Fabrication of Integrated PTFE-Filled Waveguide Butler Matrix for Short Millimeter-Wave by SR Direct Etching

Design and Fabrication of PTFE Substrate-Integrated Waveguide Butler Matrix for Short Millimeter Waves

“…The dimensions for the G-band PTFE SIW cruciform 3 dB coupler are obtained from Ref. [8] as l 1 = 0.21 mm, l 2 = 0.16 mm, t 1 = t 2 = 0.20 mm, and p 1 = 0.28 mm. Assuming that port #1 is an input port, ports #2 and #3 become an isolation port and a coupling port, respectively.…”

“…The fabrication process is considered useful for constructing waveguide-integrated circuits for millimeter-wave and submillimeter-wave bands. However, at higher frequencies of more than 100 GHz, the PTFE-filled waveguide circuit becomes weaker than paper and bends or snaps off easily unless it is fixed with resin [8].…”

“…Then, the cruciform 90 • hybrid coupler (3 dB coupler) and an intersection circuit (0 dB coupler) of the PTFE SIW structure analogous to the circuits in Ref. [8] are connected to design a Butler matrix. Then, a trial fabrication of the PTFE SIW Butler matrix is performed by the above-mentioned fabrication process utilizing the SR direct etching of PTFE and Au coating by sputter deposition and electroplating.…”

Design and Fabrication of PTFE Substrate Integrated Waveguide Coupler by SR Direct Etching

“…In addition, the mechanical strength of the G-band straight waveguide (cross section 0.90 mm x 0.40 mm) used in Ref. [12] is also evaluated . For the structure of PTFE only, the applied force is <0.04 N (undetectable) and 0.10 N under the condition "1 mm down" and "broken", respectively.…”

“…Therefore, the circuit must be supported by other substrate and fixed with adhesive as shown in Ref. [12]. The authors consider the PTFE SIW structure is one valid approach to solve the problem.…”