Noise Measurement Setup for Quartz Crystal Microbalance

Quartz crystal microbalance (QCM) is a high sensitive chemical sensor which has found widespread spectrum of applications. There are several mechanisms that are related to fluctuation phenomena. Since the aim of our research is oriented to study the sensitivity and influence of different kind of noises on sensor resolution, we modified an existing method to measure the small frequency fluctuation of QCM. The paper describes our measurement setup, in which a quartz crystal oscillator with coated active layers and a reference quartz oscillator are driven by two oscillator circuits. Each one regulates a frequency of a crystal at the minimum impedance which corresponds to the series resonance. A data-acquisition card triggers on the rise-edges of the output signal and stores these corresponding times on which the instantaneous frequency is estimated by own-written software. In comparison to other measurement setups, our approach can acquire immediate change of QCM frequency, thus, chemical processes can be even described on the basis of high-order statistics. The experiments were provided on quartz crystals with the sorption layer of polypyrrole, which is suitable for the construction of QCM humidity sensors

Power waves formulation of oscillation conditions: avoidance of bifurcation modes in cross-coupled VCO architectures

This paper discusses necessity of power-waves formulation to extend voltage-current oriented approaches based on linear concepts such as admittance/impedance operators and transfer-function representations. Importance of multi-physics methodologies, throughout power-waves formulation, for the analysis and design of crystal oscillators is discussed. Interpretation of bifurcation modes in differential cross-coupled VCO architectures in terms of gyrator-like behavior, is proposed. Impact of amplitude level control (ALC) on large-signal phase noise performances is underlined showing necessity of robust control analysis approach relative to power-energy considerations

On the 1/f Frequency Noise in Ultra-Stable Quartz Oscillators

The frequency flicker of an oscillator, which appears as a 1/f^3 line in the phase noise spectral density, and as a floor on the Allan variance plot, originates from two basic phenomena, namely: (1) the 1/f phase noise turned into 1/f frequency noise via the Leeson effect, and (2) the 1/f fluctuation of the resonator natural frequency. The discussion on which is the dominant effect, thus on how to improve the stability of the oscillator, has been going on for years without giving a clear answer. This article tackles the question by analyzing the phase noise spectrum of several commercial oscillators and laboratory prototypes, and demonstrates that the fluctuation of the resonator natural frequency is the dominant effect. The investigation method starts from reverse engineering the oscillator phase noise in order to show that if the Leeson effect was dominant, the resonator merit factor Q would be too low as compared to the available technology.Comment: 20 pages, list of symbols, 1 table, 6 figures, 43 reference

S-band SBAW microwave source, phase 2

Results of aging experiments on 1.072 GHz SBAW oscillators are discussed as well as the design, fabrication and test of 2.143 GHz SBAW delay lines. Two design approaches were implemented. The third harmonic transducer on 36 deg rotated Y cut quartz proved to be the most useful design, whereas the fifth harmonic transducer on - 50 5 deg rotated Y cut quartz suffered from high insertion loss and poor sidelobe rejection. The construction and characterization of the 2 GHz SBAW oscillator are described. Phase noise, frequency dependence on temperature, and 6-month aging were measured. Some SAW and SBAW oscillators were compared as were both the 1 and 2 GHz oscillators. The 2 GHz SBAW oscillator showed significant improvement in phase noise and temperature stability over the 2 GHz SAW oscillator developed in previous NASA programs. A technique to produce SBAW delay lines of different frequencies from a single mask is examined. The delay lines were incorporated into oscillator circuits to demonstrate the ability to select the frequency output of the SBAW oscillator