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1. (WO2009122843) FREQUENCY SYNTHESIZER AND METHOD FOR CONTROLLING OSCILLATION FREQUENCY OF OSCILLATOR 


IPC:  H03D 13/00 H03L 7/087 

Applicants:  NEC Corporation 日本電気株式会社 MAEDA, Tadashi 前多 正 

Inventors:  MAEDA, Tadashi 前多 正 
Title:  FREQUENCY SYNTHESIZER AND METHOD FOR CONTROLLING OSCILLATION FREQUENCY OF OSCILLATOR 
Abstract: 
Frequency control with a high accuracy is carried out by means of a highspeed PLL circuit driven at low voltage. A frequency control word (FCW) represents a target multiplier of a reference signal (FREF) with respect to an oscillator output (CVK). A phase detector (51) accumulates the frequency control word (FCW) at the timing of the reference signal (FREF) to detect the phase φR01 of the reference signal (FREF). A phase detector (52) accumulates the number of clocks of the oscillator output (CVK) at the timing of the reference signal (FREF) to detect the phase φV01 of the oscillator output (CVK). A phase detector (53) accumulates the number of clocks of the oscillator output (CVK) at the timing fR1 of the reference signal (FREF) which is delayed by a delay element (61) to detect the phase φV02 of the oscillator output (CVK). A phase detector (57) accumulates the number of clocks of the oscillator output (CVK) at the timing fR2 of the reference signal (FREF) which is delayed by the delay element (61) and a delay element (62) to detect the phase φV00 of the oscillator output (CVK). The sum of the phase φV00 and the phase φV01 and the difference between them are calculated. The results are divided by a divider (86) to calculate the number of clocks φ0 of the oscillator output (CVK) for the time delayed by one delay element. The sum of the phase φR01 and the phase φV01 and the difference between them are calculated to obtain a first phase error signal. The sum of the phase φR01, the phase φ0, and the phase φV02 and the difference between the sum of the phase φR01 and the phase φ0 and the phase φV02 are calculated to obtain a second phase error signal. The first and second phase error signals are combined into a composite signal, and the frequency of the oscillator is controlled by the composite signal.
