Fabrication of PTFE-filled waveguide bandpass filter using SR direct etching

A metallic waveguide is one of effective media for millimeter- and submillimeter-waves because of the advantage of low-loss. This paper describes trial fabrication of a PTFE-filled waveguide bandpass filter (BPF) with the use of the SR (synchrotron radiation) direct etching process of PTFE, sputter deposition of metal, and electroplating. PTFE is known as a difficult material to process at high precision. However, it has been reported that PTFE microstructures can be fabricated by the direct exposure to SR. In this paper, an iris-coupled waveguide BPF with 5-stage Chebyshev response is designed at Q-band, and the fabrication procedure for the PTFE-filled waveguide BPF is described. The measurement results of the fabricated BPF are shown.