A new compact SAW low loss filter for mobile radio

The key objective of low loss filters for mobile radio applications is small size. For some years, SAW manufacturers have been working on SPUDT based filters which combine the advantages of low insertion loss, simple tuning, and single level processing, nevertheless the size is still too large for pocket telephone applications. We present a new SPUDT based low loss filter utilizing an improved architecture which gives a larger impulse response for a given size by means of folded acoustic paths. This technique was used to design a 71 MHz SAW filter on quartz. This filter fits in a SIP 5 package while the classical SPUDT filter requires for equivalent characteristics a DIP 14 package, corresponding to a 50% size reduction