OSCILLATION DEVICE

• US 20120218048A1
• Filed: 02/28/2012
• Published: 08/30/2012
• Est. Priority Date: 02/28/2011
• Status: Active Grant

• Current Assignee: Nihon Dempa Kogyo Company Limited
• Original Assignee: Nihon Dempa Kogyo Company Limited
• Inventors: Akaike, Kazuo, Kobayashi, Kaoru
• Granted Patent: US 8,536,952 B2
• Time in Patent Office: Days
• US Class Current: 331/2
• CPC Class Codes: H03L 1/00 Stabilisation of generator output against variations of physical values, e.g. power supply

Abstract

Provided is an oscillation device capable of obtaining a stable oscillation frequency by compensating for a change in oscillation frequency caused with an elapse of operating time of a quartz-crystal oscillator. A difference value ΔF between a frequency difference between first and second quartz-crystal oscillators after a predetermined period of time has elapsed from a reference time and a frequency difference between the first and second quartz-crystal oscillators at the reference time is determined.

Claims

1. An oscillation device using quartz-crystal oscillators, comprising:

a first quartz-crystal oscillator structured by providing first electrodes on a quartz-crystal piece;

a second quartz-crystal oscillator structured by providing second electrodes on a quart-crystal piece;

a first oscillation circuit and a second oscillation circuit connected to said first quartz-crystal oscillator and said second quartz-crystal oscillator, respectively;

a frequency difference detecting unit determining, when an oscillation frequency of said first oscillation circuit is set to f1, an oscillation frequency of said first oscillation circuit at a reference time is set to f1rz, an oscillation frequency of said second oscillation circuit is set to f2, and an oscillation frequency of said second oscillation circuit at the reference time is set to f2rz, a value corresponding to a difference value Δ

F between a value corresponding to a difference between f2 and f2rz, and a value corresponding to a difference between f1 and f1rz;

and

a compensation value obtaining unit for aging compensation obtaining a frequency compensation value of f1 based on an elapse of time from the reference time, based on the value corresponding to the difference value Δ

F detected by said frequency difference detecting unit, and a compensation coefficient of aging, wherein;

the compensation coefficient of aging is a ratio between an amount of change in the frequency of said first oscillation circuit and an amount of change in the frequency of said second oscillation circuit with respect to an elapse of operating time from the reference time;

an output of said oscillation device is structured to be generated by utilizing an output of said first oscillation circuit; and

a set value of the output frequency is structured to be compensated based on the frequency compensation value determined by said compensation value obtaining unit.

2. The oscillation device according to claim 1, wherein:

the oscillation frequency f1 of said first oscillation circuit is an n-th overtone, and the oscillation frequency f2 of said second oscillation circuit is a frequency of fundamental wave; and

the difference value Δ

F is {(f2−

f2rz)/f2rz}−

{(f1−

f1rz)/f1rz}.

3. The oscillation device according to claim 1, wherein:

the compensation coefficient of aging is a value set at a reference temperature;

said oscillation device further comprising;

a temperature detecting unit detecting an atmospheric temperature under which said first quartz-crystal oscillator and said second quartz-crystal oscillator are placed; and

a calculating unit for temperature compensation determining, based on a relation between an amount of temperature change from the reference temperature and an amount of variation with respect to the difference value Δ

F at the reference temperature, and the atmospheric temperature determined by said temperature detecting unit, an amount of change due to the temperature change included in the difference value Δ

F at the reference time; and

said compensation value obtaining unit obtains the frequency compensation value of f1 by using a value obtained by subtracting the amount of change calculated by said calculating unit for temperature compensation from the difference value Δ

F.

4. The oscillation device according to claim 1, further comprising:

a temperature detecting unit detecting an atmospheric temperature under which said first quartz-crystal oscillator and said second quartz-crystal oscillator are placed; and

a compensation value obtaining unit for temperature compensation obtaining, based on a signal corresponding to the temperature detected by said temperature detecting unit, and a relation between the signal and a frequency compensation value of the oscillation frequency f1 of said first oscillation circuit, the frequency compensation value of f1 because the ambient temperature is deviated from the reference temperature, wherein

a set value of the output frequency is structured to be compensated based on the frequency compensation value determined by said compensation value obtaining unit for aging compensation, and the frequency compensation value determined by said compensation value obtaining unit for temperature compensation.

5. The oscillation device according to claim 1, wherein

said frequency difference detecting unit comprises:

a pulse creating section creating a pulse of difference frequency between the f1 and f2;

a DDS circuit section outputting a frequency signal whose signal value repeatedly increases and decreases with time by a frequency in accordance with a magnitude of an input direct-current voltage;

a latch circuit latching, based on the pulse created by the pulse creating section, the frequency signal output from the DDS circuit section;

a loop filter integrating a value of the signal latched by the latch circuit and outputting the integral value as a value corresponding to the difference value; and

an adding section obtaining a difference between the output of the loop filter and a value corresponding to a difference between f1rz and f2rz to set it as an input value to be input into the DDS circuit section.

6. The oscillation device according to claim 1, wherein

the quartz-crystal piece of said first quartz-crystal oscillator and the quartz-crystal piece of said second quartz-crystal oscillator are made common.