Abstract
A simple and effective method for linearization of power amplifiers (PAs) is proposed. The method is based on the second harmonic injection into the input of the PA. The second harmonic is generated in a feedback path by taking the low-power transistors of a pseudo-differential pair amplifier to their nonlinear regime. The amplitude and phase of the second harmonics are controlled by tunable matching networks of the pseudo-differential pair which include trimmer capacitors. Using a theoretical analysis, we show that the proposed method is capable of canceling the third-order intermodulation signal at the PA output. As a proof of concept, a 10-W PA in a frequency band of 1.4 - 1.6 GHz is designed and linearized. By fabricating both the reference and linearized PAs and performing measurements under several conditions, it is experimentally demonstrated that applying the proposed scheme, thanks to its adjustability, highly linearizes the PA in a wide bandwidth and a wide range of output power.
Highlights
Power amplifiers (PAs) are an essential part of every communication system whose characteristics greatly impact the system performance
This paper presents a new implementation of linearization based on the second harmonic (SH) injection at the input
At the output of the pseudo differential pair (PDP), the SH is generated by taking the low-power transistors to their nonlinear regime and is injected into the PA input
Summary
Power amplifiers (PAs) are an essential part of every communication system whose characteristics greatly impact the system performance. In order to achieve high output power (Pout) along with high-efficiency, PAs can be used very close to their saturation region [1]–[3]; due to the nonlinear effects at saturation, they would suffer from amplitude and phase distortion and undesired intermodulation signals. The use of amplitude and phase complex modulated signals with a high peak to average power ratio (PAPR) in modern communication systems calls for high linearity of PAs as well [4]. Design and implementation of high-efficiency linear PAs, necessary and important, is complicated and challenging. Linearization methods such as feedback, feedforward, and analog and digital pre-distortion
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