PURPOSE: To provide a reference signal oscillator which is approximate to the reference frequency by using two oscillators having the positive and negative frequency deviations and switching periodically and alternately the oscillation signals of both oscillators.
CONSTITUTION: The oscillation sources 1 and 2 use the crystal vibrators having a minute frequency deviation as the source oscillation clocks and are turned into the oscillator outputs with N-division. An oscillation clock synchronism detecting part 3 consists of a EOR gate 6, a delay circuit 7, and the AND gates 8 and 9 and generates the synchronism detection output. A switch signal generating part 4 receives the synchronism detection output of the part 3 and produces a switch signal synchronous with the output of the source 2. An oscillation output switching part 5 switches both sources 1 and 2 based on the output level of the circuit 4. The sources 1 and 2 have the frequency deviations in the positive and negative directions against the reference frequency and therefore these mutual frequency deviations can be absorbed when both sources 1 and 2 are periodically and alternately switched.
HITACHI MICOM SYST KK