A.P. Zagorodnov – Post-graduate Student, Institute of Precision Mechanics and Control RAS (Saratov)
A.N. Yakunin – Dr. Sc. (Phys.-Math.), Senior Research Scientist, Head of Department, Institute of Precision Mechanics and Control RAS (Saratov). E-mail: firstname.lastname@example.org
Rising demands to noise levels and to a stability of miniature generators need for current development and perfection of frequency generation methods. The next stage of the development of such generators is the use of high-overtone bulk-acoustic resonators. These resonators have frequencies from hundreds of MHz to a few of GHz, the noise level being of -123 dB/Hz at the tuning out the carrier of 100 dB/Hz at the tuning out the carrier of 10 kHz.However, the use of high-overtone bulk-acoustic resonators needs for precision stabilization of temperature. For the generator having the operation frequency of 1 GHz and frequency stability of 0.1 Hz, a deviation of resonator temperature should not exceed 3.3 mkK. To provide a high stability of the resonator temperature, it is necessary to use a generator in conditioned air with a temperature deviation not more than 1 K.
At the modern state of technique, there are not miniature devices for measuring temperature with a precision of a few mkK. It is proposed to use a scheme of digital frequency auto-tuning of the frequency (DFATF) that allows one to measure a temperature indirectly in accordance with the deviation of the resonator frequency. When using DFATF, a velocity of a resonator temperature change should not exceed 0.33 mkK/sec. In addition, a capacity of temperature stabilization system should be enough to compensate arising temperature deviations. The analysis of dynamic properties of different miniature thermo-stabilization systems show that commonly used constructions based on the heating element or thermo-electrical module (TEM) cannot be applied. Therefore, the construction, thermo-stabilizing elements of which are two TEMs with a damping layer between them, was suggested. An additional high-overtone bulk-acoustic resonator with an operation frequency of 300 MHz is used as the meter of damping layer temperature. This construction principally allows one to maintain the resonator temperature with the accuracy up to 2 mkK.
Systems of thermostat control are taken the same for each of the resonators. When the signal of a temperature deviation from the nominal value is appeared, two actions are performed.
The first action is the compensation of the arisen temperature deviation. The second one consists in the change of working regime of the correspondent TEM to prevent subsequent temperature deviation from the nominal value.
Actions of the control system are similar to the operation of sections of classic PI-regulator. However, the use of such a regulator is not possible because of periodic data about errors (temperature deviations) are absent. Nevertheless, the proportional and integral coefficients of the control system can be chosen according with the method of calculating the sections of PID-regulator.
To check out the efficiency of such a thermo-stabilization system a modeling of stepped, linear and sinusoidal change of the environment temperature was performed. At the stepped change of the environment temperature, a deviation of a resonator temperature do not exceed 3.3 mkK. At the linear change –a deviation of a resonator temperature do not exceed 3.0 mkK. At sinusoidal change –a deviation do not exceed 1.5 mkK.
Simulating the operation of the generator with a tuned control system has shown that the proposed construction and control system is fit for building a stable according to frequency miniature high-frequency low-noise generator based on high-overtone bulk-acoustic resonator.
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