JP4711305B2 - Object identification device - Google Patents

Description

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

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

  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

  An object of this invention is to provide the target object identification apparatus which is easy to process a received wave, transmitting a broadband signal.

The present invention includes a transmitter that transmits a plurality of subband signals that can be combined with a wideband signal, a receiver that receives reflected waves from an object and obtains a plurality of subband signals, and a plurality of subbands obtained. for band signals, separately performs a correlation operation between the corresponding signal in the wideband signal, a coarse search unit for calculating a rough search delay time of the received signal, the correlation function in a wide band obtained by combining a plurality of sub-band signals there are, the coarse search delay performs a correlation calculation on the basis of the correlation function including the phase shift in each sub-band at the time of setting the time, the coarse search delay time obtained Ru fine search unit seminal search delay time corrected And information for identifying an object is obtained based on both delay times obtained in the coarse search unit and the fine search unit.

  In addition, it is preferable that storage means for storing information about the broadband signal is provided, and the coarse search unit performs correlation calculation using information read from the storage means.

  The transmitter converts a plurality of subband signals into high frequency signals and transmits the subband signals, and the receiver receives a plurality of high frequency band subband signals, performs AD conversion by an AD converter, and performs the coarse search. It is preferable that the unit and the fine search unit perform processing on a plurality of subband signals after AD conversion.

Further, it is preferable that the transmitter divides the wideband signal into a plurality of subband signals separated from each other.

  In addition, the transmitter may obtain a signal whose frequency sequentially changes by frequency hopping, and multiply the signal by a pulse signal having a bandwidth of the subband signal from the pulse generator to generate the plurality of subband signals. Is preferred.

  According to the present invention, a wideband signal is divided into subbands and transmitted. Accordingly, the processing on the receiving side is also performed for each subband. Accordingly, the bandwidth to be processed is reduced and the processing becomes easy. In addition, accurate correlation information can be obtained because the coarse search for detecting the correlation of each subband signal with the transmission signal and the fine search for detecting and correcting the phase difference between the subband signals are combined.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an object identification device according to the present invention will be described based on 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 broadband signal is radiated from a plurality of transmitting antennas 104 in a direction in which the object is desired to be identified (the direction in which the object 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 object 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 as the carrier wave mixed in the transmission circuit 103 is mixed with the reception signal on the reception side. Each subband signal is 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, which 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 object (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, 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 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. .

  This is the output of the transmission circuit 403. A plurality of subband signals (radar pulses) in the RF band are radiated from the corresponding transmitting antenna 404 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 subband signals on the transmission side are distributed in the 0 to 2 GHz band, the object 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 object, and the reflected wave from the object 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 from those objects 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 to remove noise.

  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 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 from the object 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 ^{i2π (fk−0.5fb) t}
y _k (t) = y _k ^v (t) · e ^{i2π (fk−0.5fb) t}
Here, fk is the center frequency of the kth subband signal.

Each AD conversion circuit 471 converts the supplied subband signals x _k ^v (t) and y _k ^v (t) of the baseband 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.

Here, in the present embodiment, the radar pulse synthesis circuit 407 performs a rough search for obtaining a correlation between each subband signal and a corresponding transmission signal as a correlation operation for obtaining a delay time, and a plurality of subband signals as a whole. Perform both refined search considering the correlation. Therefore, these contents will be described below. In the following description, 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 of this baseband is x _k ^v (t _j ). Then, the correlator 472 calculates the correlation between x _k (t _j ) and y _k (t _j ). However, here, the mutual 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 )
^* Represents a complex conjugate.

The mutual spectrum S _k ^v (f _j ) of each channel is supplied to the bandwidth synthesis circuit 473. The bandwidth synthesis circuit 473 obtains a correlation function F _k (Δτ) 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 ^{−i 2πfjvΔτ} ] (j = 1 to J)

  Here, J is the number of subband signals, and fjv is the frequency for the baseband band index j.

  Subsequently, as shown in the following equation, a coarse search function F (Δτ) obtained by summing up the correlation functions of the respective channels is obtained.

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

The bandwidth synthesis circuit 473 searches for Δτ that maximizes F (Δτ). Here, the obtained value of Δτ is assumed to be Δτ _s .

Here, the received wave is reflected back to the object, 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 obtaining (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 ^{−. It} is expressed as ^iφ X (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 ^−i2πfΔτ 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.

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 is obtained so that the sum of correlations F (Δτ) for all subband signals is maximized, and a search result Δτ _{s of the} coarse search is obtained.

<Fine search>
Next, the bandwidth synthesizing circuit 473 obtains a delay time Δτ ′ that maximizes the correlation, using a fine-decision search function D (Δτ ′) that is a correlation function obtained by synthesizing all channels according to the following equation.

[Equation 5]
D (Δτ ′) = (1 / N) Σ [F _k (Δτ _s ) · e− ^{i (2πf0vΔτ ′ + Δφk} ] (k = 1 to N)

  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, 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 object is obtained.

  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 ′ which is the maximum value of D (Δτ ′) described above.

  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 ′ can be selected based on Δτ obtained by the coarse search. This is because Δτ due to the coarse search is considered to have no error of 360 degrees or more in phase shift.

<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 transmission side subband signal x _k (t _j ) is frequency-converted to baseband, and the frequency spectrum X _k (f _j ) obtained by further Fourier transform is calculated and held in advance. As a result, the subband signal x _k (t _j ) is obtained from the broadband signal that is the radar pulse, converted into a baseband subband signal x _k ^v (t _j ), 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 broadband signal is generated from the pulse generator 401. 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>
FIG. 15 shows a correlation function when the relative distance to the object (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 precise determination search function D (Δτ ′) has a high accuracy with a peak width of about 0.5 nsec, but a plurality of peaks having the same height are output. Therefore, it can be understood that Δτ ′ is 61.5 nsec when the correlation function is maximized because both F (Δτ) and D (Δτ ′) are maximized. When the delay time is converted into distance, 9.24 m is obtained.

  As described above, according to the present embodiment, it is possible to realize correlation calculation of a broadband signal having a bandwidth of 2 GHz using an AD converter circuit having a sampling frequency of 170 MHz.

<Other embodiments>
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 in-vehicle radar, there are a plurality of radars in the radar range such as in a traffic jam, and there is a possibility of interfering 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.

<Others>
According to the above embodiment, the wideband signal is divided into a plurality of subband signals separated from each other on the receiving side. Thereby, the calculation amount can be reduced and the delay time can be calculated efficiently. However, 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 object was obtained. However, not only the distance but also various information about the object 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 in accordance with the situation and purpose of object identification. For example, in the case of a nearby object, it is possible to employ a technique such as setting the weight to 0 for a low-frequency subband signal and decreasing the 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.

It is a block diagram which shows schematic 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 rough shift | offset | difference. It is a figure explaining the shift | offset | difference of a phase. 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.

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, 1102 pseudo random number sequence code generator, 1104 PLL circuit.

Claims (5)

A transmitter for transmitting a plurality of subband signals that can be combined with a wideband signal;
A receiver that receives a reflected wave from an object and obtains a plurality of subband signals;
A plurality of subband signals obtained, performs a correlation calculation between corresponding signals in the wideband signal individually, a coarse search unit for calculating a rough search delay time of the received signal,
A correlation function in a wide band obtained by synthesizing a plurality of subband signals , and performing a correlation calculation based on a correlation function including a phase shift in each subband when the coarse search delay time is set, and the coarse search delay and the fine search unit Ru obtained fine search delay time obtained by correcting the time,
Have
An object identification apparatus characterized in that information for identifying an object is obtained based on both delay times obtained in the coarse search unit and the fine search unit. The object identification device according to claim 1,
Storage means for storing information about the broadband signal;
The rough search unit performs correlation calculation using information read from the storage means. The object identification device according to claim 2,
The transmitter converts each of the plurality of subband signals into a high frequency signal and transmits the signal,
The receiver receives a plurality of subband signals in a high frequency band, and performs AD conversion by an AD conversion unit,
The coarse search unit and the fine search unit perform processing on a plurality of subband signals after AD conversion. In the target object identification device according to any one of claims 1 to 3,
The transmitter divides the wideband signal into a plurality of subband signals separated from each other. In the target object identification device according to any one of claims 1 to 4,
The transmitter obtains a signal whose frequency sequentially changes by frequency hopping, and multiplies the signal by a pulse signal having a bandwidth of a subband signal from a pulse generator to generate the plurality of subband signals. Target object identification device.

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