JPS6097702A - Digital temperature compensation piezoelectric oscillator - Google Patents

Abstract

PURPOSE:To obtain a digital temperature compensation piezoelectric oscillator with high accuracy, high stability and excellent in mass productivity by constituting plural different time constant circuits between a temperature compensation voltage controller and a voltage controlled varactor diode so as to be selected switchingly. CONSTITUTION:A time constant circuit 22 is inserted so as to be selected switchingly by a switch 23 between a temperature compensation voltage controller 21 and a voltage controlled varactor diode 24 to which a signal of digital temperature compensation control voltage is applied from the controller 21. When a temperature compensation voltage is applied suddenly to the voltage controlled varactor diode 24 at the actual operation, the capacitance value is unstable and it takes a time to make the oscillation frequency stable, then the switch 23 selects the time constant of the time constant circuit 22 to be longer and the oscillating frequency is changed so as to make the circuit stable. On the other hand, the time constant is selected to be short by the switch 23 at the adjustment in the manufacture process, the adjustment time is decreased. Thus, the desired purpose is attained.

Description

Detailed Description of the Invention [Field of Techniques of the Invention t4i] The present invention inserts a time constant circuit between supplying a digital temperature-compensated control voltage from a temperature-compensated all-amplifier to a voltage control g4+variable capacitance element. A switching circuit is installed in the constant circuit.It is related to a digital temperature compensated piezoelectric oscillator.

[Conventional technology] With the rise of electrical and electronic products in recent years, oscillators that use IJ reference signals in communication equipment have become important.Especially with the rise of high-end radio base stations, mobile radio equipment, etc. Stable IL and high i
'i' 7 degrees 1hi is desired -(-is.

If: Starting from the end, the oscillation layer provides a high-precision, long-term stable oscillation frequency (11). However, the crystal oscillator has a frequency temperature characteristic that is similar to the frequency temperature characteristic of the crystal oscillator, and because the oscillation frequency is empty due to temperature + It is also unsuitable as an oscillator for communication equipment that requires high frequency regulation.

For this reason, in order to achieve high integration and high stability IL, it has traditionally been considered possible to compensate for the frequency 1 wave number temperature characteristics of the crystal oscillator, and this is known as the so-called TCXO (temperature complement crystal oscillator). However, in most of these cases, the oscillation frequency can be changed by the crystal oscillator or the load capacitance. High precision, whether it has a shape or not.
In view of high stability, the present invention refers to a digital type. In other words, an analog signal from a thermosensor, such as a thermosensor, is digitized by an A-D converter, and then sent to a microcomputer.
Black degree capture IN voltage control 1111 device fat [convert to temperature compensation control voltage, this temperature? IIi IN control voltage is applied to the voltage-controlled variable capacitance element to change the load capacitance applied to the crystal stator, and the oscillation frequency is changed by the change in load capacitance to compensate for the temperature in the frequency temperature JJL characteristic. This is done over the entire required temperature range.

However, with the conventional digital TCXO circuit configuration, the temperature compensation control voltage from the digital signal is directly applied to the voltage limiting variable capacitance element at each temperature, which affects the stability of the oscillation frequency or the stability in a short time. It has a bad influence. Furthermore, it has the disadvantage of not being able to handle sudden changes in frequency-temperature characteristics.

Additionally, due to the poor frequency stability, adjustments during the manufacturing process require man-hours, which hinders mass production.

[1] The present invention has been made in view of these drawbacks, and therefore, the present invention has been made in view of these shortcomings. Weigh the fact that 1 co-supply is provided by l''.

In order to achieve such a goal, in the present invention, a time constant circuit is provided between supplying the digital temperature compensation control voltage from the Temperature IR voltage regulator to the terminal of the voltage control + variable capacitor. The present invention will be explained below based on examples.

[Embodiment 1] FIG. 1 (8) is a block diagram showing the configuration of the present invention. Here, in order to eliminate frequency deviation in accordance with the target frequency, the temperature compensation voltage controller 11 converts it into the required temperature compensation voltage iin voltage, which is then connected to a time constant circuit equipped with a switching circuit 13. 12, the voltage control 5I is applied to the variable capacitance terminal 14 at the required time constant, and is converted here to a temperature compensated control voltage or capacitance, and this is the piezoelectric vibrator 1.
5 is added as a load capacitance, and the oscillation circuit 16 is supplied with a compensated frequency. The broken line portion in the figure is the time constant circuit and switching circuit of the present invention.

FIGS. 1(b) and 1(c) show the temperature compensation 1h control voltage from the temperature compensation voltage controller 11 or the voltage control if++ variable capacitor terminal 14.
(b) shows the case of direct addition as in the conventional case. The figure (c) shows the relationship between the temperature compensation control voltage V and the frequency F when applied via the time constant circuit 12 on the time axis t.
In the same figure (b), since the temperature compensation control voltage V is suddenly applied to the voltage control variable capacitance element 14, the capacitance value becomes unstable, and the frequency becomes unstable as it is. It takes time t to stably reach the target frequency value. On the other hand, in the same figure (c), since the temperature compensation control voltage V is integrated by the time constant circuit 12 and then applied to the voltage limiting variable capacitance element 14, the change in capacitance value is smooth, so the stability of the frequency is affected. It is stable within a short time of t2 with respect to the target frequency value.

The 21st Δ is an embodiment in which the present invention is made longer, and the temperature is 1jLJi.
Digimol temperature +ii+i from 1-tribute voltage control σIHB21
1 Prize control 1 Voltage signal or voltage control 11 Variable capacitor terminal 24
A time constant circuit 22 is inserted between the two. In the figure, the time constant circuit 22 integrates the digital temperature g+1 voltage in order to lengthen the time constant, and then the voltage control circuit 22 integrates the g+1 voltage.
In addition to the I variable capacitor 24, the piezoelectric vibrator 25 is caused to oscillate by the oscillation circuit 26 using the load capacitance from the voltage controlled variable capacitance element 24, and the oscillation frequency is slowly changed to the desired j^I wave number. On the other hand, if the time constant of the time constant circuit 22 remains long, it will take time to stabilize the oscillation frequency during adjustment in the manufacturing process of the frequency temperature 1, ν, which is undesirable. Therefore, in the present invention, in actual single use, the left adjustment u4 left time constant (Ri) 22 is changed to the switching circuit 23.
The time constant is changed by . That is, in actual use, in order to prevent the voltage from being suddenly applied to the voltage control σ11 variable capacitance element 24, the time constant is made long and the oscillation frequency is changed slowly to achieve stabilization. This is because it takes too much time for the frequency to settle down during the adjustment process during the manufacturing process, which requires a lot of man-hours.

It has become difficult to mass-produce it, and it has also become difficult to make it low quality.

For this reason, during adjustment, this time constant is shortened to shorten the adjustment time, and in the present invention, this can be made variable. In the T42 diagram, capacitors C1 and 02 adjust the time constant C7 and C2 are C+
<< The capacitor is selected based on the C2 condition, and during adjustment, the C4 capacitor 11111 is used with a long time constant, and during actual use, the C2 capacitor is switched to the C2 capacitor and the time constant is shortened.

This makes it possible to shorten the time during the 1-bar adjustment, and in actual use, the voltage-controlled variable capacitance element 24 receives the digital temperature-compensated control voltage from the temperature-compensated voltage controller 21 in an integrated form. Since it is applied to the element 24, it has an effect on frequency stability.

FIG. 3 shows another embodiment using a time constant circuit 327 and a resistor i.
I changed the length of the cut on July 11th.
Adjustment 11Y in the same figure is 1, and the side is 1 and ↓.
During actual 1/k use, switch between R and 2L: L&
33, there is a relationship of R, <i < R7 between iiJ variation phrase R, 7R, and U.

The effects are as shown in Figure 2, 1.
1 liter is 1-.

FIG. 11 further shows an example of pond h constant times j/8112
Is this a device that incorporates a transistor, which is an active element? ,,R2 is made to match the condition of the resistance value of 3rd and 1st, and the time constant is adjusted by the 1st bar switching circuit b'1i43. Do 2. Moreover, on the active element I−' E i”
etc.

[Invention glue h:'J! ) Temperature? 111 Compensation i) ++Electrical voltage control υ11 Controller change capacity A By inserting a time constant circuit between the two and increasing the time constant, the temperature compensation fee fi+ can be reduced for the voltage control i1+1uJ change capacity
Is it 153 which is divided by 121 of + voltage? A smooth and stable frequency can be obtained by changing the number of frequencies.

Additionally, in order to shorten the time during adjustment, the time constant is shortened to reduce the number of man-hours.This makes it possible to create a digital temperature-compensated piezoelectric oscillator that is highly stable, highly accurate, and mass-producible.

Although some crystal oscillators have been described as piezoelectric oscillators in the present invention, it goes without saying that similar effects can be obtained with saw oscillators made of piezoelectric ceramics, lithium tantalate, or the like. In addition to the variable capacitance group, the voltage-controlled variable capacitance element may be any element whose capacitance changes with a change in voltage, such as a transistor.

[Brief explanation of drawings]

FIG. 1(a) is a flock diadem showing the configuration of the present invention. Figures 1 (b) and (c) show temperature 1! 1tli li (A diagram showing the relationship between control voltage and frequency. Figures 2, 3, and 4)
The figure is a circuit diagram showing an embodiment of the present invention. 11.21...Temperature compensation controller 12.22,
32.42...Time constant circuit 13.23.33.4
3--... Switching interval v; 114.24... Voltage controlled variable capacitance element 11i, 2 (i... Oscillation circuit

Claims (1)

[Claims] In a piezoelectric oscillator circuit that performs temperature compensation using a digital signal, a switching circuit is installed between the temperature compensation voltage regulator and the voltage controlled variable capacitance element to switch between at least two time constants with different time constants. #Onboard digital temperature compensation 1 piece piezoelectric oscillator.