一种MSK-Type信号的频率同步改进算法

MSK-Type信号的频率同步技术可以采用基于最大似然理论的估计方法.但该算法结构复杂,计算量十分庞大,不利用工程上的实现,所以对MSK-Type的频率同步大多采用非线性同步的方式.其算法主要有延迟相乘和2P-Power算法,但这种选用前馈结构的无数据辅助算法只适用于全响应的连续相位调制信号,且由于在非线性相乘过程中引入大量自噪声,从而导致同步性能下降.为解决MSK-Type调制信号频率同步算法精度低、适用范围小及不利于工程上实现等问题,本文在延迟相乘频率同步算法的基础上,提出一种改进算法.该算法通过对部分响应和全响应MSK-Type信号采用不同幂次非线性处理,消除了延迟相乘算法中的自噪声影响,与原算法相比,频偏估计精度可提高5d B左右.另外,所提算法不仅将应用范围扩展到了部分响应MSK-Type信号,扩大了同步算法的适用范围,而且还具有便于工程实现的特点.

An improved frequency synchronization algorithm for MSK-Type signals

Frequency estimation algorithm for Minimum Shift Keying-Type(MSK-Type) signals is usually based on maximum likelihood theory. However, the algorithm is complex, and it is not practically realized in engineering. So the frequency synchronization for MSK-Type signal mostly adopts nonlinear methods such as delay-multiplication and 2P-Power algorithms. But these feedforward structure of non-data aided algorithm applies only to full response MSK-Type signal, and due to the nonlinear process of multiplying, these algorithms introduce large amounts of self-noise, so that it leads to poor synchronization performance. In order to solve the problem of lower accuracy and narrower application range and unpractical realization in engineering for the existing nonlinear algorithms, an improved algorithm based on delay-multiplication frequency synchronization algorithm is proposed in this paper. After different power nonlinear processing on the MSK-Type signal with partial response and full response, the improved algorithm eliminates the effects of self-noise in the delay-multiplication algorithm. Compared with the original algorithm, the estimated accuracy for the frequency offset is improved about 5dB, and at the same time, the application range is extended to the partial response MSK-Type signal. The improved algorithm enlarges the application range and it is easy to be implemented in engineering.