Wideband mm-Wave CMOS Slow Wave Coupler

In this letter, we have presented a design of on-chip millimeter-wave 3-dB quadrature coupler that utilizes the coupled slow wave coplanar waveguide. The designed CMOS coupler covers the whole E- and W-band and occupies a silicon area of only 0.0115 mm
²
, which is significantly smaller compared to the conventional microstrip-line-based Lange couplers. Measurement of the quadrature coupler shows a -3.5 dB through and a -4.4-dB coupling at 90 GHz. A less than ±1-dB amplitude and a ±4° phase errors from 55 to 110 GHz are recorded.