A 38-46 GHz MMIC doherty power amplifier using post-distortion linearization

This letter describes the first demonstration of a fully integrated Doherty power amplifier (PA) monolithic microwave integrated circuit (MMIC) with post-distortion linearization at millimeter-wave (MMW) frequency band. The Doherty amplifier MMIC, using a 0.15-mu m GaAs HEMT process, achieves a small signal gain of 7 dB from 38 to 46 GHz with a compact chip size of 2 mm(2). The saturation output power of the Doherty amplifier is 21.8 dBm. The similar topology between the Doherty amplifier and post-distortion linearization makes it possible to improve efficiency and linearity simultaneously in MMW PA designs. After gate bias optimization of the main and peaking amplifier, the drain efficiency improved 6% at 6-dB output back-off and the inter-modulation distortion (IMD) of quasi Doherty amplifier can be improved 18 dB at 42 GHz compared with the balanced amplifier operation.