利用中頻差分檢測的pi/4-DQPSK無線電傳送機之研究

Abstract

當今數位通訊系統中的無線電傳送機設計, 經常運用到不同型式的調變技 術. 與傳統的調頻系統比較起來, 線性調變技術能提供較高的頻譜使用效 率. 但於此種調變技術下, 發射端功率放大器的非線性特性會造成信號頻 譜的展開. 所以在有效頻譜運用與有效功率運用兩者考量下,必須作個權 衡.為了有效地利用有限的頻譜資源, 高頻譜使用效率的p/4-DQPSK線性調 變技術, 被美國新一代數位蜂巢式行動電話系統所採用, 完成了1.62 bits/Hz的頻譜使用效率. 於此論文, 以中頻差分檢測的p/4-DQPSK線性 調變系統為例, 作系統模擬.本論文提出一種有效的系統模擬技術, 讓系 統設計者在作無線電傳送機系統設計時直接開出各種不同元件的實際規 格, 然後模擬得到系統各方面的特性, 以利分析. There are many different modulation techniques which have been considered for the radio modem design of the digital mobile systems. The linear modulation technique offers higher spectrum efficiency than conventional FM system. But the nonlinearity of the transmitting power amplifier tends to spread the spectrum of the signal. The compromises between spectrum efficiency and power efficiency have to be considered. A powerful system simulation technique is presented using the pi/4-DQPSK as an example. Such technique can enable system designer to issue realistic specifications for various components used in the radio MODEM system. A high capacity digital mobile system has been developed in the U.S., such narrow band TDMA system employs pi/4-DQPSK linear modulation, achieving a spectral efficiency of 1.62 bits/Hz. The pi/4-DQPSK linear modulation scheme encodes baseband information in both the amplitude and phase of the RF carrier, thereby it increases spectral efficiency. We will study the BER (bit-error-rate) performance of the pi/4-DQPSK system using IF differential detection. The simulation results are presented for static and multipath fading channels by using the EEsof Omnisys