Radar device

Abstract

To allow frequency characteristics to be estimated with high resolution.SOLUTION: A radar device includes: a signal generator that generates a signal; a carrier generator that can change the frequency of a carrier wave according to time, sets the carrier frequency for each time, and generates a transmission signal to be transmitted from a transmitting antenna; a first propagation path estimator that uses a predetermined receiving side signal and a predetermined transmitting side signal as inputs and estimates a value of a first propagation path of the set frequency for each time; a buffer unit that holds multiple values for each time estimated by the first propagation path estimator; and a second propagation path estimator that acquires the multiple values held in the buffer unit and estimates a value of a second propagation path of wideband frequencies integrated over each time.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a radar device. [Background technology]

[0002] Conventionally, there is a technology relating to a radar system that coexists with communication signals.

[0003] For example, there is a technology in which a carrier frequency is changed from each antenna over time while transmitting (see Non-Patent Document 1). Figure 1 is an image diagram showing the frequency of each pulse from each antenna in the prior art.

[0004] There is also a technology that adds information by allocating bits to transmission frequencies and antennas, thereby achieving communication and radar simultaneously (see Non-Patent Document 2). Figure 2 is an image diagram of bit allocation to antennas in the prior art. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Mulit-Carrier Agile Phased Array Radar(CAESAR), IEEE. Trans. on Signal Processing 2020 [Non-patent document 2] MAJoRCom: A Dual-Function Radar Communication System Using Index Modulation, IEEE Trans. on Signal Processing 2020 Summary of the Invention [Problem to be solved by the invention]

[0006] Coexistence with communication signals requires a wideband signal to be acquired at a high sampling rate, which can be difficult if other users are using part of the band.

[0007] For example, IEEE802.15.3d specifies protocols and bands for communications in the 300 GHz band. Given the relatively wide and numerous bands set within this specification and the propagation characteristics, it is anticipated that the same frequency band will also be used for radar applications. In this case, the following problems are anticipated when applying conventional radar systems:

[0008] Problem (1) is the problem of mutual interference. When using the conventional FM-CW method, a wide band must be secured all at once, and if some of that band is used for communication purposes, interference occurs for both, degrading communication quality and radar performance. Therefore, it is desirable to be able to sense bands not being used for communication at the time of use and divide those bands into smaller sections for use.

[0009] Problem (2) is the problem of acquiring wideband data. Acquiring data from smaller bands requires ultra-wideband filters and ultra-high-rate sampling devices. Although this eliminates the problem of interference with communications, it is unavoidable that interference will occur, and appropriate filtering is required. Therefore, it is desirable to achieve this using standard filters and sampling devices with standard rates.

[0010] Problem (3) is the difficulty of adapting conventional technologies. Conventional methods require frequency switching at the symbol level. Single-carrier modulation requires high-speed switching, while multi-carrier modulation only allows for a discrete spectrum within the band.

[0011] The technology of the present disclosure has been made in consideration of the above circumstances, and aims to provide a radar device that enables high-resolution estimation of frequency characteristics. [Means for solving the problem]

[0012] In order to achieve the above object, the radar device according to the present disclosure includes a signal generator that generates a signal, a carrier generator that is capable of changing the frequency of a carrier wave according to time, sets the carrier frequency for each time, and generates a transmission signal to be transmitted from a transmitting antenna, a first propagation path estimator that receives a predetermined receiving-side signal and a predetermined transmitting-side signal as input and estimates a value of a first propagation path of the frequency for each set time, a buffer unit that stores a plurality of values ​​for each time estimated by the first propagation path estimator, and a second propagation path estimator that acquires the plurality of values ​​stored in the buffer unit and estimates a value of a second propagation path of a wideband frequency integrated for each time. [Effects of the Invention]

[0013] The radar device of the present disclosure enables high-resolution estimation of frequency characteristics. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is an image diagram showing the frequency of each pulse of each antenna in the prior art. [Figure 2] FIG. 2 is an image diagram of bit allocation to antennas in the prior art. [Figure 3] FIG. 3 is an image diagram showing a radar signal and a communication signal according to the method of this embodiment. [Figure 4] FIG. 4 is a block diagram showing the hardware configuration of the radar device. [Figure 5] FIG. 5 is a diagram showing the functional configuration of the radar device of this embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the time characteristics and signal characteristics of a signal according to this embodiment. [Figure 7] FIG. 7 is a flowchart showing the flow of processing by the radar device. [Figure 8] FIG. 8 is a diagram illustrating an example of a preamble sequence. [Figure 9]FIG. 9 shows an example of simultaneous estimation of delay time and Doppler frequency. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, the influence of interference is avoided by transmitting a signal with a constant bandwidth while changing the frequency. Furthermore, by aggregating the received signals, high-resolution estimation of the delay time of the reflected wave is achieved at a low sampling rate. FIG. 3 is an image diagram showing a radar signal and a communication signal according to the method of this embodiment. FIG. 3 shows an example in which the radar signal is transmitted while changing the bandwidth to a frequency band other than the bandwidth of the communication signal, but the transmission mode of the band in this example is not limited to this example.

[0016] Furthermore, the following (1) to (3) are exemplary key points of the configuration according to this embodiment: (1) Determine whether communication is occurring by sensing. (2) Repeatedly transmit a signal sequence and change the carrier frequency. (3) Accumulate received signals and process them all at once.

[0017] Fig. 4 is a block diagram showing the hardware configuration of the radar device 100. As shown in Fig. 4, the radar device 100 has a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a storage 14, an input unit 15, a display unit 16, and a communication interface (I / F) 17. Each component is connected to each other via a bus 19 so as to be able to communicate with each other.

[0018] The CPU 11 is a central processing unit that executes various programs and controls each part. That is, the CPU 11 reads programs from the ROM 12 or the storage 14 and executes the programs using the RAM 13 as a work area. The CPU 11 controls the above-mentioned components and performs various arithmetic processing in accordance with the programs stored in the ROM 12 or the storage 14. In this embodiment, the ROM 12 or the storage 14 stores various programs.

[0019] The ROM 12 stores various programs and various data. The RAM 13 temporarily stores programs or data as a working area. The storage 14 is configured with a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive) and stores various programs including the operating system and various data.

[0020] The input unit 15 includes a pointing device such as a mouse and a keyboard, and is used to input various types of information. The display unit 16 is, for example, a liquid crystal display, and displays various types of information. The display unit 16 may also function as the input unit 15 by employing a touch panel system.

[0021] The communication interface 17 is an interface for communicating with other devices such as terminals, and uses standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark).

[0022] Next, a description will be given of each functional configuration of the radar device 100. Each functional configuration is realized by the CPU 11 reading out a program stored in the ROM 12 or the storage 14, expanding the program in the RAM 13, and executing the program.

[0023] Fig. 5 is a diagram showing the functional configuration of the radar device of this embodiment. As shown in Fig. 5, the radar device 100 includes a receiving antenna 110A, a transmitting antenna 110B, a first calculation unit 112A, a second calculation unit 112B, a sensing unit 114, a frequency control unit 116, a signal generation unit 118, a baseband signal generation unit 120, a divider 122, a buffer unit 124, an estimation control unit 126, and various filter units 130. Note that for ease of explanation, some names may be omitted.

[0024] The filter unit 130 includes a band pass filter (BPF) unit 130A1, a low pass filter (LPF) unit 130B1, and a fast fourier transform (FFT) unit 130C1 on the received signal side, and a BPF unit 130A2, an LPF unit 130B2, and an FFT unit 130C2 on the transmitted signal side. It also includes an inverse fast fourier transform (IFFT) unit 130D for estimation. Since the various filters can be general filters and only need to perform filtering on each signal input, detailed description thereof will be omitted.

[0025] The baseband signal generating unit 120 is an example of a signal generator of the present disclosure. The second calculation unit 112B and the frequency control unit 116 are an example of a carrier generator of the present disclosure. The divider 122 is an example of a first channel estimator of the present disclosure. The sensing unit 114 is an example of a sensor of the present disclosure. The estimation control unit 126 and the IFFT unit 130D are an example of a second channel estimator of the present disclosure.

[0026] The receiving antenna 110A receives a received signal at a predetermined time. The transmitting antenna 110B transmits a transmitted signal at a predetermined time. The signal input to the divider 122 is a signal obtained by applying a Fourier transform to the received signal on the receiving side and the transmitted signal on the transmitting side.

[0027] The sensing unit 114 senses the usage status of the communication band of other users from the received signal, and the frequency band of the communication signal used by the user is determined from the sensing result.

[0028] The frequency control unit 116 can change the frequency of the carrier wave according to time, sets the carrier wave frequency for each time, and outputs the set carrier wave frequency to the signal generation unit 118 to generate a transmission signal to be transmitted from the transmission antenna 110B. Based on the sensing results, the frequency control unit 116 selects a signal other than the communication signal used by the user and determines the carrier wave frequency. The transmission signal is obtained by calculating the carrier wave frequency and baseband signal in the calculation unit 112B.

[0029] The baseband signal generating unit 120 generates a baseband signal and transmits it to the second calculation unit 112B. The signal generated by the baseband signal generating unit 120 is composed of two components: a preamble sequence, which is a signal pattern known to other users, and a data sequence from an arbitrary signal sequence unknown to other users. In the signal, the first T patterns of the preamble sequence are identical to the last T patterns.

[0030] The divider 122 divides the signal on the receiving side for each time by the signal on the transmitting side to estimate the value of the first propagation path for the signal at that time. The buffer unit 124 holds the signal of the estimation result for each time.

[0031] The estimation control unit 126 acquires the number of signals accumulated in the buffer unit 124 for each time period and determines whether a sufficient number of signals has been accumulated to estimate the second propagation path. The accumulation threshold may be determined arbitrarily depending on the communication environment, situation, and standard. If it is determined that a sufficient number of signals has been accumulated, the estimation control unit 126 instructs the IFFT unit 130D to estimate the second propagation path.

[0032] When a sufficient amount of signals has been accumulated in the buffer unit 124, the IFFT unit 130D acquires the multiple values ​​held in the buffer unit 124, integrates each of the values ​​for each time period, and applies an inverse Fourier transform to estimate the value of the signal of the second propagation path of the wideband frequency integrated for each time period.

[0033] 6 is a diagram showing an example of the time characteristics and signal characteristics of a signal according to this embodiment, which illustrates the case where the signal is applied to single carrier transmission.

[0034] In the example shown in (6A), the received signal has time characteristics and frequency characteristics. Frequency control unit 116 outputs frequencies f1 and f2 as carrier frequencies. In the example shown in (6B), the transmitted signal is transmitted at frequency f1 at time T1 and at frequency f2 at time T2, resulting in different bands. In the example shown in (6C), the received signal input to divider 122 is a signal obtained by applying a Fourier transform to the received signal on the receiving side for each time T (T1, T2). In the example shown in (6D), frequency characteristics and time characteristics are estimated as values ​​of the first propagation path for each time. There are time characteristics corresponding to the bands f1 and f2, but it is difficult to distinguish small time differences within a single global band. In the example shown in (6E), data for f1 and f2 are integrated and processed using IFFT. By integrating and processing the data in this way, it is possible to estimate the characteristics of small time differences.

[0035] Next, the operation of the radar device 100 according to the embodiment of the present disclosure will be described. Fig. 7 is a flowchart showing the flow of processing by the radar device 100. This processing is a series of processes up to estimating the second propagation path. The CPU 11 reads a program from the ROM 12 or the storage 14, loads it into the RAM 13, and executes it, thereby performing the series of processes.

[0036] In step S100, the CPU 11, functioning as the estimation control unit 126, acquires the number of signals accumulated in the buffer unit 124 for each time period and determines whether a sufficient number has been accumulated for estimating the second transport path. If it is determined that a sufficient number has been accumulated, the process proceeds to step S114, and if it is determined that a sufficient number has not been accumulated, the process proceeds to step S102.

[0037] In step S102, the CPU 11 sets an observation band of the carrier frequency band as the frequency control unit 116. Also, the CPU 11 acquires the sensing result of the received signal immediately before from the sensing unit 114. The sensing result includes the frequency band used by the user.

[0038] In step S104, the CPU 11, functioning as the frequency control unit 116, determines whether or not the user is using the observation band based on the sensing result. If it is determined that the user is using the observation band, the process returns to step S102 and resets the observation band to an unused band, but if it is determined that the user is not using the observation band, the process proceeds to step S106.

[0039] In step S106, CPU 11 generates a transmission signal by outputting the carrier frequency of the set observation band to signal generating unit 118, and transmits the signal from transmitting antenna 110B.

[0040] In step S108, the CPU 11 receives a reception signal from the reception antenna 110A, filters the signal, and outputs it as a reception-side signal to the divider 122. The CPU 11 also filters the baseband signal of the baseband signal generation unit 120 used to generate the transmission signal, and outputs it as a transmission-side signal to the divider 122.

[0041] In step S110, the CPU 11 functions as the divider 122 to divide the signal on the receiving side for each time by the signal on the transmitting side, thereby estimating the value of the first propagation path for the signal at that time.

[0042] In step S112, the CPU 11 stores the signal of the estimation result for the estimated time in the buffer unit 124. After the processing, the process returns to step S100.

[0043] In step S114, the CPU 11, as the IFFT unit 130D, assumes that a sufficient amount of signal has been accumulated and acquires the multiple values ​​stored in the buffer unit 124, integrates each of the values ​​at each time and applies an inverse Fourier transform to estimate the value of the signal of the second propagation path of the wideband frequency integrated at each time.

[0044] In step S116, the CPU 11 outputs the estimation result of the signal value of the second channel.

[0045] As described above, the radar device according to this embodiment makes it possible to estimate frequency characteristics with high resolution.

[0046] Now, let's take a closer look at the preamble sequence of a signal. Figure 8 shows an example of a preamble sequence. In this example, the preamble sequence has a cyclic structure, and the first T patterns and the last T patterns are identical. This allows the pattern to be included in the FFT target region even in the delayed waves of each received signal.

[0047] Figure 9 shows an example of simultaneous estimation of delay time and Doppler frequency. Time is divided into short time and long time intervals and converted into two dimensions, and delay time and Doppler frequency can be estimated by two-dimensional processing.

[0048] The present disclosure is not limited to the above-described embodiments, and various modifications and applications are possible without departing from the spirit and scope of the present invention. For example, the second channel estimator may estimate the second channel using compressed sensing. Furthermore, the radar device may be mounted on a moving object, and the carrier generator may set the signal band and sampling rate based on the traveling speed.

[0049] In the above embodiments, the processing performed by the CPU after reading the software (program) may be performed by various processors other than the CPU. Examples of such processors include programmable logic devices (PLDs) whose circuit configuration can be changed after fabrication, such as field-programmable gate arrays (FPGAs), and dedicated electrical circuits, such as application-specific integrated circuits (ASICs), which are processors with circuit configurations specifically designed to perform specific processing. The processing may be performed by one of these processors, or by a combination of two or more processors of the same or different types (e.g., multiple FPGAs, or a combination of a CPU and an FPGA). The hardware structure of these processors is, more specifically, an electrical circuit that combines circuit elements such as semiconductor devices.

[0050] In the above embodiment, the program for executing the process is pre-stored (installed) in a ROM or storage device, but the present invention is not limited to this. The program may be provided in a form recorded on a non-transitory recording medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. The program may also be downloaded from an external device via a network.

[0051] [Note] (Appendix 1) a signal generator for generating a signal; a carrier wave generator that can change the frequency of the carrier wave according to time, sets the carrier frequency for each time, and generates a transmission signal to be transmitted from a transmission antenna; a first propagation path estimator that receives a predetermined receiving-side signal and a predetermined transmitting-side signal as input and estimates a value of a first propagation path of a frequency at each set time; a buffer unit that stores a plurality of time values ​​estimated by the first channel estimator; a second channel estimator that acquires the plurality of values ​​stored in the buffer unit and estimates a second channel value of a wideband frequency that is integrated over each time period; A radar device comprising:

[0052] (Appendix 2) The communication device further includes a sensor for sensing the usage status of the communication band of other users, 2. The radar device according to claim 1, wherein the carrier generator determines a carrier frequency based on a sensing result.

[0053] (Appendix 3) The radar device according to claim 1 or 2, wherein the first channel estimator estimates a value of the first channel at the time by applying a Fourier transform to the receiving-side signal and the transmitting-side signal and dividing the receiving-side signal by the transmitting-side signal.

[0054] (Appendix 4) 4. The radar device according to claim 1, wherein the second channel estimator integrates each of the time values ​​stored in the buffer unit and applies an inverse Fourier transform to estimate the value of the second channel.

[0055] (Appendix 5) 5. The radar device according to claim 1, wherein the signal generated by the signal generator is composed of a preamble sequence, which is a signal pattern known to other users, and a data sequence from an arbitrary signal sequence unknown to other users.

[0056] (Appendix 6) 6. The radar device according to claim 5, wherein the first T patterns of the preamble sequence are identical to the last T patterns of the preamble sequence. [Explanation of symbols]

[0057] 100 radar equipment 110A receiving antenna 110B Transmitting Antenna 112A 1st calculation section 112B 2nd calculation section 114 Sensing unit 116 Frequency Control Unit 118 Signal Generator 120 Baseband signal generator 122 Divider 124 Buffer Section 126 Estimation control unit 130 Filter section

Claims

1. a signal generator for generating a signal; a carrier wave generator that can change the frequency of the carrier wave according to time, sets the carrier frequency for each time, and generates a transmission signal to be transmitted from a transmission antenna; a first propagation path estimator that receives a predetermined receiving-side signal and a predetermined transmitting-side signal as input and estimates a value of a first propagation path of a frequency at each set time; a buffer unit that stores a plurality of time values ​​estimated by the first channel estimator; a second channel estimator that acquires the plurality of values ​​stored in the buffer unit and estimates a second channel value of a wide frequency band integrated over time; A radar device comprising:

2. The communication device further includes a sensor for sensing the usage status of the communication band of other users, The radar device according to claim 1 , wherein the carrier wave generator determines a carrier wave frequency based on a sensing result.

3. 2. The radar device according to claim 1, wherein the first propagation path estimator estimates the value of the first propagation path at the time by applying a Fourier transform to the signal on the receiving side and the signal on the transmitting side and dividing the signal on the receiving side by the signal on the transmitting side.

4. 2. The radar device according to claim 1, wherein the second propagation path estimator integrates each of the time values ​​stored in the buffer unit and applies an inverse Fourier transform to estimate the value of the second propagation path.

5. 2. The radar device according to claim 1, wherein the signal generated by said signal generator is composed of two parts: a preamble sequence which is a signal pattern known to other users; and a data sequence from an arbitrary signal sequence which is unknown to other users.

6. 6. The radar device according to claim 5, wherein the first T patterns of the preamble sequence are the same as the last T patterns of the preamble sequence.

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