Journal of Navigation and Port Research (한국항해항만학회지)

Korean Institute of Navigation and Port Research (한국항해항만학회)
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Study on Compensation Method of Anisotropic H-field Antenna

Loran H-field 안테나의 지향성 보상 기법 연구

  • Park, Sul-Gee (Korea Research Institute of Ships and Ocean Engineering) ;
  • Son, Pyo-Woong (Korea Research Institute of Ships and Ocean Engineering)
  • 박슬기 (한국해양과학기술원 부설 선박해양플랜트연구소) ;
  • 손표웅 (한국해양과학기술원 부설 선박해양플랜트연구소)
  • Received : 2019.05.13
  • Accepted : 2019.06.26
  • Published : 2019.06.30
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Abstract

Although the needs for providing resilient PNT information are increasing, threats due to the intentional RFI or space weather change are challenging to resolve. eLoran, which is a terrestrial navigation system that use a high-power signal is considered as a best back-up navigation system. Depending on the user's environment in the eLoran system, the user may use one of E-field or H-field antennas. H-field antenna, which has no restriction on setting stable ground and is relatively resistant to noise of general electronic equipment, is composed of two loops, and shows anisotropic gain pattern due to the different measurement at the two loops. Therefore, the H-field antenna's phase estimation value of signal varies depending on its direction even at the static environment. The error due to the direction of the signal should be eliminated if the user want to estimate the own position more precisely. In this paper, a method to compensate the error according to the geometric distribution between the H-field antenna and the transmitting station is proposed. A model was developed to compensate the directional error of H-field antenna based on the signal generated from the eLoran signal simulator. The model is then used to the survey measurement performed in the land area and verify its performance.

위성항법시스템의 안정적인 항법정보 제공에 대한 요구사항은 점차 증가하고 있지만, 의도적인 전파교란 및 자연환경 변화에 의한 성능 저하는 현실적으로 완벽히 해결하기 어렵다. 이러한 위성항법 시스템의 단점을 보완하기 위한 대표적인 항법시스템으로 고출력 신호를 이용한 지상파항법시스템인 eLoran이 주목받고 있고, 의도적인 전파교란에 강인하다는 장점이 있다. 사용자는 eLoran 시스템에서 사용 환경에 따라 E-field 또는 H-field 수신 안테나 중에서 적합한 것을 사용한다. 안정적인 접지 연결에 대한 제약이 없고, 상대적으로 주변 전자장비의 잡음에 강인한 H-field 안테나는 두 개의 루프로 구성되어 루프 간의 위상과 이득차이로 인해 등방성을 가지지 못한다. 그러므로 H-field 안테나는 정지위치에서도 수신한 신호의 방향에 따라 측정치의 변화가 발생하는 단점이 있고, 보다 정확한 측위 결과를 위해서는 신호의 방향에 따른 오차를 제거해야한다. 본 논문에서는 H-field 안테나와 송신국간의 기하학적 방향에 따른 오차를 제거하기 위한 지향성 보상기법을 제안하였다. eLoran 모의 신호생성기를 활용하여 오차를 분석하고 모델링하여 보상하는 기법을 개발하였고, 시뮬레이션과 차량실험을 통해 제안한 기법의 성능을 검증하였다.

Keywords

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Fig. 1 The gain pattern of the H-field loop antenna

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Fig. 2 Simulation configuration

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Fig. 3 TOA-based Loran ASF of Case 1 (a) 9930M (b) 9930W (c) 7430M (d) 7430X (e) 7430Y

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Fig. 4 TOA-based Loran ASF sorted by H-field antenna’s heading (a) 9930M (b) 9930W (c) 7430M (d) 7430X (e) 7430Y

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Fig. 5 TOA-based Loran ASF of Case 1 with corrected estimated directional ASF of H-field antenna (a) 9930M (b) 9930W (c) 7430M (d) 7430X (e) 7430Y

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Fig. 6 TOA-based Loran ASF of Case 2 (a) 9930M (b) 9930W (c) 7430M (d) 7430X (e) 7430Y

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Fig. 7 TOA-based Loran ASF of Case 2 with corrected directional ASF modeling (a) 9930M (b) 9930W (c) 7430M (d) 7430X (e) 7430Y

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Fig. 8 TOA-based Loran ASF over heading(blue) and the directional ASF modeling(red) (a) 9930M (b) 9930W (c) 7430M (d) 7430X (e) 7430Y

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Photo 1 Experimental setup for field test

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Fig. 9 The trajectory of the field test using ground vehicle

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Fig. 10 TDOA-based Loran ASF of field test (a)7430M-9930M (b)7430M-9930W (c)7430M-7430X (d)7430M-7430Y (e)7430X-7430Y (f)7430X-9930M (g)7430X-9930W (h)7430Y-9930M (i)7430Y-9930W (j)9930M-9930W

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Fig. 11 TDOA-based Loran ASF sorted by H-field antenna’s heading(blue) and directional ASF(red) (a)7430M-9930M (b)7430M-9930W (c)7430M-7430X (d)7430M-7430Y (e)7430X-7430Y (f)7430X-9930M (g)7430X-9930W (h)7430Y-9930M (i)7430Y-9930W (j)9930M-9930W

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Fig. 12 TDOA-based Loran ASF of field test with corrected directional ASF modeling (a)7430M-9930M (b)7430M-9930W (c)7430M-7430X (d)7430M-7430Y (e)7430X-7430Y (f)7430X-9930M (g)7430X-9930W (h)7430Y-9930M (i)7430Y-9930W (j)9930M-9930W

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Fig. 13 The horizontal error of TDOA-based Positioning with directional ASF correction(red) and without directional ASF correction(blue)

Table 1 The parameter settings for the H-field antenna’s directional characteristics

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Table 2 Improvement of TDOA-based directional ASF correction

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