RU2444122C1 - Quartz resonator - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: resonator comprises a vacuumised casing, where a base is fixed with a heated placed on it in the form of a light diode, installed on a metal plate, and contact tabs, where a quartz piezoelement is installed with applied exciting electrodes and sensors of an interdigital transducer. The base is made in the form of a metal support ring with arranged areas of its fixation in the vacuumised casing. The areas of the metal support ring fixation in the casing and areas of the metal plate fixation on the support ring are arranged in the form of dielectric insulators, where metal rods are placed. The vacuumised casing is provided with metallisation of the inner surface. Outputs of exciting electrodes are connected to a circuit of a double-frequency self-oscillator, and outputs of the light diode and outputs of interdigital transducers are connected to a heat regulation circuit.

EFFECT: invention provides for long-term stability of frequency and reduction of its temperature-dynamic coefficient.

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Description

The invention relates to the field of electronics and can be used in frequency stabilization devices.

Known quartz resonator thermostat (SRT) with an internal temperature control system containing a piezoelectric quartz plate (PP) placed in a vacuum housing with exciting electrodes deposited on it, as well as a film heater and a temperature sensor, used to statically plate at a given temperature [1]. This MCT has a short time to establish the frequency from the moment of switching on, which is due to the placement of the heater directly on the PCB. The disadvantage of this resonator is the significant temperature instability of the frequency, which is a consequence of the presence of thermal gradients on the PP due to the intense heat flux from the heater located directly on the piezoelectric element into the environment through the PP fastening system.

Also known are devices made according to [2, 3], containing a metal or dielectric base located in a vacuum housing, on which quartz PP with excitation electrodes, heaters and a temperature sensor deposited on it is mounted using contacts isolated from the base, as well as a system transistor temperature control located in the center of the base and used to regulate the current through the film heaters. Due to the placement of a transistor inside the MCT, which dissipates significant power in the stationary thermal mode, causing additional heating of the MCT volume, a significant decrease in the heat flux from the film heaters to the environment through the fastening of the PP is achieved, which leads to a sharp decrease in temperature gradients along the PP and, as a result, a noticeable increase temperature stability of SRT. The conclusions of the exciting electrodes of the piezoelectric element are connected to the oscillator circuit; the outputs of the transistor, heater and temperature sensor are included in the thermal control circuit.

However, a quartz resonator with a metal base has a relatively long standby time, due to the long-term establishment of the stationary temperature of the metal base heated by the transistor installed on it, which is caused by significant heat capacity and relatively low thermal conductivity of the base. In this case, the use of metals with high thermal conductivity for the manufacture of the base leads to an increase in the heat flux from the PP and the transistor through the base to the environment, and a significant decrease in the mass of the base due to a decrease in thickness is impossible due to the difficulties involved in fixing isolated contacts in it. In the second case, the dielectric base provides a slightly shorter availability time for the quartz resonator, but the adhesive connection of the heater transistor with it worsens the long-term and temperature stability of the frequency due to the release of gases from the adhesive connection. Such a dielectric ring with its attachment points is difficult to manufacture, be it ceramic or glass. In the case of the use of a dielectric ring, the resonator is characterized by low mechanical strength of the fastening of the dielectric ring in the evacuated housing, as well as the fastening of the metal plate to this ring. The disadvantages of such a PP should also include the fact that at the initial moment of heating the transistor is in a saturated state, giving all the power to the heater, and this inevitably leads to heat leakage through the petals to the plate that has not yet been heated. Thus, temperature-dynamic frequency instability (TDKCH) arises, which is decisive when the minimum warm-up time for PP and SRT as a whole is reached. It should be noted that such CMTs have low long-term stability caused by the aging of a film heater and a thermistor temperature sensor. Hence the low accuracy of temperature control, and the separation of the temperature sensor and the piezoelectric element leads to a temperature gradient and the lack of technological repeatability of such MCT thermostats. These shortcomings make the described quartz resonators unsuitable for mass production because of their complexity and low yield, as well as extremely unreliable for use in modern highly stable reference generators.

Of the known devices, the closest to the claimed one is MCT [4], in which the task is solved in a quartz resonator containing a vacuum housing, inside of which a support base made in the form of a ring with fastening places located on it in a vacuum housing is fixed, and mounted on a support base a metal plate with its attachment points to the support base and a transistor placed on it to regulate the heating current, as well as a quartz piezoelectric element mounted on contact l petals and equipped with applied exciting electrodes, a heater and a temperature sensor. According to the invention, the supporting base is made of metal, and the indicated mounting points of the supporting base in the housing and the mounting points of the metal plate on the supporting base are made in the form of dielectric insulators in which the metal rods are placed. The vacuum housing is provided with metallization of at least part of the inner surface, and the contact petals can be made as part of the specified metal plate or mounted on a support ring.

Such a decision to create a CMT prototype does not remove almost all the disadvantages of analogues, such as: high TDHF and time to reach the operating mode, low accuracy of maintaining the temperature of stating and aging of the piezoelectric element due to relaxation of the heater film, the gradient between the heater and the temperature sensor is preserved, which means low technological repeatability of SRT products. Here, this constructive solution for the use of a heater in the form of a transistor leads to a simple dependence: an attempt to reduce the time to reach the operating mode of the SRT due to the increase in forced heating of the PC leads to an increase in uncontrolled TCD, thus not reducing the transient process when setting the frequency in the prototype. In addition, the increase in power dissipation on the film heater leads to accelerated aging of PP due to relaxation, which leads to aging of the PP as a whole, and, as studies [5, 6] show, the temperature of the film heater cannot exceed 200 ° С.

The purpose of this invention is to solve the problem and create a CMT devoid of the disadvantages inherent in the prototype. The technical result that the implementation of the invention provides is to reduce long-term instability and the temperature-dynamic frequency coefficient, as well as the time to reach the operating mode and increase the temperature stability of the SRT frequency without increasing its power consumption. This goal is achieved in that the heater is made in the form of an LED mounted on a metal plate, the luminous flux of which is focused on the central part of the quartz piezoelectric element, in which a nonmetallized hole with a diameter sufficient to completely absorb the light flux emitted by the LED is formed on the central part of one of the electrode coatings and the distance between the surface of the LED lens and the non-metallic hole in the exciting electrode is selected from the condition luminous flux power, moreover, the quartz piezoelectric element is made of two-frequency in the form of a disk or truncated lens and is located normal to the light flux, and on its peripheral surface sensors are made in the form of interdigital transducers (IDT), one of which is located in the region of the mounting lobe of the exciting electrode and the second is located relative to it at an angle of 90 °.

New in the invention is the design of the heater and the implementation of the piezoelectric element dual-frequency in disk or truncated form with sensors placed on its surface in the form of interdigital transducers. The above technical result is provided by the entire combination of essential features.

The invention is illustrated by drawings, which depict:

figure 1 - design of the resonator (without internal connections);

figure 2 is a view of the design of the lens piezoelectric element-LED (enlarged);

figure 3 is a view of the structure (without housing) from above for a lens piezoelectric element with interdigital transducers;

figure 4 is a diagram of the inclusion of a resonator in a generator with a temperature controller.

The resonator (Figs. 1-4) contains a vacuum case 1, in which a base 2 is fixed with an LED 3 mounted on it, mounted on a metal plate 4, and contact tabs 5, in which a quartz piezoelectric element 6 is installed with exciting electrodes 7 applied to it, IDT sensors 8. Base 2 is made in the form of a metal support ring with its mounting points in the evacuated housing 1. The mounting points of the supporting metal ring in the housing and the mounting points of the metal plate 4 on the polar ring are formed as dielectric (e.g., glass) insulators 9 which has metal rods 10. The evacuated housing 1 is provided with a metallized inner surface 11. The findings of the exciting electrodes 7 are connected to the circuit of a dual-frequency oscillator 13, as shown in figure 4; the conclusions of the LED 3 and the conclusions of the interdigital transducers 8 are connected to the temperature control circuit 12.

The resonator with internal temperature control works as follows. When a supply voltage is applied, the oscillator circuit 13 through the electrodes 7 excites the oscillations of the piezoelectric element 6 at two frequencies: stabilized and temperature, and the temperature control system 12, due to a temperature mismatch with the value corresponding to the statization temperature, opens the LED 3, which emits a directed focused stream of light 14 of a given power through the hole 13 in the exciting PP electrode, thereby ensuring forced heating of the PP due to the scattering of the light flux 15 in the PP material at the same time but ensuring rapid heating of the metal plate on which the LED housing is attached to the thermally conductive gasket 16. In this case, the heat influx via the contact lugs of the metal plate to and from PP PP therethrough substantially compensated and temperature gradient at the surface of the PCB is created only at the attachment points of the exciting electrodes. In this case, the arising TDHF is eliminated using IDTs located as shown in Fig. 3, the signal from which is fed to one of the inputs of the thermostat. Reducing the influence of TDKCH is achieved due to the fact that when the temperature of the heater changes, the duration of the transition process of establishing a new value of the resonant frequency is determined not only by the temperature coefficient of the frequency of the PP, but also by its TCD, The PP is heated unevenly due to the temperature difference at the points of attachment of the rods to the exciting electrodes and the periphery of the PP, which leads to a difference in the propagation velocity of acoustic waves from the center of the PP to the IDT, which can be distinguished using a phase detector in the heater. At the same time, the implementation of sensors in the form of IDT reduces the inertia of the feedback loop of the regulation of the TDKCH correction link. The exact value of the temperature at the PP is determined by the temperature mode of the vibrations received at the second input of the thermostat. Thus, the forced heating of the PCB is achieved by the combined heat flux dissipated simultaneously in the PCB body by scattering the light flux of the LED and the metal plate due to the power dissipation on the LED housing. After reaching the set temperature on the piezoelectric element 6, the temperature control system 12 enters a stationary mode of operation, providing the specified frequency stability of the stabilized oscillation mode. As a result, the transient in the resonator is practically absent, which leads to a significant reduction in the time of establishing the frequency and serves to achieve the goal.

Literature

1. Reference "Piezoelectric resonators". Edited by P.E. Kandyba, P.G. Pozdnyakova. - M .: Radio and communications, 1992, p. 362-364.

2. Pat. RF № 2101854, IPC Н03Н 9/19, issue 01/10/98

3. I.V. Abramson, A.N. Dikiji, "Improvement of Characteristics of Quartz Resonator-termostat Winh Direct Heating the Piezoelement", Proceedings of 1992 IEEE Annual Frequency Control Symposium ", p. 499-504, 1992.

4. Pat. RF № 2155442, IPC H03H 9/19, H03H 9/15, issue 08/27/2000

5. Malov V.V. Piezoresonance sensors. - 2nd ed. reslave. and add. - M .: Energoatomizdat, 1989 - 272 p.

6. Ivanchenko Yu.S. Multi-frequency quartz stabilization. - Novorossiysk: Moscow State University named after Admiral F.F. Ushakov, 2007 .-- 506 p.

Claims (1)

A quartz resonator with internal temperature control, containing a vacuum housing, inside of which a made support base is fixed in the form of a metal ring with fastening places located on it, a metal plate is installed on the support base with its fastening places to the support base and a transistor placed on it to control the heating current, as well as a quartz piezoelectric element mounted on contact petals and equipped with exciting electrodes applied to it, a heater and a sensor temperature, and the mounting points of the supporting base in the housing and the mounting points of the metal plate on the supporting base are made in the form of dielectric insulators in which the metal rods are placed, the contact tabs are made as part of the indicated metal plate and mounted on the supporting ring, while the evacuated housing is provided with metallization at least part of the inner surface, characterized in that to reduce long-term instability and temperature-dynamic frequency coefficient s, as well as the time to reach the operating mode and increase the temperature stability of the frequency, the heater is made in the form of an LED mounted on a metal plate, the luminous flux of which is focused on the central part of the quartz piezoelectric element, in which a nonmetallized hole with a diameter is formed on the central part of one of the electrode coatings, sufficient to completely absorb the light flux emitted by the LED, and the distance between the surface of the lens of the LED and a non-metallic hole in the excitation electrode is selected from the condition of the maximum output power of the light flux, and the quartz piezoelectric element is made of two-frequency in the form of a disk or truncated lens and is normal to the light flux, and on its peripheral surface sensors are made in the form of interdigital transducers, one of which is located in the region of the lobe mounting the exciting electrode, and the second is located relative to it at an angle of 90 °.

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