Compact 41-93 GHz symmetric quadrature hybrid based on multi-conductor coupled line in 65 nm CMOS process

The development of a compact 41-93 Gliz symmetric quadrature hybrid based on multi-conductor coupled lines in standard 65 nm bulk CMOS process is presented. The equivalent two-line model of the multi-conductor coupled line is derived and analysed with even/odd mode theory and ABCD matrix. With the multi-conductor coupled-line sections, high coupling coefficient, compact size, and wideband operation can be realised; meanwhile, keeping the responses of four ports fully symmetric, which is suitable for circuit applications demanding port symmetry. Designed compact symmetric quadrature hybrid is implemented with 65 nm bulk CMOS process. Measured results show the CMOS quadrature hybrid has good phase difference within 90 +/- 2.5 degrees and amplitude balance <+/- 0.5 dB from 41 to 93 GHz, or a 75.5% fractional bandwidth, with an extremely compact size of 93 mu m x 149 mu m (0.0138 mm(2)), or 0.0514 lambda(0) x 0.0244 lambda(0).