非周期长码直扩信号码片速率估计

Chip-rate Estimation for Non-periodic Long-code DSSS Signals

本文针对非周期长码直扩信号参数难以估计的问题,建立了非周期长码直扩信号的一种表示模型;推导分析了非周期长码直扩信号延迟相乘后的自相关函数,此自相关函数具有周期性峰值,两个相邻峰值之间的间隔倒数就是扩频码的码片速率;同时还推导分析了噪声对此自相关函数的影响,合理选择延迟量理论上可以消除噪声影响;根据上述特点,提出了一种非周期长码直扩信号的扩频码码片速率估计方法。该方法首先估计基带信号延迟相乘后的自相关函数,然后消除噪声产生的峰值,最后通过估计峰值间隔,得到扩频码的码片速率。仿真结果表明了本方法的有效性。

Aimed at the problems of the parameter estimation of non-periodic long-code Direct Sequence Spread Spectrum （DSSS）, in this paper, a representation model for non-periodic long-code DSSS is built up, and the autocorrelation function of its delay-product is derived and analyzed. The autocorrelation function has periodic peaks, and a reciprocal of the space between two adjoining peaks is the chip-rate of pseudo-random sequence. The effect of the noise to the autocorrelation function is also analyzed, and theoretically the effect of the noise could be canceled by choosing the right delay. On the basis of these properties an estimation method of the chip rate of pseudo-random sequence of non-periodic long-code DSSS is proposed. At first, the autocorrelation is calculated after the received base signal is delayed and multiplied. Then the peak which is generated by noise is canceled. At last, the interval between two adjoining peaks is estimated and the chip rate is got. The computer simulations results show that the proposed method is effective.