Design of a miniaturized 90-degree quadrature hybrid coupler with harmonic suppression ability using π-shaped lumped elements

This research presents a new design and fabrication of a quadrature hybrid coupler using π-shaped lumped elements. The proposed π-shaped elements have resulted in ultra-size reduction and harmonic suppression ability simultaneously. The proposed coupler correctly works at 800 MHz, the insertion loss is less than 0.15 dB and more than 26 dB, isolation and return loss are obtained at the operating frequency. The size of the proposed coupler is only 12.8 mm ×12.2 mm, which is equal to 0.046 λg × 0.044 λg, where λg is of the guided-wavelength at 800 MHz. The conventional coupler has a large size of 0.25 λg × 0.25 λg, which is equal to 68.5 mm × 68.5 mm. The proposed coupler provides about 96% size reduction compared to the conventional coupler. Moreover, the proposed quadrature hybrid coupler has wide harmonic suppression from 2.1 GHz to 10 GHz.