Band-stop SAW notch filter using multiple resonators

A bandstop SAW filter with good rejection response has been proposed by cascading multiple two-port-SAW resonator by means of its impedance characteristics. The notch filter with wide bandwidth is designed due to the series resonators. Three different SAW resonators are designed for extend the bandwidth of the passband response. By combining proposed SAW notch filter with a commercial bandpass filter, the sharp rejection response at the left side of passband is achieved. In order to measure the bandstop SAW filer, a typical package is used to put the SAW resonator die on the PCB board. The paper discusses the principle of these filters, and then proceeds with theoretical simulation and experimental demonstration. The described bandstop filter has small dimensions of 3.0 × 3.0 × 1.3 mm, a good rejection responses of 48 dB max at the left side of the passband. The fully matched SAW bandstop filter has achieved excellent selectivity performance with the up-to-data smallest package size.