SAW Resonator Reflector Design for Gamma Loading Improvement

For the 5G user experience, coverage and capacity are the key elements. Carrier aggregation (CA) is the foundation for 5G and an effective tool to extend the coverage. When two filters are connected at the common node and working simultaneously, like in CA, each filter insertion loss (IL) will degrade slightly compared to its standalone (SA) operation mode, due to a loading loss. In other words, one filter was not an ideal open at the other filter's passband frequency, signal is partially leaking into the other path. In the case of Surface Acoustic Wave (SAW), or Temperature Compensated (TC) SAW is used for the antenna side first series resonator, the resonator has ripples above reflector stopband in the conductance plot. If frequency allocation of filters in a multiplexer is at those ripple frequencies, the ripples can cause IL degradation to the other filters. This paper introduces the design methodologies so that the ripples above the stopband are reduced, this helps to improve the CA band filter performance.