JPS61135206A - Stabilized crystal oscillator - Google Patents

Abstract

PURPOSE:To obtain a highly stabilized crystal oscillator by using a received standard radio wave as a reference signal to form a phase synchronizing crystal oscillator. CONSTITUTION:A standard radio wave received through an antenna 1 is divided by a frequency divider 6 and supplied to an input R terminal for reference signal of a phase comparator 7. While the oscillation output of a voltage controlled crystal oscillator VCXO10 is supplied to an input S terminal for reference signal. The comparator 7 compares the phases of the rises with each other between the input signals of both terminals S and R and delivers a signal corresponding to an obtained phase difference. This output signal is impressed to the control terminal of the VCXO10 via an LPF8. Thus the VCXO10 always receives the phase synchronization with the frequency accuracy of the standard radio wave and therefore secures the extremely high stability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a next-stabilized crystal oscillator that uses a crystal resonator to configure the oscillator.

[Technical background of the invention and its problems]

Most electronic devices always use oscillators to generate electrical signals, but the frequency accuracy of these oscillators becomes a problem to varying degrees. Especially for mobile radio Q: ±5×
Accuracy of 10 or higher is required.

Frequency accuracy is strictly required depending on the communication method and communication capacity.

There is a nine-crystal oscillator using a crystal resonator that satisfies these requirements. This crystal resonator is characterized by high stability of the natural resonance frequency of the material itself and high Qt, so by combining it with an appropriate oscillation circuit,
Extremely stable frequency output can be obtained. The temperature characteristics of this crystal oscillator also vary greatly depending on the cutting direction and vibration mode, so in order to obtain a high frequency stability, it is necessary to use an AT plate and a 9-thickness oscillation oscillator. Figure 4 shows the temperature characteristics of the AT plate, which shows a cubic curve, and by changing the cutting angle by a very small amount (2i'i degrees), the characteristics change greatly as shown in Figure 5. . Therefore.

To obtain a highly stable oscillator over a wide temperature range, K selects a high-quality crystal material, strictly determines the cutting direction, and manufactures a vibrator using a cut-out substrate. A temperature-compensated crystal oscillator is used, which uses a temperature-sensitive element such as a star or a varactor to convert temperature into reactance, and compensates for the frequency-temperature characteristics of a crystal resonator. This is also 0
．． The frequency stability is about 1 to 3 × 10, and to make it even more stable, it must be used in a constant temperature chamber, but it consumes a lot of power, takes a long time to stabilize the temperature in a constant temperature chamber, and has a large external size. There were problems such as the size of the product becoming large and the price becoming extremely high.

In addition to changes in frequency due to temperature changes, there is also a time-dependent change characteristic that gradually changes over a long period of time, and in order to reduce this, as mentioned above, carefully selected It had to be manufactured, making it even more expensive.

[Purpose of the invention]

This invention was made with the intention of solving the above-mentioned drawbacks.
The present invention attempts to provide an inexpensive and highly stable stabilized crystal oscillator by receiving standard radio waves and constructing a phase-locked crystal oscillator using the radio waves as a reference signal.

[Summary of the invention]

The present invention is characterized in that an oscillator using a crystal resonator receives a standard radio wave as a means for frequency stabilization and constitutes a phase-locked crystal oscillator.

〔Effect of the invention〕

According to the present invention, since the voltage controlled crystal oscillator (VCxo) is configured in phase synchronization with the standard radio wave as described above, it is possible to easily obtain frequency stability of about 1×1O. Furthermore, since there is no need to use a constant temperature oven, power consumption can be reduced, the overall price can be reduced, and the device can be made smaller.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 shows an example in which the present invention is applied to a reference oscillator of a receiver. In Fig. 9, 1 is a standard radio wave (10MH2) t-
In the receiving antenna, 2 and 4 are tank circuits that resonate with IOMH2K'', and 3 and 5 are amplifiers.The amplified telephonic signal is divided into 1/1.000 by frequency divider 6, and then sent to a phase comparator. 7 is input to the standard signal input R terminal.On the other hand, a voltage controlled crystal oscillator (consisting of a crystal resonator, a varactor, etc.)
VCXO > i o oscillation output 10M) Iz is also frequency divider 9
The signal is frequency-divided to 1/1.000 and input to the signal input S lever of the phase comparator 7.

The phase comparator 7 compares the rising phases of the two input signals S and K, and outputs a signal according to the phase difference. This output signal is passed through a bottom filter 8 and converted into a DC voltage, and then applied to a varactor, that is, a control terminal # of a voltage controlled crystal oscillator 10. By doing so, the voltage controlled crystal oscillator 10 is always phase synchronized with frequency accuracy of #, quasi-radio wave (JJY), and becomes extremely stable.

This frequency accuracy cannot be generalized because it changes somewhat due to the Doppler effect due to changes in the height of the ionosphere when the standard radio wave propagates.
A frequency accuracy of about 1X10-' can be obtained during E-mode, and about 5X10-' at night.

In this way, a highly accurate reference oscillation frequency can be easily obtained without using an i-temperature sensor, etc., so the device has the advantage of being downsized and cost-reduced as a whole.

FIG. 2 is a book showing another embodiment of the invention. In this embodiment, when an out-of-synchronization occurs due to unreceivable standard radio waves or a drop in level, the out-of-synchronization detection circuit 11 detects the out-of-synchronization.
By inspecting the vehicle and outputting the DC voltage of the previous state,
This is a precaution to maintain a synchronized state. Other configurations are the same as in Figure 1, so
Identical parts are given the same reference numerals and explanations will be omitted.

FIG. 3 shows another embodiment of the invention. In this embodiment, standard radio waves are received for a certain period of time, and the arithmetic control unit 12
The average value is taken at that frequency and synchronization is applied at that frequency, and the previous state is maintained at other times. The rest of the configuration is the same as that shown in FIG. 1, so a description thereof will be omitted.

With such a configuration, highly accurate oscillation frequency output can be obtained. It should be noted that the present invention is not limited to the above-mentioned embodiments, but may be implemented with various modifications within the scope of the invention.

[Brief explanation of drawings]

Fig. 1 is a block diagram of one embodiment of this invention, Fig. 2 is a block diagram of another embodiment of this invention, Fig. 3 is a block diagram of another embodiment of this invention, and Fig. 4 @ is an ATCut crystal. An example of frequency-temperature characteristics of a resonator is shown in FIG. 5, which is a configuration diagram of a conventional temperature-compensated crystal oscillator. 1... Antenna, 2, 4... Tank circuit, 3, 5...
... Amplifier, 6,9... Frequency divider % 7... Phase comparator, 8... Low-pass filter, 10... Voltage controlled crystal oscillator, 11... Out-of-synchronization detection circuit, 12 ...Arithmetic control circuit. Agent Patent attorney Kensuke Norichika (and 1 other person) Figure 1 Figure 2

Claims (3)

[Claims] (1) A means for receiving a standard radio wave, a crystal voltage controlled oscillator, a frequency divider for dividing the frequency of the standard radio wave and the output of the crystal voltage controlled oscillator, and a frequency divider for dividing the frequency of the standard radio wave and the output of the crystal voltage controlled oscillator. A stabilized crystal oscillator comprising: a phase comparator that detects a phase difference; and an output of the phase comparator that is applied to a control terminal of the crystal voltage controlled oscillator after passing through a low-pass filter. (2) When the phase synchronization is lost due to unreceivable reception of the standard wave or a drop in level, etc., the output of the phase comparator in the state before the synchronization is maintained by being applied to the control terminal of the crystal voltage controlled oscillator. A stabilized crystal oscillator according to range 1. (3) Claim 1, characterized in that it is used for a receiving device of a navigation system using a navigation satellite.
Stabilized crystal oscillator as described in section.