JPS63312704A - Digitally temperature compensated crystal oscillator - Google Patents

Abstract

PURPOSE:To obtain a satisfactory digital temperature compensating crystal oscillator by executing the temperature compensation with a temperature detecting part having a linear function characteristic, a ROM to store beforehand a frequency dividing ratio as control information to compensate and a programmable frequency-divider. CONSTITUTION:A crystal oscillator 11 to use a crystal vibrator, in which a frequency has the characteristic of a linear function to temperature, has a role as a temperature sensor. For the output of the oscillator 11, the frequency is measured by a frequency counter 13. To the gate signal of the counter 13, the output of an oscillator 12 is frequency-divided and used. The output of the counter 13 is temperature information and the digital signal is inputted to a ROM 14. In the ROM 14, a frequency dividing ratio, in which the output of the oscillator 12 goes to be constant in an oscillation frequency to a temperature change, is stored as the control information. The control information stored in the ROM 14 is inputted to a program frequency-dividing ratio, and by changing the frequency-dividing ratio, the frequency is made constant.

Description

Detailed Description of the Invention [@Rakudo Application Field 1 The present invention relates to a digital temperature-compensated crystal oscillator that performs temperature compensation using a ROM that stores compensation control information and a programmable frequency divider.

When compensating the frequency-temperature characteristics of the crystal resonator 26, conventionally, as shown in the block diagram of FIG. There is a temperature detection section 21 for sensing, and an analog signal generated from the temperature detection section 21 is converted into a digital signal as temperature information by an A/D conversion section 22, and temperature compensation control information of the crystal sensor 26 is stored in a ROM circuit 23 in advance. is stored, temperature compensation information corresponding to each temperature is output as a digital signal, this digital signal is converted to an analog signal by the D/A converter 24, and a variable capacitor connected in series with the crystal camera 26 is connected. There is a digital temperature compensated crystal oscillator (D-TCXO) that is input to the diode 25 and performs temperature compensation. 27 is an oscillation section.

[Problem to be Solved by the Invention 1 The ROM shown in FIG. 2 is a digital circuit, but in order to accommodate the temperature compensation signal in the ROM, the temperature detection section, A/D conversion section, and D/A Since the conversion section and oscillation section are analog circuits, there are variations in products. Also, in order to have temperature characteristics, it is necessary to store the γ quality award report including those γ quality characteristics in RO~I,
This required a lot of man-hours and was also a factor in lacking accuracy. Furthermore, the oscillation part is a voltage controlled oscillator (VCO)
Therefore, the circuit configuration was complicated.

[Configuration 1 of the present invention The configuration of the present invention includes a temperature detection unit that detects temperature, an A/D conversion unit that converts temperature information into a digital signal, and control information that determines the temperature characteristics of a crystal oscillator. This is a digital temperature compensated crystal oscillator consisting of a ROM that stores I2 and a programmable frequency divider whose frequency dividing ratio changes to divide the output of the crystal oscillator by the output 1 of ROhi.

[Operation and Embodiment 1] FIG. 1 is a block diagram showing an embodiment of the present invention.

As a temperature detection section, a crystal oscillator using a crystal oscillator whose frequency is a linear function with respect to temperature]J has a role as a temperature sensor. The crystal oscillator 12 is a crystal oscillator I2 that serves as a reference for temperature compensation, and in this embodiment is an oscillator using a T-cut crystal resonator. The frequency of the output of the crystal oscillator 11 is measured by a frequency counter 13.

At this time, the frequency-divided output of the crystal oscillator 12 is used as the gate signal of the frequency counter 13. The output of the frequency counter 13 is temperature information, and this digital signal is
Input to OM14. The ROM 14 stores, as control information, a frequency division ratio so that the oscillation frequency of the output of the crystal oscillator I2 remains constant regardless of temperature changes. Then, the control information written in ROA=114 is input to the programmable frequency divider 15 based on the temperature information, and the frequency is kept constant by changing the frequency division ratio. In addition, R
In order to store the control information of the frequency division ratio in the OM14, only the crystal oscillator 11 and the crystal oscillator 12, which are analog circuits surrounded by a dashed line in FIG. You can get information.

That is, since the frequency counter 13, ROM 14, and programmable frequency divider 15 are digital circuits, they do not have temperature characteristics. In the conventional digital temperature compensated crystal oscillator, it is necessary to take into account the temperature characteristics of the analog part caused by converting an analog signal to a digital signal and back to an analog signal. In the present invention, the only analog circuit is the crystal oscillator 11:12, and temperature compensation can be performed by accurately measuring the frequencies of the two oscillators. In addition, a crystal oscillator 1 as a temperature detection section
1 is a frequency sensor, so it can read more digits and obtain more accurate information than a normal temperature sensor.

FIG. 3 is a block diagram showing another embodiment of the digital temperature compensated crystal oscillator.

A temperature detecting section 21 and an A/D converting section 22 may be provided instead of the crystal oscillator 11 and frequency counter 13 shown in FIG. The part surrounded by a dashed line is an analog circuit.

Furthermore, the frequency of the output from the programmable frequency divider 15 is low because it has been divided, but the frequency can be increased by connecting the output of the programmable frequency divider 15 to a PLL circuit. . Alternatively, a multiplier may be used.

[Effect of the present invention J] The present invention provides a temperature detection section having a characteristic of a -order function and a frequency division ratio as control information to be compensated for in advance. R
Since temperature compensation is performed using a frequency converter, the analog circuit is a temperature detection section and a crystal oscillator, and when temperature compensation information is stored in ROM, the temperature detection section of the analog circuit with temperature characteristics and the reference All that was required was to place a crystal oscillator in a temperature bath and accurately measure the frequency, making it extremely simple. Furthermore, digital circuits have the advantage of being easily integrated into ICs. Furthermore, since the crystal oscillator of the present invention obtains a stable frequency by changing the frequency division ratio, the oscillator is not a conventional voltage controlled oscillator (VCO).
), an oscillator with a simple configuration may be sufficient.

[Brief explanation of the drawing]

1 and 3 are block diagrams of the digital temperature compensated crystal oscillator of the present invention. FIG. 2 is a program diagram of a conventional digital temperature auxiliary fountain oscillator. 11.21...Temperature detection unit 12...Crystal oscillator 13...Frequency counter 1=1...Ding OM 15...Programmable minute Shuki patent detoner
Kinseki Co., Ltd. 1st JJ Figure 2 Figure 3

Claims (2)

[Claims] (1) A temperature detection section that detects temperature, an A/D conversion section that converts temperature information into a digital signal, a ROM that stores control information that compensates for the temperature characteristics of the crystal oscillator, and an RO
A digital temperature-compensated crystal oscillator comprising: a programmable frequency divider whose frequency division ratio for dividing the output of the crystal oscillator changes depending on the output of the crystal oscillator. (2) The digital temperature compensated crystal oscillator according to claim 1, wherein the temperature detection section is a crystal oscillator.