Reconfigurable RF Quadrature Patch Hybrid Coupler

A highly reconfigurable radio frequency patch hybrid coupler with a simple topology is presented for the first time. Due to the introduction of lumped equivalent circuit and flexibility of varactor loaded patterned ground plane, the complex reconfigurability in port arrangement and coupling coefficient can be implemented. Varying the capacitance across different planes allows the electronic switching between different operating modes of the patch hybrid coupler. When the auxiliary patch and patterned ground plane is placed closer to the two output ports, tunable coupling coefficient can also be implemented by changing the capacitance. This results in wide band reconfigurability for the coupling coefficient range. For demonstration purposes, a patch hybrid coupler operating at 2.4 GHz is designed and measured to validate the port reconfigurable concept. Also, a patch hybrid coupler with tunable coupling coefficient operating at 3.5 GHz is designed, fabricated, and measured. This circuit gives a reconfigurable coupling coefficient ranging from -4.2 to -10 dB while maintaining good performance.