Recent advances on the measurement of quartz crystal units up to 500 MHz and above by the use of a Pi network with error correction

The Pi-network method according to IEC-publication 444 (DIN 45105) is the generally acknowledged measurement technique for quartz crystal units up to 125 MHz. Above this frequency limit, this measurement method leads to insufficient precision or is no longer possible, resp., due to the stronger influence of the static capacitance Co. Therefore, up to 200 MHz a measurement method is partially in use, which applies physical Co-compensation by means of a modified Pi-network with parallel coil or an equivalent circuit. A new measurement method, the idea of which was first published by F. Neuscheler (1987), uses the conventional arrangement with the classical Pi-network applying an error correction method based on an extended calibration procedure. This method is meanwhile successfully proved up to 1 GHz and was compared with other possible measurement methods. The paper describes the measurement principle and presents some results of comparative measurements