本文選題：直擴MSK + 捕獲�。� 參考：《南京理工大學》2017年碩士論文

【摘要】：擴頻通信技術(shù)具有低截獲性、多用戶隨機選址能力、抗干擾性能強等特點;最小頻移鍵控(Minimum Shift Keying,MSK)信號具有對非線性失真不敏感、旁瓣衰減快、頻譜利用率高、包絡恒定等優(yōu)點。直擴MSK通信系統(tǒng)兼具直接序列擴頻技術(shù)與MSK調(diào)制技術(shù)的優(yōu)勢,在很多軍用和民用領域得到廣泛應用。本文針對直擴MSK信號全數(shù)字解擴接收機及其算法展開研究。本文采用并行和串行兩種方法來實現(xiàn)直擴MSK信號的產(chǎn)生。在串行產(chǎn)生方法中,提出一種基于凸優(yōu)化的轉(zhuǎn)換濾波器設計方法,實現(xiàn)將直擴BPSK信號轉(zhuǎn)換成直擴MSK信號的過程。在碼捕獲的過程中,針對多普勒頻偏會影響碼捕獲相關(guān)峰這一問題,提出基于延遲相關(guān)的碼捕獲算法,以消除多普勒頻偏對相關(guān)峰的影響。鑒于延遲相關(guān)算法不能同時捕獲偽碼相差和多普勒頻偏,提出一種基于多普勒補償?shù)膫未a-多普勒聯(lián)合捕獲算法,提高多普勒頻偏估計范圍,但該算法的估計精度和估計范圍受到運算復雜度的限制。為了找到一種兼顧估計精度、估計范圍和運算復雜度的捕獲算法,本文首次將壓縮感知理論引入碼捕獲中,提出一種基于壓縮感知的聯(lián)合捕獲算法,仿真表明這種算法不僅能夠同時捕獲偽碼相差和多普勒頻偏,還能進一步提高多普勒估計精度和范圍,同時降低運算復雜度。在直擴MSK信號的跟蹤部分,分別采用全數(shù)字超前-滯后延遲鎖相環(huán)和Costas環(huán)進行擴頻碼和載波相位跟蹤,并通過仿真確定最優(yōu)環(huán)路參數(shù)。最后將本文設計的直擴MSK信號解擴接收機與常規(guī)解擴解調(diào)方法的誤碼性能進行比較,得出本文設計的接收機能夠避免信噪比損失,更適合低信噪比工作環(huán)境的結(jié)論。
[Abstract]:The spread spectrum communication technology has the characteristics of low interception, multi-user random location ability, strong anti-jamming performance and so on. The minimum frequency shift keying minimum Shift key MSKS signal has the advantages of being insensitive to nonlinear distortion, fast sidelobe attenuation, high spectral efficiency and constant envelope.Direct sequence spread spectrum (DSS) and MSK modulation (DSS) are the advantages of DSSS communication system, and have been widely used in many military and civil fields.In this paper, the full digital despreading receiver and its algorithm for direct spread sequence (MSK) signal are studied.In this paper, parallel and serial methods are used to realize the generation of DS MSK signals.In the serial generation method, a transform filter design method based on convex optimization is proposed to realize the process of converting the DSSS BPSK signal into the DSSS MSK signal.In the process of code acquisition, a code acquisition algorithm based on delay correlation is proposed to eliminate the influence of Doppler frequency offset on the correlation peak.In view of the delay correlation algorithm can not simultaneously capture pseudo-code phase and Doppler frequency offset, a pseudo-code-Doppler joint acquisition algorithm based on Doppler compensation is proposed to improve the range of Doppler frequency offset estimation.However, the estimation accuracy and estimation range of the algorithm are limited by the computational complexity.In order to find a capture algorithm which takes into account the estimation accuracy, the estimation range and the computational complexity, this paper first introduces the theory of compressed sensing into code acquisition, and proposes a joint acquisition algorithm based on compressed sensing.Simulation results show that the proposed algorithm can not only capture the pseudo-code phase difference and Doppler frequency offset simultaneously, but also improve the accuracy and range of Doppler estimation and reduce the computational complexity.In the tracking part of DSSS MSK signal, the spread spectrum code and carrier phase tracking are carried out by using digital lead-lag delay phase-locked loop and Costas loop respectively, and the optimal loop parameters are determined by simulation.Finally, the performance of the DSS MSK signal despreading receiver designed in this paper is compared with that of the conventional despreading demodulation method, and the conclusion is drawn that the receiver designed in this paper can avoid the loss of SNR and is more suitable for the working environment of low SNR.
【學位授予單位】：南京理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN914.42

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