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-μm 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.
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