A Compact 20-35 GHz Quadrature Coupler using 0.15um pHEMT Coplanar Waveguide Technology

A coplanar waveguide (CPW) mode 20-35 GHz quadrature coupler has been demonstrated in this study. Good microwave performance and compact size can be achieved simultaneously. The measured return loss is better than 16.6 dB and insertion loss of S₂₁ and S₃₁ are 3.6 plusmn 0.2 dB. The measured phase difference is 88 plusmn 2deg from 20 to 35 GHz. Total chip size including RF pads is 0.72 times 0.48 cm². Comparing the performance and chip-size between an non-bending and a bending couplers, the bending one shows 0.4 dB worse in simulated insertion loss than the other but the chip-size is 50 percent in reduction. This circuit is adaptable for the applications in wideband double balanced mixers and power amplifiers.