一種符號內跳頻∕多頻移鍵解調方法的抗干擾能力之分析

Jamming Immunity of an Intrasymbol FH∕MFSK Demodulation Algorithm

系所名稱：電信工程研究所 學位別：碩士 畢業學年：83年 指導教授：蘇育德 如果接收機的解調方式作適當的設計，符號內跳頻或(所謂怯速跳頻)/多頻移鍵展頻調變，是一種有效的電子反反制(electroniccounter-countermeasures，ECCM)方法。本篇論文就一種簡單且穩定的接收機，即限幅多向度結合器(clippeddiversitycombiner)，對其在多波道單音干擾(multitonejamming)下的系統性能，予以詳盡的分析。本文所考慮的干擾方式包括帶頻式多波道單音干擾(bandmultitonejamming)及獨立式多波道單音干擾(independentmultitonejamming)。我們同時討論相闋的設計問題及參數，諸如限幅器的量化位階(quantizationlevel)、門檻值(threshold)的設定，熱雜訊(thermalnoise)的效應和附加訊息(sideinformation)的利用等。如果給予適當的系統參數，我們發現整個接收機的抗干擾能力有明顯的改善。固定位元率(bitrate)及更實際被採用的固定跳躍率(hoppingrate)，是我們所考慮的兩種模式。如後者說應用時，則沒有所謂最佳向度(optimumdiversity)存在，相較於傳統的單位位元能量(energyperbit)，達到一定錯誤率所需要的單位頻率能量(energyperhop)，應是一種較佳的系統性能量度方式。

Intrasymbol frequency-hopped or fast frequency-hopped (FH)M-ary frequency shifted keyed (MFSK) spread spectrum modulation is an effective electronic counter-countermeasures(ECCM) if the demodulation algorithm is properly designed. Many demodulation algorithms for his class of signals have been proposed and analyzed. This thesis concentrates on the jamming immunity analysis of a simple and robust receiver-theclipped diversity combiner-for intrasymbol FH signals against multitone jamming.We present exact analysis and investigate related design issues and parameters such as quantization level, clipper threshold, the effect of thermal noise, and the use of side information. We demons七rate how significant improvement can be obtained with an appropriate system design. The jamming schemes under consi吐eration include band multitone jamming and independent jamming. We examine the constant bit rate as well as the more practical conssant hopping rate operating scenarios. When the latter option is considered, there is no optimum diversity and the required energy per hop to achievea predetermined bit error rate is a better performance measure than the conventional energy per bit used in a fixed bit rate operation condition.