Balanced bandpass filter using TE01δ-mode dielectric resonator

In this paper, a surface-mounted dielectric resonator-based balanced bandpass filter is proposed. By utilizing the TE01 delta mode as a dominant mode of the cylindrical dielectric resonator, it can be excited in differential mode to achieve good common-mode suppression in differential filter passband. To validate the design idea, a second-order balanced narrowband bandpass filter with center frequency at 5.53 GHz has been designed, fabricated, and measured. The design parameters of the proposed filter are: insertion loss 0.2, 3 dB Bandwidth (BW) 67.1 MHz, and return loss 23 dB, and common-mode separation is more than 30 dB. There is good agreement between the simulated and measured results.