JP3155113B2 - Temperature compensated crystal oscillation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature-compensated crystal oscillation circuit used in consumer information devices such as mobile communications and portable radios.

[0002]

2. Description of the Related Art A conventional temperature-compensated crystal oscillation circuit has a
The circuit configuration is roughly divided into two types or a mixed type circuit configuration of both types as shown in FIGS. The oscillating circuit shown in FIG. 2 is of a type in which the temperature characteristic of the oscillating frequency is compensated in an analog manner using the load capacitance dependency of the oscillating frequency.

[0003] That is, in FIG. 2, a temperature sensing element 11 composed of a combination of thermistors converts a temperature change into a voltage change. This voltage change changes the load capacitance of the oscillating unit 14 composed of the capacitor 12 and the variable capacitance diode 13. The oscillation frequency 17 generated by the reference crystal unit 15 and the oscillation circuit 16 changes due to the change in the load capacitance. By using such a principle and appropriately combining the temperature characteristics of the capacitor 12, the variable capacitance diode 13, and the thermistor used for the temperature sensing element 11, the oscillation frequency Fout1 which is highly stable against temperature change can be obtained.
7 can be realized.

The above is the principle of the analog temperature compensation circuit. Next, FIG. 3 will be described. This is a temperature compensation circuit combining dual oscillation and digital control.
That is, a single reference crystal oscillator 18 and an oscillation circuit 19 simultaneously oscillate a natural frequency Fs20 and a reference frequency Fo21 having a large temperature coefficient, and each of the signals 22 and 23 having different characteristics produces two signals. To separate.
This portion is the dual oscillation section 24, and oscillating two kinds of signals with one crystal oscillator is called "dual oscillation". These two types of signals are input to the digital control unit 25. At this time, the frequency Fs20 has a role of a temperature sensor. In the digital controller 25, the reference frequency Fo21 is subjected to temperature compensation by the sensor frequency Fs20. Then, finally, the oscillation frequency Fout 26 that is highly stable against the temperature change is output.

[0005] The above is the principle of the temperature compensated oscillation circuit that combines dual oscillation and digital control. The details of this type of oscillation circuit have been announced as a dual crystal oscillator at, for example, the 20th EM Symposium (Wave Device / Frequency Control Symposium).

[0006]

In the analog temperature compensating circuit shown in FIG. 2, the difference in the thermal conductivity caused by the physical properties of the temperature sensitive element 11 and the reference crystal resonator 15 causes the frequency to be reduced in the transient state. There is a drawback that the temperature compensation accuracy is deteriorated. As a countermeasure for this, in recent years, a temperature compensation circuit combining dual oscillation and digital control as shown in FIG. 3 (hereinafter abbreviated as a dual temperature compensation circuit) has been proposed.

[0007] The dual temperature compensation circuit has three major features. The first is that there is no difference in the thermal conductivity described above in order to extract the reference frequency and the sensor frequency from one crystal resonator. Second, digital temperature compensation is employed. Thirdly, the dual temperature compensation circuit has higher accuracy and higher accuracy than an analog temperature compensation circuit because of the three major features that the oscillation circuit section becomes smaller due to the adoption of the dual oscillation circuit. It can be concluded that it is suitable for miniaturization.

[0008] Usually, the quartz oscillator used in the dual temperature compensation circuit is an AT or SC cut. But,
Strict design conditions are required to achieve two electrically stable natural oscillations in the main body of the crystal unit for dual oscillation, so that not only the shape of the crystal unit becomes very large, but also the production yield of the unit. Also has the major disadvantage of being low. For the above reasons, there is a problem that not only the production efficiency of the dual temperature compensation circuit is low but also the size of the circuit cannot be reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems caused by such a crystal oscillator, to improve the production efficiency of a dual temperature compensation circuit, and to reduce the size.

[0010]

[Means for Solving the Problems] In order to solve the above problems, two types of crystal units having different temperature characteristics and vibration modes are used instead of a configuration in which two natural frequencies are simultaneously oscillated by one crystal unit. Are connected in parallel to adopt a dual oscillation configuration.

One of these two types of quartz oscillators is:
It is a strip-shaped AT or SC cut. The other one is a small tuning-fork type crystal resonator or a long side vertical crystal resonator that functions as a temperature sensor.

[0012]

Operation As shown in FIG. 4, the outer shape of a typical crystal oscillator (AT or SC cut) for a dual temperature compensation circuit has a very large shape. The main vibration modes serving as the reference frequencies for the AT or SC cut are both thickness shear vibrations (hereinafter abbreviated as TS modes). For the purpose of exciting only the TS mode, it is known that a small-sized vibrator shown in FIG. 5 can be manufactured with a high yield instead of a very large shape as shown in FIG. In the oscillating circuit to be used, it is a mainstream oscillator. Incidentally, it goes without saying that the vibrator piece shape of the TS mode vibrator shown in FIG. 5 is a strip shape.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In recent years, a small temperature sensor using a quartz oscillator has been well known. As this crystal temperature sensor, a tuning fork type crystal oscillator or a long side vertical oscillator is used. These vibrators can be downsized more than the TS mode vibrator shown in FIG. FIG. 6 shows an external view of the shape of the crystal temperature sensor.

As described above, if two electrically stable vibrations are not required for one vibrator, a very small crystal vibrator can be realized. That is, in the TS mode resonator shown in FIG. 5, for example, a tube type of (1) of 3 mm × 8 mm, a tube type of (2) of 2 mm × 6 mm, and a surface mount type of (3) of about 7 mm × 4 mm × 3 mm are realized. ing. Further, in the crystal resonator for a temperature sensor shown in FIG.
× 6mm, (2) 1.5mm × 6mm, (3) 1mm × 5mm
And the surface mount type of (3) of about 5 mm × 3 mm × 2 mm is realized. Therefore, it is clear that a combination of the two can realize a smaller crystal unit as compared with the dual oscillation resonator shown in FIG.

Next, FIG. 7 shows an electrical equivalent circuit of the vibrator for the TS mode and temperature sensor. This equivalent circuit diagram is
It is common to all vibration modes, and the only difference is the value of the internal equivalent constant. That is, FIG.
Is an equivalent circuit of a TS mode crystal resonator, which is composed of an equivalent capacitance C1 27, an equivalent resistance R1 28, an equivalent inductance L1 29, and an inter-electrode capacitance Co30. FIG. 7 (2) shows an equivalent circuit of the temperature sensor oscillator, which is composed of an equivalent capacitance C1'31, an equivalent resistance R1'32, an equivalent inductance L1'33, and an inter-electrode capacitance Co'34, respectively. I have.

FIG. 8 shows an equivalent circuit when these two vibrators are connected in parallel. When connected in parallel, the equivalent circuit is divided into two, a TS mode section 35 and a temperature sensor section 36. However, only the interelectrode capacitance 37 is the sum of the two. That is, since this equivalent circuit can be regarded as one crystal resonator having two vibrations, it becomes equivalent to the equivalent circuit of the dual oscillation resonator. In addition, since the two crystal units are combined, the difference in thermal conductivity between the two units is small enough to be ignored.

As described above, by connecting the TS mode crystal unit and the temperature sensor crystal unit in parallel, not only the property of the dual oscillation unit can be realized, but also the total oscillation by separating the unit into two small units. Thus, the size of the crystal unit can be effectively reduced. Furthermore, the good production efficiency of these two small vibrators also improves the efficiency of circuit manufacturing.

FIG. 1 is a block diagram showing the present invention. In the dual oscillating unit 1, a TS that is a reference oscillation source
A mode crystal resonator 2 and a temperature sensor crystal resonator 3 are connected in parallel. Needless to say, the TS mode crystal resonator 2 and the temperature sensor crystal resonator 3 are small-sized resonators shown in FIGS.

That is, the containers for both crystal units are
Tube type or surface mount type. Oscillation circuit 4 and filters 5 and 6 separate the signal into two oscillation frequencies Fts7 and Fs8. Here, the oscillation frequency Fs8 is the temperature sensor frequency. These two frequencies are input to the digital control unit 9. In this digital controller 9, the oscillation frequency Fts7 is changed to the temperature sensor frequency Fs.
8 receives temperature compensation. As a result, an oscillation frequency Fout 10 that is highly stable against a temperature change is output.

Incidentally, in the embodiment of FIG. 1, the detailed configurations of the oscillation circuit 4, the filters 5, 6 and the digital control unit 9 resulting from differences in the frequency and temperature characteristics of the two vibrators are merely design matters. Therefore, it has no essential effect on the present invention.

[0021]

As described above, a tuning fork type crystal oscillator or a long side vertical oscillator is used as a temperature sensor, and the temperature sensor crystal oscillator and the reference oscillation crystal oscillator are connected in parallel. This has the effect of reducing the size of the dual oscillation crystal unit and improving production efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a temperature-compensated crystal oscillation circuit according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional analog temperature-compensated crystal oscillation circuit.

FIG. 3 is a block diagram showing a configuration of a temperature-compensated crystal oscillation circuit in which a conventional dual oscillation circuit and digital control are combined.

FIG. 4 is a perspective view showing the dimensions and shape of a typical crystal oscillator for a dual temperature compensation circuit.

FIGS. 5 (1), (2) and (3) are perspective views showing the dimensions and shape of a reference frequency oscillation thickness-slip quartz crystal resonator used in the present invention.

FIGS. 6 (1), (2), (3), and (4) are perspective views showing dimensions and shapes of a crystal resonator for a temperature sensor used in the present invention.

FIGS. 7 (1) and (2) are diagrams showing an electrical equivalent circuit and equivalent constants of a reference frequency oscillation thickness shear and temperature sensor crystal resonator used in the present invention.

FIG. 8 is a diagram showing an electrical equivalent circuit and equivalent constants of a reference-frequency oscillation thickness shear resonator and a temperature sensor crystal resonator used in parallel in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dual oscillation part 2 TS mode crystal oscillator 3 Crystal oscillator for temperature sensor 4 Oscillation circuit 5, 6 Filter 7 Oscillation frequency Fts 8 Oscillation frequency Fs 9 Digital control part 10 Oscillation frequency Fout

Continuation of the front page (56) References JP-A-56-33586 (JP, A) JP-A-56-160891 (JP, A) JP-A-58-166808 (JP, A) JP-A-51-34653 (JP, A) , A) JP-A-54-54075 (JP, A) JP-A-3-229502 (JP, A) JP-A-56-43806 (JP, A) Fully open 1975-58935 (JP, U) Fully open 54-173654 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H03B 5/30-5/42

Claims (3)

(57) [Claims] 1. A quartz oscillator for a reference oscillation, wherein a tuning fork type quartz oscillator or a long side vertical quartz oscillator is used as a temperature sensor, and the quartz oscillator for the sensor is provided separately from the quartz oscillator for the sensor. Temperature compensation type crystal oscillation characterized in that the sensor oscillator and the reference oscillation crystal oscillator are simultaneously oscillated by an oscillation circuit to digitally correct the temperature characteristics of the reference oscillation frequency. Circuit configuration. 2. The temperature-compensated crystal oscillation circuit according to claim 1, wherein the reference oscillation crystal resonator is designed to excite only thickness shear vibration. 3. The temperature according to claim 1, wherein the containers for the reference oscillation crystal unit and the sensor crystal unit are of a small tube type or a surface mount type, respectively. Compensated crystal oscillation circuit.