Design And Implementation Of Frequency Synthesizer Based On DDS And PLL

First, we introduce the work principle, basic structure and capability of the Phase locked loop and the direct digital frequency synthesizer. Phase locked loop is based on frequency synthesize method of phase locked technology. It utilizes good narrowband track of the phase locked loop characteristic, which makes output frequency lock highly level off reference frequency or hypo-highly concordant wave, that makes locked frequency in accordant with frequency stabilization and spectrum purity of the reference frequency. The direct digital frequency synthesizer is a kind of fully digitized frequency synthesizer, which consists of the phase accumulator, the sine wave look-up table, the digital to analog converter. It is of high frequency resolution, fast frequency switching speed, low phase noise, his ability to switch frequency while maintaining constant phase, and the ability to producing arbitrary waveforms. After comparing both of technique of the frequency synthesizer, direct digital frequency synthesizer has merits with output step little and well-pleasing noise, but low spurious .However, phase locked loop can remedy these demerits of the direct digital frequency synthesizer,give the design methods of direct digital frequency synthesizer hybrid phase locked loop frequency synthesizer after research. We make a circuit adopting the method of direct digital frequency synthesizer hybrid phase locked loop, and the scheme of subject, the functional realization of each module, and the ultimate testing result of this subject is represented and analyzed in detail. It offers some technical reference to application and development on frequency synthesis technique of direct digital frequency synthesizer inspire phase locked loop.