HTS Penta-Band Bandpass Filter for Radio Astronomy Broadband Receiver in the UHF Band

In this work, we proposed a high-temperature superconducting penta-band bandpass filter consisting of five single-band bandpass filters demonstrating an improved design freedom applied to a broadband filter for radio astronomy broadband receiver in the UHF band. We also proposed a new feeding structure that can control the current distribution on the feedline to increase the number of resonator positions and enable strong external coupling between the resonator and feedline. The first spurious resonance is frequency-shifted to 4.5 times the fundamental resonance by using a stepped impedance resonator structure for the first band (0.7 GHz) resonator and by mating the resonator ends. The fractional bandwidth of the filter is 11.3% (0.7 GHz), 17.5% (1.4 GHz), 11.1% (1.6 GHz), 4.1% (2.1 GHz), and 2.5% (2.7 GHz). Our experimental findings show that the measured frequency response of the filter is in good agreement with the simulated one.