Linearity Improved Doherty Power Amplifier Using Non-Foster Circuits

In this paper, linearity improved Doherty power amplifier (DPA) is proposed for linearity improvement by modifying the input capacitor value of peaking amplifier. The non-foster circuits are substituted for the conventional λ/4 transmission line in front of peaking amplifier, which the 90° phase shifter and impedance matching can be performed by the proposed structure. Furthermore, the input capacitor value of peaking amplifier FET can be modified through modifying bias voltage and match resistance of non-foster circuits. Therefore, the AM-PM distortion of peak amplifier is suppressed, and the linearity of total DPA is improved. Compared to a conventional DPA, the third-order inter-modulation distortion of proposed DPA is reduced by 12 dB without cutting efficiency.