Recently low-loss surface-acoustic-wave (SAW) filters become key components in radio communication systems. The planning and development of new systems in the GHz range led to a challenge for the SAW technology towards some applications in the RF-stage of GHz receivers and transmtters. Therefore, parameters such as size, insertion loss and fabrication cost have to be shaped advantageously .The paper presents SAW-filter techniques suitable for low-loss operation and based on a newly developed submicron photolithography as the appropnate mass roduction low-cost pattern fabrication process. Two &ers have been designed and realized at 1.7 GHz and 2.5 GHz, which corresponds electrode widths of 0.6 pm and 0.4 pm respectively. The filters provide an insertion loss of 6 dB and a stopband rejection of about 40 dB.
An improved dual track configuration with a transducer coupling between the tracks has been developed in order to obtain a low-loss filter with high stopband rejection, small passband ripple and small size, which is needed in mobile communication systems. Thereby a new partial finger-splitting and an optimized binary withdrawal weighting together with a non-resonant unidirectional configuration were applied. Filters at 450 MHz were fabricated on 36'rotYX-LiTa03 using simple single layer technology. An insertion loss of 3 to 4 dB was achieved over a bandwidth of 6.5 MHz with a passband ripple less than k . 5 dB. The stopband rejection is better than 50 dB.
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