International Journal of Microwave and Wireless Technologies

Research Article

Polymer-based micromachined rectangular coaxial filters for millimeter-wave applications

Aline Jaimes-Veraa1a2, Ignacio Llamas-Garroa1 c1, Maolong Kea3, Yi Wanga3, Michael J. Lancastera3 and Lluís Pradella2

a1 Centre Tecnologic de Telecomunicacions de Catalunya (CTTC), 08860 Barcelona, Spain. Phone: + 34-664345564.

a2 Signal Theory and Communications Department, Technical University of Catalonia, 08034 Barcelona, Spain.

a3 School of Electronic, Electrical and Computer Engineering, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.


In this paper, micromachined devices for millimeter-wave applications at U- and V-bands are presented. These structures are designed using a rectangular coaxial line built of gold-coated SU-8 photoresist layers, where the coaxial center conductor is suspended in air by stubs. The designs include a stepped coplanar waveguide (CPW)-to-coaxial transition at 63 GHz, with an insertion loss of 0.39 dB at 67.75 GHz and a return loss better than −10 dB across the band of operation between 54.7 and 70.3 GHz. Two filters have been designed; one centered at 42 GHz with a 10% bandwidth, and another at 63 GHz with a 5% bandwidth. Measured insertion losses of 0.77 and 2.59 dB were obtained for these filters, respectively. Measured return loss lower than 13.8 dB over the passband was achieved for both designs. The structures presented in this paper involve a low-cost manufacturing process suitable to produce integrated subsystems at millimeter waves.

(Received October 29 2010)

(Revised January 13 2011)

(Online publication March 01 2011)


  • Micromachining;
  • Coaxial cables;
  • Filter;
  • SU-8;
  • Millimeter-waves


c1 Corresponding author: I. Llamas-Garro Email: