This paper gives a detailed description of a novel linearization technique using a transistor base-collector junction diode. The novel linearization technique effectively improves the gain compression and phase distortion of the heterojunction bipolar transistor (HBT) with no additional dc consumption, leading to highly efficient linear amplification of the π/4 DQPSK modulation signals. An AIGaAs/daAs HBT monolithic microwave integrated circuit (MMIC) linear power amplifier was fabricated using the novel linearization technique for the handsets used in the 1.9 GHz Japanese Personal Handy Phone System (PHS). The fabricated HBT MMIC power amplifier exhibits an output power of 21 dBm and a power-added efficiency as high as 37% at an operation voltage of 2.7 V. At this rated output power, the adjacent channel power rejection in ±600 kHz offset frequency bands is -55 dBc and the error vector magnitude is 4.3%. This measured linearity is well within the PHS standard.
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