200 khz pcm timing tank electromechanical filter

This paper describes the design method and experimental results of a timing tank electromechanical filter for low‐speed digital subscriber transmission networks. A composite longitudinal‐mode vibrator consisting of a piezoelectric ceramic sandwiched by consant‐modulus alloy plates is proposed for the filter. This type of vibrator is convenient to weld with its couplers and supporter. The temperature characteristic of the filter can be compensated by the two types of material. It is confirmed that the filter permits electronic characteristics and physical size compatible with LSIs used for PCM apparatus. The resonance frequencies and capacitance ratios of the vibrators and the conditions for suppressing higher‐order or resonance modes are analyzed. 200‐kHz timing tank filters based on the described analysis are fabricated and their characteristics described.