[FPGA tutorial case 28] one of DDS direct digital frequency synthesizers based on FPGA -- principle introduction

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1. Software version

vivado2019.2

2. Theoretical knowledge of this algorithm

       DDS The working process is ： At the reference clock fc Under the influence of , Phase accumulator to frequency control word FCW Linear accumulation , Make it high W Bit as address code through waveform lookup table ROM Transformation , produce D Bit corresponds to the digital sequence of the signal waveform , Then the digital to analog converter DAC It is transformed into step analog voltage waveform and then interpolated by a low-pass filter LPF Smooth it into continuous sinusoidal waveform as output . Ideal single frequency signal S(t) It can be expressed as ：

 

        To illustrate DDS Working principle of phase quantization , The phase change of a sine wave in a complete cycle can be expressed as a phase circle