An Integrated Lumped-Element Quadrature Coupler With Impedance Transforming

Design equations for the parameters of a lumped-element quadrature coupler with impedance transforming are derived. Considering on-chip implementations, it has a smaller size as compared to a quarter-wavelength transmission-line-based coupler. A 2.47-GHz quadrature coupler with impedance transforming is implemented using GaAs technology for verification. The measurement results show that the fabricated coupler achieves an insertion loss of 3.39 dB with a phase imbalance of 0.8° for through and coupled outputs at 2.47 GHz.