In this paper, a new method is proposed to design a linearity-enhanced load modulated balanced amplifier (LMBA). This method optimizes the phase difference parameter to achieve a predefined amplitude-to-phase (AM–PM) characteristic while ensuring proper load modulation and high efficiency at output back-off state. The predefined AM–PM characteristic is chosen to be the inverse of the control transistor to improve the overall linearity of the LMBA. For proof-of-concept validation purposes, a linearity-enhanced LMBA circuit prototype is designed to provide linear overall AM–PM characteristics at 2.1 GHz. Meanwhile, its input matching network is designed to minimize the AM–AM distortion by properly selecting the source impedances. Under continuous wave excitation, the fabricated LMBA show that the drain efficiency is 40.2% at 9 dB output back-off power level and the saturated drain efficiency is 50.6%. Besides, the gain compression under continuous-wave stimuli is 3.02 dB. Furthermore, under excitation by carrier aggregated signals with modulation bandwidths of up to 40 MHz and a peak-to-average power ratio equal to 9 dB, the LMBA prototype maintains an adjacent channel leakage ratio of better than −35.6 dBc with a drain efficiency excessing 40%, without any additional linearization schemes.
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