Ultra-Wideband Surface Acoustic Wave Filters Based on the Cu/LiNbO3/SiO2/SiC Structure

Wideband filters could contribute to high-throughput wireless communication, and surface acoustic wave (SAW) filters have been widely applied. To obtain ultrawideband SAW filters on SiC wafers, we study the Cu/15°Y-X LiNbO
3
/SiO
2
/SiC structure. SAW resonators with various sizes are simulated, fabricated and analyzed. Based on the results of the resonators, we design and fabricate filters whose series and shunt resonators have different wavelengths and different Cu thicknesses. A typical filter is packaged and measured. The center frequency is 1.46 GHz and the 3-dB fractional bandwidth reaches as large as 31.08%. The minimum insertion loss is only 0.84 dB and the temperature coefficient of frequency at higher edge of 3-dB bandwidth is -54.4 ppm/°C. We believe that better performances can be achieved if our design is further optimized. This work verifies that ultrawideband and low-loss filters can be obtained on SiC wafers, which has high commercial possibilities during the development of wireless system.