直接数字合成调频信号的研究

本文提出了直接数字合成调频信号的一种新方法，它采用两级相位累加器对波形存储器寻址的结构。在第一级寻址结构中产生的调制信号幅度序列和载波频率值在加法器中相加，并将相加的结果作为第二级相位累加器的频率控制字；再将第二级寻址结构中产生的调频信号序列通过数字－模拟转换器和低通滤波器，就实现了调频信号的直接数字合成。仿真结果表明本文提出的直接数字合成调频信号的方法是可行的。采用该方法合成调频信号具有硬件电路

Direct Digital Synthesizing Frequency Modulated Signal

A novel method of direct digital synthesizing frequency modulated signal is presented in this paper.Frequency modulated signal is synthesized by two stages of phase accumulator which they address the waveform memories of their own.In the first stage,the amplitude sequence of modulating signal is generated by addressing waveform memory and added by the frequency value of carrier wave in the adder.The parallel output of the adder is served as the frequency control word of the second phase accumulator.Frequency modulated signal sequence is generated from waveform memory addressed by the second phase accumulator.After it pass through digital-analog converter and low pass filter,frequency modulated signal is synthesized by the direct digital synthesizing method.The feasibility of the method presented in this paper is proved by simulation.Using the method to synthesizing frequency modulated signal has some advantages,such as the simplicity of hardware circuit,the high stability of carrier frequency,the wide deviation of frequency,and so on.