DDS working principle DDS technology is a new frequency synthesis method, first proposed by JOSEPH TIERENY and other three people, which has high output frequency resolution, low power consumption, fast frequency switching and frequency switching. The phase of the output signal is continuous. To this end, understanding the DDS module plays an important role in digital signal processing and its hardware implementation. The structure of the DDS is mainly composed of four large structures such as a phase accumulator, a waveform memory, a digital-to-analog (D/A) converter, and a low-pass filter. The structure block diagram is as follows: 这里写图片描述

图, the phase accumulator is composed of an N-bit adder and an N-bit accumulating register, which is an extremely important part of the DDS module. Driven by the reference frequency clock, the DDS module starts to work; when each reference clock is used, the accumulator accumulates the value of the frequency control word FW and the register output, and then adds the added result to the register, and The accumulation register transfers the data generated when the last reference clock is applied to the accumulator by feedback. In this way, under the action of the clock, the frequency control words can be accumulated continuously. At this time, the data output from the phase accumulator is used as an address in the waveform memory by searching the amplitude table corresponding to the address, and the conversion from phase to amplitude can be completed.

In the DDS module, the formula for the output frequency is这里写图片描述  输出信号的频率分辨率为 这里写图片描述  从上两式可以看出,在参考信号与加法器或寄存器的位数给定时,信号最终的输出频率主要由频率控制字决定。故当频率控制字变化时,输出频率也跟着变化,从而可以实现调频的基本功能。