THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. 2019 Aug.; 30(8), 607617. http://dx.doi.org/10.5515/kjkiees.2019.30.8.607 ISSN 1226-3133 (Print)ISSN 2288-226X (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-IT1801-06). (Department of Electrical Engineering, Kookmin University) Manuscript received August 1, 2019 ; Revised August 26, 2019 ; Accepted August 26, 2019. (ID No. 20190801-001S) Corresponding Author: Byung-Jun Jang (e-mail: bjjang@kookmin.ac.kr) c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved. 607
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug. 2019. Multiple-Output) DF. LTE 5G DF, Wi-Fi MIMO DF. 2019 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... 2-1 지향성안테나이용 DF, DF DF 608
, 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().,,,.. 180 RF [6]. DF, (trade-off)., DF, DF. 3 Gaussian (1) [7]. exp (1), 609
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug. 2019. (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) 3 90.., (4). log log (4) (5). log (4) (5) (6) (7) DF, 3 db. 2. DF.., 2 2, 4 DF [6]. 360 DF 4 4. 2 / 4 / /. Watson-Watt DF,. [1]. (7) 610
(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
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug. 2019.., 1 3 3 1 +. (8). cos cos,. (8) (9). sin DC. sin (8) (9) (10) (10) sin.,. TACAN(Tactical Air Navigation). TACAN 15 Hz 1 9 135 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 802.11.ad Wi-Fi.,,.. DF [2]. 3-3 스위치만을이용한단일채널 DF 3-2, Buttler Matrix. 612
,. 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), 0 1 1 +250 khz CW CTE [3]. +250 khz CW BLE BLE. RF (2 usec), 2 usec..., DF,. (phase comparison interferometer),. [13].. 배열안테나기반다중채널 DF DF 613
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug. 2019.. 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
(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
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