Reduction of 3rd order intermodulation distortion through the use of a high pass transmission line implementation of "derivative superposition", and through the use of channel doped HEMTS

This paper describes the implementation of an amplifier with low 3rd order intermodulation distortion by using a combination of "Derivative Superposition" and high pass lumped element transmission lines. Measured results of a surface mount component version of the circuit are given, showing suppression of 3rd order intermodulation distortion in the order of -20 dBm compared to that of a similar single HEMT circuit, together with improved gain compression performance at high input signal powers. We also examine the potential benefit of the use of Doped Channel HEMTs and estimate a potential reduction in 3rd order intermodulation distortion of 10 dB.