전자공학회논문지 (Journal of the Institute of Electronics and Information Engineers)

  • 제52권1호
  • /
  • Pages.7-16
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  • 2015
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  • 2287-5026(pISSN)
  • /
  • 2288-159X(eISSN)
대한전자공학회 (The Institute of Electronics and Information Engineers)
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중첩 상승여현 펄스 정형 OQ2PSK 변조

OQ2PSK Modulation with Overlapped Raised-Cosine Pulse Shaping

  • 전상엽 (한국외국어대학교 정보통신공학과) ;
  • 정재경 (한국외국어대학교 정보통신공학과) ;
  • 김명진 (한국외국어대학교 정보통신공학과)
  • Jeon, Sang Yeop (Department of Information and Communications Engineering, Hankuk University of Foreign Studies) ;
  • Chung, Jae-Kyung (Department of Information and Communications Engineering, Hankuk University of Foreign Studies) ;
  • Kim, Myoung Jin (Department of Information and Communications Engineering, Hankuk University of Foreign Studies)
  • 투고 : 2014.09.23
  • 심사 : 2014.12.29
  • 발행 : 2015.01.25
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초록

MSK보다 스펙트럼의 부엽 억제 특성이 우수한 GMSK를 직교 다중화한 quadrature multiplexed GMSK (QM-GMSK)는 quadrature-quadrature PSK($Q^2PSK$)나 quadrature MSK(QMSK)에 비해 보다 주엽의 폭은 다소 넓지만 부엽이 크게 억제되므로 실제 스펙트럼 효율이 상대적으로 더 높다. QM-GMSK에서 기저대역 기본 펄스를 반파장 정현파의 제곱으로 근사화시키면 QM-GMSK 변조에서 필요한 가우시안 저역통과필터(GLPF)를 사용하지 않고 송신기를 구현할 수 있어서 구조가 간단해지는데, 이것이 offset-$Q^2PSK$($OQ^2PSK$)이다. $OQ^2PSK$는 별도의 필터 사용이 요구되지 않으면서 QM-GMSK와 유사한 스펙트럼 특성을 갖는 장점이 있다. 본 논문에서는 $OQ^2PSK$에서 심볼 길이보다 긴 RC(raised-cosine) 또는 SRC(squared raised-cosine) 펄스를 사용하여 중첩 펄스정형함으로써 $OQ^2PSK$보다 스펙트럼 특성을 개선시킨 기법을 제안한다. 제안된 방식을 사용하면 더욱 부엽의 크기가 억제된 스펙트럼 특성을 얻을 수 있으면서 비트오율 성능이 $OQ^2PSK$와 대등한 결과가 얻어지는 것을 확인하였다.

The transmitter of quadrature multiplexed GMSK (QM-GMSK) is composed of two quadrature multiplexed GMSK modulators. QM-GMSK has a slightly increased spectrum main lobe compared with $Q^2PSK$ or QMSK, but it has highly suppressed side lobes. As a result, practical spectrum efficiency of QM-GMSK is achieved. By replacing the baseband elementary pulses of QM-GMSK with their approximate, the squared sinusoid of half-period, offset-$Q^2PSK$($OQ^2PSK$) is obtained. The $OQ^2PSK$ signal has similar spectral properties to QM-GMSK. The transmitter of $OQ^2PSK$ can be simply implemented without the Gaussian lowpass filter, which is required in QM-GMSK transmitter. In this paper, we propose an overlapped pulse shaping in $OQ^2PSK$ with RC(raised-cosine) or SRC(squared raised-cosine) pulses of length longer than the symbol period. Power spectrum of the proposed modulation scheme exhibits further suppressed side lobes, hence enhanced spectrum efficiency is obtained. Simulation results indicate that BER performance of the proposed scheme is comparable to that of $OQ^2PSK$.

키워드

참고문헌

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