Ross S. Wilson

Class-F power amplifier with 80.1% maximum PAE at 2 GHz for cellular base-station applications

A GaN HEMT class-F power amplifier (PA) achieving a high maximum power added efficiency (PAE) is presented. The class-F PA exhibits maximum PAE of 80.1 % with an output power of 40.7 dBm at 2 GHz. The PA maintains PAE higher than 50% at 6-dB input back off. The PA shows PAE higher than 70% over 200-MHz frequency range from 1.9 GHz to 2.1 GHz. Source-pull and load-pull techniques in largesignal analysis were conducted to achieve optimum impedance terminations at fundamental and harmonics.

Linearization and Imbalance Correction Techniques for Broadband Outphasing Power Amplifiers

This paper presents adaptive phase-only memory digital pre-distortion (DPD) and gain/phase/delay imbalance correction techniques for outphasing power amplifiers (PAs). Least squares adaptation is used for the phase-only DPD and imbalance correction techniques. The performance of these techniques is verified by co-simulations and measurements of an outphasing PA implemented with two identical class-F PAs and a Chireix combiner. The Chireix combiner with compensating stubs added to achieve high efficiency introduces nonlinearity. The proposed adaptive phase-only memory DPD corrects for the nonlinearity due to the Chireix combiner. The proposed gain/phase/delay imbalance correction technique achieves total lower/upper adjacent channel power ratio (ACPR) improvements of 43.8/37.6 dB for 5-MHz and 46.2/38.3 dB for 10-MHz long-term-evolution signals in measurements. The fractional-sample delay imbalance correction reduces distortion at low input amplitudes and demonstrates on the order of a 10-dB ACPR improvement compared to full-sample delay imbalance correction.

Characterization of Class-F Power Amplifier With Wide Amplitude and Phase Bandwidth for Outphasing Architecture

A 2.14 GHz gallium nitride class-F power amplifier (PA) achieving both high efficiency and phase linearity over a wide frequency range is presented. The broadband PA is designed as one channel of outphasing architecture in cellular base-stations and analyzed in amplitude and phase domains. In amplitude domain, the PA exhibits measured maximum power added efficiency (PAE) of 80.1% with an output power of 40.7 dBm at 2 GHz. The PA achieves PAE higher than 55% over 500 MHz frequency range. The optimum second-harmonic load impedance enables the broadband operation. In phase domain, phase linearity of the PA is characterized by using phase modulation signals derived from single-carrier 10 MHz, two-carrier 40 MHz, and two-carrier 60 MHz long term evolution signals with 6.5 dB peak-to-average power ratio.

Nonlinearity Modeling of a Chireix Outphasing Power Amplifier

This paper presents the nonlinearity modeling of a 2.14-GHz gallium nitride Chireix outphasing power amplifier (PA). The outphasing PA consists of two branches of class-F PAs achieving high efficiency and good phase linearity and a transmission-line-based Chireix power combiner. An analytical model of outphasing PAs with a Chireix power combiner is developed to explain observed distortion due to the combiner. The validity and accuracy of the proposed analytical model are demonstrated by comparing with simulated and measured results of the outphasing PA with 10-MHz long term evolution (LTE) signal. Furthermore, measurements with 5-/10-MHz LTE signals are performed to demonstrate the correction of the nonlinearity of the outphasing PA using linearization techniques.