Design of a Simultaneous Frequency- And Power-Dividing Ratio-Reconfigurable Quadrature Coupler with Simple Tuning Approach

A simple simultaneous frequency- and power-dividing ratio- reconfigurable quadrature coupler using lumped elements is presented for reconfigurable radio applications. The theoretical analysis shows it can achieve perfect matching and isolation at all tuning states. The closed-form design equations are derived. For verification, a simultaneous frequency- and power-dividing ratio-reconfigurable quadrature coupler is designed based on the design equations. The measured 3-dB quadrature coupler is tuned from 1.8 GHz to 4.36 GHz with return loss and isolation of better than 20 dB. In addition, the measured power-dividing ratio can be tuned from -16 to 5.0 dB at 3 GHz while maintaining 20-dB return loss and isolation. As compared with state of the arts, the main merit of the proposed quadrature coupler is achievement of simultaneously wide tuning range of frequency and power-dividing ratio with the simple tuning mechanism and improved amplitude balance performance.