A Novel 3.5 GHz Low-Loss Bandpass Filter Using I.H.P. SAW Resonators

Regarding higher frequency above 3 GHz, up until now BAW filters have been believed to be better solution than SAW filters due to their increase of electrodes resistance. This paper describes a new high performance SAW filter surpassing BAW, with 3.5 GHz center frequency employing I.H.P. SAW technology which is new type SAW structure with high Q factor. Experimental studies for one-port resonators in 3.6 GHz show very high Bode-Q max of 2500 and optimum aperture lengths of IDTs. Using the results, a ladder type filter for LTE Band 42 was designed and fabricated. Very low insertion loss of 1.7 dB max has been achieved in the passband of 3.5+/-0.1 GHz. Steeper skirt characteristics and adequate attenuation have been also realized.