Continuous-Mode Inverse Class-GF Power Amplifier With Second-Harmonic Impedance Optimization at Device Input
Sina Eskandari, Yulong Zhao, Mohamed Helaoui, Fadhel M. Ghannouchi, Ammar B. Kouki
Abstract
In this article, a continuous-mode inverse class GF (CCGF <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) power amplifier is introduced based on a new closed-form expression for the drain current. This analytical expression is utilized to exploit second source harmonic impedance manipulation in order to expand the design space of the output matching circuit resistively. This approach allows to diminish the complexity of the design of the load matching network at the fundamental and harmonic frequencies and to achieve wider bandwidth while simultaneously improving drain efficiency across the new optimum admittance points. Using the nonlinear model of a commercially available 10-W gallium nitride (GaN) device, load-pull and source-pull techniques are used to design a wideband CCGF <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The designed amplifier is fabricated using the selected transistor in low-temperature co-fired ceramic (LTCC) technology. Measurement results show that, over the frequency band between 3.05 and 3.85 GHz, a drain efficiency of more than 70%, 11-12.4-dB gain, and 39.9-41.4-dBm output power at 3-dB gain compression have been achieved. Although not designed for linearity, the fabricated amplifier shows an adjacent channel power ratio better than 26 dBc under a 20-MHz long-term evolution (LTE) signal having a 10.45-dB peak-to-average power ratio.