Low loss wide band microwave filters using SAW devices combined with microstrip lines

We propose a new type of low loss wide band microwave filters, in which SAW devices and microstrip lines are combined effectively. Characteristics of this filter in pass band mainly depend on microstrip lines, while the cut-off characteristics depend on SAW device and microstrip line. Simulations using an equivalent circuit model show that wide band and low loss characteristics can be obtained. Also, in experiments, a prototype filter with basic structure achieves excellent characteristics; insertion loss is less than 1dB, bandwidth is approximately 40% and center frequency is 3.9 GHz. Shape factor between -1dB and -10dB is about 0.85 is obtained in our simulation.