JPH0856120A - Reference oscillator circuit - Google Patents

Abstract

PURPOSE:To use a high accuracy reference oscillator effectively from application of power by using the output of a TCXO or a crystal oscillator for the reference signal for the warming-up of an OCXO at application of power and selecting the output of the OCXO after the end of warming-up. CONSTITUTION:The output of a TCXO (temperature compensation crystal oscillaror) or a crystal oscillator 12 and the output of an OCXO (crystal oscillator with constant temperature oven) 13 are inputted to a switch 14, which is controlled by a CPU 15. The output of the selected TCXO or crystal oscillator 12 and the OCXO 13 is inputted to a frequency synthesizer 16. Just after applicaton of power, the characteristic of the TCXO or the crystal oscillator indicates a linear characteristic as time elapses, but the characteristic of the OCXO does not have specified accuracy because the characteristic requires warm-up time just after application of power. Then the OCXO has the specified characteristic for 3 to 30minutes and the output of the TCXO or the crystal oscillator and the output of the OCXO are switched by a switch based on data stored in a CPU.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference oscillator switching circuit used in a frequency synthesizer of a wireless communication device.

[0002]

2. Description of the Related Art Conventionally, a frequency synthesizer (for example, PLL (Phase Locked Loo) of a transceiver is used.
p) circuit and DDS (Direct Digital)
The high-precision oscillator circuit used to generate the reference signal of the SyntheSizer circuit uses TCXO (temperature-compensated crystal oscillator) or OCXO (crystal oven with constant temperature chamber). The crystal oscillator, TCXO, and OCXO were used properly.

In the case of an HF communication device, the following is true. When the required accuracy is 10 ppm to 5 ppm, a normal crystal oscillator (FIG. 4 (a)) is used, and when it is 5 ppm to 0.5 ppm, the TCXO is used. (FIG. 4 (b)) shows 0.5 ppm to 0.2
At 5 ppm, OCXO (Fig. 4 (c)) is used.

[0004]

[Problems to be Solved by the Invention] However, OC
The XO is a very high precision oscillator, which is very effective for improving the performance of a wireless device, but usually requires a warm-up time of 3 to 30 minutes because it uses an oven. Therefore, there is a problem that the accuracy is considerably worse during the warm-up time than when the power is turned on, and normal transmission and reception cannot be performed. Especially, for amateur radio that is required to be used after the power is turned on. , OCXO is difficult to adopt.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to solve the above-mentioned problems and to provide a radio communication device which uses a high precision reference oscillator using OCXO and can perform transmission / reception when the power is turned on. .

[0006]

The present invention is a switch for selecting either TCXO (temperature-compensated crystal oscillator) or the output of a crystal oscillator and an OCXO (crystal oscillator with constant temperature chamber) and inputting the oscillation frequency to a frequency synthesizer. And a CPU for controlling the switch and a PLL or DDS circuit for inputting a signal selected by the switch.

[0007]

The present invention provides a TCXO or a crystal oscillator and an OCXO.
With two reference oscillators, the output of TCXO or crystal oscillator is used as the reference signal during the warm-up time of OCXO from the time of power-on, and after the warm-up is completed, the output of OCXO is switched by the CPU. To do.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a TCXO (temperature compensated crystal oscillator).
Or, it has two reference oscillators, a crystal oscillator and an OCXO (crystal oscillator with constant temperature chamber), and uses the output of the TCXO or crystal oscillator as a reference signal during the warm-up time of the OCXO after the power is turned on, and after the warm-up is completed. OC
Switch to XO output. The output of these reference oscillators is switched by the CPU or the like according to the time elapsed after the power is turned on.

FIG. 1 is a block diagram showing the configuration of the present invention. The output of the TCXO or crystal oscillator 12 and the OCXO1 is shown.
3 is input to the switch 14, and the switch 14 is controlled by the CPU 15. The output of the reference oscillator of the selected TCXO or crystal oscillator 12, OCXO13 is
Input to the frequency synthesizer 16.

FIG. 2 shows 2 ppm TCXO and 0.25 pp
FIG. 3 is a diagram showing expected characteristics when used in combination with OCXO of m.
The characteristics of the crystal oscillator show a linear characteristic with the passage of time, but the characteristics of the OCXO do not reach the specified accuracy immediately after the power is turned on because the warm-up time is required. The accuracy of the OCXO becomes specified between the two, and at that time, based on the data stored in the CPU, the output of the TCXO or the crystal oscillator and the OC
Switch the output of XO with a switch.

FIG. 3 is a flow chart showing the operation of the CPU 15 used for selecting the reference oscillator of the present invention. When it is confirmed in step 31 that the power supply is turned on, the switch is turned to TCXO in step 32. After switching the switch for switching to, the TCXO and the crystal oscillator start to be used, and the OCXO enters the warm-up time. In step 33, the warm-up time is 3
When it is determined that the time has reached 0 minutes or more, the switch is switched to OCXO in step 34, and a highly accurate reference oscillation signal can be sent to the frequency synthesizer.

[0012]

As described above, according to the present invention, the problem that transmission / reception cannot be performed when the power is turned on when the OCXO is a single unit is improved.
Since a 2 ppm oscillator is equipped and a higher precision reference oscillator is optionally installed, a product in which the configuration of the above invention is changed by adding an option is conceivable.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is an expected characteristic diagram when a combination of TCXO and OCXO is used.

FIG. 3 is a CPU used to select a reference oscillator of the present invention.
The flowchart which showed operation | movement.

FIG. 4 is a diagram showing that oscillators have been separately used according to the precision required by a frequency synthesizer.

[Explanation of symbols]

 12 TCXO or crystal oscillator 13 OCXO 14 switch 15 CPU 16 frequency synthesizer

Claims (1)

[Claims] 1. A reference oscillator circuit used in a frequency synthesizer, a temperature-compensated crystal oscillator or crystal oscillator, a crystal oscillator with a constant temperature oven, and an output from the temperature-compensated crystal oscillator or the crystal oscillator and the crystal oscillator with constant temperature oven. And a CPU for controlling the switch for inputting the oscillation frequency to the frequency synthesizer, and immediately after the power is turned on under the control of the CPU, the temperature-compensated crystal oscillator or crystal oscillator is activated. A reference oscillator circuit, which is used, and after the warm-up time of the crystal oscillator with a constant temperature bath has elapsed, the oscillation frequency is switched to the oscillation frequency from the crystal oscillator with a constant temperature chamber.