Digital controlled oscillator and frequency variable oscillator

Abstract

A digital controlled oscillator includes: a delay circuit which includes m elements transmitting a pulse signal with delay; a timing signal generator generating a timing signal corresponding to timing-selection data from passing signals, based on the timing-selection data specifying any of timings which are obtained by dividing a circulation period of the pulse signal by m×n; and an output signal generator which sets the timing-selection data based on control data specifying a period of an output pulse signal and the timing-selection data, and generates the output pulse signal based on the timing-selection data by using the timing signal. The timing signal generator generates the timings obtained by dividing the circulation period by m×n by using pulse edge shift circuits which generate n shift signals whose timings differ by a unit delay from one input signal, the unit delay being 1/n of delay time in the element.