Hybrid coupler for compact ultra-wideband UHF transceivers

3-dB miniaturized hybrid coupler suitable for in-band full duplex transceivers is given here to work in UWB UHF bandwidth from 1.5 GHz to 2.5 GHz with 90° phase deference of the output ports. The coupler is shaped by two notched elliptical microstrip lines coupled out of an elliptical shaped slot. A technique for impedance matching is combined with structural modification to increase coupler performance. The design is accomplished on Rogers RO4350B laminate with a 0.51-mm-thickness. Simulation and measurements results show that this coupler has 3±1.2 dB coupling across the target bandwidth. The achieved ultra-wideband coupling is accompanied by return-loss and smooth isolation > 25 dB. The fabricated device occupies a compact area of 30 mm × 16 mm × 1.1 mm (0.2 λ× 0.1 λ× 0.007λ), a suitable candidate for UHF applications.