device according to the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating an overall configuration of a radar apparatus according to an embodiment. The wideband signal generation circuit 101 generates a wideband signal having a bandwidth of 0 to 2 GHz, for example. The generated wideband signal is divided into a plurality of subband signals having different frequencies by the radar pulse generation circuit 102. The plurality of subband signals on the transmission side are supplied to different transmission circuits 103, respectively.

  In the transmission circuit 103, a predetermined carrier wave (for example, 24 GHz) is mixed and up-converted into a high-frequency signal. The up-converted wideband signal is radiated from a plurality of transmitting antennas 104 in a direction in which a target is desired to be identified (a direction in which the target exists).

  Here, since the plurality of transmission circuits 103 are provided independently, the frequencies of the carrier waves to be mixed here do not have to be the same and can be arbitrarily selected.

  Transmission waves (a plurality of transmission side subband signals) radiated from the transmission antenna 104 are reflected by the target and received by the plurality of reception antennas 105.

  Note that the transmission antennas 104 and the reception antennas 105 are provided according to the respective subband signals, and therefore can be appropriately set according to the frequency of radio waves to be transmitted and received. A plurality or one may be used.

  Reception signals received by the plurality of reception antennas 105 are supplied to the plurality of reception circuits 106. The plurality of reception circuits 106 are provided corresponding to each of the plurality of transmission circuits 103 described above, and a signal having the same frequency and phase as the carrier wave mixed in the transmission circuit 103 is mixed with the reception signal. Receiving side subband signals are obtained. The receiving side subband signal obtained in the receiving circuit 106 is supplied to the radar pulse synthesizing circuit 107.

  Here, FIG. 2 is a diagram for explaining the wideband signal obtained by the wideband signal generation circuit 101 and the subband signal generation and transmission and reception subband signals in the radar pulse generation circuit 102.

  That is, as shown in the left diagram of FIG. 2, the broadband signal is a broadband signal 201 of about 0 to 2 GHz. The radar pulse generation circuit 102 divides the wideband signal 201 into narrowband subband signals 202. The subband signals 202 are separated from each other on the frequency axis. The plurality of subband signals are transmitted and received.

  The plurality of subband signals converted into the baseband band are supplied to the radar pulse synthesizing circuit 107, where they are converted into digital data, and then subjected to correlation calculation with the transmission signal, and the delay of the reception signal with respect to the transmission signal Time is calculated and output. In this correlation calculation, two types of correlation calculations, a coarse search and a fine search, are performed, which will be described later.

  The delay time that is the calculation result of the radar pulse synthesizing circuit 107 is supplied to the distance measuring unit 108, and the relative distance to the target (target) to be identified is calculated from the supplied delay time.

  FIG. 3 shows a specific configuration of the circuit of FIG. The pulse generator 401 generates a broadband signal having a bandwidth of about 2 GHz. The signal generated by the pulse generator 401 is a chirp signal in which the frequency of the output signal changes sequentially on the time axis as shown on the left side of FIG. 4, or the pulse width on the time axis as shown on the right side of FIG. Is a sufficiently narrow impulse-shaped pulse signal corresponding to a broadband signal.

  On the frequency axis, the pulse signal is a wideband signal having an occupied band of 0 Hz to 2 GHz and a bandwidth of 2 GHz as shown in FIG.

  The broadband signal generated by the pulse generator 401 is supplied to the radar pulse generation circuit 402. The radar pulse generation circuit 402 includes a power distributor 421 and a band pass filter 422 corresponding to the number of subband signals. The power distributor 421 distributes power to a desired number (a predetermined number of subband signals) of the wideband signal supplied from the pulse generator 401, and extracts a plurality of bandpass filters 422 respectively. To supply. For example, eight band pass filters 422 are provided. Each band-pass filter 422 has a bandwidth of several tens to several hundreds (for example, 85 MHz), and the center frequencies thereof are spaced apart from each other within a band of 0 to 2 GHz. Therefore, in the plurality of bandpass filters 422, narrowband subband signals separated from each other obtained by dividing a wideband signal of 0 to 2 GHz band are obtained.

For example, as shown in FIG. 6, the bandwidth fb of each subband is 85 MHz, and the center frequencies f _k (k = 1 to 8) of the subbands are 42 MHz, 125 MHz, 375 MHz, 875 MHz, 1375 MHz, and 1542 MHz, respectively. 1792 MHz and 1959 MHz. Here, the k-th subband signal is defined as x _k (t).

  The transmission-side subband signal from each bandpass filter 422 is supplied to the corresponding mixer 432 of the transmission circuit 403. A carrier wave (frequency fc) is supplied from the corresponding local oscillator 431 to each of the plurality of mixers 432. Accordingly, each subband signal supplied from the bandpass filter 422 is frequency-converted (up-converted) into an RF band signal by the mixer 432. That is, as shown in FIG. 7, the subband signal of 0 to 2 GHz is frequency-converted into the subband signal of fc to fc + 2 GHz band.

  The output of each mixer 432 is amplified to a suitable amplitude as a transmission signal by a corresponding power amplifier 433, and then band-limited to only a necessary band including each up-converted subband signal by a bandpass filter 434. .

  A plurality of subband signals (radar pulses) in the RF band, which are outputs from the transmission circuit 403, are radiated from the corresponding transmission antenna 404 toward the target. For example, in the case of an on-vehicle radar that is for forward monitoring, it is radiated only to the front, but for all the surroundings, it is radiated toward the entire periphery. In addition, since the subband signals on the transmission side are dispersed within the band of 2 GHz from fc, the target can be identified with high resolution.

  As described above, the carrier frequency fc supplied by each local oscillator 431 is preferably different from each other. Thereby, each subband signal can be transmitted using an arbitrary band.

  The transmitted radar pulse including the plurality of subband signals is reflected by the target, and the reflected wave from the target is received by the plurality of receiving antennas 405. A reception circuit 406 is connected to the reception antenna 405, and a reception signal is supplied thereto. The reception circuit 406 includes a plurality of band pass filters 461 corresponding to each of the plurality of reception antennas 405, and the reception signal is first supplied to the band pass filter 461. Each band-pass filter 461 extracts a signal in a frequency band corresponding to each of a plurality of transmission signals, and a signal in a band of a reflected wave by those targets is extracted. A low noise amplifier 462 is connected to the band pass filter 461, and the received signal from the band pass filter 461 is amplified here and supplied to the mixer 463. A signal from the corresponding local oscillator 467 is supplied to the mixer 463. The oscillation frequency of the local oscillator 467 is set corresponding to the carrier frequency fc of the local oscillator 431 on the transmission side, and is thereby down-converted by the mixer 463 and converted into a reception side subband signal in the 0 to 2 GHz band. Is done.

  The outputs from the plurality of mixers 463 are respectively supplied to the corresponding band pass filters 464, where the signals in the band of each subband signal are selected and noise is removed.

  A reception side subband signal corresponding to each transmission side subband signal of each bandpass filter 464 obtained in this way is output from the reception circuit 406 and supplied to the radar pulse synthesis circuit 407. The radar pulse synthesizing circuit 407 includes a plurality of AD conversion circuits 471, and signals from the plurality of band pass filters 464 are supplied to the corresponding AD conversion circuits 471, respectively.

  The AD conversion circuit 471 converts the supplied subband signal into a digital signal. Here, each AD conversion circuit 471 is also supplied with a corresponding transmission-side subband signal from the radar pulse generation circuit 402, and this transmission-side subband signal is also converted into a digital signal.

  In this way, the digital transmission side and reception side subband signals (eight channels in this example) obtained in each AD conversion circuit 471 are respectively supplied to the corresponding correlators 472, and the transmission side and reception side subband signals are supplied. Correlation calculation between subband signals is performed. The result of this correlation calculation is supplied to the bandwidth synthesis circuit 473. This bandwidth synthesis circuit 473 corrects the delay time based on the difference in spectrum phase based on the difference in frequency in one subband, and also correlates the whole (all channels) integrating a plurality of subband signals. And the corrected delay time Δτ is obtained.

  In this way, the arrival delay time Δτ of the reception wave with respect to the transmission wave is obtained, and this is supplied to the distance measurement unit 408. Then, based on the obtained arrival delay time Δτ, the distance measuring unit 408 obtains the relative distance R to the target by R = cΔτ / 2. Here, c is the speed of light.

<Conversion to baseband>
FIG. 8 shows a modification of the configuration of FIG. In this example, the output from the band-pass filter 422 on the transmission side is frequency-converted to the baseband as shown in FIG. That is, the signal from the bandpass filter 422 is supplied to the mixer 491, where it is mixed with the signal from the local oscillator 492. The oscillation frequency of the local oscillator 492 is set to the center frequency f _k of the subband signal from the band pass filter 422 (k = 1 to 8 in the above example). Therefore, all the outputs of the mixers 491 are frequency-converted into baseband signals having a center frequency of fb (subband signal bandwidth) / 2.

Here, when the transmission side subband signal is x _k (t) and the reception side subband signal is y _k (t), the baseband subband signals x _k ^v (t), y _k ^v (t) The following relationship holds between:

[Equation 1]
x _k (t) = x _k ^v (t) · e ⁱ² π ^{(fk−0.5fb) t}
y _k (t) = y _k ^v (t) · e ⁱ² π ^{(fk−0.5fb) t}
Here, fk is the center frequency of the kth subband signal.

Each AD conversion circuit 471 converts the supplied baseband subband signals x _k ^v (t), y _k ^v (t) into digital signals. Here, since the AD conversion circuit 471 digitally converts the subband signal y _k ^v (t) in the baseband, the sampling frequency necessary for the AD conversion circuit 471 is 2 · fb (Hz) or more. For example, 170 MHz is employed as the sampling frequency. Thus, according to this example, an effect that the sampling frequency of the AD conversion circuit 471 can be reduced can be obtained.

Next, the configuration of the bandwidth synthesis circuit 473 in this embodiment will be described with reference to FIG. In this embodiment, in the bandwidth synthesis circuit 473, as a correlation calculation for obtaining a delay time, a rough search for obtaining a correlation between each subband signal and a corresponding transmission signal and all of the plurality of subband signals are integrated. Perform both refined search considering correlation. Therefore, these contents will be described below. In the following description, the baseband subband signals x _k ^v (t) and y _k ^v (t) in FIG. 8 are used.

<Coarse search>
First, the rough search will be described. Correlator 472 obtains a delay time by correlation calculation with a corresponding subband signal (transmission subband signal) in the wideband signal to be transmitted. Here, the subband signal of the radar pulse on the transmission side corresponding to the subband signal y _k (t _j ) on the reception side is set to x _k (t _j ), and the signal in this baseband is x _k ^v (t _j ). Then, the correlator 472 obtains the correlation between x _k (t _j ) and y _k (t _j ). However, here, the cross spectrum S _k between X _k ^v (f _j ) and Y _k ^v (f _j ), which is a spectrum obtained by Fourier transforming x _k ^v (t _j ) and y _k ^v (t _j ). ^{Find v} (f _j ).

[Equation 2]
S _k ^v (f _j ) = X _k ^v (f _j ) · Y _k ^{v *} (f _j )
Note that ^* represents a complex conjugate.

Next, a correlation function F _k (Δτ) is _obtained by the following equation for the mutual spectrum S _k ^v (f _j ) of each channel.

[Equation 3]
_{F k (Δτ) = (1} / (J-1)) Σ [S k v (f j) · e -i2 π fjv Δτ] (j = 1~J)
Here, J is the number of subband signals, and fjv is the frequency for the baseband band index j.

The correlation function F _k (Δτ) is supplied to the averaging unit 502, where a coarse determination search function F (Δτ) obtained by summing (averaging) the correlation functions of the respective channels is obtained as in the following equation.

[Equation 4]
F (Δτ) = Σ [F _k (Δτ)] (k = 1 to n)

The coarse determination search function F (Δτ) is supplied to the maximum value search unit 504, where Δτ that maximizes F (Δτ) is searched. Here, the obtained value of Δτ is Δτ _s1 .

Here, the received wave is reflected back to the target, and if the transmission side signal is delayed by the delay time, the correlation between the transmission side signal and the reception side signal becomes the largest. For example, as shown in FIG. 9, the transmission wave and the reception wave are blunted and sampled relatively coarsely, while giving a predetermined delay time τ to the transmission wave, the mutual spectrum X (f) · Y ^* Consider the case of finding (f).

  By changing τ, the delay time τ that maximizes the correlation between the transmitted wave and the received wave as a whole is obtained.

Here, when the Fourier transform of the transmission wave x (t) is X (f), the Fourier transform of x (t + Δτ), which is shifted in time by Δτ for x (t), is X ′ (f) = e ^{−. i} φX (f). Here, 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, as shown in FIG. 10, when the transmission wave is delayed by Δτ on the time axis, the phase of the component is greatly rotated at a high frequency on the frequency axis after Fourier transform (FFT).

Accordingly, X (f) · Y ^* (f) · e ⁻ⁱ² is obtained by correcting the mutual spectrum X (f) · Y ^* (f) of x (t) and y (t) by Δτ. It can be expressed as π ^f Δτ.

Moving Δτ corresponds to rotating the phase of Y ^* (f), and the most likely delay time Δτ can be obtained by searching for a place where the correlation value becomes maximum as shown in FIG.

  As a result, the delay time Δτ can be obtained by a separate calculation for each subband signal.

Then, Δτ that maximizes the coarse search function F (Δτ), which is the sum of correlations for all subband signals, is obtained, and a coarse search result Δτ _s1 is obtained.

<Fine search>
Next, the delay time Δτ _s1 obtained by the coarse search is sent to the residual correction unit 506. The residual correction unit 506 multiplies e ^{−i (2} π ^f0v Δτ ⁺ Δφ ^k ) for the correlation function F _k (Δτ _s1 ) for each subband signal obtained based on the delay time Δτ _s1 by the following equation. To perform residual correction.

  Here, 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, and N is the number of subbands. .

Then, the correlation function subjected to the residual correction is sent to the synthesizing unit 508, where a precise determination search function D ₁ (Δτ), which is a correlation function obtained by synthesizing all channels, is obtained.

[Equation 5]
D ₁ (Δτ) = (1 / N) Σ [F _k (Δτ _s1 ) · e ^{−i (2} π ^f0v Δτ ⁺ Δφ ^k ] (k = 1 to N)

A fine-decision search function D ₁ (Δτ), which is a correlation function obtained by combining all channels, is sent to the maximum value search unit 510, where a delay time Δτ at which the correlation is maximum is obtained. That is, Δτ that maximizes D (Δτ) is obtained. Here, the obtained Δτ becomes the delay time of the radar pulse, and this delay time Δτ is expressed as Δτ1.

  The delay time Δτ1 is sent to the distance measuring unit 108 in FIG. 1, and the relative distance R to the target detected from Δτ1 is obtained here.

  Here, such a fine search will be described. As shown in FIG. 12, the delay time is obtained by compensating the phase of one of the subband signals by the coarse search. However, this is an operation for each subband signal. Therefore, as shown in FIG. 13, when the entire band of the wideband signal is viewed, the phase is rotated with respect to the mutual spectrum of the other subband signal even if the phase is not rotated with respect to the mutual spectrum of one subband signal. It may be.

Therefore, if the delay time is changed minutely and the maximum value is obtained for the correlation that controls the subband signals of all channels, the rotation of the phase based on the difference in frequency for each subband can be compensated. This corresponds to obtaining Δτ that is the maximum value of D ₁ (Δτ).

  Here, in this embodiment, the subband signal is a signal having discrete center frequencies that are separated from each other. Therefore, it is not possible to determine a phase shift in units of 360 degrees. That is, it cannot be determined whether the phase shift is 0.1 rotation or 1.1, 2.1, or 3.1 rotation.

However, in this embodiment, the coarse search is performed before the fine search. Therefore, the correct Δτ ₁ can be selected based on Δτ _s1 obtained by the coarse search. This is because Δτ _s1 by the coarse search is considered to have no error of 360 degrees or more in phase shift.

  Here, in the present embodiment, when the first target is identified as described above, the second target is identified. Here, the correlation function (decision search function) of the second target is difficult to find in the maximum value search due to the interference of the first target having a stronger signal level. That is, due to the side lobe of the first target, even if the second strongest peak in the decision search function is detected, the second target cannot always be detected.

  Therefore, in the present embodiment, the influence of the first target is excluded from the determined search function to be detected.

For this reason, the delay time Δτ ₁ for the first target detected in the maximum value search unit 510 is supplied to the coarse replica generation unit 512, and here is a coarse determination search function when it is assumed that only the first target exists. A first target rough decision search function replica is calculated.

First, assuming that only the first target having the delay time Δτ ₁ exists, the received signal is expressed as follows.

[Equation 6]
_{y rep (t) = a 1rep} · x (t-Δτ 1)

Therefore, the first target coarse decision search function replica of the coarse decision search function is obtained from the received signal y _rep (t) as follows.

[Equation 7]
F _rep (Δτ) = ΣF _{rep # k} (Δτ)

Here, F _{rep # k} (Δτ) is a correlation function of subband signals of x (t) and y _rep (t) estimated by calculation, and F (Δτ) F _rep (Δτ) Normalization is performed so that the first peak values are equal.

The first target coarse determination search function replica F _rep (Δτ) calculated in this way is supplied to the subtraction unit 514, and from the rough determination search function F (Δτ) that is a correlation function output from the averaging unit 502. Then, the first target rough decision search function replica F _rep (Δτ) is subtracted to obtain the second target coarse decision search function F _c2 (Δτ) in which the interference of the first target is eliminated.

[Equation 8]
F _c2 (Δτ) = F (Δτ) −F _rep (Δτ)

The obtained rough determination search function F _c2 (Δτ) for the second target is supplied to the maximum value search unit 516, where a rough position (delay time) τ _{s2 of} the second target is obtained by the maximum value search. .

In this way, the influence of the presence of the first target is eliminated, and the coarse search for the second target is completed. Next, a fine search for the second target is performed using the delay time τ _s2 that is the result of the coarse search of the second target.

For this purpose, the delay time τ _s2 that is the result of the coarse search is supplied to the residual correction unit 518. The residual correction unit 518 is supplied with F _k (Δτ) that is an output from the correlator 472 for each subband, and for each delay band τ _s2 for each correlation function of each subband (each channel). The phase is adjusted by finely adjusting the delay time, and the obtained correlation function for each subband is supplied to the synthesis unit 520. The synthesizing unit 520 obtains a second target precise determination search function D ₂ (Δτ), which is a correlation function obtained by synthesizing all the channels.

[Equation 9]
D ₂ (Δτ) = (1 / N) Σ [F _k (Δτ _s2 ) · e ^{−i (2} π ^f0v Δτ ⁺ Δφ ^k ] (k = 1 to N)

On the other hand, the delay time Δτ ₁ obtained by the maximum value search unit 510 is supplied to the fine replica generation unit 522.

The fine replica generation unit 522 calculates a replica signal (first target fine search replica) D _rep (Δτ) of the fine decision search function when it is assumed that only the first target exists by the following equation.

[Equation 10]
D _rep (Δτ) = (1 / N) Σ [F _k (Δτ _s2 ) · e ^{−i (} 2π ^f0v Δτ ⁺ Δφ ^k ] (k = 1 to N)

Then, in the subtraction unit 524, the first target fine search replica) D _rep (Δτ), which is the output of the fine replica generation unit 522, is subtracted from the fine decision search function D ₂ (Δτ), which is the output of the synthesis unit 520, A second target refinement search function D _c2 (Δτ) that eliminates the influence of the first target is obtained.

[Equation 11]
D _c2 (Δτ) = D ₂ (Δτ) −D _rep (Δτ)

The output of the subtraction unit 524 is sent to the maximum value search unit 526, where the maximum value search is performed, and the delay time Δτ ₂ of the second target is obtained.

  As described above, the precise search function that is an output from the synthesis unit 520 includes the influence of the received signal due to the first target, but the output of the subtraction unit 524 eliminates the interference of the first target. ing. Therefore, accurate second target detection can be performed by the maximum value search of the maximum value search unit 526.

<Detection of n targets>
FIG. 19 shows a configuration for detecting n targets. The configuration of detecting the first target is the same as that of the correlator 472, the averaging unit 502, the maximum value search unit 504, the residual correction unit 506, the synthesis unit 508, and the maximum value search unit 510 shown in FIG. It is.

In this configuration, a previous memory 530 that stores a coarse determination search function F _cn (Δτ) after subtraction of a coarse determination search function replica supplied to the maximum value search unit 516 that is an output from the subtraction unit 514, and a fine replica generation unit The integration memory 532 for sequentially integrating and storing D _repn-1 (Δτ), which is the output of the above.

The coarse replica generation unit 512 is supplied with the delay time Δτ _{n-1 of the (n−1) th} target that is the previous coarse search result, and the n−1th target when only the (n−1) th target exists. A target rough decision search function replica F _repn-1 (Δτ) is obtained. The n- _1th coarsely determined search function replica F _repn-1 (Δτ) is supplied to the subtracting unit 514, and this subtracting unit 514 uses the previous n−1 target detection from the previous memory 530. The coarse decision search function F _cn-1 (Δτ) is supplied. Accordingly, the subtraction unit 514 calculates F _cn (Δτ) = F _cn−1 (Δτ) −F _repn−1 (Δτ), and the rough determination search function F _cn (Δτ) for the nth target is obtained. Calculated. That is, the coarse decision search function stored in the memory 530 in the previous time is obtained by sequentially subtracting the previous coarse decision search function replica calculated each time, and the output from the subtraction unit 514 is the target detected so far. The influence of is removed.

For example, in the case of the detection of the second target, the rough replica generation unit 512 calculates the first target rough determination search function replica F _rep1 (Δτ) when it is assumed that only the first target exists, and the subtraction unit 514 Is calculated as F _c2 (Δτ) = F _c1 (Δτ) −F _rep1 (Δτ). In the above description, the description of “c1” in the case of n = 1 is omitted, but both are the same.

The fine replica generation unit 522 _{obtains the} (n−1) th fine search replica D _repn-1 (Δτ) when only the (n−1) th target exists from the delay time Δτ _{n−1 of the} previous target. It is done. Then, the (n-1) th fine search replica D _repn-1 (Δτ) is supplied to the integration memory 532 and integrated there. That is, the output of the integration memory 532 is D _rep1 (Δτ) + D _rep2 (Δτ) +... + D _repn (Δτ).

Also, the residual correction unit 518 corrects the phase of the correlation function F _k (Δτ) of each of the k subbands based on the delay time Δτ _sn of the nth target obtained by the maximum value search unit 516, and delays the delay time. Are combined by the combining unit 520 to obtain the nth target precise determination search function D _n (Δτ).

The subtraction unit 524 subtracts all the fine search replicas of the target that have been detected so far, which are the outputs from the integration memory 532, from the nth target fine determination search function D _n (Δτ), and eliminates these effects. The refined search function D _cn (Δτ) thus obtained is obtained.

Then, this precise determination search function D _cn (Δτ) is supplied to the maximum value search unit 526 to obtain the delay time Δτ _n of the nth target. When the next target is detected, the calculated delay time Δτ _n is supplied to the coarse replica generation unit 512 and the fine replica generation unit 522 as the next Δτ _n−1 .

  Thus, according to this configuration, the influence of the target identified up to the previous time is eliminated by the subtraction units 514 and 524, and the delay time is detected. Accordingly, n targets can be detected sequentially and accurately.

<Simplified configuration>
In the above-described embodiment, the configuration for identifying the first target is provided independently. However, it is not necessary to detect the first target independently. In FIG. 20, a part of the configuration in FIG. 18 is omitted. When the first target is detected, the output of the averaging unit 502 is first supplied to the previous memory 530. On the other hand, when the first target is detected, there is no previous detection result, no delay time is supplied to the coarse replica generation unit 512 and the fine replica generation unit 522, and the output from these is zero.

Accordingly, the output of the subtracting unit 514 is F _c0 (Δτ) = F (Δτ), that is, the coarse determination search function F (Δτ) output from the averaging unit 502, and this is supplied to the maximum value searching unit 516. Note that ΔF (Δτ) may be directly supplied to the subtraction unit 514 without being stored in the previous memory 530.

In the maximum value search unit 516, the delay time Δτ _sn of the first target, which is the result of the coarse search, is calculated as in the above example. The delay time Δτ _sn is supplied to the residual correction unit 518. The output of the integration memory 532 is supplied to the subtraction unit 524, but the output thereof is 0 at the first time. Therefore, the maximum value search unit 526 uses the precise determination search function D (Δτ) to set the first target. The delay time Δτ _{1 for} is calculated.

Below the second target, the replica is calculated using the delay time Δτ ₁ obtained by the first target identification, and the delay time is calculated in the same manner as described above.

Furthermore, FIG. 21 shows a configuration in which only a coarse search is performed. In the above-described embodiment, both the coarse search and the fine search are performed. However, when the delay time detection accuracy may be poor, only the coarse search may be performed. As a result, the circuit can be simplified. In this configuration, the detection delay time Δτ _sn is output as the output of the maximum value search unit 516. Further, when detecting the target below the second target, the delay time Δτ _sn is supplied to the rough replica generation unit 512 as Δτ _sn−1 last time. This configuration can also maintain the effect of reliably detecting a plurality of targets by replica subtraction.

<Division of received signal>
FIG. 22 shows an example in which the received signal is divided and received. As described above, the transmission wave is a wideband signal composed of a plurality of subband signals, and is a pulse signal transmitted at a constant repetition interval. The target is identified by detecting the delay time of the received signal. The delay time is related to the distance of the target, and the target can be divided for each distance by dividing the received signal according to the reception timing.

  In this embodiment, within the transmission repetition interval of the transmission signal, the reception signal is divided into a plurality of sections, and the above-described multiple target identification (delay time detection) processing is performed on each of the divided signals.

  For example, in the section R1 in FIG. 22, the above-described delay time detection is performed using only the received signal received in the section R1 (the received signal in the other section is 0) as the input of the correlation process. And the same process is repeated about each area R2-Rk.

  With such a configuration, it is possible to perform processing while eliminating interference due to received signals in other sections. Therefore, the number of targets to be identified in each process can be reduced, and the number of repetitions of the process for detecting the target in one process can be reduced, thereby reducing the false recognition rate.

<Use of memory>
FIG. 14 shows the configuration of still another embodiment. In this example, instead of inputting the transmission-side subband signal x _k (t) or x _k ^v (t) from the transmission-side bandpass filter 422 to the radar pulse synthesis circuit 407, the radar pulse synthesis circuit 407 stores the memory. 474, and the memory 474 stores the transmission-side subband signal used for correlation calculation.

Here, in this memory 474, the frequency spectrum X _k (f _j ) obtained by frequency-converting the transmission side subband signal x _k (t _j ) into the baseband and further Fourier-transforming is preliminarily calculated and held. As a result, a subband signal x _k (t _j ) is obtained from the broadband signal that is a radar pulse, converted into a subband signal x _k ^v (t _j ) in the baseband, and further subjected to Fourier transform X _k ^v It is not necessary to perform the process of obtaining (f _j ) in the radar pulse synthesis circuit 407.

  In order to detect the arrival delay time, it is necessary to know the timing (transmission timing) at which the pulse generator 401 generates a broadband signal. The delay of the transmission side subband signal can be achieved by shifting the timing of reading from the memory 474 from the timing of the generation of the wideband signal.

<Example of waveform>
FIG. 15 shows a correlation function when the relative distance to the target (target) is 9.246 m. The coarse decision search function F (Δτ) has coarse accuracy, but only one correlation peak appears in the vicinity of 60 nsec. On the other hand, the fine-decision search function D (Δτ) has a high accuracy with a peak width of about 0.5 nsec, but a plurality of peaks with the same height appear. Therefore, it can be understood that Δτ is 61.5 nsec that maximizes the correlation function because both F (Δτ) and D (Δτ) are maximized. When the delay time is converted into distance, 9.24 m is obtained.

  Thus, even with one target, side lobes appear in the coarse decision search function F (Δτ) and the fine decision search function D (Δτ). As the target distance increases, the peak becomes smaller, and the adverse effect of the pre-detection target increases. According to the present embodiment, this adverse effect is reduced by replica subtraction for the pre-detected target.

<Others>
FIG. 16 shows an example in which a frequency hopping circuit is used instead of the pulse generator in FIGS. In this frequency hopping circuit, a subband signal in the baseband shown in FIG. 9 is generated from the pulse generator 1101. For example, a pulse signal (baseband transmission side subband signal) having a bandwidth of fb = 87 MHz and a center frequency of fb / 2 = 43.5 MHz. This subband signal is supplied to the mixer 1105. The mixer 1105 is supplied with a carrier wave for frequency hopping from a PLL (phase lock loop) circuit 1104.

  That is, the PLL circuit 1104 is supplied with a signal from the local oscillator 1103 and a signal from the pseudo random number sequence code generator 1102, and the PLL circuit 1104 receives the signal from the local oscillator 1103 from the pseudo random number sequence code generator 1102. Multiply according to the signal. Thereby, the PLL circuit 1104 outputs signals f1 to f8 shown in FIG. Such multiplication of the output of the PLL circuit 1104 can be easily achieved by changing the coefficient of the multiplier in the PLL circuit according to the coefficient from the pseudo random number sequence code generator 1102.

  Here, the pseudo random number sequence code generator 1102 generates, for example, a GOLD sequence code. Here, the power of the pulse signal generated from the pulse generator 1101 is constant, and the power of the subband signal that is the output of the mixer 1105 is constant as shown on the left side of FIG. On the other hand, the frequency of the pulse signal changes at random as shown on the right side of FIG. That is, the mixer 1105 sequentially outputs signals of frequencies f0 to fn (for example, n = 8) according to the GOLD sequence code.

  In this way, the transmission side subband signals f1 to f8 in FIG. 6 are obtained as the output of the mixer 1105. Here, in this embodiment, since a plurality of transmission-side subband signals are obtained in order in time series, the radar pulse generation circuit 402, the transmission circuit 403, the reception circuit 406, and the radar pulse synthesis circuit 407 are temporally related. About what can be switched and used, it can be switched and used in time. Further, the transmitting antenna 404 and the receiving antenna 405 can be shared to some extent. In particular, the correlator 472 of the radar pulse synthesis circuit 407 may perform the correlation calculation sequentially.

  Thus, in this embodiment, since a subband signal is directly generated, it is not necessary to generate a wideband signal. Therefore, the apparatus can be configured easily and the cost can be reduced. Also, by assigning a unique initial value to each of the pseudo random number sequence code generators 1102, the correlation between different radars is lowered, and the reflected wave of its own radar wave can be transmitted to other radars even in an environment where a plurality of radars exist. It can also be identified from the wave. That is, if a different code sequence is provided for each radar, interference from other radars can be suppressed. In an on-vehicle radar, there are a plurality of radars in the radar range such as in a traffic jam, and there is a possibility that they interfere with each other. At this time, by identifying the code series in the reflected wave, the reflected wave of the own radar can be identified from the reflection of the radar of another company. The code sequence may be other than the GOLD sequence code.

  According to the above embodiment, the wideband signal is divided into a plurality of subband signals separated from each other on the receiving side. Thus, the amount of calculation can be reduced and efficient delay time detection can be performed, but the present invention is not necessarily limited to this, and it may be divided into subband signals so as to cover the entire band of the wideband signal.

  Further, by using impulse type radar pulses, transmission / reception can be performed without using a carrier wave.

  In the above embodiment, the relative distance to the target was obtained. However, not only the distance but also various information about the target such as the relative speed and the relative acceleration can be obtained based on the correlation information between the transmission signal and the reception signal.

  Furthermore, in the above-described embodiment, no difference is made for each subband in the subband synthesis. However, processing may be performed with a weight applied to the center frequency of the subband signal according to the target identification situation and purpose. For example, in the case of a nearby target, it is possible to employ a technique such as setting a weight to 0 for a low-frequency subband signal and decreasing a weight for an intermediate frequency.

  Further, the frequency characteristics of the transmitted broadband signal may not be uniform. Accordingly, conditional correlation calculation can be performed on the receiving side, and processing according to the target to be detected can be performed. Further, the transmission source can be identified by appropriately using up-chirp or down-chirp for the transmission chirp signal.

  As described above, in the present embodiment, the subband signal is used, but it is possible to have information on the transmission signal indicating what transmission signal the subband signal is generated based on. Therefore, the correlation calculation on the receiving side can be changed to an appropriate one according to the detection target in accordance with the information about the transmission signal.

  Further, it is possible to change the weighting of the transmission signal based on the frequency characteristics of the reception signal and perform feedback control so that the reception signal becomes appropriate for detection.

  Further, FIG. 23 shows another configuration example. In this configuration, a broadband signal is transmitted, and the reception signal is divided into subband signals on the reception side. The processing after the division into subband signals is the same as that described above.

  The pulse generator 301 generates a broadband signal having a bandwidth of about 2 GHz. The signal generated by the pulse generator 301 is a chirp signal in which the frequency of the output signal changes sequentially on the time axis as shown on the left side of FIG. 4, or the pulse width on the time axis as shown on the right side of FIG. Is a sufficiently narrow impulse-shaped pulse signal corresponding to a broadband signal.

  On the frequency axis, this pulse signal is a wideband signal having an occupied band of 0 Hz to 2 GHz and a bandwidth of 2 GHz as shown in FIG.

  The broadband signal generated in the pulse generator 301 is supplied to the transmission circuit 302. The transmission circuit 302 includes a local oscillator 321, a mixer 322, a power amplifier 323, and a band pass filter 324. The wideband signal is supplied to the mixer 322, where it is mixed with a carrier wave having a frequency fc (for example, 26 GHz) supplied from the local oscillator 321 and frequency-converted (up-converted) into a signal in the RF band (24 GHz to 28 GHz in this case). . That is, as shown in FIG. 6, a 0-2 GHz wideband signal is frequency-converted into a signal in the fc-2 GHz-fc + 2 GHz band.

  The output of the mixer 322 is amplified to an amplitude suitable as a transmission signal by the power amplifier 323, and then band-limited to only a necessary band including the up-converted wideband signal by the bandpass filter 324.

  An RF band broadband signal (radar pulse), which is an output of the transmission circuit 302, is radiated from the transmission antenna 303 toward the object. For example, in the case of an on-vehicle radar that is for forward monitoring, it is radiated only to the front, but for all the surroundings, it is radiated toward the entire periphery. Further, since the wideband signal has a band of 2 GHz, the object can be identified with high resolution.

  The transmitted radar pulse is reflected by the object, and the reflected wave from the object is received by the receiving antenna 304. A reception circuit 305 is connected to the reception antenna 304, and a reception signal is supplied thereto. The reception circuit 305 includes a band pass filter 351, and the reception signal is first supplied to the band pass filter 351. The band-pass filter 351 removes noise in the received signal and extracts a signal in the band of the reflected wave from the object with respect to the radar pulse. A low noise amplifier 352 is connected to the band pass filter 351, and the received signal is amplified here and supplied to the mixer 354. The signal from the local oscillator 353 is also supplied to the mixer 354. The oscillation frequency of the local oscillator 353 is a carrier frequency fc, which is down-converted by the mixer 354 and a broadband signal (IF signal) in the 0 to 2 GHz band is extracted.

  The IF signal in the 0 to 2 GHz band is supplied to the subband division circuit 306. The subband dividing circuit 306 has a power distributor 361, and the wideband signal in the 0 to 2 GHz band is divided into a desired number (a predetermined number of subband signals), and each is divided. Is supplied to a plurality of band pass filters 362 for extracting a signal in the band. Although only three are shown in the figure, for example, eight bandpass filters 362 are provided. Each band-pass filter 362 has a bandwidth of several tens to several hundreds (for example, 85 MHz), and the center frequencies thereof are spaced apart from each other within a band of 0 to 2 GHz. Thus, in the plurality of bandpass filters 362, narrowband subband signals spaced apart from each other obtained by dividing a wideband signal in the 0 to 2 GHz band are obtained.

  The subband signal obtained in this way is processed by the same configuration as in FIG.

It is a block diagram which shows the whole structure of the radar apparatus of embodiment. It is a figure explaining conversion etc. to a subband signal. It is a block diagram which shows the example of 1 structure of the radar apparatus of embodiment. It is a figure which shows the example of a radar pulse. It is a figure which shows a broadband signal. It is a figure which shows a subband signal. It is a figure which shows the up-converted transmission signal. It is a figure which shows the structure of the radar apparatus of a modification. It is a figure explaining the frequency conversion to a baseband band. It is a figure which shows a fine shift | offset | difference. It is a figure explaining phase gap. It is a figure which shows the phase shift in a subband. It is a figure which shows the phase shift between subbands. It is a figure which shows the structure of other embodiment. It is a figure which shows the example of a rough decision search function and a fine decision search function. It is a figure which shows the structure which utilizes frequency hopping. It is a figure which shows the state of frequency hopping. It is a figure which shows the structure of the bandwidth synthetic | combination circuit of the radar apparatus of embodiment. It is a figure which shows the other structural example of the bandwidth synthetic | combination circuit of the radar apparatus of embodiment. It is a figure which shows the further another structural example of the bandwidth synthetic | combination circuit of the radar apparatus of embodiment. It is a figure which shows the further another structural example of the bandwidth synthetic | combination circuit of the radar apparatus of embodiment. It is a figure explaining the division | segmentation of a received signal. It is a figure which shows the structure of the radar apparatus of another structural example.

Explanation of symbols

  101 Broadband signal generation circuit, 102, 402 Radar pulse generation circuit, 103, 403 Transmission circuit, 104, 404 Transmission antenna, 105, 405 Reception antenna, 106, 406 Reception circuit, 107 Radar pulse synthesis circuit, 108 Distance measurement unit, 301 , 401, 1101 Pulse generator, 407 Radar pulse synthesis circuit, 421 Power divider, 422, 434, 461, 464 Band pass filter, 431, 467, 492, 1103 Local oscillator, 432, 463, 491, 1105 Mixer, 433 Power amplifier, 462 Low noise amplifier, 471 AD conversion circuit, 472 correlator, 473 Bandwidth synthesis circuit, 474 memory, 502 averaging unit, 504, 510, 516, 526 Maximum value search unit, 506, 518 Residual correction unit 508, 520 Combining unit, 512 Coarse replica generating unit, 514, 524 Subtracting unit, 522 Fine replica generating unit, 530 Previous memory, 532 Integration memory, 1102 Pseudo random number sequence code generator, 1104 PLL circuit.

Claims (4)

A transmitter that transmits a transmission signal composed of a wideband signal or a plurality of subband signals that can be combined with the wideband signal;
A receiver that receives a reflected wave from the target and obtains a received signal;
For a plurality of subband signals obtained from the received signal, a coarse decision search function calculation unit for calculating a coarse decision search function indicating a correlation with a corresponding signal in the wideband signal;
A first coarse search unit for extracting a first target having the largest correlation from the coarse decision search function obtained by the coarse decision search function calculating unit and detecting a delay time of a signal received from the first target;
First coarse search replica generation for generating a first target coarse search replica that is a coarsely determined search function obtained on the basis of the first target obtained by the first coarse search unit assuming that only the first target exists And
A subtracting unit for subtracting the first target coarse search replica generated by the first coarse search replica generating unit from the coarse determination search function;
A coarse search function of the subtraction result obtained by the subtraction unit, a second coarse search unit that extracts a second target having the largest correlation among them and detects a delay time of a signal received from the second target;
Have
A target identification apparatus for obtaining information for identifying the first and second targets based on the delay times of the first and second coarse search units. A transmitter that transmits a transmission signal composed of a wideband signal or a plurality of subband signals that can be combined with the wideband signal;
A receiver that receives a reflected wave from the target and obtains a received signal;
For a plurality of subband signals obtained from the received signal, a coarse decision search function calculation unit for calculating a coarse decision search function indicating a correlation with a corresponding signal in the wideband signal;
A first coarse search unit for extracting a first target having the largest correlation from the coarse decision search function obtained by the coarse decision search function calculating unit and detecting a delay time of a signal received from the first target;
Based on the phase difference between the correlation functions for the plurality of subband signals in the received signal having the delay time obtained by the first coarse search unit, a first search function is calculated by combining the bands of the correlation functions. A precise search function calculation unit;
A first fine search unit for obtaining a delay time of a signal received from a first target having the largest correlation among the fine decision search functions obtained by the fine decision search function calculating unit;
First coarse search replica generation for generating a first target coarse search replica that is a coarsely determined search function obtained on the basis of the first target obtained by the first fine search unit assuming that only the first target exists And
A subtraction unit for subtracting the first target coarse search replica generated by the first coarse search replica generation unit from the coarse determination search function for the received signal;
A coarse search function of the subtraction result obtained by the subtraction unit, a second coarse search unit that extracts a second target having the largest correlation among them and detects a delay time of a signal received from the second target;
Based on the phase difference between the correlation functions for the plurality of subband signals in the received signal having the delay time obtained in the second coarse search unit, a second refinement search function is calculated by combining the bands of the correlation functions. A decision search function calculator;
First fine search replica generation for generating a first target fine search replica which is a fine decision search function obtained on the basis of the first target obtained by the first fine search unit on the assumption that only the first target exists And
A subtraction unit for subtracting the first target fine search replica generated by the fine search replica generation unit from the fine decision search function obtained by the second fine decision search function calculation unit;
A second refinement search unit for obtaining a delay time of the signal received from the second target from the refinement search function of the subtraction result obtained by the subtraction unit;
Have
A target identification apparatus for obtaining information for identifying a first target and a second target based on a delay time of the first and second fine search units. A transmitter that transmits a transmission signal composed of a wideband signal or a plurality of subband signals that can be combined with the wideband signal;
A receiver that receives a reflected wave from the target and obtains a received signal;
For a plurality of subband signals obtained from the received signal, a coarse decision search function calculation unit for calculating a coarse decision search function indicating a correlation with a corresponding signal in the wideband signal;
A rough search replica generation unit that generates a previous detection target rough search replica that is a rough determination search function obtained based on the previous detection target and assuming that only the previous detection target exists based on the previous detection target; ,
A subtracting unit that sequentially subtracts a previously detected target coarse search replica generated by the coarse search replica generation unit from the coarse determination search function;
About the coarse determination search function of the subtraction result obtained by this subtraction unit, the coarse search unit that extracts the current detection target having the largest correlation among them and detects the delay time of the signal received from the current detection target;
Based on the phase difference between the correlation functions for the plurality of subband signals in the received signal of the current detection target delay time obtained by the coarse search unit, the fine search function is calculated by synthesizing the bands of the correlation functions. A decision search function calculator;
A fine search that generates and accumulates a previously detected target fine search replica that is a refined search function that is obtained based on the previous detected target and assuming that only the previous detected target exists based on the previously detected target. A replica generation integration unit;
A subtracting unit for subtracting the integration of the detected target precise search replica generated by the precise search replica generating integration unit from the precise determination search function obtained by the precise determination search function calculating unit;
From the fine-decision search function of the subtraction result obtained by this subtraction unit, a fine search unit for obtaining the delay time of the signal received from the detection target this time,
A target identification apparatus for sequentially obtaining information for identifying a plurality of targets based on a delay time of the fine search unit. In the target identification device according to any one of claims 1 to 3,
The received signal is divided into a plurality of sections obtained by dividing the transmission cycle of the transmission signal, and is a received signal in each section, and obtains information for identifying a target for the received signal in each section. .

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