JP2012088279A - Radar device and mobile target detecting method to be applied for radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform detection or suppression of multi-pass, disturbance wave, etc., while capable of coping also with a high-speed mobile, by utilizing a multicarrier waveform as a transmission wave.SOLUTION: A detection method is provided with: a transmission waveform generation section; a wave separating section for separating reception signals of each element antenna for every subcarrier bandwidth; a signal synthesis section for synthesizing the wave separating subcarrier signals for every subcarrier signal positioned at the same frequency arrangement; and a target detection section. A speed estimation section is further provided for setting the number of subcarriers and the interval of subcarriers of the multicarrier transmission wave based on estimated speed information of the target, and the transmission waveform generation section creates the multicarrier transmission wave according to the number of subcarriers and the interval of the subcarriers, and the wave separating section extracts a first signal group consisting of the subcarrier signals in the bandwidth which is arranged with the subcarrier according to the number of subcarriers and the interval of the subcarriers, and the target detection section detects the target from a synthesis processing result regarding the first signal group.

Description

  The present invention is a radar that adaptively controls a transmission waveform based on target moving speed information, and processes a received signal using information related to the transmission waveform, thereby improving target detection performance and interference suppression performance. The present invention relates to a moving target detection method applied to an apparatus and a radar apparatus.

  It is important for search radars to detect and capture targets as far as possible. As a typical ranging method of a radar, a pulse compression method or an FMCW (Frequency Modulated Continuous Wave) method is known. These are based on the principle of measuring distance by time delay and frequency, respectively.

  The pulse compression method is excellent in clutter suppression performance and interference suppression performance. However, when high-speed correlation processing is required and high distance resolution is required, there is a problem that the scale of the signal processing system increases.

  On the other hand, the FMCW system is a system that can obtain a high distance resolution with relatively low-speed signal processing, and is often used in radar devices that require cost reduction. However, since the FMCW system uses a CW transmission wave, there are transmission / reception isolation problems and unnecessary wave (clutter) problems from unnecessary reflectors at short distances with small propagation loss.

  In recent years, the use of multi-carrier signals such as OFDM (Orthogonal Frequency Division Multiplexing) signals, such as passive radar using terrestrial digital broadcast waves, for radar has been studied (for example, see Patent Document 1). .

  In a multipath environment, a reduction in received electric field level due to multipath fading depending on the propagation path environment is inevitable. In particular, the above-described conventional technology based on a single frequency cannot be essentially handled.

  Furthermore, the phase relationship between the direct wave and the reflected wave (multipath) also depends on the distance to the target. For this reason, the detection performance is significantly deteriorated in a specific region. However, in such an environment, it is effective to apply a multicarrier signal having high multipath tolerance.

Japanese Patent No. 3918735

However, the prior art has the following problems.
In radar, it is essential to deal with moving objects. However, a multicarrier signal such as an OFDM signal uses the orthogonality of the frequency interval between subcarriers, and as the moving speed increases, intersubcarrier interference due to Doppler shift becomes a problem. Therefore, in order to apply the multicarrier waveform to the radar, it is important to deal with a moving body (high-speed moving target) that moves at high speed.

  The present invention has been made to solve the above-described problems. When a multi-carrier waveform is used as a transmission wave, the present invention can cope with a high-speed moving object, and can perform multi-path. An object of the present invention is to obtain a radar apparatus capable of simultaneously detecting and suppressing interference waves, and a moving target detection method applied to the radar apparatus.

  A radar apparatus according to the present invention generates a multicarrier transmission wave and transmits it via a transmission antenna, and a signal reflected from the multicarrier transmission wave to a target via a reception antenna including a plurality of element antennas. A demultiplexing unit that demultiplexes the reception signal of each element antenna as a subcarrier signal for each subcarrier band, and a subcarrier signal of each element antenna that is demultiplexed for each subcarrier band by the demultiplexing unit, A radar apparatus comprising: a signal synthesis unit that synthesizes each subcarrier signal of each element antenna having the same frequency arrangement; and a target detection unit that detects a target using the signal synthesized by the signal synthesis unit. By analyzing the signal synthesized by the synthesis unit, the target moving speed is estimated as estimated speed information, and based on the estimated estimated speed information, And a speed estimation unit that sets the number of subcarriers and subcarrier intervals of the multicarrier transmission wave within a predetermined band, and the transmission waveform generation unit performs multicarrier transmission according to the number of subcarriers and subcarrier interval set by the speed estimation unit Wave is generated, and the generated multi-carrier transmission wave is transmitted via the transmission antenna. The demultiplexing unit is configured to transmit the subcarrier in the band in which the subcarriers are arranged according to the number of subcarriers and the subcarrier interval set by the speed estimation unit. The signal synthesizer receives the first signal group and discriminates it into a first signal group composed of carrier signals and a second signal group composed of subcarrier signals in a band in which no subcarriers are arranged. With respect to the subcarrier signal of each element antenna demultiplexed for each subcarrier band, It is intended to be combined with each Yaria signal.

  The moving target detection method according to the present invention is a moving target detection method applied to a radar apparatus, which generates a multicarrier transmission wave and transmits it via a transmission antenna, and multicarrier transmission. A demultiplexing step of receiving a signal reflected by a wave through a receiving antenna composed of a plurality of element antennas, and demultiplexing the received signal of each element antenna as a subcarrier signal for each subcarrier band, and a demultiplexing step Using the signal synthesis step of synthesizing the subcarrier signals of each element antenna demultiplexed for each subcarrier band for each subcarrier signal of each element antenna in the same frequency arrangement, and the signal synthesized in the signal synthesis step A target detection step for detecting the target, and analyzing the signal synthesized in the signal synthesis step to Is estimated as estimated speed information, and further includes a speed estimation step for setting the number of subcarriers and the subcarrier interval of the multicarrier transmission wave within the band to be observed based on the estimated speed information, and generating a transmission waveform The step generates a multicarrier transmission wave according to the number of subcarriers and the subcarrier interval set in the speed estimation step, transmits the generated multicarrier transmission wave via a transmission antenna, and the branching step is a speed estimation step. A first signal group composed of subcarrier signals in a band in which subcarriers are arranged and a second signal group composed of subcarrier signals in a band in which no subcarriers are arranged In the signal synthesis step, the first signal group is received and the first signal is received. Regard the group, in which the synthesis for each sub-carrier signal of each antenna element in a sub-carrier signal of each antenna element that is demultiplexed into each sub-carrier band at the same frequency allocation.

  According to the radar apparatus and the moving target detection method applied to the radar apparatus according to the present invention, on the transmission side, a transmission waveform adapted to the number of subcarriers according to the moving speed based on the estimated speed information of the moving target. On the receiving side, the received signal is demultiplexed and combined using information on the number of subcarriers corresponding to the moving speed, and a radar signal such as target detection based on the signal with improved SNR. By executing processing, when a multi-carrier waveform is used as a transmission wave, it can be handled even if the target is a high-speed moving object, and at the same time, detection and suppression of multi-paths, interference waves, etc. It is possible to obtain a radar device that can be used and a moving target detection method applied to the radar device.

It is a block diagram of the radar apparatus in Embodiment 1 of this invention. It is explanatory drawing which shows an example of the transmission waveform produced | generated by the transmission waveform production | generation part in Embodiment 1 of this invention. It is a specific block diagram of the duplexer in the first embodiment of the present invention. It is a flowchart which shows a series of processes of the radar apparatus in Embodiment 1 of this invention. It is a block diagram of the radar apparatus in Embodiment 2 of this invention. It is a specific block diagram of the duplexer in the second embodiment of the present invention. It is a flowchart which shows a series of processes of the radar apparatus in Embodiment 2 of this invention. It is explanatory drawing which shows an example of the transmission waveform produced | generated by the transmission waveform production | generation part in Embodiment 3 of this invention.

  A preferred embodiment of a radar apparatus according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a radar apparatus according to Embodiment 1 of the present invention. The radar apparatus in FIG. 1 includes a reception antenna 10, a demultiplexing unit 20, a signal synthesis unit 40, a target detection unit 50, a transmission antenna 70, a transmission waveform generation unit 80, and a speed estimation unit 90.

  Here, the receiving antenna 10 is an array antenna composed of K element antennas 11 (1) to 11 (K). The demultiplexing unit 20 includes K demultiplexers 21 (1) to 21 (K), which are individual components.

  In FIG. 1, the receiving antenna 10 and the transmitting antenna 70 are described separately, but the present invention is not limited to such a configuration. A configuration in which the element antenna 11 is shared as a transmission / reception antenna is also possible. Further, although the transmission antenna 70 is illustrated as a single element, it may of course be an array antenna.

  In an actual apparatus, various devices and circuits for converting the received high-frequency signal to frequency and converting it into baseband digital data are necessary, but these are omitted in FIG. Further, in the transmission system, each functional block for converting a digital signal into a high frequency signal is similarly omitted. That is, the components shown in FIG. 1 are described only for main functions in the present invention.

  In the first embodiment, an active radar system is assumed in which a radar device transmits a signal itself to detect a reflected wave from a target. Therefore, the transmission wave can be arbitrarily generated. More specifically, the radar apparatus according to the first embodiment can generate a transmission waveform suitable for target detection and tracking according to the target moving speed. In order to realize this idea, in the first embodiment, a multicarrier signal (waveform) is applied as a transmission wave.

  Next, the operation of the radar apparatus according to the first embodiment having the configuration shown in FIG. 1 will be described in detail. First, the transmission processing procedure will be described. When generating a multicarrier signal that is a transmission waveform, the transmission side generates a multicarrier transmission wave in consideration of which frequency (band) the subcarrier is arranged in accordance with the target moving speed.

  Specifically, first, as shown in FIG. 1, the speed estimation unit 90 analyzes the output signal from the signal synthesis unit 40 obtained in the process of reception processing, thereby estimating the target mobile unit. Get speed information. Furthermore, the speed estimation unit 90 sets the number of subcarriers and the subcarrier interval of the multicarrier transmission wave within the band to be observed based on the estimated speed information.

  Next, the transmission waveform generation unit 80 receives the number of subcarriers and the subcarrier interval corresponding to the target estimated speed information from the speed estimation unit 90, and based on the number of subcarriers and the subcarrier interval, a desired waveform is obtained. A multicarrier transmission wave is generated.

  FIG. 2 is an explanatory diagram illustrating an example of a transmission waveform generated by the transmission waveform generation unit 80 according to Embodiment 1 of the present invention. FIG. 2A in the upper stage is an explanatory diagram showing a basic setting mode, and is hereinafter referred to as a normal correspondence mode. 2B is an explanatory diagram showing a setting mode based on the number of subcarriers set according to the estimated speed information of the high-speed movement target detected by the speed estimation unit 90 and the subcarrier interval. In the following, it will be referred to as a high-speed compatible mode.

  The diagrams shown on the left in each of the normal correspondence mode in FIG. 2 (a) and the high-speed correspondence mode in FIG. 2 (b) show the frequency arrangement of the subcarriers, and the horizontal axis indicates the frequency and the arrow indicates. Each line indicated represents a subcarrier 100. Also, the diagrams shown on the right side of the normal correspondence mode in FIG. 2A and the high-speed correspondence mode in FIG. 2B show the relationship between the pulse length and the data structure with the horizontal axis as time. .

  In the normal correspondence mode shown in FIG. 2A, basically, subcarriers (N) are arranged in the entire observation band. The subcarrier interval is arbitrary, but if it is an OFDM (Orthogonal Frequency Division Multiplexing) signal, the interval satisfies the orthogonal relationship.

  A signal obtained by converting a signal having the frequency arrangement shown on the left side into a time waveform by inverse Fourier transform is shown on the right side. In order to withstand multipath, a part of the waveform in the latter half is added (copied) as a cyclic prefix (CP) to the previous stage. This part is also called a guard interval.

  In this manner, in the normal correspondence mode, the transmission waveform having the pulse length as shown on the right side of FIG. The CP length is set to an appropriate value according to propagation path characteristics such as multipath delay dispersion, and may not be added depending on circumstances.

  In a multicarrier waveform including an OFDM signal, generally, subcarriers are densely arranged and are vulnerable to Doppler shift accompanying target movement. This is because interference between adjacent carriers due to frequency shift occurs.

  Therefore, in the present invention, by setting the number of subcarriers and the subcarrier interval according to the estimated speed information of the high-speed movement target by the speed estimation unit 90, the mode is shifted to the high-speed compatible mode as shown in FIG. Yes. That is, the transmission waveform generation unit 80 shifts from the normal support mode to the high speed support mode based on the number of subcarriers and the subcarrier interval specified based on the estimated speed information detected by the speed estimation unit 90. In addition, a transmission signal (multicarrier transmission wave) in which the number of subcarriers N in the normal correspondence mode is reduced and the interval between adjacent subcarriers is wide is generated.

  This means that when the sampling frequency is constant, the symbol length is shortened when viewed as a time waveform. Thereby, the influence of the Doppler shift can be reduced. When it is desirable that the distance resolution as a radar is constant, a plurality of OFDM symbols are concatenated to make the pulse length uniform.

  In the case of the high-speed correspondence mode shown in FIG. 2B, four symbols are connected to form one pulse. It is generally said that when the Doppler shift amount exceeds 2.5% of the carrier interval, inter-carrier interference cannot be ignored. Therefore, the speed estimation unit 90 can determine the number N of subcarriers so that the carrier interval does not exceed 2.5%. As an example, the speed estimation unit 90 can set the number N of subcarriers in inverse proportion to the target moving speed within a range not exceeding 2.5%.

  Alternatively, it is also effective for the speed estimation unit to prepare a correspondence table between the moving speed and the number of subcarriers in a storage unit (not shown) in advance and to read and set the number N of subcarriers corresponding to the estimated speed information. is there. In this way, when the setting of the number of subcarriers and the subcarrier interval of the transmission waveform is determined by the speed estimation unit 90, a transmission signal is generated by the transmission waveform generation unit 80 and is radiated from the transmission antenna 70 to the space. .

  Next, a reception processing procedure for detecting a target will be described. When the transmission signal generated as described above is emitted from the transmission antenna 70, each element antenna 11 (1) to 11 (K) of the reception antenna 10 includes a reflected wave from the target by the transmission signal. An incident signal is received.

  The received incident signal is input to the demultiplexing unit 20, and frequency-separated in units of subcarriers in the demultiplexers 21 (1) to 21 (K), respectively. In performing this separation processing, each of the duplexers 21 (1) to 21 (K) is based on the number of subcarriers N set in the transmission processing procedure from the speed estimation unit 90 and information on the subcarrier interval. Set internal operation. This specific operation will be described with reference to FIG.

  FIG. 3 is a specific configuration diagram of the duplexer 21 (k) according to Embodiment 1 of the present invention, and shows an example where the transmission waveform is an OFDM signal. Each of the K duplexers 21 (k) (k = 1 to K) includes a series-parallel converter 22, an FFT unit 23, and a discrimination circuit 24.

  The serial-parallel converter 22 rearranges the output signals from the element antenna 11 (k) into N signal groups. Next, an FFT (Fast Fourier Transform) unit 23 separates the N signal groups into subcarriers.

  Here, N represents the number of subcarriers (also referred to as the FFT size or the number of FFT points), and is dynamically controlled based on the estimated speed information by the speed estimation unit 90 described above. Given. Also, the discrimination circuit 24 extracts only subcarriers in which signal components (modulated waves, CW waves, etc.) are actually arranged, corresponding to the subcarrier interval, from among the subcarriers separated from the N signal groups. And output to the signal synthesis unit 40.

  The signal synthesizer 40 receives the subcarriers extracted by the demultiplexers 21 (1) to 21 (K), and the subs of the element antennas 11 (1) to 11 (K) in the same frequency arrangement. The carrier signal is synthesized and output. As a result, signal-to-noise ratio (SNR) can be improved and target detection performance can be improved.

  Specifically, the signal combining unit 40 may operate as so-called maximum ratio combining diversity that performs in-phase combining with a weight corresponding to the amplitude of the output of each element antenna 11 (1) to 11 (K). Thus, based on the signal with improved SNR, the target detection unit 50 performs radar signal processing such as target detection, acquisition, and tracking.

  Next, the series of processes described above will be described using a flowchart. FIG. 4 is a flowchart showing a series of processes of the radar apparatus according to Embodiment 1 of the present invention. First, in step S401, the speed estimation unit 90 dynamically sets the number N of subcarriers and the subcarrier interval according to the estimated speed information estimated for the moving target. As an initial value, the number N of subcarriers set in advance in the normal correspondence mode shown in FIG. 2A can be used.

  Next, in step S402, the transmission waveform generation unit 80 generates a transmission pulse signal according to the number N of subcarriers set by the speed estimation unit 90 and the subcarrier interval (see FIG. 2B). Next, in step S <b> 403, the transmission antenna 70 transmits the transmission pulse signal generated by the transmission waveform generation unit 80.

  Next, in step S404, the receiving antenna 10 receives the reflected wave from the target. Further, the demultiplexing unit 20 receives information on the number of subcarriers N and the subcarrier interval set in the transmission processing procedure from the speed estimation unit 90, and controls the number of FFT points based on the number of subcarriers N. The signal received by the receiving antenna 10 is demultiplexed in units of subcarriers. Further, the demultiplexing unit 20 extracts a subcarrier signal to which a signal component is assigned according to the subcarrier interval.

  Next, in step S405, the signal synthesizer 40 extracts subcarriers to which signal components extracted by the discrimination circuit 24 in the demultiplexer 20 from the received signals demultiplexed in units of subcarriers are assigned. Using the signal, the maximum ratio synthesis of the target signal is performed.

  Next, in step S406, the target detection unit 50 performs radar signal processing such as target detection using the final output signal whose SNR is improved by the signal synthesis unit 40. On the other hand, in step S407, the speed estimation unit 90 estimates the speed of the moving object using the final output signal whose SNR is improved by the signal synthesis unit 40.

  The speed estimation unit 90 sequentially executes this speed estimation and generates estimated speed information. Furthermore, returning to the previous step S401, the speed estimation unit 90 dynamically sets the number N of subcarriers and the subcarrier interval according to the estimated speed information generated in step S407.

  Through such a series of processing, the transmission side sequentially emits the next transmission pulse by generating a transmission waveform by feeding back the number N of subcarriers and the subcarrier interval according to the estimated speed information. On the other hand, on the receiving side, the received signal is demultiplexed and combined using information on the number of subcarriers and the subcarrier interval according to the moving speed to generate a signal with improved SNR. The radar apparatus according to the first embodiment executes such a series of processes periodically or while repeating at a necessary timing.

  As described above, according to the first embodiment, the transmission side generates a transmission waveform adapted to the number of subcarriers according to the moving speed and the subcarrier interval based on the estimated speed information of the moving target. Yes. Furthermore, on the receiving side, the received signal is demultiplexed and combined using information on the number of subcarriers and subcarrier interval according to the moving speed, and target detection is performed based on the signal with improved SNR. The radar signal processing is executed. As a result, it is possible to obtain a radar apparatus that can realize stable tracking and capturing even for a high-speed moving target.

Embodiment 2. FIG.
In the second embodiment, a radar apparatus further provided with a configuration for removing interference waves or multipath waves will be described. FIG. 5 is a configuration diagram of the radar apparatus according to Embodiment 2 of the present invention. The radar apparatus in FIG. 5 includes a reception antenna 10, a demultiplexing unit 20, an interference removal unit 30, a signal synthesis unit 40, a target detection unit 50, an interference detection unit 60, a transmission antenna 70, a transmission waveform generation unit 80, and a speed estimation unit. 90.

  Compared with the configuration of FIG. 1 in the first embodiment, the radar apparatus in the second embodiment is different in that it further includes an interference removing unit 30 and an interference detecting unit 60. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and will be described below with a focus on the interference removal unit 30 and the interference detection unit 60 which are different configurations.

  The transmission processing procedure is the same as in the first embodiment. The main difference is a reception processing procedure for detecting a target, and details will be described below. The signals frequency-separated in units of subcarriers in the demultiplexers 21 (1) to 21 (K) are based on the subcarrier arrangement in the transmission processing procedure, and the interference removing unit 30 is used for subcarrier signals in the band being used. In addition, subcarrier signals in unused bands are output to the interference detector 60, respectively. This specific operation will be described with reference to FIG.

  FIG. 6 is a specific configuration diagram of the duplexer 21 (k) according to Embodiment 2 of the present invention, and shows an example where the transmission waveform is an OFDM signal. Each of the K duplexers 21 (k) (k = 1 to K) includes a series-parallel converter 22, an FFT unit 23, and a discrimination circuit 24.

  The operations of the serial-parallel conversion unit 22 and the FFT unit 23 in FIG. 6 are the same as those in the first embodiment shown in FIG. On the other hand, the discrimination circuit 24 at the final stage converts the N signals frequency-separated into subcarriers corresponding to the subcarrier interval into output signals (a first signal group consisting of M signals) to the interference removing unit 30. And an output signal to the interference detection unit 60 (corresponding to a second signal group consisting of L signals). Here, for N, M, and L, the relationship of N ≧ M + L is established. Further, the arrangement (positions) of M pieces and the number thereof are determined in consideration of propagation path characteristics and the like, and are uniform (equal intervals) within the band, are random, or are concentrated at specific locations. You can do it.

  Next, based on the L subcarrier signals received from the discrimination circuit 24 in the demultiplexing unit 20, the interference detection unit 60 checks the presence or absence of an interference wave that becomes a disturbance. The L subcarrier signals input to the interference detection unit 60 correspond to frequencies in which no signal component is arranged in the transmission waveform generation unit 80, that is, they are not used for transmission waves. Therefore, the presence / absence of an interference wave (jamming wave) can be identified only by determining the reception level of the input subcarrier signal.

  Since a plurality of subcarrier signals are obtained for each element antenna, the interference detection unit 60 can easily improve the identification accuracy by averaging these reception levels.

  In this way, when the interference detection unit 60 detects the presence of an interference wave, the interference removal unit 30 performs a process of removing the interference wave component from the received signal. Already, L subcarrier signals including only interference wave components are demultiplexed for each element antenna. Therefore, the interference removal unit 30 calculates a weighting factor that forms a null (a point with low reception sensitivity) in the interference wave direction using these L subcarrier signals, and acts on each of the M subcarrier signals. By doing so, interference waves can be removed.

  In this way, the plurality of subcarrier signals from which the interference wave components are removed are output from the interference removal unit 30 to the signal synthesis unit 40. Then, the signal combining unit 40 combines the subcarriers in the same frequency arrangement to further improve the SNR (Signal-to-Noise Ratio), so that the target detection unit 50 in the subsequent stage Improve target detection performance.

  Since the interference wave component has already been removed, the signal combining unit 40 may operate as so-called maximum ratio combining diversity that performs in-phase combining with a weight corresponding to the amplitude of each output. In this way, based on the signal from which the interference wave is removed and the SNR is improved, the target detection unit 50 performs radar signal processing such as target detection, acquisition, and tracking.

  Next, the series of processes described above will be described using a flowchart. FIG. 7 is a flowchart showing a series of processes of the radar apparatus according to Embodiment 2 of the present invention. First, in step S701, the speed estimation unit 90 dynamically sets the number N of subcarriers and the subcarrier interval according to the estimated speed information estimated for the moving target. As an initial value, the number N of subcarriers set in advance in the normal correspondence mode shown in FIG. 2A can be used.

  Next, in step S702, the transmission waveform generation unit 80 generates a transmission pulse signal according to the number N of subcarriers and the subcarrier interval set by the speed estimation unit 90 (see FIG. 2B). Next, in step S <b> 703, the transmission antenna 70 transmits the transmission pulse signal generated by the transmission waveform generation unit 80.

  Next, in step S704, the receiving antenna 10 receives the reflected wave from the target. Further, the demultiplexing unit 20 receives the information on the subcarrier number N and the subcarrier interval set in the transmission processing procedure from the speed estimation unit 90, and controls the number of FFT points based on the subcarrier number N. The signal received by the receiving antenna 10 is demultiplexed in units of subcarriers. Then, the demultiplexing unit 20 outputs N signals frequency-separated in units of subcarriers according to the subcarrier interval, and outputs an output signal (M) to the interference removal unit 30 and an output signal to the interference detection unit 60. Discriminate into (L).

  Next, in step S <b> 705, the interference detection unit 60 detects an interference wave using subcarriers (L) on which no signal component is arranged among the demultiplexed subcarriers. When an interference wave is detected by the interference detection unit 60, the interference removal unit 30 uses the subcarrier signal group of the interference wave to generate an interference wave from the subcarriers (M) including the reflected wave from the target. Remove ingredients.

  Thereafter, in step S706, the signal synthesis unit 40 performs a maximum ratio synthesis process of the target signal component between the element antennas. Next, in step S707, the target detection unit 50 performs radar signal processing such as target detection using the final signal output from the signal synthesis unit 40 from which the interference wave is removed and the SNR is improved. Execute.

  On the other hand, in step S708, the speed estimation unit 90 estimates the speed of the moving object using the final signal output from the signal synthesis unit 40 from which the interference wave is removed and the SNR is improved. The speed estimation unit 90 sequentially executes this speed estimation and generates estimated speed information. Furthermore, returning to the previous step S701, the speed estimation unit 90 dynamically sets the number N of subcarriers and the subcarrier interval according to the estimated speed information generated in step S708.

  Through such a series of processing, the transmission side sequentially emits the next transmission pulse by generating a transmission waveform by feeding back the number N of subcarriers and the subcarrier interval according to the estimated speed information. On the other hand, the receiving side uses the information on the number of subcarriers and subcarrier spacing according to the moving speed to perform demultiplexing processing, interference cancellation processing, and combining processing on the received signal to generate a signal with improved SNR. is doing. The radar apparatus according to the second embodiment executes such a series of processes periodically or at a necessary timing.

  As described above, according to the second embodiment, in addition to the effects of the first embodiment, it is possible to have resistance against interference components such as interference waves and multipath waves. That is, the target can be tracked and captured stably even in a harsh environment.

Embodiment 3 FIG.
In the third embodiment, a modified example of the first and second embodiments will be described.
(1) About target speed estimation The target detection unit 50 assumes general radar signal processing, and may include a function of analyzing speed information including the target Doppler frequency. Therefore, in such a case, the speed information obtained by the target detection unit 50 may be fed back to the speed estimation unit 90. Of course, the speed estimation unit 90 may use speed information obtained by other means by referring to the outside.

(2) Transmission waveform FIG. 8 is an explanatory diagram showing an example of a transmission waveform generated by the transmission waveform generation unit according to Embodiment 3 of the present invention. For transmission pulse generation in the high-speed compatible mode, as shown in FIG. 8, the number N of subcarriers is the same as that in the normal compatible mode (that is, the number of FFT points is fixed), and other than the subcarriers in which signal components are actually arranged. It is also possible to assign a zero carrier 103 to which no signal component is arranged.

  Also in this case, the interval between adjacent carriers is widened as in the case of FIG. 2, and it can be expected to obtain Doppler shift resistance. As shown on the right side of FIG. 8, the symbol length in the time domain in this case is the same as in the normal correspondence mode.

(3) Response when target speed estimation is difficult Note that it is difficult to specify the number of subcarriers according to the moving speed because target speed estimation is difficult. Can be taken. In this case, a plurality of subcarrier numbers N and subcarrier intervals are set, transmission pulses corresponding to the subcarriers are generated and sequentially transmitted, and each received pulse signal is processed to obtain the parameter with the best characteristics. It is also possible to perform feedback control such as selection.

  10 receiving antennas, 11, 11 (1) to 11 (K), each element antenna, 20 demultiplexing unit, 21, 21 (1) to 21 (K) demultiplexer, 22 series-parallel conversion unit, 23 FFT unit, 24 Discrimination circuit, 30 interference removal unit, 40 signal synthesis unit, 50 target detection unit, 60 interference detection unit, 70 transmission antenna, 80 transmission waveform generation unit, 90 speed estimation unit.

Claims (7)

A transmission waveform generation unit that generates a multicarrier transmission wave and transmits it via a transmission antenna;
A demultiplexing unit that receives a signal reflected by the multicarrier transmission wave to a target via a reception antenna including a plurality of element antennas, and demultiplexes the reception signal of each element antenna as a subcarrier signal for each subcarrier band;
A signal synthesizer for synthesizing the subcarrier signals of each element antenna demultiplexed by the demultiplexing unit for each subcarrier band for each subcarrier signal of each element antenna in the same frequency arrangement;
A radar apparatus comprising: a target detection unit that detects the target using the signal combined by the signal combining unit;
By analyzing the signal synthesized by the signal synthesis unit, the target moving speed is estimated as estimated speed information, and based on the estimated speed information, the multicarrier transmission wave in the band to be observed is estimated. A speed estimation unit for setting the number of subcarriers and the subcarrier interval;
The transmission waveform generation unit generates a multicarrier transmission wave according to the number of subcarriers and the subcarrier interval set by the speed estimation unit, and transmits the generated multicarrier transmission wave via the transmission antenna. ,
The demultiplexing unit does not arrange the first signal group composed of subcarrier signals in the band in which the subcarriers are arranged and the subcarriers according to the number of subcarriers and the subcarrier interval set by the speed estimation unit. Discriminated into a second signal group consisting of subcarrier signals in the band,
The signal synthesizer receives the first signal group, and with respect to the first signal group, the subcarrier signals of the element antennas demultiplexed for each subcarrier band with respect to the element antennas having the same frequency arrangement. A radar apparatus characterized by combining each subcarrier signal. The radar apparatus according to claim 1, wherein
An interference detection unit that receives the second signal group from the demultiplexing unit and detects an interference wave based on the second signal group;
The first signal group is disposed between the demultiplexing unit and the signal combining unit, receives the first signal group from the demultiplexing unit, and detects an interference wave in the interference detection unit. An interference canceller that suppresses the interference wave with respect to
The signal combining unit receives the first signal group after suppressing the interference wave from the interference removing unit, and with respect to the first signal group, each of the element antennas demultiplexed for each subcarrier band A radar apparatus, wherein a subcarrier signal is synthesized for each subcarrier signal of each element antenna having the same frequency arrangement. The radar apparatus according to claim 1 or 2,
The radar apparatus, wherein the speed estimation unit sets the number of subcarriers so as to be inversely proportional to the estimated speed information. The radar apparatus according to claim 1 or 2,
The speed estimation unit has a correspondence table in which a correspondence relationship between estimated speed information and the number of subcarriers is set in advance, and extracts the number of subcarriers corresponding to the estimated speed information estimated from the correspondence table. Thus, the radar apparatus is characterized in that the number of subcarriers corresponding to the estimated speed information is set. The radar apparatus according to any one of claims 1 to 4,
The speed estimation unit sets the number of subcarriers of a multicarrier transmission wave within a band to be observed as a fixed value, and based on the estimated speed information, the subcarriers that actually arrange signal components A radar apparatus, characterized in that the subcarrier interval is set by allocating zero carriers that do not arrange signal components. The radar apparatus according to any one of claims 1 to 5,
The target detection unit estimates the moving speed of the target from the target Doppler frequency,
The speed estimator uses the moving speed of the target received from the target detector as estimated speed information instead of estimating the estimated speed information by analyzing the signal synthesized by the signal synthesizer. A characteristic radar device. A moving target detection method applied to the radar device according to any one of claims 1 to 6,
A transmission waveform generation step of generating a multicarrier transmission wave and transmitting the transmission wave via a transmission antenna;
A demultiplexing step of receiving a signal reflected by the multicarrier transmission wave to a target via a receiving antenna including a plurality of element antennas, and demultiplexing the reception signal of each element antenna as a subcarrier signal for each subcarrier band;
A signal synthesizing step for synthesizing the subcarrier signals of each element antenna demultiplexed for each subcarrier band by the demultiplexing step for each subcarrier signal of each element antenna in the same frequency arrangement;
A target detection step of detecting the target using the signal synthesized in the signal synthesis step, and
By analyzing the signal synthesized in the signal synthesis step, the target moving speed is estimated as estimated speed information, and based on the estimated speed information, the multicarrier transmission wave in the band to be observed is estimated. A speed estimation step for setting the number of subcarriers and the subcarrier interval;
The transmission waveform generation step generates a multicarrier transmission wave according to the number of subcarriers and the subcarrier interval set in the speed estimation step, and transmits the generated multicarrier transmission wave via the transmission antenna. ,
In the demultiplexing step, a first signal group composed of subcarrier signals in a band in which subcarriers are arranged according to the number of subcarriers and the subcarrier interval set in the speed estimation step, and no subcarriers are arranged. Discriminated into a second signal group consisting of subcarrier signals in the band,
The signal combining step receives the first signal group, and with respect to the first signal group, the subcarrier signals of the element antennas demultiplexed for each subcarrier band with respect to the element antennas having the same frequency arrangement. A moving target detection method characterized by combining each subcarrier signal.

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