数字应答机相参转发的实现

针对数字应答机中相参转发的技术问题，提出了改变直接数字频率合成(DDS)频率控制字或相位累加器溢出值实现相参转发的方法，并对转发性能、资源需求进行了分析比较，结果表明，在同等条件下改变相位累加器溢出值的方法性能稍优，但消耗的逻辑资源显著减少。该方法将DDS溢出值设置为与转发比相关的常数，避免了利用乘法器进行实时运算的过程，能有效实现高精度转发，且消耗资源少，转发比可任意设置。该方法已成功在多个工程中应用，满足测量系统精度的要求。

Implementation of coherent repeating in digital transponders

For coherent repeating technical problems emerging in digital transponders,a method is proposed for coherent repeating through changing frequency control word of Direct Digital Frequency Synthesis(DDS) or overflow value of phase accumulator. The requirements on repeating performance and resource are analyzed and compared. The results show that the method of changing overflow value of phase accumulator is better and consumes less logic resource under the same conditions.This method sets DDS overflow value as a constant relative to turnaround ratio to avoid real-time operation procedure using multiplier and implement high accuracy repeating with less resource consumption and the turnaround ratio can be set arbitrarily. The method has been applied successfully in several engineering applications and meets the accuracy requirements of measurement system.