Design of Multi-band/Wide-band High Efficiency Power Amplifiers
Date
2018-04-18
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Abstract
As an important component of the RF front-end in the transmitter, the power amplifier (PA) is used to convert the DC supply power into RF power. As the PA consumes most of the power in the transmitter, minimizing power dissipation of the PA would have a significant effect on the efficiency of the whole system. During recent decades, several works have been done to enhance the PA efficiency. However, there must be a trade-off between efficiency, linearity, gain, output power and bandwidth, which are five crucial attributes of the PA. With the development of the wireless communication system, multiple standards at different frequency bands are highly demanded to be integrated into one system while the increasing data rate requires a wide frequency spectrum and therefore broadband components. The multi-band/wide-band signals also lead to high peak-to-average power ratio. Thus, PAs are required to operate at multi-band/wide-band with high efficiency within a wide output power back-off (OPBO) range. For this reason, this thesis focuses on the PA theory and design method for multi-band, wide-band and wide-OPBO purpose. For the first time, a quad-band impedance inverter with arbitrary frequency ratio is proposed. Based on this impedance inverter, a concurrent quad-band Doherty has been designed at 0.75GHz, 1.75GHz, 2.65GHz and 3.55GHz with efficiency up to 50% at 6dB OPBO. For the first time, this thesis present a new theory for harmonically tuned PAs with maximally flat waveform, named class X PAs. The theory was developed for arbitrary harmonic tuning with arbitrary number of harmonics. The analytic close-form formulas for the voltage and current waveforms are provided. Design space for the Class-X PA with only first three harmonics is derived. To validate the theory, a wide-band PA has been designed with output power above 38dBm, efficiency higher than 70% over an octave bandwidth. The harmonic tuning method is also applied to the outphasing system in order to improve the efficiency. A harmonically tuned class-F outphasing system at 27.1MHz is designed with three third harmonic tuning cases to validate the theory. A harmonically tuned class-F-1 outphasing system at 2.14GHz is designed with efficiency of 68% at 6dB OPBO
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Keywords
power amplifier, multi-band, wide-band, Class-X, Doherty, outphasing, high efficiency
Citation
Li, X. (2018). Design of Multi-band/Wide-band High Efficiency Power Amplifiers (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/31805