用FIR数字滤波器实现高精度时延的一种新方法

本文提供了一种实现高精度、连续可变数字时延的新方法。该方法利用FIR数字滤波器的线性相位特性，通过调节权向量，可连续改变信号时延。具有时延精度高、运算量小、可实现宽带时延等显著特点。该方法可用于宽带数字波束形成、自适应时延估计以及目标回波的时域分析等技术领域。本文对该方法的基本原理、设计方法及仿真结果进行了阐述，并给出了有关应用实例。

A method for high precision time delay implementation by a FIR degital filter

in digital beamforming, correlation, and many other application, digital time delay of high precision is frequently needed. Previous methods ask for computation-intensive techniques such.as over-sampling, digital interpolation, phase weighting in frequency domain, and so on. These methods have a common problem that they can not avoid quantization of the time delay. As a result of the quantization, it is difficult to as just the delay continuously.
In this paper, a new approach is proposed to solve the problem in addition to a requirement for a great reduction of computations. This may facilitate its implementation by VLSI DSP chips. It is proved that a properly designed FIR degital filter can provide a continuously adjustable time delay by adjusting its weights.The length of the FIR filter can be very short (4 to 5 weights), and the precision of the delay can be very high(up to 10^-5 Ts for example). Theoretical principles, design steps,togather with some illustrative examples are given. Hardware test implemented by TMS320C25 chips for a digital beamformer shows very good agreement between experimental and theoretical result.