Abstract
Recent development and technology advancement in wireless communication systems to accommodate higher data rate poses a great challenge for wideband operation. This is due to the employment of modulation scheme, such as OFDM, which is subject to high peak to average ratio. Hence communication systems, such as LTE have to operate in multiple operating bands at the moment in order to transmit the OFDM signals linearly with high gain. The power amplifier serves as the bottle neck for high gain linear operation over wide bandwidth. This paper addresses this issue and further presents a novel integrated feedback and analog pre-distortion linearization technique as a solution to achieve wideband flat gain and linear output power while preserving the power amplifier’s power added efficiency (PAE). A maximally flat gain is achieved through the dual parallel feedback technique. The analog pre-distorter on the other hand introduces an optimum third order nonlinear signal components cancellation mechanism over wide frequency range. A prototype of 700 MHz to 2.5 GHz power amplifier is implemented in $0.25~\mu \text{m}$ PHEMT. It achieves an input and output return loss of less than −10 dB followed by flat power gain of 20 dB across the operating band, while sustaining an unconditional stability performance up to 20 GHz. With 1-dB compression point output power (P1dB) of 24.0 dBm, the PA delivers an OIP3 of more than 40 dBm with peak PAE of 66%. The fully integrated circuit consumes an area of 0.8 mm2. The proposed circuit serves to be a good solution to be integrated as a part of the wideband transmitter system for picocell application.
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