GNSS接收机离散化处理对解扩性能影响的研究

建立了扩频信号防混叠滤波、采样和量化与解扩输出关系的数学解析模型，推导得到解扩输出信噪比的解析表达式。分析与仿真表明，当量化位数大于等于4比特，解扩得到总的信噪比损失可以分解为由量化引起的损失和滤波加采样引起损失的乘积，且量化器最优限幅系数只与量化位数相关；当量化位数小于4比特时，信噪比损失在一定条件下可近似为量化损失和滤波加采样损失的乘积。当量化位数大于4比特、滤波器带宽大于5倍码率、采样频率大于4倍码率时，再增大上述参数引起的信噪比损失波动小于0.05dB，对解扩性能提升不明显。本文结论可为实用型GNSS接收机前端离散化处理优化设计提供理论指导。

Research of Discrete Processing Influence on De-spreading Performance of GNSS Receiver

The analytical model of anti-aliasing filtering, sampling and quantization is established. The formulation of de-spread output SNR under the influence of three factors is deduced. Analysis and simulation show that the total SNR loss can be separated to the product of quantization , filtering and sampling loss when the quantization length up to 4bit, besides, the optimized clipping level coefficient only relates to quantization length. When the quantization length is less than 4bit, the total SNR loss approximates to the product of the quantization and sampling plus filtering loss. In the condition of quantization length up to 4bit, filter bandwidth up to 5 times of pseudo-random (PN) code rate, sample rate up to 4 times of PN code rate, increasing the parameters mentioned above cause SNR loss less than 0.05dB, thus cannot increase the de-spread performance obviously. The result of this paper can be used to optimize the design of the front-end of low-cost GNSS receiver.