Narrow-Band and Low-Loss Bandpass Filter for 5G Built of Silica-Based Post-Wall Waveguide

A 28.5-GHz fifth-order Chebyshev bandpass filter (BPF) with a 2-GHz bandwidth (7% fractional bandwidth) built of silica-based post-wall waveguide (PWW) is presented for 5G applications. The dielectric loss tangent of the substrate is as low as 0.00036 at 44 GHz. The coupled resonators are designed in such a way that the sizes of the resonators are nearly the same, while still allowing the coupling between them to be well-controlled. The dimensions of the BPF is 11×10 mm
²
. The insertion loss of the BPF, not including the I/O interfaces for probing measurement, is less than 0.8 dB. Two designs of I/O interfaces for the PWW-based BPF are also presented.