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

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_r) and resistance (R_r) 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_r/F_r < ±10 ^-7, ΔR_r/R_r < ±4% in the frequency range 1-100 MHz. By means of the presented T-network, a direct measurement of the series resonance frequency (F_s) 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.