250 MHz SAW filters for SS/FDMA system employing ST-cut quartz substrates

Surface acoustic wave (SAW) filters are key devices in developing the bandwidth-variable filter matrix for the subchannel switched frequency division multiple access (SS/FDMA) system. This paper addresses the design and fabrication of two 250 MHz SAW filters employing temperature-stable ST-cut quartz substrates. The specafications for these filters are decided with due consideration of practical use by INTELSAT-type satellites. Measured electrical responses of the individual and combined channels show satisfactory performance. Computer simulations are performed using the measured responses to assess the effects of the SAW filters on digital carriers. Finally, the effects of the temperature and ageing stability characteristics are discussed based on the measured and calculated responses.