Analysis of Dual Band PA Nonlinear Performances by Application of Digital Linearisation Model

A dual band power amplifier designed to sustain high efficiency at two diverse working frequencies, 2.1 GHz and 5 GHz, is linearised by the technique that uses baseband signal processing in the digital domain. Generation of the dual band PA matching circuits consist of two individual steps. Firstly, transformation of the selected complex impedances at the two operating frequencies into the real impedance identical for the both observed frequencies is performed. Secondly, synthesis of the dual band filter in order to provide matching of the real impedance with the termination impedances is carried out. The linearisation of the dual band amplifier is accomplished by the 2
^nd
order nonlinear baseband signals, which modulate the carrier 2
^nd
harmonic. The generated signals in this manner are then induced at the gate and drain of the dual band PA transistor. The assessment of the linearisation influence was performed for the two baseband signals spaced in frequency by diversified intervals up to 80 MHz for output levels-Pout from 25 dBm to 35 dBm for both considered frequencies.