Microstrip Dual-Band Bandpass Filter Using U-Shaped Resonators

Coupled resonators are widely used in the design of filters with dual-passband responses.
In this paper, we present a dual-band bandpass filter using only couplings between adjacent resonators
without cross-couplings. The dual-band bandpass filter with centre frequencies of 1747 MHz and
1879 MHz respectively is designed and fabricated using microstrip U-shaped resonators. Using the
coupled resonator pair as a dual-band cluster, a miniaturised structure is achieved as compared to the
conventional topology. The measured responses agree closely with the simulations.