Ultra selective HTS bandpass filter for 3G wireless application

This paper presents an ultra selective HTS filter that meet existing 3G wireless band. The filter consists of 22 resonators and five cross coupling structures that produce ten transmission zeros near the band edges. A quadruplet cross coupling technique was introduced into the design for the transmission zero implementation. To accommodate twenty-two resonators within a limited wafer size, a compact new topological resonator was also developed. The filter was fabricated using a YBCO thin film on a 2-in MgO wafer. Measured skirt slope has exceeded 30 dB/100 kHz and the filter has a 90 dB out-ofband rejection at 350 kHz from its band edge. This filter surpasses the rejection of an ideal 50-pole Chebyshev filter.