Novel Narrow-Band Balanced Bandpass Filter Using Rectangular Dielectric Resonator

For the first time, a novel narrow-band balanced bandpass filter (BPF) using two coupled rectangular dielectric resonators (DRs) is proposed. According to the electromagnetic (EM) field properties of the DR, the TE_11δ mode, as a dominate mode of the DR, can be differentially excited for constructing the fundamental passband of the balanced BPF. Meanwhile, the TM_11δ mode of the DR, functions as a common-mode response in this design, is tuned far away from TE_11δ in spectrum by optimizing the DR size so that the common-mode suppression in the differential passband can be improved significantly. To validate the proposed design concept, a second-order narrow-band balanced BPF is designed, fabricated and measured. The measured results show good agreement with the simulation data.