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Title: Efficiency Improvement of Multi-band Wireless Transceivers using Advanced Digital Signal Processing Algorithms
Author: Kwan, Andrew
Advisor: Ghannouchi, Fadhel
Keywords: Engineering--Electronics and Electrical
Abstract: Innovations in wireless communications has led to an exponential increase in the amount of users and data traffic. While highly spectral efficient modulation schemes and multi-band/wideband signal transmission enables high data traffic throughput, multiple challenges exist in the design and implementation of these transceivers, especially since these transceivers draw a high amount of power. Designers of wireless transceivers require more effort to increase their overall efficiency compared to the technology that exists for narrowband wireless transceivers. This dissertation introduces several techniques for optimizing wireless transceivers using advanced architectures and digital signal processing algorithms. The research focus is specifically for multi-band and wideband signal transmission, where design complexity increases over traditional transceiver architectures. A subsampling receiver architecture is used as an alternative for wireless receivers. This type of receiver enables direct sampling and digitization of RF signals without a downconversion stage, which reduces the complexity and increases the flexibility of the receiver. The subsampling architecture is utilized in a variety of applications, including as a feedback loop replacement in a dual-band digital predistortion (DPD) architecture. The results show that using subsampling can concurrently capture both signal bands at the same time while providing comparable linearization performance with conventional DPD architectures. DPD is a suitable technology for linearity enhancement and efficiency improvement of wireless transmitters. However, extension to wideband and multi-band topologies requires high digital sampling rates. A technique is introduced to reduce the sampling rate requirements in the feedback loop of the transmitter in a wideband and multi-band scenarios, where a reduction of up to twice the sampling rates can be achieved while able to produce accurate linearization performance. Envelope tracking increases the efficiency of the transmitter power amplifier (PA) at large output back-off power, performed by adjusting the voltage supplied to the PA based on the input signal characteristics. Using the digital signal processing techniques outlined in the thesis, the results obtained show that ET and DPD together can provide up to 9% efficiency improvement over just DPD alone, and are suitable for future generations of wireless transmitters.
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