SAW ring filters with insertion loss of 1 dB

This paper presents low loss ring SAW filters on 49°YX, 64°YX, 128°YX LiNbO₃ realized on the basis of the reflecting multistrip couplers (RMSCs). Using the RMSCs with 3 electrodes per λ (λ-is the SAW wavelength at the center frequency) and self-resonance approach when filter specified real input/output impedances are achieved by IDT static capacitance compensation with radiation susceptance, ring filters have shown very low insertion losses of 0.8-1 dB, 3 dB fractional bandwidth of 2-5% with very low ripple of 0.1 dB stopband attenuation over 50 dB at 10-33% offset from the center frequency of 45 MHz. At 50 Ohm 148, 164, 172 MHz ring filters on 128°YX for the low power transceivers have provided insertion loss of 1 dB, 1 dB bandwidth of 2-2.3 MHz, the stopband attenuation over 55 dB at 25 MHz offset from the center frequency. Two cascaded filters at 164.5 MHz have shown insertion losses below 3 dB and stopband attenuation over 90 dB. The chip size is 5×4×0.7 mm