Frequency modulator apparatus of phase selection type, and frequency synthesizer of phase selection type

Abstract

A phase-selective type frequency modulator capable of easing the restriction on a phase range of a modulated clock signal. The phase-selective type frequency modulator includes a multiphase clock signal generating circuitfor generating N-phase clock signals; a control circuitfor sequentially activating one of first group of clock selection signals indicating a clock signal to be selected from the N-phase clock signals; an edge appearance time adjustment circuitfor adjusting a rising edge appearance time and/or a trailing edge appearance time of the first group of clock selection signals outputted from the control circuitto output second group of clock selection signals; and a modulated clock signal generating circuitfor selecting one clock signal from the N-phase clock signals in accordance with an activated state of the second group of clock selection signals outputted from the edge appearance time adjustment circuitto output a modulated clock signal MCK.