具有處理能力的衛星轉頻器之架構與效能

Abstract

本論文探討具抗干擾(anti-jam, AJ)能力的衛星轉頻器之架構及效能。我們所考慮的上傳鏈路(uplink)除有加成性的白高斯背景雜訊(AWGN)另有惡意的干擾，即所謂的部份頻寬雜訊干擾(partial-band noise jamming)。我們發現具有處理(processing)或再生(regenerative)功能之衛星轉頻器可以提供強大的抗干擾能力。為強化抗干擾能力我們使用了慢跳頻式的差分相位相移鍵信號並加上了渦輪編碼。

經過差分相位相移鍵調變的渦輪編碼信號可視為等同於一個串聯編碼架構，其中內部碼(inner code)為碼率為一的特殊迴旋碼而外部碼(outer code)則為渦輪碼。基於此種等效模式，我們提出一種迭代的解碼結構並且藉由數值的模擬檢驗此種不同於以往的解碼排程的效率。我們更進一步使用塊間重排(IBP)的渦輪碼使得在解碼時可藉由迭代交換不同區塊之間的解碼訊息以有效的更正錯誤。實驗數值證實這種改錯碼能夠在跳頻速率很低時仍維持相當良好的性能。另一方面，傳統的渦輪碼需有較高的跳頻速率方能滿足系統的抗干擾能力性能要求。

We consider a secure satellite link in which a slow frequency-hopped (FH), turbo-coded DPSK signal is used in the uplink. Several detector structures are proposed and both processing and bent-pipe transponders are considered although our emphasis is on the former class. Regarding the turbo-coded DPSK signal as an equivalent serially concatenated coding scheme with the inner code being the rate-1 DPSK encoder, we propose an iterative decoder architecture and examine the effectiveness of different decoding schedules. We also consider two interleaver structures for the corresponding turbo codes. The first one is a conventional block oriented interleaver while the second one is the so-called inter-block permutation (IBP) interleaver. Numerical results indicate that sufficient AJ margin is achievable with the proposed signal waveform and decoding scheme. Furthermore, the IBP-interleaved turbo coded system offer additional tradeoff between hopping rate and performance. It offers sufficient AJ capability even the FH rate is relatively low.