Design and applications of a 3:1 bandwidth GaAs monolithic spiral quadrature hybrid

The design, performance, and circuit applications of a 2-6-GHz GaAs monolithic spiral quadrature coupler are presented. The 90-degree coupler uses lumped spiral inductors and MIM capacitors and is very small in size (14 mils*26 mils). The mutually coupled inductors were realized using a bifilar spiral transformer to achieve a coupling coefficient of k=0.7 and to reduce chip size. The measured relative phase difference between the coupled and direct ports over the 3:1 bandwidth is 90+or-6 degrees. Results on a hybrid-coupled reflection phase shifter and an image-reject downconverter based on this monolithic quadrature hybrid are also presented.<>