Jean-Jacques Gagnepain

Environmental sensitivities of quartz oscillators

The frequency, amplitude, and noise of the output signal of a quartz oscillator are affected by a large number of environmental effects. The physical basis for the sensitivity of precision oscillators to temperature, humidity, pressure, acceleration and vibration, magnetic field, electric field, load, and radiation is examined. The sensitivity of quartz oscillators to radiation is a very complex topic and poorly understood. Therefore, only a few general results are mentioned. The sensitivity to most external influences often varies significantly both from one oscillator type to another and from one unit of a given type to another. For a given unit, the sensitivity to one parameter often depends on the value of other parameters and on history. Representative sensitivity to the above parameters is given.<<ETX>>

Oscillator noise analysis: multivariance measurement

Since the noise altering the output signal of oscillators may be modeled as power laws in the spectral density of frequency deviation, oscillator noise analysis is the measurement of the level of each power law noise. The principle of this new multivariance method consists of obtaining the noise-type contributions with different variances and different integration time values. All the data obtained from the different variances with the different integration times are then operated simultaneously. Thus, the most probable measurement, in the sense of least squares, is obtained for each type of noise. This method lends itself to an estimation of the uncertainty of the noise-type contribution measurement, taking into account the dispersion of the variance results. >

Sensitivity of quartz oscillators to the environment: characterization methods and pitfalls

The advantages and disadvantages of characterizing a complete quartz crystal oscillator or characterizing only the quartz resonator by using a passive phase bridge are discussed. Measurements of temperature sensitivities, including quasistatic or dynamic thermal conditions, are presented. One important point is how to measure the real temperature of the device under test (quartz crystal, for instance) rather than the temperature of the probe. Methods for measuring acceleration and pressure sensitivities are presented, and spurious effects of temperature changes are considered. Problems are discussed in connection with the measurement of the sensitivity to magnetic fields, and to electric fields. Methods used for measuring these sensitivities and the many pitfalls that can be encountered are the focus of the investigation.<<ETX>>

Characterization methods for the sensitivity of quartz oscillators to the environment

The distinction is shown between characterizing a complete oscillator, and characterizing only the quartz resonator by using a passive phase bridge. Advantages and disadvantages of the two approaches are discussed. Then measurements of temperature sensitivities, including quasistatic or dynamic thermal conditions are presented. One important points how to measure the real temperature of the device under test (quartz crystal for instance) rather than the temperature of the probe. Methods for measuring acceleration and pressure sensitivities are presented taking spurious effects of temperature changes into consideration. Various problems are discussed in connection with the measurement of the sensitivity to magnetic fields and electric fields.<<ETX>>

A new 'filtered Allan variance' and its application to the identification of phase and frequency noise sources

Digital noise generators are described as is their use to generate sample series that simulate frequency samples as given by a counter. Applying the Allan variance to the samples of six generators (white phase, flicker phase, white frequency, flicker frequency, frequency random walk, filtered flicker frequency) yields the expected theoretical slopes. The method used consists in filtering the f/sup -1/ and f/sup 0/ phase noise by means of a digital filter in the time domain, (using the Z transform), which yields f/sup -3/ and f/sup -2/ noises, which thus can be identified by Allan variances. The combination of the digital filter and the Allan variance corresponds to a novel variance, which is described and compared to the well-known modified Allan variance.<<ETX>>

Quartz Crystal Parameters Measurement System

A device for measurement of quartz crystal resonator parameters is presented. This device is using a synthesizer, the frequency of which is swept step by step to find the resonance of the crystal. With a phase loop, which controls the synthesizers interpolator, the resonance frequency and the bandwidth of the crystal can be measured. A low-cost computer gives the values of the resistance and the Q factor. The time constants of the crystal and of the phase loop are studied to determine the best measurement speed of this automatic device.