直扩MSK信号的快速捕获与跟踪技术研究

发布时间：2019-01-26 12:10

【摘要】：MSK信号具有包络恒定、频谱利用率高、带外辐射功率低、对非线性失真不敏感等优点,特别适合功率受限以及存在非线性失真、多普勒频移和多径衰落的无线通信领域。MSK结合扩频通信体制,兼具MSK信号的优点和扩频通信体制的保密性好、截获率低、抗干扰能力强等特点,在战术数据链、民用航空地空数据链、导弹制导指令传输、卫星通信等领域得到了广泛应用。因此开展直扩MSK信号的快速捕获与跟踪技术研究具有重要意义。本文研究了伪随机序列的特性,选择具有优良自相关与互相关性能的Gold序列作为扩频码。提出基于II型MSK调制的双伪码直扩MSK通信系统,推导出直扩MSK信号的数学表示,设计了直扩MSK调制器、中频全数字解扩解调接收机的实现方案,仿真分析了直扩MSK信号产生及解扩解调处理过程。针对高动态环境下直扩MSK信号的捕获与跟踪技术开展了较深入的研究。采用基于FFT频率补偿-时域匹配的直扩MSK信号快速捕获方案,针对FFT频率估计精度受限影响码捕获性能的问题,提出改进的高精度频率估计算法,在保持FFT点数不变的情况下,可显著提高频率估计精度,并对整个快速捕获系统的性能进行了分析。采用全数字非相干超前-滞后延迟锁定环的码相位跟踪方案,给出了全数字超前-滞后延迟锁定环的参数选择与设计方法,详细地分析了环路参数ζ与BL对码跟踪环路性能的影响。设计了双伪码直扩MSK信号载波跟踪的Costas环结构,推导出Costas环的鉴相特性,通过MATLAB仿真验证了Costas环可有效实现载波相位跟踪。
[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.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN914.42

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