【摘要】：MSK信號具有包絡(luò)恒定、頻譜利用率高、帶外輻射功率低、對非線性失真不敏感等優(yōu)點(diǎn),特別適合功率受限以及存在非線性失真、多普勒頻移和多徑衰落的無線通信領(lǐng)域。MSK結(jié)合擴(kuò)頻通信體制,兼具M(jìn)SK信號的優(yōu)點(diǎn)和擴(kuò)頻通信體制的保密性好、截獲率低、抗干擾能力強(qiáng)等特點(diǎn),在戰(zhàn)術(shù)數(shù)據(jù)鏈、民用航空地空數(shù)據(jù)鏈、導(dǎo)彈制導(dǎo)指令傳輸、衛(wèi)星通信等領(lǐng)域得到了廣泛應(yīng)用。因此開展直擴(kuò)MSK信號的快速捕獲與跟蹤技術(shù)研究具有重要意義。 本文研究了偽隨機(jī)序列的特性,選擇具有優(yōu)良自相關(guān)與互相關(guān)性能的Gold序列作為擴(kuò)頻碼。提出基于II型MSK調(diào)制的雙偽碼直擴(kuò)MSK通信系統(tǒng),推導(dǎo)出直擴(kuò)MSK信號的數(shù)學(xué)表示,設(shè)計(jì)了直擴(kuò)MSK調(diào)制器、中頻全數(shù)字解擴(kuò)解調(diào)接收機(jī)的實(shí)現(xiàn)方案,仿真分析了直擴(kuò)MSK信號產(chǎn)生及解擴(kuò)解調(diào)處理過程。針對高動(dòng)態(tài)環(huán)境下直擴(kuò)MSK信號的捕獲與跟蹤技術(shù)開展了較深入的研究。采用基于FFT頻率補(bǔ)償-時(shí)域匹配的直擴(kuò)MSK信號快速捕獲方案,針對FFT頻率估計(jì)精度受限影響碼捕獲性能的問題,提出改進(jìn)的高精度頻率估計(jì)算法,在保持FFT點(diǎn)數(shù)不變的情況下,可顯著提高頻率估計(jì)精度,并對整個(gè)快速捕獲系統(tǒng)的性能進(jìn)行了分析。采用全數(shù)字非相干超前-滯后延遲鎖定環(huán)的碼相位跟蹤方案,給出了全數(shù)字超前-滯后延遲鎖定環(huán)的參數(shù)選擇與設(shè)計(jì)方法,詳細(xì)地分析了環(huán)路參數(shù)ζ與BL對碼跟蹤環(huán)路性能的影響。設(shè)計(jì)了雙偽碼直擴(kuò)MSK信號載波跟蹤的Costas環(huán)結(jié)構(gòu),推導(dǎo)出Costas環(huán)的鑒相特性,通過MATLAB仿真驗(yàn)證了Costas環(huán)可有效實(shí)現(xiàn)載波相位跟蹤。
[Abstract]:MSK signals have the advantages of constant envelope, high spectral efficiency, low out-of-band radiation power and insensitivity to nonlinear distortion, which are especially suitable for power limitation and nonlinear distortion. Doppler frequency shift and multipath fading wireless communication field. MSK combined with spread spectrum communication system has the advantages of MSK signal and good security of spread spectrum communication system, low interception rate, strong anti-jamming ability, etc., in tactical data link, Civil aviation ground-to-air data link, missile guidance command transmission, satellite communication and other fields have been widely used. Therefore, it is of great significance to study the rapid acquisition and tracking of DS MSK signals. In this paper, we study the properties of pseudorandom sequences and select Gold sequences with excellent autocorrelation and cross-correlation performance as spread spectrum codes. A double pseudo code MSK communication system based on II type MSK modulation is proposed. The mathematical representation of DSSS MSK signal is derived. The realization scheme of DSSS MSK modulator and if all digital despreading demodulation receiver is designed. The process of direct spread sequence MSK signal generation and despreading demodulation is simulated and analyzed. In this paper, the acquisition and tracking techniques of DS MSK signals in high dynamic environment are studied. A fast acquisition scheme for direct spread sequence (MSK) signals based on FFT frequency compensation and time domain matching is adopted. Aiming at the problem that the limited accuracy of FFT frequency estimation affects the performance of code acquisition, an improved high precision frequency estimation algorithm is proposed, which keeps the number of FFT points unchanged. The accuracy of frequency estimation can be improved significantly, and the performance of the whole fast acquisition system is analyzed. Based on the code phase tracking scheme of all digital incoherent lead-lag delay locking loop, the parameter selection and design method of all digital lead-lag delay locking loop are presented. The influence of the loop parameters 味 and BL on the performance of the code tracking loop is analyzed in detail. The structure of Costas loop for carrier tracking of double pseudo code direct spread sequence (MSK) signals is designed, and the phase discrimination characteristics of Costas loop are deduced. The MATLAB simulation verifies that Costas loop can effectively realize carrier phase tracking.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN914.42

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