A millimeter-wave transformer between microstrip line and flexible post-wall waveguide on liquid crystal polymer substrates

We propose a simple transformer between microstrip line and flexible post-wall waveguide fabricated on liquid-crystal polymer substrates. Matching to 50 Ω impedance is accomplished by a combination of blind-via and microstrip-elements. The estimated loss of the transformer associated with the mode conversion and the measured loss of the PWW is 0.6 dB and 0.9 dB/mm at 60 GHz, respectively. We also found out that the transmission property of the PWW for bending remains unchanged.