THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE Aug.; 30(8),

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1 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE Aug.; 30(8), ISSN (Print)ISSN X (Online) Direction Finding Technology: Tutorial, Review, and Research Prospects 장병준 Byung-Jun Jang 요약.. MIMO, (Bluetooth) IoT.,,,.,. Abstract Direction finding is a traditional technique that was initially used in radio surveillance. Since its inception, antenna-based direction finding technology has become the core technology in various fields, such as radar(to find the direction of the target) and mobile communication(where MIMO-based multi-antennas are used). Moreover, use of the direction finding technology in the field of IoT, such as in Bluetooth, is increasing. Thus, the importance of direction finding technology is growing in various fields. However, it continues to be treated as a sub-technology of radio surveillance, radar, and wireless communication. The aim of this paper is to help readers systematically understand direction finding technology. Accordingly, a systematic classification and analysis of each characteristic of direction finding technology, along with recent research and development trends for it, are discussed in the paper. Key words: Direction Finding, Angle of Arrival, Radar, MIMO, Beamforming, Localization. 서론 (direction finding: DF),,, [1].,,,, DF., MIMO(Multiple-Input 2019 (SRFC-IT ). (Department of Electrical Engineering, Kookmin University) Manuscript received August 1, 2019 ; Revised August 26, 2019 ; Accepted August 26, (ID No S) Corresponding Author: Byung-Jun Jang ( bjjang@kookmin.ac.kr) c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved. 607

2 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug Multiple-Output) DF. LTE 5G DF, Wi-Fi MIMO DF Bluetooth 5.1 DF DF [2][4]. DF, DF,,. DF [5]. DF, DF. DF DF. DF (active) (passive).,. (passive) DF. DF DF DF. DF DF. DF 1 DF. DF. DF 표 1. Table 1. Classification of direction finding technologies. DF based on antenna directivity DF based on array antenna Single channel Multiple channel Technology - Directional antenna maximum-signal DF - Monopulse DF - Pseudo-doppler DF - Beam-switching array - Time modulated array (TMA) - Phase comparison interferometer - Classical DF - Subspace DF - Neural network, AI based DF. DF. DF., DF. 1 DF,.,.. 안테나지향성기반 DF 지향성안테나이용 DF, DF DF 608

3 , DF., 360 DF.. DF DF.,..,. 1 DF. [1],[3]. 2-2 모노펄스기반 DF DF. DF DF. 그림 1. Fig. 1. Maximum-signal direction finding based on directional antenna. 그림 2. Fig. 2. Monopulse direction finding. DF 2. left right, Sum() Delta().,,, RF [6]. DF, (trade-off)., DF, DF. 3 Gaussian (1) [7]. exp (1), 609

4 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug (5) R. (5) (4) LUT(Look Up Table), LUT. (5) 3 db (relative sensitivity) (5) (6) (7). 그림 3. Gaussian Fig. 3. The amplitude comparison of two Gaussian beams. (6) 3 db, K., (2) (3). exp exp (2) (3) (squint angle) , (4). log log (4) (5). log (4) (5) (6) (7) DF, 3 db. 2. DF.., 2 2, 4 DF [6]. 360 DF / 4 / /. Watson-Watt DF,. [1]. (7) 610

5 (a) DF (a) Mulitple channel DF 그림 4. Watson-Watt Fig. 4. Watson-Watt monopulse direction finding.. 배열안테나기반단일채널 DF DF. DF.., (array factor: AF). AF DF. DF 5(a), 5(b). (local oscillator),., [1]., DF,,,,. DF DF DF [2],[3],[9][11]. (b) DF (b) Single channel DF 그림 5. DF Fig. 5. Direction finding based on array antenna. 3-1 단일채널기반 Psuedo-Doppler DF Psuedo-doppler DF. 6 CW(Continuous Wave). 그림 6. Psuedo-Doppler Fig. 6. Principle of psuedo-doppler direction finding. 611

6 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug , (8). cos cos,. (8) (9). sin DC. sin (8) (9) (10) (10) sin.,. TACAN(Tactical Air Navigation). TACAN 15 Hz Hz. TACAN [8]. 3-2 빔스위칭이용 DF 5(b) RF. RF 그림 7. Fig. 7. Direction finding of multiple beam switching antenna. 2 SPDT(Single Pole Double Throw), M SPMT(SIngle Pole Multiple Throw). RF,. Beam switching array(bsa), 7. Buttler Matrix [9] SPMT. Buttler Matrix [10],,. 5G 60 GHz IEEE ad Wi-Fi.,,.. DF [2]. 3-3 스위치만을이용한단일채널 DF 3-2, Buttler Matrix. 612

7 ,. GHz. GHz DF. DF 8 2 SPDT DF Time-modulated array(tma). TMA SPDT ( ) (sidelobe), (mainlobe)., TMA Fourier Sum(), Delta () DF Sum() Delta() FFT DF [11]. TMA [12]. DF 2019 BLE 5.1 DF. BLE 5.1 DF 9 Bluetooth CTE(Constant Tone Extension) CW. Bluetooth 그림 8. TMA Fig. 8. Principle of time-modulated array direction finding. 그림 9. Bluetooth 5.1 Fig. 9. Principle of Bluetooth 5.1 direction finding. ±250 khz FSK(Frequency Shift Keying), khz CW CTE [3] khz CW BLE BLE. RF (2 usec), 2 usec..., DF,. (phase comparison interferometer),. [13].. 배열안테나기반다중채널 DF DF 613

8 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug DF. DF, DF. DF 5(a). DF, DF,. DF 10. DF Subspace MUSIC, ESPRIT, AI [14],[15]. DF, IC., DF DF., 5G MIMO. DF 11 [14]. ( ), ( ). 그림 10. Fig. 10. Classification of mutlti-channel direction finding. 그림 11. M Fig. 11. M-element array antennawith arriving signals. D AWGN (11). (11), (12). (12), AWGN.,. ( ). (13),. Ergodic. 614

9 (14) uncorrelated,. Pseudospectrum. Barlett AoA, Pseudospectrum (15). (15) (15) (16) Fourier. sin sin (16) minimum variance distortionless response(mvdr). Maximum likelihood,. (signalto-interference ratio: SIR).,. (17). (18) MVDR 그림 12. DF Fig. 12. Performance comparison between two direction finding algorithms. MATLAB. 6 ( ) 2 ( ) ±. 0.1( ), Barlett AoA MVDR 12. DF.. AI DF. AI, DF AI [15]. AI DF.. 결론 615

10 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug ,.,. Wi-Fi, Bluetooth,.,. References [1] G. Kratschmer "Introduction into theory of direction finding," in Radiomonitoring & Radiolocation 2010/2011, Munich, Rhode & Schwarz, [2] E. Rastorgueva-Foi, M. Costa, M. Koivisto, K. Leppanen, and M. Valkama, "Dynamic beam selection for beam- RSRP based direction finding in mmw 5G networks," in 2018 International Conference on Indoor Positioning and Indoor Navigation(IPIN), Nantes, 2018, pp [3] N. B. Suryavanshi, K. V. Reddy, and V. R. Chandrika, "Direction finding capability in bluetooth 5.1 standard," in 2019 International Conference on Ubiquitous Communications and Network Computing, 2019, pp [4] J. W. Yu, "MIMO/3-D beamforming antenna", The Proceeding of the Korean Institute of Electromagnetic Engineering and Science, Nov. 2014, vol. 25, no. 6, pp [5] M. S. Lee, I. S. Na, J. H. Go, and J. O. Park, "Development trends of electromagnetic wave localization technology", The Proceeding of the Korean Institute of Electromagnetic Engineering and Science, Nov. 2016, vol. 27, no. 6, pp [6] D. J. An, J. H. Lee, "Performance of amplitude comparison monopulse radar", The Journal of Korean Institute of Electromagnetic Engineering and Science, vol. 29, no. 12, pp , Dec [7] T. B. Le, J. Vesely, "A beam coding technique for direction finding of moving object," in th International Conference Radioelektronika, Pardubice, 2019, pp [8] S. J. Park, K. H. Koo, "Design and implementation of mobile electronically scanned TACAN antenna", The Journal of Korean Institute of Electromagnetic Engineering and Science, vol. 26, no. 1, pp , Jan [9] S. Park, S. Kim, J. Sohn, and H. Shin, "Design of a 28 GHz switched beamforming antenna system based on 4 4 Butler matrix", The Journal of Korean Institute of Electromagnetic Engineering and Science, vol. 26, no. 10, pp , Oct [10] J. S. Song, S. Seo, H. J. Kim, S. C. Cho, and J. H. Oh, "Design of beamforming scheme using single RF chain based on SPA antenna", The Journal of Korean Institute of Communications and Information Sciences, vol. 41, no. 6, pp , Jun [11] S. Lee, H. Yoon, H. Choo, and B. J. Jang, "Implementation of real-time direction finding system using timemodulated array with two antenna elements and one USRP", The Journal of Korean Institute of Electromagnetic Engineering and Science, vol. 28, no. 4, pp , Apr [12] D. Masotti, A. Costanzo, M. Del Prete, and V. Rizzoli, "Time-modulation of linear arrays for real-time reconfigurable wireless power transmission," in IEEE Transactions on Microwave Theory and Techniques, vol. 64, no. 2, pp , Feb [13] M. H. Cha, "Accuracy analysis of 2-D direction finding based on phase comparison", The Journal of Korean Institute of Electromagnetic Engineering and Science, vol. 28, no. 8, pp , Aug [14] F. Gross, Smart Antennas for Wireless Communications with MATLAB, New York, NY, McGraw-Hill, [15] S. Abeywickrama, L. Jayasinghe, H. Fu, S. Nissanka, and C. Yuen, "RF-based direction finding of UAVs using DNN," in 2018 IEEE International Conference on Communication Systems(ICCS), Chengdu, 2018, pp

11 [/] : ( ) : ( ) : ( ) : LG() : : : (CP) : [ 주관심분야 ] RF,, 617