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

摘要

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 circuit 101 for generating N-phase clock signals; a control circuit 104 for 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 circuit 103 for 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 circuit 104 to output second group of clock selection signals; and a modulated clock signal generating circuit 102 for 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 circuit 103 to output a modulated clock signal MCK.