JP2000101346A - Structure for highly stable piezoelectric oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means that improves frequency stability of the highly stable crystal oscillator. SOLUTION: An amplifier section 2, consisting of transistors(Trs), capacitors and resistors or the like, a temperature control circuit 3 resulting from eliminating a thermistor Th, a heater H and a power Tr2 from a temperature control section, and a crystal vibrator X are mounted on a printed circuit board 1 by using reflow processing or the like. Thermally related elements such as the thermistor Th, the heater H and the power Tr2 are mounted on a flexible printed circuit board 4 close to each other, and one end of the printed circuit board 4 is electrically connected to the printed circuit board 1 by using solder or the like. Then half of the outer circumferential face of the crystal vibrator X is adhered and fixed to the part of the flexible printed circuit board 4, on which the thermally relating elements are mounted, so that they are closely in contact with each other by using a member with satisfactory thermal conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly stable piezoelectric oscillator, and more particularly to a highly stable crystal oscillator having improved frequency stability.

[0002]

2. Description of the Related Art Quartz oscillators are widely used in communication devices, wireless communication devices, etc., and are required to have improved frequency stability, and their importance is increasing. In particular, with the spread of cellular type mobile phones, the demand for highly stable oscillators used in many base stations has been steadily increasing. As is well known, a crystal oscillator is widely used as a stable frequency source, but when high stable oscillation as described above is required, a crystal oscillator is placed in a thermostat set at a temperature higher than room temperature. Housed thermostatic crystal oscillators have been used. However, with the recent demand for miniaturization, a highly stable oscillator having a more simplified configuration is being used. FIG. 2 is a block diagram showing a configuration of a conventional high-stable oscillator. The amplifier OSC includes a transistor, a capacitor, a resistor, and the like, a crystal oscillator Xtal, and a temperature controller TC that keeps the temperature of the oscillator Xtal constant. It is composed of FIG. 3 is a cross-sectional view showing the structure of the high-stability oscillator. After the amplification section OSC and the temperature control section TC are mounted on the printed circuit board PB by reflow or the like, the thermistor constituting the temperature control section is shown. Th,
The crystal resonator Xtal is mounted so as to overlap the heater H and the power transistor Tr2. An adhesive having good thermal conductivity is filled between the crystal unit Xtal and the substrate PB. Further, it is general that a high stability oscillator is configured by housing the entire components mounted on the printed circuit board PB in a metal case. Note that here the power transistor
Since Tr2 generates heat when energized, it is arranged close to the crystal unit Xtal to use the heat as an auxiliary heat source.

FIG. 4 shows an electric circuit used in the temperature control section TC of the high stability oscillator. A series circuit of a thermistor Th and a resistor R1 is connected between a power supply Vcc and the ground.
The midpoint is connected to the base of the first transistor Tr1. Further, the collector of the first transistor Tr1 is a resistor R
2 and the power supply Vcc, and the transistor Tr1
Are grounded via a resistor R3. Then, the output of the first transistor Tr1 is supplied to the base of the second transistor Tr2 via the resistor R4 connected between the collector of the first transistor Tr1 and the base of the second transistor Tr2 (power transistor). A heater H is connected between the collector of the second transistor Tr2 and the power supply Vcc, and the emitter of the transistor Tr2 is grounded to form a temperature controller TC.

The operation of the temperature control unit TC is determined by the thermistor Th
When the ambient temperature changes to a higher temperature, the resistance of the thermistor Th decreases, the base potential of the first transistor Tr1 increases, and as a result, the collector current of the first transistor Tr1 increases. When the collector current of the first transistor Tr1 increases, the voltage drop of the resistor R2 increases, the base potential of the second transistor decreases, the collector current decreases, and the operation of the heater H decreases. When the ambient temperature of the thermistor Th changes to the low temperature side, the change will be opposite to the above description. in this way,
The temperature control unit TC detects the temperature around the thermistor Th,
In response to this, the current flowing through the heater H is controlled so that the temperature around the thermistor Th, that is, the temperature of the crystal resonator Xtal is always kept constant.

[0005]

However, in the above high-stability oscillator, as shown in FIG. 3, since the heat generated from the heater H is conducted not only to the quartz oscillator but also to the printed circuit board PB, There is a problem that the control response of H becomes slow, and the frequency stability of the highly stable oscillator is deteriorated. For example, it is possible to solve this problem by using a strong heat source as the heater H. However, in recent years, there has been an increasing demand for downsizing and low power consumption of the oscillator, which has also been limited. Similarly, the thermistor Th is not only a crystal unit Xtal but also a printed circuit board.
Since heat is also conducted from the PB, a temperature difference occurs between the temperature of the crystal resonator Xtal and the temperature detected by the thermistor Th, and there has been a problem that accurate temperature control cannot be performed. The present invention has been made to solve the above problem, and has as its object to provide a highly stable oscillator having a stable frequency.

[0006]

To achieve the above object, a high-stability oscillator according to the present invention has a piezoelectric oscillator, an amplifier for exciting the piezoelectric oscillator,
A heater for heating the piezoelectric vibrator, a temperature-sensitive element for detecting the temperature of the piezoelectric vibrator, and a temperature controller for keeping the temperature of the piezoelectric vibrator constant based on the output of the temperature-sensitive element In a highly stable piezoelectric oscillator composed of
At least the temperature sensitive element, the heater, and the power transistor that constitutes the temperature control unit are mounted on a flexible substrate, and this is used as a contact with the outer periphery of the piezoelectric vibrator. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a sectional view showing the structure of a highly stable oscillator according to the present invention. First, an amplifying unit 2 including a transistor, a capacitor, a resistor, and the like, a temperature control unit 3 excluding a thermistor Th, a heater H, and a power transistor Tr2 from a temperature control unit, and a crystal unit X are reflowed on a printed circuit board 1. Mount using On the other hand, a thermistor Th and a heater
H, a heat-related element composed of a power transistor Tr2 is mounted close to, and one end of the heat-related element is electrically connected to the printed circuit board 1 using solder or the like. Then, the upper half of the outer periphery of the crystal unit X and the heat-related element mounting portion of the flexible printed circuit board 4 are adhered and fixed with a member having good thermal conductivity so as to be in close contact with each other.

As described above, since the heater H, the thermistor Th, and the power transistor Tr2 are mounted on the upper surface of the crystal unit X via the thin flexible printed circuit board 4, the heat generated from the heater H is transmitted to the upper air and the lower air. The heat is dissipated to the crystal resonator X.

However, in air, the thermal insulation is higher,
Most of the heat of the heater H is efficiently supplied to the crystal resonator, so that the temperature fluctuation of the crystal resonator X is reduced, and the frequency stability of the highly stable oscillator is improved. Similarly, the difference between the temperature of the crystal resonator X and the temperature exhibited by the thermistor Th is small, and accurate temperature control can be performed.

[0010]

According to the present invention, as described above, the temperature of the crystal unit can be sensed more accurately,
Since the heat capacity load seen from the heater is reduced, the response time of the temperature control unit is shortened, and the temperature stability is improved. As a result, there is an excellent effect that the frequency stability of the highly stable oscillator is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a highly stable oscillator according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional high stability oscillator.

FIG. 3 is a cross-sectional view showing the structure of a conventional high stability oscillator.

FIG. 4 is a diagram showing an electric circuit of a temperature controller of a conventional high stability oscillator.

[Explanation of symbols]

 1. Printed circuit board 2. Oscillator 3. Temperature controller 4. Flexible printed circuit board X. Crystal oscillator Th. Thermistor H. Heater Tr2. Power transistor

Claims (1)

[Claims] A piezoelectric vibrator; an amplifier for exciting the piezoelectric vibrator; a heater for heating the piezoelectric vibrator;
A temperature-sensitive element for detecting the temperature of the piezoelectric vibrator, and a high-stability piezoelectric oscillator comprising a temperature control unit that keeps the temperature of the piezoelectric vibrator constant based on the output of the temperature-sensitive element; A structure of a highly stable piezoelectric oscillator, wherein a temperature sensitive element, a heater, and a power transistor constituting the temperature control unit are mounted on a flexible substrate, and the flexible substrate is closely attached to an outer periphery of the piezoelectric vibrator.