WR-3 Waveguide Bandpass Filters Fabricated Using High Precision CNC Machining and SU-8 Photoresist Technology

Research output: Contribution to journalArticlepeer-review


  • Hao Yang
  • Bo Liu
  • Hui Wang
  • Manju Henry
  • Peter G. Huggard

External organisations

  • Rutherford Appleton Laboratory


This paper presents two WR-3 band (220-325 GHz) filters, one fabricated in metal using high precision computer numerically controlled milling and the other made with metallized SU-8 photoresist technology. Both are based on three coupled resonators, and are designed for a 287.3-295.9-GHz passband, and a 30-dB rejection between 317.7 and 325.9 GHz. The first filter is an extracted pole filter coupled by irises, and is precision milled using the split-block approach. The second filter is composed of three silver-coated SU-8 layers, each 432 µm thick. The filter structures are specially chosen to take advantage of the fabrication processes. When fabrication tolerances are accounted for, very good agreement between measurements and simulations are obtained, with median passband insertion losses of 0.41 and 0.45 dB for the metal and SU-8 devices, respectively. These two filters are potential replacements of frequency selective surface filters used in heterodyne radiometers for unwanted sideband rejection.


Original languageEnglish
Pages (from-to)100 - 107
JournalIEEE Transactions on Terahertz Science and Technology
Issue number1
Early online date7 Dec 2017
Publication statusPublished - Jan 2018


  • Micromachining, SU-8, terahertz components, waveguide filter