LFM ground penetrating radar system based on radio frequency direct acquisition

Abstract

The utility model discloses an LFM ground penetrating radar system based on radio frequency direct acquisition. The LFM ground penetrating radar system comprises a radio frequency front end, an RFSOC 47DR radio frequency board card and a high-speed storage board card which are connected in sequence. Compared with a traditional pulse ground penetrating radar, a continuous step frequency ground penetrating radar and a pulse type step frequency ground penetrating radar, the LFM linear frequency modulation ground penetrating radar of the radar system has higher operation speed and more accurate target identification precision, and can fully adapt to accurate detection of a target in a high-speed operation state of the radar.

Description

TECHNICAL FIELD

[0001] The utility model relates to radar detection technology, concretely is a kind of LFM ground penetrating radar system based on radio frequency direct sampling. BACKGROUND

[0002] In prior art, Li Xiaotian of Jilin University and others adopt Vivadi antenna array and vector network analyzer to build a set of full polarization ground penetrating radar system in the detection application of ground penetrating radar to road collapse, drive vector network analyzer and antenna switch driver through PC control unit in the system, and design data processing method suitable for system in system rear end, realize effective detection to collapsed road surface;Miao Yongfei of Harbin Institute of Technology and others realize phase continuous fast frequency hopping using DDS digital chip AD9914, adopt Kintex evaluation board and spartan evaluation board through multi-board joint debugging mode to carry out logic control and processing algorithm execution respectively in hardware system, and obtain good detection result in subsequent highway experiment;Tao Chun Kang of Hangzhou University of Electronic Science and Technology and others adopt discrete component design step frequency ground penetrating radar system, carry out joint acquisition to signal through NI acquisition card and Labview platform, and utilize FPGA programming to acquire and process data, finally display the detection result of target in PC end, and the experimental result realizes the application of step frequency wideband radar in shallow ground detection;Liang Wenjing of Jilin University and others build multiple-input multiple-output polarization step frequency ground penetrating radar system with vector network analyzer as core, realize effective detection to underground target by suppressing noise through superimposed CMP data through detection experiment to typical target body;Peng Jian of China Architecture Eighth Bureau and others design and realize a kind of ultra-wideband step frequency continuous wave ground penetrating radar digital signal receiver with TS201 chip as processing core, DDS chip, AD acquisition board and DSP processing board, which successfully realizes real-time synthetic aperture imaging and target detection to ground surface shallow buried target in 5-20m range within 6m azimuth in front within 5-20m range within 6m azimuth in front under the condition that carrier speed is less than 40km / h. SUMMARY

[0003] The purpose of the present application is to overcome the shortcomings of the prior art and provide a LFM ground penetrating radar system based on radio frequency direct sampling. This radar system has higher operating speed and more accurate target recognition accuracy than traditional pulse ground penetrating radar, continuous step frequency ground penetrating radar and pulse step frequency ground penetrating radar. It can fully adapt to the accurate detection of targets under the condition of high-speed radar operation.

[0004] The technical solution to achieve the purpose of the present application is as follows:

[0005] An LFM ground penetrating radar system based on radio frequency direct sampling, comprising a radio frequency front end, an RFSOC 47DR radio frequency board and a high-speed storage board connected in sequence, wherein:

[0006] The radio frequency front end is provided with a first omnidirectional antenna E1, a second omnidirectional antenna E2, a first 33db gain low noise amplifier LNA and a second 33db gain low noise amplifier LNA, the first omnidirectional antenna E1 and the first 33db gain low noise amplifier LNA are connected in radio frequency by an SMA joint radio frequency connection line to form a first branch connected to the radio frequency board; the second omnidirectional antenna E2 and the second 33db gain low noise amplifier LNA are connected in radio frequency by an SMA joint radio frequency connection line to form a second branch connected to the radio frequency board, the first branch and the second branch are symmetrically arranged, the radio frequency front end is used to amplify the original signal output by the RFSOC 47DR radio frequency board by using a low noise amplifier, and output the amplified signal to a transmitting antenna, and finally radiate outward by the transmitting antenna, when the electromagnetic wave encounters a medium layer with different dielectric constants in the process of electromagnetic wave propagation, the electromagnetic wave will be reflected and refracted, and the receiving antenna will receive the reflected echo of the electromagnetic wave.

[0007] The RFSOC 47DR radio frequency board is the core control part of the entire LFM ground penetrating radar system, and the greatest advantage of the board is that it can solve the problem of heterogeneous radio frequency chips, FPGA chips and data processing chips in the design of traditional radar systems, the model is xczu47dr-ffve-1156-2-e, the RFSOC 47DR radio frequency board is internally provided with a high-speed radio frequency transceiver link, an FPGA logic control unit and a data processing unit, and only bus configuration in the FPGA is needed to realize control of the radio frequency transceiver link and signal processing, so that the RFSOC 47DR radio frequency board runs faster;

[0008] The high-speed storage board has a model ZYNQ UltraScale ZU19EG, and the high-speed storage board and the RFSOC 47DR radio frequency board are connected by an optical fiber copper cable, in the process of system operation, after the RFSOC 47DR radio frequency board completes the reception of radar echo data, the data is sent to the storage board through the optical front interface QSFPAURORA protocol and stored in the storage board.

[0009] The first omnidirectional antenna E1 and the second omnidirectional antenna E2 both adopt Y2-UWBTX-Z16 omnidirectional antennas.

[0010] The system operation process of the technical solution is as follows:

[0011] 1) At the beginning of the system power on, first by ARM core (cortex A-53) by SPI protocol to clock chip LMK01020, LMX2572 write corresponding register value, through 2572 and 01020 two chips produce basic ADC clock, DAC clock, FPGA running basic clock, synchronization signal, thus complete the initialization design of the system;

[0012] 2) After completing the initialization configuration, the transmitting end DAC and the receiving end ADC will simultaneously transmit and receive the LFM signal, and when the data acquisition part of the receiving end completes the collection (buffering) of the LFM signal, it will send the echo data to the storage board card through the QSFP interface to realize data storage, and after completing the storage of a frame of data, it will start the next round of LFM signal transmission and reception;

[0013] 3) After completing all data acquisition, the host computer directly reads out the stored echo data through the Ethernet interface, and performs matched filtering on the echo data and the original LFM signal to realize radar imaging.

[0014] In the technical solution, the carrier-free LFM signal technology does not need to modulate the signal to a specific carrier, but directly generates an electrical signal or other form of signal whose frequency changes linearly with time, and transmits it through an antenna or other device. At the receiving end, the received linear frequency modulation signal is directly processed to extract information using its frequency change with time. The carrier-free LFM signal has a large bandwidth, and the frequency modulation characteristic makes it have good anti-interference performance in a noisy environment. Some interference signals cannot be well matched with the linear frequency modulation signal after matched filtering, and thus are suppressed.

[0015] In the technical solution, the radio frequency direct sampling technology directly samples the radio frequency signal, skipping the mixing and intermediate frequency processing link in the traditional receiver. The radio frequency direct sampling technology uses a high-speed analog-to-digital converter to directly digitize and sample the radio frequency signal at a high sampling rate.

[0016] In the technical solution, the high-performance FPGA (Field Programmable Gate Array) built-in in the RFSOC 47DR radio frequency board can perform real-time and high-speed processing on the digital echo signal collected by the ADC. For the ultra-wideband stepped frequency system, it is necessary to quickly perform operations such as filtering, decimation, etc. on the data collected at different frequency steps. The FPGA can efficiently complete these complex digital signal processing tasks to extract useful information such as the distance and amplitude of the target. A wideband stepped frequency signal is generated through the DAC. In the design, the sampling frequency, pulse repetition period, etc. of the DAC are accurately controlled to complete high-speed frequency sweeping.

[0017] The mixer in the RFSOC is set as a coarse mixer in the technical solution, and a multi-channel synchronization configuration is performed at the PS end, an LFM signal is configured as a pulse width of T=4us, a sampling point number of n=65536, a bandwidth B=1800MHz, a starting frequency f0=200MHz, a cutoff frequency f1=2000MHz, a frequency modulation slope K=B / T according to a sampling rate Fs=4.096GHz of the RFSOC, a total time length of the system for completing emission and reception of one LFM signal is 15us, the received LFM echo signal is sent from the RFSOC radio board card to the high-speed storage through the QSFP interface (AURORA64 / 66) protocol, and in subsequent signal processing, the host computer realizes detection and identification of the underground target by reading the echo signal in the storage and the original LFM signal for pulse compression.

[0018] The technical solution solves the problems that the ground penetrating radar system cannot run at a high speed and the system defects of the UWB LFM signal system ground penetrating radar.

[0019] Compared with the traditional pulse ground penetrating radar, the continuous step frequency ground penetrating radar and the pulsed step frequency ground penetrating radar, the LFM linear frequency modulation ground penetrating radar has a higher running speed and a more accurate target identification accuracy, and can fully adapt to the accurate detection of the target under the condition of the high-speed running of the radar. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The system structure schematic diagram of the embodiment. DETAILED DESCRIPTION

[0021] The content of the application will be further described below in combination with the drawings and the embodiments, but is not limited to the application.

[0022] Embodiment:

[0023] Referring to Figure 1 A LFM ground penetrating radar system based on a radio frequency direct sampling, comprising a radio frequency front end, an RFSOC 47DR radio board card and a high-speed storage board card connected in sequence, wherein:

[0024] The radio frequency front end is provided with a first omnidirectional antenna E1, a second omnidirectional antenna E2, a first 33db gain low noise amplifier LNA and a second 33db gain low noise amplifier LNA, the first omnidirectional antenna E1 and the first 33db gain low noise amplifier LNA are connected to a first branch access radio frequency board card through an SMA joint radio frequency connecting line; the second omnidirectional antenna E2 and the second 33db gain low noise amplifier LNA are connected to a second branch access radio frequency board card through an SMA joint radio frequency connecting line, the first branch and the second branch are symmetrically arranged, the radio frequency front end is used for amplifying the original signal output by the RFSOC 47DR radio frequency board card through a low noise amplifier, and outputting the amplified signal to a transmitting antenna, and finally radiating outward by the transmitting antenna, when the electromagnetic wave encounters a medium layer with different dielectric constants in the process of electromagnetic wave propagation, the electromagnetic wave will be reflected and refracted, and the receiving antenna will receive the reflected echo of the electromagnetic wave.

[0025] The RFSOC 47DR radio frequency board card is the core control part of the entire LFM ground penetrating radar system, and the greatest advantage of the board card is that, compared with the design of a traditional radar system, there is a problem of heterogeneity of radio frequency chips, FPGA chips and data processing chips, the model is xczu47dr-ffve-1156-2-e, the RFSOC 47DR radio frequency board card is internally provided with a high-speed radio frequency transceiver link, an FPGA logic control unit and a data processing unit, and the control of the radio frequency transceiver link and the signal processing can be realized only by bus configuration in the FPGA, so that the RFSOC 47DR radio frequency board card runs faster;

[0026] The model of the high-speed storage board card is ZYNQ UltraScale ZU19EG, the high-speed storage board card is connected with the RFSOC 47DR radio frequency board card through an optical fiber copper cable, and in the process of system operation, after the RFSOC 47DR radio frequency board card completes the reception of radar echo data, the data is sent to the storage board card through an optical front interface QSFPAURORA protocol and stored in the storage board card.

[0027] The first omnidirectional antenna E1 and the second omnidirectional antenna E2 both adopt Y2-UWBTX-Z16 omnidirectional antennas.

[0028] The system operation process of the technical solution is as follows:

[0029] 1) When the system is powered on at the beginning, first, the ARM core (cortex A-53) writes the corresponding register value to the clock chip LMK01020 and LMX2572 through the SPI protocol, generates basic ADC clock, DAC clock, FPGA running basic clock and synchronization signal through the two chips 2572 and 01020, and thus completes the initialization design of the system;

[0030] 2) After the initialization configuration is completed, the DAC of the transmitting end and the ADC of the receiving end will simultaneously transmit and receive the LFM signal. When the data acquisition part of the receiving end completes the collection (buffering) of the LFM signal, the echo data will be sent to the storage board card through the QSFP interface to realize data storage, and after a frame of data is stored, the next round of LFM signal transmission and reception will be started.

[0031] 3) After all the data collection is completed, the host computer directly reads out the stored echo data through the Ethernet network interface, and performs matched filtering on the echo data and the original LFM signal to realize radar imaging.

[0032] The stepped frequency signal system and the RFSOC radio frequency direct sampling hardware used in this example greatly simplify the ground penetrating radar system relative to the traditional ground penetrating radar system, improve the operating efficiency of the radar system, and at the same time, the ground penetrating radar system has the advantages of high flexibility, powerful performance, small size and low power consumption. In the experiment, through free space, sandpit, asphalt pavement and three control test analyses, it is concluded that the ground penetrating radar system can effectively detect both the target in the free space and the underground target.

Claims

1. A radio frequency direct sampling based LFM ground penetrating radar system, characterized in that, It comprises a radio frequency front end, an RFSOC 47DR radio frequency board card and a high-speed storage board card connected in sequence, wherein: The radio frequency front end is provided with a first omnidirectional antenna E1, a second omnidirectional antenna E2, a first 33db gain low noise amplifier LNA and a second 33db gain low noise amplifier LNA, the first omnidirectional antenna E1 and the first 33db gain low noise amplifier LNA are connected in a first branch to access the radio frequency board card through an SMA joint radio frequency connection line; the second omnidirectional antenna E2 and the second 33db gain low noise amplifier LNA are connected in a second branch to access the radio frequency board card through an SMA joint radio frequency connection line, the first branch and the second branch are symmetrically arranged, the radio frequency front end is used to amplify the original signal output by the RFSOC 47DR radio frequency board card through a low noise amplifier, output the amplified signal to a transmitting antenna, and finally radiate outward by the transmitting antenna; when electromagnetic waves encounter medium layers with different dielectric constants during electromagnetic wave propagation, electromagnetic waves are reflected and refracted, and the receiving antenna will receive the reflected echo of electromagnetic waves at that time; The RFSOC 47DR radio frequency board card is of the model xczu47dr-ffve-1156-2-e, and is internally provided with a high-speed radio frequency transceiver link, an FPGA logic control unit and a data processing unit, and only needs to be configured through a bus in the FPGA to realize control of the radio frequency transceiver link and signal processing; The high-speed storage board card is of the model ZYNQ UltraScale ZU19EG, and is connected to the RFSOC 47DR radio frequency board card through an optical fiber copper cable; during system operation, after the RFSOC 47DR radio frequency board card completes the reception of radar echo data, the data is sent to the storage board card through an optical front interface QSFPAURORA protocol and stored in the storage board card.

2. The RF direct sampling based LFM ground penetrating radar system of claim 1, wherein, The first omnidirectional antenna E1 and the second omnidirectional antenna E2 both adopt Y2-UWBTX-Z16 omnidirectional antennas.

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