JP2006020000A - Crystal oscillation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in a conventional oscillator that, if a frequency changes due to deterioration of the device by aging, the frequency must be regularly re-measured to perform zero adjustment, and measuring instruments must be prepared therefor and the frequency must be adjusted while being measured. <P>SOLUTION: In this device, of two oscillators, a second oscillator is not powered usually to prevent deterioration, and a first oscillator is usually operated. The second oscillator is operated regularly or with an arbitrary interval and frequency deviation in the first oscillator is corrected using the second oscillator as reference, thereby forming an oscillator capable of obtaining a stable frequency. Further, while the second crystal oscillator does not work, a control circuit calculates a correction amount per time from the past data to perform frequency adjustment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a crystal oscillation device that obtains a highly stable frequency.

  2. Description of the Related Art Oscillators that obtain frequency stability using a thermostatic chamber among crystal oscillators are widely used as clock sources and signal sources. A crystal oscillator that requires high stability maintains temperature characteristics using a thermostatic chamber. Furthermore, an SC-cut crystal resonator is used rather than an AT-cut, and a point having a higher temperature is used, and thermal deterioration of the crystal resonator is accelerated. In addition, deterioration due to vibration causes a change in frequency.

  However, the temperature of the thermostatic chamber is higher than that of room temperature, and since it is constantly exposed to high temperatures, the components of the crystal resonator and the peripheral oscillation circuit deteriorate, so that the frequency changes with time.

  Therefore, the amount of change over time is measured, and it is examined whether the frequency can be automatically corrected. The first crystal oscillator and the second crystal oscillator are provided, and the frequency calibration of the first crystal oscillator is performed based on the second crystal oscillator. It is carried out.

JP 09-214336 A

  In addition to the prior art documents specified by the prior art document information described above, the applicant has not found any prior art documents related to the present invention by the time of filing of the present application.

  The problem to be solved by the present invention lies in how to detect a frequency fluctuation due to deterioration of a crystal resonator and an oscillation circuit exposed to a high temperature, and to adjust based on what.

  Patent Document 1 discloses a circuit that controls a voltage-controlled oscillator by detecting and dividing a difference component between two oscillators. However, Patent Document 1 has a different configuration in that both oscillators always oscillate.

  In the present invention, there are a first crystal oscillator and a second crystal oscillator, the first crystal oscillator is always operated, the second crystal oscillator is operated for a certain period, and is operated as a reference oscillator of the first crystal oscillator.

  According to the present invention, it is possible to provide an oscillation device that maintains a stable frequency by operating the second crystal oscillator at regular time intervals and adjusting the frequency deviation from the first crystal oscillator. Then, during the fixed time, the amount of change in frequency per hour was calculated by the control circuit and adjusted by the frequency adjustment circuit to obtain a stable frequency.

  The present invention comprises a first crystal oscillator and a second crystal oscillator, and compares the output frequency of the first crystal oscillator with the output frequency when the second crystal oscillator is activated by a frequency comparison circuit, A frequency adjustment that adjusts the frequency of the first crystal oscillator by measuring the frequency at a constant interval by a circuit and calculating the frequency difference obtained with reference to the second crystal oscillator and the amount of frequency change per time from the previous measurement. A crystal oscillation device including a circuit.

Hereinafter, embodiments will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the present invention.
In this embodiment, the first crystal oscillator 1 is an oscillator that is a thermostatic chamber-containing crystal oscillator and serves as an output frequency of the oscillation device. When the second crystal oscillator is operating, the frequency comparison circuit 3 measures the frequency difference of each crystal oscillator with the second crystal oscillator as a reference. The frequency comparison circuit 3 uses a counter and a second crystal oscillator 5 as a reference frequency.
The control circuit 4 operates a power supply control circuit for operating the second crystal oscillator 5 based on a signal from the time measuring circuit 7 that determines the measurement interval.
The frequency difference between the first crystal oscillator 1 and the second crystal oscillator 5 is input to the control circuit 4, the difference from the previous time is calculated with digital data, the data is changed by the frequency deviation, and the adjustment amount is stored in the frequency adjustment circuit. Data is sent, converted from digital to analog, and the frequency of the first crystal oscillator is controlled by a variable capacitance diode or the like.

FIG. 2 is a chart showing the timing of frequency adjustment. The frequency is adjusted by operating the second crystal oscillator twice during the time interval T1, and the previous frequency change amount is calculated during Δt1. , And make adjustments to complement the amount that changes in the meantime. Therefore, when the frequency adjustment is performed four times during the time T1 in the chart and only once during the time interval T1, the frequency correction amount becomes many times ΔF as shown by the dotted line.
Below the chart is a chart showing the power on / off of the second crystal oscillator.
The feature of the present invention is that the frequency adjustment is performed based on the data of the control circuit even when the second crystal oscillator is not operating.

  Since the second crystal oscillator is not normally turned on compared to the first crystal oscillator, there is no thermal deterioration and no mechanical deterioration, so that a stable frequency can be obtained when the power is turned on.

  The present invention can be used as a reference frequency signal generator for a broadcasting station, a base station of a radio station, a measuring instrument, etc. as a highly stable crystal oscillator.

FIG. 1 is a block diagram illustrating the present invention. FIG. 2 shows changes in frequency with time and adjustment amounts.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st crystal oscillator 2 Frequency adjustment circuit 3 Frequency comparison circuit 4 Control circuit 5 2nd crystal oscillator 6 Power supply control circuit 7 Clock circuit

Claims (3)

  A first crystal oscillator and a second crystal oscillator, and the output frequency of the first crystal oscillator and the output frequency when the second crystal oscillator is activated are compared by a frequency comparison circuit; A frequency adjustment circuit for adjusting the frequency of the first crystal oscillator by calculating the frequency difference obtained by measuring the frequency with the second crystal oscillator as a reference and the frequency change amount per time from the previous measurement. A crystal oscillation device characterized by comprising:   2. The crystal oscillation device according to claim 1, further comprising a power supply control circuit for operating the second crystal oscillator.   2. The crystal oscillation device according to claim 1, wherein the second crystal oscillator is a crystal oscillator using a thermostatic chamber.

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