Improvement of return loss bandwidth of balanced amplifier using metamaterial-based quadrature power splitters

A new balanced amplifier (BA) using metamaterial- based quadrature power splitters (QPSs) is presented in this letter. Instead of using conventional 90° couplers, the developed BA is implemented by two parallel amplifiers with broadband metamaterial-based QPSs at input and output ends. Since the QPSs can provide a broadband quadrature phase difference between two outputs, the input/output reflections from two amplifiers can be effectively cancelled over a wide bandwidth. The developed BA demonstrates the input/output return loss of better than 10 dB from 1.2 to 3.5 GHz with 97.9% relative bandwidth.