A novel microwave microstrip surface acoustic wave filter with gigahertz band low-loss wide bandwidth for broad spectrum communication

A novel GHz-band low-loss wide bandwidth microwave microstrip, surface acoustic wave (SAW) filter used for the spread spectrum communication system has been designed and fabricated. The 16-mum-input/output-interdigital-transducer (IDT) LiNbO3 61.00-MHz-SAW filter with microwave square open-loop resonators has an insertion loss of 3.987 dB. This device is also a 1 GHz microwave microstrip SAW filter with four coupled microstrip square open-loop resonators and two planar interdigital capacitors with S-21 and S-11, having bandwidths of -2.962dB and -25.497dB, respectively, and 800 MHz. It is speculated that the characteristics of these low-loss wide bandwidth (BW = 80%) microstrip SAW filters are influenced by the interaction between electromagnetic wave and piezoelectric SAW. To confirm this speculation, devices with the same design have been fabricated on 128degrees-rotated YX-cut LiNbO3,GaAs S-I and 9000 Angstrom SiO2/Si substrates. Significant variations of performance are observed among these devices.