JP2008258710A - Temperature compensation piezoelectric oscillator, and temperature compensating method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress frequency variation accompanying momentary temperature variation by optimizing the output of a compensation voltage signal by a temperature compensating circuit with high thermal response when frequency variation due to temperature characteristics of a piezoelectric vibrator with low thermal response is temperature-compensated in case of abrupt variation in ambient temperature. <P>SOLUTION: A piezoelectric oscillator 10 has a piezoelectric oscillation circuit configured to output a prescribed oscillation frequency and a temperature compensating circuit which is connected to the piezoelectric oscillation circuit to detect the ambient temperature, and then generates a temperature compensation voltage signal for making the piezoelectric oscillation circuit output a stable frequency. Provided is a delay circuit 18 for the temperature compensating circuit which operates to generate a time constant equal to the time constant of temperature characteristic variation of the piezoelectric vibrator. The temperature compensation voltage output can be delayed so that the time constant of temperature characteristic variation of the piezoelectric vibrator is made to be coincident with the time constant of variation in compensation amount by the temperature compensation output voltage of the temperature compensating circuit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a temperature-compensated piezoelectric oscillator and a temperature compensation method thereof, and more particularly to a temperature-compensated piezoelectric oscillator suitable for mounting on a mobile electronic device using GPS and a temperature compensation method thereof.

A piezoelectric oscillator used in an electronic device such as a GPS receiver is desired to have a small amount of change in oscillation frequency per unit time with respect to a change in environmental temperature in order to prevent malfunction of the electronic device.

Specifically, as shown in FIG. 9, when the ambient temperature that is the ambient temperature of the oscillator changes from T1 to T2 from time t1 to time t2 ((1) in FIG. 9), the oscillation frequency f1 of the oscillator at time t1. And the absolute value | f1−f2 | = Δf of the difference between the oscillation frequency f2 of the oscillator at a time t2 after a predetermined time from t1 needs to be within a predetermined allowable value ((2) in the figure). If Δf is larger than the allowable value, a malfunction such as a shift in the required position information occurs as a result of the positioning process in the GPS receiver.

The following techniques are known as conventional techniques for preventing such malfunctions. That is, if a thermostatic chamber type piezoelectric oscillator (OCXO) as described in Patent Document 1 is used as a positioning piezoelectric oscillator, the change amount Δ of the oscillation frequency per unit time with respect to the temperature change Δ
f can be reduced. Since OCXO keeps the inside of the container in which the piezoelectric vibrator and the oscillation circuit IC are housed at a constant temperature, it is not easily affected by changes in the environmental temperature, and Δf can be reduced.

However, since OCXO is equipped with a heater, it consumes a large amount of power, and since the outer size of the container is increased to make it less susceptible to environmental temperature, it is used as a GPS receiver for mobile devices such as mobile phones. Not suitable.

Therefore, a temperature-compensated piezoelectric oscillator (TCXO), which is a small and power-saving piezoelectric device, is used for mobile electronic devices. This TCXO maintains frequency stability in a wide range of temperatures by canceling out the frequency temperature characteristics of a piezoelectric vibrator such as a crystal vibrator by a temperature compensation circuit (Patent Document 2).
JP 2005-143060 A Japanese Unexamined Patent Publication No. Hei 6-29742

However, even when TCXO is used, the temperature compensation circuit has a faster thermal response than the quartz resonator with respect to an instantaneous temperature change, so that fluctuation occurs in the output frequency of the TCXO. That is, immediately after an instantaneous temperature change occurs, there is a problem that the compensation amount by the temperature compensation circuit is too large. FIG. 10 is an explanatory diagram of this state. When an instantaneous environmental temperature change is detected, the temperature of the IC (indicated by a square in FIG. 10) on which the temperature compensation circuit is mounted is the temperature of the piezoelectric vibrator (
In FIG. 10, it shows by a rhombus. ) Lower temperature change, 10-20 from the time of switch on
The frequency fluctuation range increases in the range of seconds. When such a phenomenon occurs due to the influence of heat from a power amplifier or the like that is close to the mobile board when it is mounted, especially in mobile phones with a GPS function, slight fluctuations in the output frequency of the TCXO will affect the GPS sensitivity. give.

The present invention pays attention to the above-mentioned conventional problems, and when temperature compensation is performed for the frequency change due to the temperature characteristics of the piezoelectric vibrator having low thermal responsiveness when the environmental temperature is suddenly changed, the temperature compensating circuit has high thermal responsiveness. An object of the present invention is to make the output of the compensation voltage signal appropriate so as to suppress the frequency fluctuation accompanying the instantaneous temperature change.

In the present invention, since the temperature compensation circuit has a faster thermal response than the quartz crystal, by delaying the thermal response of the temperature compensation circuit, the difference in the reaction time with the quartz crystal is adjusted to be small and the stability of the frequency is maintained. It is a thing. That is, the reaction time of the temperature compensation circuit is changed by the delay circuit in order to smooth the frequency fluctuation with respect to the instantaneous temperature change.

A temperature-compensated piezoelectric oscillator according to the present invention detects an environmental temperature and generates an environmental temperature signal. The temperature compensation is connected to the temperature sensor and generates a temperature-compensated voltage signal based on the environmental temperature signal. A temperature-compensated piezoelectric oscillator having a circuit and a voltage-controlled piezoelectric oscillator connected to the temperature-compensating circuit and having a piezoelectric vibrator and controlling an oscillation frequency of an output signal based on the temperature-compensated voltage signal A delay circuit for delaying the environmental temperature signal or the temperature compensation voltage signal is provided between the temperature sensor and the temperature compensation circuit, or between the temperature compensation circuit and the voltage controlled piezoelectric oscillator. It is a feature.

With this configuration, the temperature compensation signal can be delayed in accordance with the thermal reaction of the piezoelectric vibrator. For this reason, the reaction time difference between the piezoelectric vibrator and the temperature compensation circuit can be reduced, and the frequency fluctuation can be smoothed against an instantaneous temperature change.

Further, the delay circuit makes the time constant of the temperature compensation signal input to the voltage controlled piezoelectric oscillator coincide with the time constant of the temperature characteristic change of the piezoelectric vibrator. In this way, the temperature compensation operation can be matched with the thermal response of the piezoelectric vibrator.

Furthermore, when the environmental temperature changes from Ta to Tb, the time constant of the temperature compensation signal input to the voltage control type piezoelectric oscillator is τ1, and the temperature compensation signal of the temperature compensation circuit is the voltage control type piezoelectric transducer. If the time constant of the frequency change of the output signal of the voltage controlled piezoelectric oscillator when the environmental temperature changes from Ta to Tb without being input to the oscillator is τ2, the τ1 and the τ2 The time constant of the delay circuit is set so that the values are substantially equal to each other.

With this configuration, the temperature compensation signal from the temperature compensation circuit to the voltage control type piezoelectric oscillator can be delayed by the delay of the start time of the frequency change due to the thermal reaction of the voltage control type piezoelectric oscillator.
It is desirable that the delay circuit includes time constant adjusting means. Since the time constant can be adjusted, it can be adjusted according to the application of the temperature compensated piezoelectric oscillator.

The temperature compensation circuit is an analog temperature compensation circuit. The temperature compensation circuit is a digital temperature compensation circuit, and the delay circuit is connected to output to a subsequent piezoelectric oscillation circuit via an A / D converter of the temperature compensation circuit.
Regardless of whether the temperature compensation circuit is an analog type or a digital type, it is possible to suppress frequency fluctuations accompanying instantaneous temperature changes.

The delay circuit is composed of an RC integrating circuit in which a resistor and a capacitor are connected in series and the capacitor is used as an output, and the time constant adjusting means is composed of a capacitor value switching means. A configuration may be adopted in which a GIC circuit (generalized impedance conversion circuit) is interposed in the time constant adjusting means. Further, it is desirable that the time constant adjusting means is configured as an externally mounted component.

The temperature compensation method for a temperature compensated piezoelectric oscillator according to the present invention also includes a delay circuit for delaying the environmental temperature signal or the temperature compensated voltage signal, between the temperature sensor and the temperature compensated circuit, or between the temperature compensated circuit and the voltage control type. A temperature compensation method for a temperature-compensated piezoelectric oscillator provided with a piezoelectric oscillator, the time constant of change in compensation amount by the temperature compensation signal output from the temperature compensation circuit, and the temperature compensation of the temperature compensation circuit The temperature compensated voltage output is delayed so that the time constant of the frequency change of the output signal of the voltage controlled piezoelectric oscillator in a state where no signal is input to the voltage controlled piezoelectric oscillator is matched. is there.

According to such a configuration, a function capable of changing the time constant of the delay circuit for the temperature compensation circuit is added, and the time constant of the temperature compensation circuit is made to coincide with the time constant of the temperature characteristic change of the piezoelectric vibrator. It is possible to cope with each package having different thermal resistance. In the temperature-compensated piezoelectric oscillator, the time constant of the frequency change (frequency before compensation) of the piezoelectric vibrator with respect to the environmental temperature change and the time constant of the temperature compensation voltage input to the VCO are almost preceded by the VCO. A time constant adjusting circuit whose operation is delayed by the delay circuit is provided. Therefore, it is effective for applications such as GPS that require frequency stability against thermal shock.

Hereinafter, specific embodiments of a temperature compensated piezoelectric oscillator and a temperature compensation method thereof according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a circuit block diagram of the piezoelectric oscillator according to the first embodiment. A temperature compensated piezoelectric oscillator 10 according to this embodiment includes a voltage controlled piezoelectric oscillator (VCXO) 12, and a known temperature compensation circuit 14 is connected to the previous stage in order to compensate for the temperature characteristics of the VCXO 12. The VCXO 12 includes a circuit that oscillates a piezoelectric vibrator such as a crystal vibrator or a ceramic vibrator, a variable reactance element, and the like.

In the case of FIG. 1, the temperature compensation circuit 14 has an analog configuration, obtains an environmental temperature signal from an input signal from the temperature sensor 16, and supplies a temperature compensation voltage for compensating the temperature characteristics of the VCXO 12 to the elements such as a thermistor. The output is performed using the temperature characteristic, and the operation is performed so as to cancel the frequency temperature characteristic of the piezoelectric vibrator.

In addition to such a main configuration, in this embodiment, the analog temperature compensation circuit 14 and the VC
A delay circuit 18 comprising an RC integration circuit is connected in series between XO12. The delay circuit 18 includes a resistor 20 and a plurality of capacitors 22 (22 having different capacitances connected in parallel to the resistor 20.
a, 22b,...), and one of the capacitors 22 is connected to the switch circuit 2.
4 is selected and connected. The delay time by the delay circuit 18 is determined by the capacitance of the selected capacitor. Therefore, the switch circuit 24 corresponds to time constant adjusting means. Adjustment is performed by an external input unit 26.
After switching by a memory (not shown), the set value is held.

Here, when the value of the capacitor 22 selected by the time constant setting means is determined, the delay time of the temperature compensation voltage output from the analog temperature compensation circuit 14 to the VCXO 12 is determined by the value. This time constant is selected so as to coincide with the time constant of the temperature characteristic change of the piezoelectric vibrator. This is determined in accordance with the use environment of the temperature compensated piezoelectric oscillator 10 according to the embodiment. For example, when a power amplifier or the like is present at a GPS-mounted mobile board mounting location, the temperature change changes suddenly. Since the temperature change is large, the time constant should be set large. In any case, the environmental temperature may be set to fill the time lag until the temperature received by the temperature sensor 16 of the temperature compensation circuit 14 and the VCXO 12 is affected by the temperature.

FIG. 2 shows a temperature compensated piezoelectric oscillator 10a according to the second embodiment. This is the same as the first embodiment except that the connection position of the delay circuit 18 is different. That is,
A delay circuit 18 is connected in series between the temperature sensor 16 and the analog temperature compensation circuit 14.

FIG. 3 shows a temperature compensated piezoelectric oscillator 10b according to the third embodiment. This uses a digital temperature compensation circuit 28 and a digital temperature sensor 30 for temperature compensation. In this example, the temperature compensation circuit 28 inputs the temperature signal as a digital signal, reads out the temperature compensation data stored in the memory in advance, and converts it into an analog signal by the D / A converter 32. Thus, the signal is input to the delay circuit 18. Configuration of delay circuit 18, followed by VCXO1
The configuration of 2 is the same as that of the first embodiment. Of course, the temperature sensor 30 is analog and A
The digital temperature compensation circuit 28 may be input by performing D / D conversion.

FIG. 4 shows a temperature compensated piezoelectric oscillator 10c according to the fourth embodiment. This embodiment is an example using a digital temperature compensation circuit 28 as in the third embodiment, but the delay circuit 18 is connected in series between the analog temperature sensor 16 and the digital temperature compensation circuit 28. is there. In this example, the output signal of the delay circuit 18 is converted into a digital signal by the A / D converter 34 and input to the temperature compensation circuit 28, where the compensation voltage signal is read from the memory and output as a digital signal. A signal converted into an analog signal by the A converter 32 is input to the VCXO 12. Others are the same as in the third embodiment.

Such temperature-compensated piezoelectric oscillators 10 (10a, 10b, 1) according to the first to fourth embodiments.
The operation of 0c) will be described with reference to FIGS. FIG. 5 is an explanatory diagram when the delay circuit 18 is not used, and FIG. 6 is an explanatory diagram when the delay circuit 18 according to the embodiment is used. Conventionally, as shown in FIG. 5A, when the environmental temperature changes stepwise (Ta → Tb), the thermal response of the temperature compensation circuits 14 and 28 is faster than that of the piezoelectric vibrator. The temperature compensation voltage signal changes greatly faster than the frequency fluctuation due to the temperature change. Therefore, FIG.
), The time constant τ1 of the temperature compensation voltage signal is shorter than the time constant τ2 of the change in the frequency fluctuation of the piezoelectric vibrator. The graph of the frequency fluctuation of the piezoelectric vibrator shown in FIG. 5 (2) shows the output signal of the VCXO 12 when no temperature compensated voltage signal is input in the temperature compensated piezoelectric oscillator 10 according to the first to fourth embodiments. Frequency. As a result, due to the difference between the two time constants τ, a frequency change of Δf occurs in the output as the temperature compensated piezoelectric oscillator 10 as shown in FIG. 5 (3), and a stable frequency cannot be output.

On the other hand, when the environmental temperature changes abruptly in the same manner (FIG. 6 (1)), the time constant τ1 of the compensation amount change by the temperature compensation output voltage of the temperature compensation circuits 14 and 28, and the temperature of the piezoelectric vibrator Since the temperature compensated voltage output can be delayed so as to match the time constant τ2 of the characteristic change (FIG. 6 (2)), the output as the temperature compensated piezoelectric oscillator 10 is shown in FIG. 6 (3). Thus, the frequency change Δf is canceled and a constant and stable frequency can be output.

In particular, in the case of the third embodiment, in addition to the above effects, when this temperature compensated piezoelectric oscillator 10 is used for an FM communication device, the temperature compensation is performed by delaying the signal of the digital temperature compensation circuit 28. If the rate of change of the oscillation frequency of the piezoelectric oscillator 10 is reduced and the change rate of the transmission frequency of the FM communication device due to the change of the oscillation frequency is reduced, the frequency component of the generated FM noise is lower than the audible frequency. Thus, the advantage that noise can be made harmless is also obtained.

FIG. 7 shows a modification of the delay circuit. In this modification, since the capacitor 22 connected in parallel with the resistor 20 uses a relatively large capacity, GIC (Ge
nerated Immitance Converter) circuit 36 is connected. The GIC circuit 36 can create an arbitrary impedance z. That is, z = jω (R1 · R3) /
With a transfer function of (C · R2 · R4), a wide range of capacitor capacities can be obtained in a pseudo manner depending on how the resistance values are allocated. For this reason, by using a circuit simulator such as the GIC circuit 36 for the capacitor portion of the delay circuit, a pseudo large-capacity grounding capacitor can be obtained from the low-capacitance capacitor, and the delay time can be widened. There is an advantage that integration is possible.

FIG. 8 shows another modification of the delay circuit, in which a capacitor 22 of the delay circuit is externally mounted on an oscillator (OSC) package 38. Thereby, a capacitor having an arbitrary capacity can be used. Also, a terminal for externally mounting the capacitor is provided, and the time constant can be easily changed externally.

According to the above embodiment, the time constant can be easily adjusted by switching the capacitor switch, and the time constant adjusting function can be integrated with the oscillator. Also, in order to reduce the frequency fluctuation of the temperature compensated oscillator due to the instantaneous temperature change, the time constant can be changed by switching the capacitor value of the delay circuit, and the time constant can be switched, so the package with different thermal resistance The delay time can be adjusted every time.

1 is a block configuration diagram of a temperature compensated piezoelectric oscillator according to a first embodiment. FIG. It is the same block block diagram concerning 2nd Embodiment. It is the same block block diagram concerning 3rd Embodiment. It is the same block block diagram concerning 4th Embodiment. It is explanatory drawing which shows the conventional temperature change, a temperature compensation characteristic, and the frequency change of an oscillator. It is explanatory drawing which shows the temperature change of this invention, a temperature compensation characteristic, and the frequency change of an oscillator. It is a circuit diagram which shows the modification of a delay circuit. It is explanatory drawing which similarly shows the other modification of a delay circuit. It is an environmental temperature change figure for explanation of the conventional temperature compensation type piezoelectric oscillator. FIG. 10 is a change diagram of the oscillation frequency of the conventional temperature compensated piezoelectric oscillator based on the temperature change of FIG. 9.

Explanation of symbols

10 ......... Temperature compensated piezoelectric oscillator, 12 ......... Voltage controlled piezoelectric oscillator (VCXO), 14
......... Analog temperature compensation circuit, 16 ......... Temperature sensor, 18 ......... Delay circuit, 20 ...
... Resistance, 22 (22a, 22b, 22c, 22d) ......... Capacitor, 24 ......... Switch circuit, 26 ......... Input section, 28 ......... Digital temperature compensation circuit, 30 ......... Digital temperature sensor 32... D / A converter, 34... A / D converter, 38.

Claims (10)

A temperature sensor that detects the ambient temperature and generates an ambient temperature signal;
A temperature compensation circuit connected to the temperature sensor and generating a temperature compensation voltage signal based on the environmental temperature signal;
A voltage controlled piezoelectric oscillator connected to the temperature compensation circuit, having a piezoelectric vibrator, and controlling an oscillation frequency of an output signal based on the temperature compensated voltage signal;
A temperature compensated piezoelectric oscillator having
A delay circuit for delaying the environmental temperature signal or the temperature compensation voltage signal is provided between the temperature sensor and the temperature compensation circuit, or between the temperature compensation circuit and the voltage controlled piezoelectric oscillator. A temperature compensated piezoelectric oscillator. The temperature compensation type piezoelectric oscillator, wherein the delay circuit is configured such that a time constant of the temperature compensation signal inputted to the voltage control type piezoelectric oscillator coincides with a time constant of a temperature characteristic change of the piezoelectric vibrator. The time constant of the temperature compensation signal input to the voltage controlled piezoelectric oscillator when the environmental temperature changes from Ta to Tb is τ1,
Frequency change of the output signal of the voltage controlled piezoelectric oscillator when the environmental temperature changes from the Ta to the Tb in a state where the temperature compensated signal of the temperature compensating circuit is not input to the voltage controlled piezoelectric oscillator When the time constant of is τ2,
2. The temperature-compensated piezoelectric oscillator according to claim 1, wherein the time constant of the delay circuit is set so that the τ1 and the τ2 are substantially equal to each other. 2. The temperature compensated piezoelectric oscillator according to claim 1, wherein the delay circuit includes time constant adjusting means. 2. The temperature compensated piezoelectric oscillator according to claim 1, wherein the temperature compensation circuit is an analog temperature compensation circuit. The temperature compensation circuit is a digital temperature compensation circuit, and the delay circuit is connected to output to a voltage controlled piezoelectric oscillator at a subsequent stage via an A / D converter of the temperature compensation circuit. The temperature compensated piezoelectric oscillator according to claim 1. 5. The delay circuit according to claim 4, wherein the delay circuit comprises an RC integrating circuit in which a resistor and a capacitor are connected in series and the capacitor is used as an output, and the time constant adjusting means comprises a capacitor value switching means. Temperature compensated piezoelectric oscillator. 5. The temperature compensated piezoelectric oscillator according to claim 4, wherein a GIC circuit is interposed in the time constant adjusting means. 5. The temperature compensated piezoelectric oscillator according to claim 4, wherein the time constant adjusting means is mounted as an externally mounted component. A temperature compensation method for a temperature compensated piezoelectric oscillator according to claim 1,
The time constant of the change in compensation amount by the temperature compensation signal output from the temperature compensation circuit, and the voltage controlled piezoelectric oscillator in a state where the temperature compensation signal of the temperature compensation circuit is not input to the voltage controlled piezoelectric oscillator. To match the time constant of the frequency change of the output signal,
A temperature compensation method for a temperature compensated piezoelectric oscillator, characterized by delaying a temperature compensated voltage output.

Images