A modular SAW filter design approach for multiband filtering

This paper presents two novel modular ladder type surface acoustic wave (SAW) filters. The first topology realizes a shift of center frequency and bandwidth (BW) and the second topology a shift of band edge. In the designs, the acoustic resonators are reused and the need for passive elements is reduced. Experimental results are presented for the 700 MHz frequency band currently allocated to Long Term Evolution (LTE). Parasitics caused by the packaging, interconnect and non-ideal switches are incorporated in the design using a linear circuit solver and three dimensional electro-magnetic (3D EM) commercial simulator. The measured results agree well with the simulations. In the filter with shifted center frequency and BW, two filter states with a BW of 1.4% and 1.7% are realized with a center frequency shift of 3.1%. In the filter with shifted lower band edge, two filter states with a BW of 3% and 1.7% are obtained.