Crystal oven

About: Crystal oven is a research topic. Over the lifetime, 955 publications have been published within this topic receiving 10380 citations. The topic is also known as: oven-controlled crystal oscillator & OCXO.

Measuring method of active impedance of crystal oscillator circuits

Abstract: Crystal oscillator circuits have been used widely in such electronic equipment as communication devices and measurement instruments. However, until the crystal is connected, usually it is uncertain if the circuit oscillates or it is difficult to determine how one adjusts the circuit for a desired oscillation frequency. With a view to alleviating these situations and improving the design method for the crystal oscillator circuits, a method is developed for accurately measuring with a bridge the two-terminal impedance (equivalent series capacitance and negative resistance) of the active circuit seen from the connecting terminal of the crystal. A bridge measurement method for the small-signal negative resistance related to the starting characteristics of the oscillator is discussed. In conjunction with the bridge measurement developed earlier for large signal operations under oscillation, a complete bridge measurement has become possible from the small signal region to the large signal region. The present bridge measurement method is useful in providing a basic specification for the active circuit side for a given crystal. It is also shown that the present bridge method is useful for evaluation of accuracy of other measurement instruments such as impedance analyzers.

Start-Up Acceleration of Quartz Crystal Oscillator Using Active Inductance Double Resonance and Embedded Triggering Circuit

Abstract: Low-frequency double-resonance quartz crystal oscillator was developed with active inductance circuit aiming the start-up of stable oscillation of tuning fork-type quartz crystal resonator at 32.768 kHz within 0.37 ms. The initial oscillation is triggered by a part of crystal oscillator forming a CR oscillator. The negative resistance ranges to 4 MΩ at gmf of 4.1 μA/V. In a limited frequency range, the circuit shows negative reactance Ccci = -3.4 pF equivalent to inductance Lcc = 9.8 H. The Allan standard deviation indicated 10-11 to 10-10, showing high stability comparable to general quartz crystal oscillator.

Temperature‐compensated crystal oscillator using a two‐port crystal resonator

Abstract: In general, the oscillation frequency of a quartz crystal oscillator is shifted by varying the load capacitance of the quartz crystal resonator. Since the relation between load capacitance and oscillation frequency of the crystal resonator is nonlinear, the rate of change of frequency is slightly different from the load capacitance before and after the frequency shift. When the variation of oscillation frequency due to aging is compensated using the temperature-compensated crystal oscillator (TCXO) or the voltage-controlled temperature-compensated crystal oscillator (VCTCXO) or the oscillation frequency is shifted, the frequency compensation amount set by the temperature compensation circuit is different before and after the compensation. Thus, the frequency versus temperature characteristics vary. To solve this problem, the author has developed a special quartz crystal resonator with two-port electrodes. Since this crystal resonator has two load capacitances, the compensation of the temperature characteristics and the shift of oscillation frequency can be conducted independently. Thus, the problem of the changes in the temperature characteristics due to the oscillation frequency shift of a TCXO has been solved. This problem could not be solved using the conventional quartz crystal oscillator having only one capacitance. In this paper, measurement is made under the condition that the oscillation frequency of the TCXO using a two-port crystal resonator is shifted by ± 15 ppm and the performance is compared with that of TCXO using a conventional crystal resonator. the measurement has revealed that the change of frequency versus temperature characteristics is extremely small when the oscillation frequency of the TCXO using a two-port crystal resonator is shifted.

Stable ring oscillator for ultra low supply voltages

Abstract: This paper presents an alternative to crystal based oscillators for reference frequencies in highly integrated SoCs. The frequency reference through the usage of an active bias controlled ring oscillator operating with a supply voltage from 300 to 500 mV for an temperature from −40 to 125 ° C. The oscillator shows a very good temperature and supply voltage frequency stability coming from the active biasing using a stable current reference.