Quartz crystal unit measurement method based on transmission line T-network

Abstract

A method for the investigation of quartz crystal units by phase technique with application of a special T·network is presented. The construction of the T-network using microwave techniques, is proposed. The transmission line T-network enables an accurate measurement of basic parameters of crystal units-resonance frequency (F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) and resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) to be made in a wide frequency range. As opposed to the well-known π-network, this T-network allows unique, more precise determination of its parameters and, in consequence, achievement of higher measurement accuracies. Results of an investigation of this T-network, T-513 model, show actually attainable accuracies of measurements ΔF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> /F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> < ±10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> , ΔR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> < ±4% in the frequency range 1-100 MHz. By means of the presented T-network, a direct measurement of the series resonance frequency (F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) is possible, too. Knowledge of the T-network parameters renders determination of the measurement accuracy possible also if a different technique than the phase one is used, e.g., FM technique. The method using the transmission line T-network was proposed for acceptation to IEC as a basic method for the measurement of quartz crystal units by phase technique.