Frequency Doubling Integrated Push-Push Active Microstrip Transponder

A novel frequency doubling active microstrip antenna transponder circuit incorporating two in-house designed monolithic microwave integrated circuit (MMIC) amplifiers is presented. As well as receiving the input signal, the receiving microstrip antenna also divides the input power into two equal parts and produces phase shift of 180° between two outputs. The outputs are fed to two non-linearly biased MMIC amplifiers which are connected so that the first harmonic power adds while the fundamental is suppressed. The transponder circuit responds to an input signal at 10 GHz. The experimental results achieved from the transponder circuit are presented in the paper.