A Digital Frequency Synthesizer with a Phase Accumulator

Hiroomi HIKAWA  Shinsaku MORI  

IEICE TRANSACTIONS (1976-1990)   Vol.E72   No.6   pp.719-726
Publication Date: 1989/06/25
Online ISSN: 
Print ISSN: 0000-0000
Type of Manuscript: PAPER
Category: Radio Communication

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Frequency synthesizers are widely used in the radio communication systems and as the signal generators. Usually, the frequency synthesizers are built as a PLL, and the requirements for both switching speed and frequency step size are in conflict. In this paper, a new digital frequency synthesizer using a phase accumulator is proposed, and a new phase frequency detector is described. The frequency of the phase accumulator is used as a reference generator and its frequency can be changed with a fine resolution at a high frequency, which offers a rapid frequency switching. Since the phase accumulator generates binary data, a new phase estimation technique is used and is extended to have an ability to detect the frequency error. Due to a high reference frequency which offers a high loop gain and the better characteristics of the phase-frequency detector, the speed of the frequency switching is improved. The properties of the proposed frequency synthesizer is investigated by experiments and theoretical analysis and is compared with the conventional PLL frequency synthesizer, resulting in that the proposed system has faster frequency switching speed and better signal purity than those of the conventional PLL frequency synthesizer.