Design of Bandpass Filter With Dielectric‐Tube Supported Metal Rod Transmission Line at Millimeter Wave Band

ABSTRACT This paper presents a design process of a bandpass filter (BPF) with a dielectric‐tube supported metal rod transmission line (DTM line). First, the equivalent circuit was shown, and the outline of the design was presented. Next, each dimension was designed using HFSS as electromagnetic field simulator, and an ideal characteristic with the BPF was confirmed. Finally, the prototype and the measured result were presented. The prototype BPF achieved an insertion loss of 1.7 dB at 81 GHz with a fractional bandwidth of 2.4%. In addition, the result was compared with those of BPFs with other transmission lines, and it was shown that the prototype BPF had higher performance than BPFs with the lines that used printed substrates at the same frequency bands.