High performance digital frequency synthesizer

A novel digital frequency synthesizer which uses a phase accumulator as a reference generator is proposed. The frequency of the phase accumulator can be changed with fine resolution at high frequency. Since the phase accumulator output is binary numerical data, a new phase comparison technique is extended to have an effective characteristic which can detect the frequency error, and an auxiliary phase detector is used to remove the low-frequency components. The performance of the proposed system has been verified by experiments and theoretical analysis. The frequency switching and output spurious spectral components are compared with those of the conventional system, and it is found that the proposed system has a faster frequency switching speed with better signal purity. The high reference frequency which offers a high loop gain and the effective phase-frequency characteristics account for the better properties of the proposed system