FPGA, ()., () (ECM: Electronic Countermeasures)., (ECCM: Electronic Counter-Countermeasures).,,. (system) (subsystems),,,,, [1]. (sidelobes),.,.,.. RF

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1 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. 215 Apr.; 26(4), ISSN (Print)ISSN X (Online) FPGA Design and Implementation of FPGA Based Real-Time Adaptive Beamformer for AESA Radar Applications 김동환 김은희 박종헌 김선주 Dong-Hwan KimEun-Hee Kim*Jong-Heon Park**Seon-Joo Kim 요약. FPGA. FPGA. VPX FPGA. QR., FPGA., FPGA. Abstract Adaptive beamforming algorithms have been widely used to remove interference and jamming in the phased array radar system. Advances in the field programmable gate array(fpga) technology now make possible the real time processing of adaptive beamforming (ABF) algorithm. In this paper, the FPGA based real-time implementation method of adaptive beamforming system(beamformer) in the pre-processor module for active electronically scanned array(aesa) radar is proposed. A compact FPGA-based adaptive beamformer is developed using commercial off the shelf(cots) FPGA board with communication via OpenVPX(Virtual Path Cross-connect) backplane. This beamformer comprises a number of high speed complex processing including QR decomposition & back substitution for matrix inversion and complex vector/matrix calculations. The implemented result shows that the adaptive beamforming patterns through FPGA correspond with results of simulation through Matlab. And also confirms the possibility of application in AESA radar due to the real time processing of ABF algorithm through FPGA. Key words: AESA, Pre-Processor Module, Adaptive Beamformer, MVDR, FPGA. 서론,, 3(The 3rd R&D Institute, Agency for Defense Development) * (Department of Defense System Engineering, Sejong University) **(Edeltech) Manuscript received January 15, 215 ; Revised March 11, 215 ; Accepted March 31, 215. (ID No ) Corresponding Author: Dong-Hwan Kim ( kdh812@add.re.kr) 424 c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved.

2 FPGA, ()., () (ECM: Electronic Countermeasures)., (ECCM: Electronic Counter-Countermeasures).,,. (system) (subsystems),,,,, [1]. (sidelobes),.,.,.. RF (subarray) A/D,. A/D. 그림 1. Fig. 1. Subarray architecture for digital beamforming.,. 1.,. (nulls) [2][4].,. (DSP: Digital Signal Processor), FPGA. DSP,, DSP 425

3 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 26, no. 4, Apr (task),., FPGA DSP, DSP DSP. FPGA (systolic array)., FPGA (I/O), DSP,. (COTS) FPGA,,, [5].,.. 설계및 M&S 2-1 적응빔형성기구성 (prototype) (PCU: Processing Control Unit) (PPM: Pre-Processor Module). 2. (MRM: Multichannel Receiver Module) 16( 12 그림 2. Fig. 2. Configuration and functional data flow diagram for ABF. 4) X, 2, ADC/ DDC, 4. 4,. (redundancy), 426

4 FPGA,. [5]. 2-2 적응빔형성알고리즘, [6]. LCMV (Linearly Constrained Minimum Variance),.,.. min, subject to (1) w, R x, C, g [7]. (Lagrange multiplier) w LCMV. (2) (2) C v( ), v( ). ( ) = sin sin (3) d,, λ. g 1(unity), (main beam),. (C=v( ), g=1) MVDR(Minimum Variance Distortionless Response). (2), w MVDR [8]. (4) w MVDR R x.,., QRD(QR Decomposition) - RLS(Recursive Least Squares) [9]. 2-3 적응빔형성 M&S 2-2 FPGA, FPGA 부배열모델링 5 X (AESA), 12 ADC DDC. 24(Az) 21(El), 54, 6, 7 4(Az) 3(El) (4) 427

5 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 26, no. 4, Apr λ/ 시뮬레이션결과 matlab. (Az), (El) 2, 3, (Az, El)=(, ) (jammer), (c), (d) (a), (b), (, ) , 4 (, ). 4 (, ).. 2 MHz (LFM) Beam Pattern 1 8 Beam Pattern Elevation(deg) Elevation(deg) -1-1 Azimuth(deg) (a) (3) (a) DBF pattern(3d) Azimuth(deg) (b) (2) (b) DBF pattern(2d) Beam Pattern 1 8 Beam Pattern Elevation(deg) Elevation(deg) Azimuth(deg) (c) (3) (c) ABF pattern(3d) 5 1 그림 3. (a), (b) (c), (d) Fig. 3. DBF (a), (b) and ABF (c), (d) patterns Azimuth(deg) (d) (2) (d) ABF pattern(2d) 428

6 FPGA -2 Elevation pattern -2 DBF+PC ABF+PC -4-4 Gain(dB) Elevation(deg) Gain(dB) Azimuth pattern Azimuth(deg) 그림 4. ()/() Fig. 4. Elevation pattern(top) and azimuth pattern(bottom) of DBF and ABF. 그림 6. Fig. 6. Results of beamforming and pulse compression. Real. JNR(Jammer to Noise Ratio) SNR (Signal to Noise Ratio) 4 db 2 db. 6. (correlation),.. FPGA 구현및결과 1.5 x 14 input signal 그림 5. real Fig. 5. Input real signal waveform for pulse compression., 1 usec,, (3, 3 ), 5. 5 그림 7. FPGA Fig. 7. Configuration of COTS FPGA board for ABF implementation. 429

7 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 26, no. 4, Apr 하드웨어구성 7 Mercury COTS FPGA. Xilinx FPGA XC6VLX24T-2 3, FPGA. 15, LUTS 14 Mbit RAM 768 DSP 48E1 Slices 3-2 FPGA 기능블록구성 FPGA,,,,,,. FPGA 가중치연산블록 training QRD. QRD Givens rotations McWhirter [1],[11] 그림 Fig. 9. Block diagram of systolic array for 4 4 matrix inversion (5) (6) 그림 8. FPGA Fig. 8. Block diagram of FPGA s functional configuration. 1 FPGA. X-node Y-node 66 clock latency, X-node 54 clock 1, Y- node latency 13 clock, Throughput 1/clock, 1 Y- node 54 clock 41(54-13) Y-node. X-node Y-node

8 FPGA 그림 1. FPGA Fig. 1. Conceptual architecture of FPGA for weight calculation. 12 training 1(12 1 ) 5 FPGA, 2 MHz 1 usec (42 usec ), FPGA 77 %. 12 FPGA 적응빔형성블록 2-3 matlab 13. matlab, FPGA. FPGA 펄스압축블록, LFM. FFT zero padding FFT, IFFT. 14. 그림 11. X () Y () Fig. 11. Architecture of X-node(top) and Y-node(bottom). FFT IP LogiCORE IP Fast Fourier Transform v8., FFT 5122,48 431

9 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 26, no. 4, Apr 그림 12. Fig. 12. Flow chart and runtime for weight calculation., 32 bit single precision. 2 MHz, latency 17 usec, FPGA 38 %., FPGA, 16 FPGA.. 결론, COTS FPGA. MVDR, 그림 13. () FPGA() Fig. 13. Adaptive beamforming pattern using matlab(top) and FPGA(bottom). 그림 14. Fig. 14. Block diagram of pulse compression. QRD-RLS. FPGA, 1 usec (42 usec ),. FPGA 432

10 FPGA References 그림 15. FPGA Fig. 15. FPGA flow diagram for pulse compression. 그림 16. Fig. 16. Runtime for pulse compression.., (),. FPGA. [1] Merrill I. Skolnik, RADAR Handbook, Third Edition, Mc- Graw-Hill, pp , 28. [2] H. Steyskal, R. A. Shore, and R. L. Haupt, "Methods for null control and their effects on the radiation pattern", IEEE Trans. Antennas and Propagation, vol. AP-34, no. 3, pp , Mar [3] W. F. Gabriel, "Adaptive processing array systems", Proc. of the IEEE, vol. 8, no. 1, pp , Jan [4] S. P. Applebaum, "Adaptive arrays", IEEE Trans. Antennas and Propagation, vol. AP-24, no. 5, pp , Sep [5],,,, " ",, 25(2), pp , [6] Barry D. Van Veen, Kevin M. Buckley, "Beamforming: A versatile approack to spatial filtering", IEEE ASSP Magazine, vol. 5, no. 2, pp. 4-24, Apr [7] Otis Lamont Frost, "An algorithm for linearly constrained adaptive array processing", Proceedings of the IEEE, vol. 6, no. 8, pp , Aug [8] William L. Melvin, James A. Scheer(Editors), Principles of Modern Radar, Advanced Techniques, SciTech Publishing, pp , 213. [9] Deepak Boppana, Kully Dhanoa, and Jesse Kempa, "FP- GA based embedded processing architecture for the QRD- RLS algorithm", 12 th Annual IEEE Symposium on Field- Programmable Custom Computing Machines, pp , Apr. 24. [1] J. G. McWhirter, "Systolic array for recursive least squares by inverse iterations", Workshop on VLSI signal processing, pp , Oct [11],,, " CO- RDIC / Extended QRD-RLS ",, 47(6), pp ,

11 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 26, no. 4, Apr : ( ) 27 2: ( ) 27 2: [ 주관심분야 ],, Adaptive Filter 199 3: () 2 1: 2 8: 26 12: () 27 3: () [ 주관심분야 ] ASIC, DSP Programming, : () 24 8: () 27 1: LIG ISR 213 9: [ 주관심분야 ], : ( ) : [ 주관심분야 ],, 434