An m-derived ladder high-pass SAW filter

Since excellent characteristics can be realized in the gigahertz range with a small size, SAW filters have been used widely as RF (radio frequency) filters for mobile communications terminals. In particular, since the insertion loss of the RF filter impacts the receiving sensitivity and transmitting power efficiency of the terminals, the demand for lower loss is substantial. In this paper, a one-port SAW resonator is used as the series element and a series circuit consisting of a capacitor and an inductor is used as the shunt element in an m-derived ladder filter. Its configuration, design procedure, and design and test results are presented. In spite of a simple circuit configuration, this filter can realize a low loss characteristic. The fabricated filter for 900 MHz exhibited excellent properties with an insertion loss of less than 1 dB and an out-of-band attenuation of more than 33 dB. The effectiveness of this filter is therefore demonstrated. (C) 2004 Wiley Periodicals, Inc.