THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. 2018 Apr.; 29(4), 308 315. http://dx.doi.org/10.5515/kjkiees.2018.29.4.308 ISSN 1226-3133 (Print) ISSN 2288-226X (Online) LFM Radar Implemented in SDR Architecture 윤재혁 유승오 이동주 예성혁 Jae-Hyuk Yoon Seung-Oh Yoo Dong-Ju Lee Sung-Hyuck Ye 요약 S-band. 3.5 GHz LFM(Linear Frequency Modulation) 1 m, 2 km. 150 MHz, 43 dbm, 26 dbi, 8 db, RCS 1 m 2, 2 km SNR 30 db., SDR(Software Defined Radar) LFM. Abstract In this paper, we present the basic design results for high-resolution radar development at S-band frequency that can precisely measure the miss distance between two targets. The basic system requirement is proposed for the design of a 3.5 GHz linear frequency-modulated (LFM) radar with maximum detection distance and distance resolution of 2 km and 1 m, respectively, and the specifications of each module are determined using the radar equation. Our calculations revealed a signal-to-noise ratio 30 db with a bandwidth of 150 MHz, transmission power of 43 dbm for the power amplifier, gain of 26 dbi for the antenna, noise figure of 8 db, and radar cross-section of 1 m 2 at a target distance of 2 km from the radar. Based on the calculation results and the theory and method of LFM radar design, the hardware was designed using software defined radar technology. The results of the subsequent field test are presented that prove that the designed radar system satisfies the requirements. Key words: Linear Frequency Modulation, Range Profile, Doppler Processing, High Resolution, SDR, Radar. 서론.,. LFM(Linear Frequency Modulation) (Agency for Defense Development). 8 (Agency for Defense Development 8 th Institute) Manuscript received December 28, 2017 ; Revised February 6, 2018 ; Accepted April 11, 2018. (ID No. 20171228-127) Corresponding Author: Jae-Hyuk Yoon (e-mail: jh_yoon@add.re.kr, kgandtmac@gmail.com) 308 c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved.
[1] [3]. LFM,., EM,,. FEKO 3D EM, SDR(Software Defined Radar) LFM. 2-1 LFM 개념. LFM 개념및신호처리 /. CPI(Coherent Pulse Interval) FFT(Fast Fourier Transform). 1,. t. f.. (1) LFM, t (i) (Δt) 2. fc, f start, f stop, T. 2 LabVIEW, 3 LFM STFT(Short-Time Fourier Transform) -. (1) (2) 2-2 Range Profile 4. ADC(Analog-Digital Converter) (convolution) FFT 그림 1. LFM Fig. 1. LFM transmitting and receiving concept. 그림 2. LFM Fig. 2. Code of LFM signal generation. 309
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 29, no. 4, Apr. 2018. (a) STFT (a) Before STFT (b) STFT (b) After STFT 그림 3. 150 MHz LFM STFT Fig. 3. STFT result of 150 MHz LFM signal. SDR(Software Defined Radar) [2].. (4), 5., t T (6). T, B,, k (=B/T) [4]. (4) (5) (6) (a) (a) Time domain (b) (b) Frequency domain 그림 4. Fig. 4. Method for pulse compression of LFM. - (compression gain). (side-lobe) SNR( ). 5. (7). (3) (3), c, B. (B),., FPGA, DSP, RTOS(Real-Time OS) 그림 5. Fig. 5. Pulse compression result of pulse and frequency modulation pulse. 310
x, i, c,. 30 m 6. (7) 2-3 Range-Doppler Image.. 7. CPI 2,., CPI 2 FFT., FFT = [5]. 1 Window 3 db main-lobe width, maximum side-lobe, side-lobe roll-off rate Window., maximum side-lobe side-lobe roll-off rate blackman window. 8 표 1. Table 1. Window properties. Window type -3 db Main-lobe width (bins) Window properties -6 db Main-lobe width (bins) Maximum side-lobe (db) Side-lobe roll-off rate (db/decade) Rectangle 0.88 1.21-13 20 Hanning 1.44 2.00-32 60 Hamming 1.30 1.81-43 20 Blackman 1.64 2.30-58 60 Flat top 2.94 3.56-44 20 그림 6. 30 m Fig. 6. Measurement result of 30 m target from radar. 그림 7. Fig. 7. Doppler processing. 그림 8. Blackman - Fig 8. Range-Doppler map according to Blackman window. 311
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 29, no. 4, Apr. 2018. Hanning window,. - y CPI FFT. (8) FFT c,, FFT. 9. 10 - FFT 그림 9. - Fig 9. Range-Doppler processing code.. CPI FFT CPI( )=FFT( ).. Hardware Configuration and Block Diagram of Code 3-1 Hardware Configuration 11. SDR FPGA, 1 m 150 MHz ADC/DAC National Instrumnets USRP-2954R. 2 km SNR 30 db. 43 dbm Duty Cycle 50 % 40 dbm, 52 dbi, 3.5 GHz 8.57 cm, 27 Celsius, 8 db, 160 MHz, RCS(Radar Cross Section) 1 m 2, 2 km 35 db SNR(Signal to Noise Ratio). (AGC: Automatic Gain Control), 34.5 db (8) (a) FFT=16, V=0.12 m/s (b) FFT=64, V=0.03 m/s 그림 10. CPI - Fig. 10. Range-Doppler map according to number of FFT. 그림 11. Fig. 11. Hardware configuration. 312
. 1,. 2. 1 m 150 MHz I Q 150 MS/s ADC ADC 16 bits 600 MB/s. PCI Express PXI Express, PXI Express bus. 3-2 Block Diagram of Code 11 PXI controller 12. ADC, PGA (Programmable Gain Amplifier). I, Q. CFAR(Constant False Alarm Rate), MTI(Moving Target Indicator) - 그림 12. Fig. 12. Block diagram of code... 검증결과 GPS, CADFEKO EM. EM CAD,, pitch, roll, yaw source(lfm ). Linearly spaced discrete points 3.5 3.65 GHz 256 step. PO(Physiscal Optic), λ/25 Mesh. *.ffe guided missile( ) (RCS: Radar Cross Section) (electric-field) (real) (imaginary). phi theta IFT(Inverse Fourier Transform) 3. 13 1 m 2 m. target missile( ),. ATACMS, OO 1/4, 5 m.,, RF, 313
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 29, no. 4, Apr. 2018. Target Missile 시뮬레이션 결과 그림 13. FEKO Fig. 13. FEKO simulation result. 에 대한 교정이 필요하다. 이는 송신 안테나와 수신 안테 나 사이에 누설 전파 값을 기준으로 교정하였다. SDR 장 비 설치 사진은 그림 14에서 확인할 수 있으며 측정 환경 은 그림 15를 통해 확인할 수 있다. 표적탄과 유도탄 사이의 거리는 10 m부터 시작하여 2 m 간격으로 이동시키며 계측하였고 계측 결과는 그림 16 의 그래프를 통해서 확인할 수 있다. 레이다와 두 표적간 의 각도를 일직선으로 위치시켜 측정하였기 때문에 2 m 간격의 유도탄 이동 시 거리 프로파일 상에서 확연히 구 분됨을 확인할 수 있다. 또한, 두 표적간의 거리를 SDR 계측값, 줄자, GPS 측정값 그리고 시뮬레이션 결과를 비 Guided Missile 측정을 위한 장비 배치도 그림 15. Fig. 15. Layout of equipments for measurement. 거리 프로파일 그림 16. SDR Fig. 16. SDR range profile. 교하여 표 2에서 정리하였다. SDR의 LFM 대역폭 150 MHz 로 설정하였을 때 거리 해상도가 약 0.9993 미터가 되며 표 2. 두 표적간의 거리에 대한 FEKO 시뮬레이션과 GPS, 줄자, SDR 계측결과 Table 2. FEKO simulation, GPS, ruler and SDR measurement for the distance between two target. 장비 설치 그림 14. SDR Fig. 14. Installed SDR equipments. 314 Unit (Meter) Ruler meas. GPS meas. FEKO simul. SDR meas. Target missile 118 118.12 117.99 117.92 Guided missile(2 m) 116 116.00 115.99 115.92 Guided missile(4 m) 114 114.01 113.99 113.92 Guided missile(6 m) 112 112.02 111.99 111.92 Guided missile(8 m) 110 110.04 109.99 109.92 Guided missile(10 m) 108 108.18 107.99 107.92
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