ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Displaying 31 - 32 of 32
Description
Recent advancements in communication standards, such as 5G demand transmitter hardware to support high data rates with high energy efficiency. With the revolution of communication standards, modulation schemes have become more complex and require high peak-to-average (PAPR) signals. In wireless transceiver hardware, the power amplifier (PA) consumes most of the transceiver’s DC power and is typically the bottleneck for transmitter linearity. Therefore, the transmitter’s performance directly depends on the PA. To support high PAPR signals, the PA must operate efficiently at its saturated and backoff output power. Maintaining high efficiency at both peak and backoff output power is challenging. One effective technique for addressing this problem is load modulation. Some of the prominent load-modulated PA architectures are outphasing PAs, load-modulated balanced amplifiers (LMBA), envelope elimination and restoration (EER), envelope tracking (ET), Doherty power amplifiers (DPA), and polar transmitters. Amongst them, the DPA is the most popular for infrastructure applications due to its simpler architecture compared to other techniques and linearizability with digital pre-distortion (DPD). Another crucial characteristic of progressing communication standards is wide signal bandwidths. High-efficiency power amplifiers like class J/F/F-1 and load-modulated PAs like the DPA exhibit narrowband performance because the amplifiers require precise output impedance terminations. Therefore, it is equally essential to develop adaptable PA solutions to process radio frequency (RF) signals with wide bandwidths. To support modern and future cellular infrastructure, RF PAs need to be innovated to increase the backoff power efficiency by two times or more and support ten times or more wider bandwidths than current state-of-the-art PAs. This work presents five RF PA analyses and implementations to support future wireless communications transmitter hardware. Chapter 2 presents an optimized output-matching network analysis and design to achieve extended output power backoff of the DPA. Chapters 3 and 4 unveil two bandwidth enhancement techniques for the DPA while maintaining extended output power backoff. Chapter 5 exhibits a dual-band hybrid mode PA design targeted for wideband applications. Chapter 6 presents a built-in self-test circuit integrated into a PA for output impedance monitoring. This can alleviate the PA performance degradation due to the variation in the PA's output load over frequency, process, and aging. All RF PAs in this dissertation are implemented using Gallium Nitride (GaN)-based high electron mobility transistors (HEMT), and the realized designs validate the proposed PAs' theories/architectures.
ContributorsRoychowdhury, Debatrayee (Author) / Kitchen, Jennifer (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Ozev, Sule (Committee member) / Aberle, James (Committee member) / Arizona State University (Publisher)
Created2024
Description
The world has seen a revolution in cellular communication with the advent of 5G (fifth-generation), which enables gigabits per second data speed with low latency, massive capacity, and increased availability. These modern wireless systems improve spectrum efficiency by employing advanced modulation techniques, but result in large peak-to-average power ratios (PAPR) of the transmitted signals that degrades the efficiency of the radio-frequency power amplifiers (PAs) in the power back-off (PBO) region. Envelope tracking (ET), which is a dynamic supply control technology to realize high efficiency PAs, is a promising approach for designing transmitters for the future. Conventional voltage regulators, such as linear regulators and switching regulators, fail to simultaneously offer high speed, high efficiency, and improved linearity. Hybrid supply modulators (HSM) that combine a linear and switching regulator emerge as promising solutions to achieve an optimized tradeoff between different design parameters. Over the years, considerable development and research efforts in industry and academia have been spent on maximizing HSM performance, and a majority of the most recently developed modulators are implemented in CMOS technology and mainly targeted for handset applications. In this dissertation, the main requirements for modern HSM designs are categorized and analyzed in detail. Next, techniques to improve HSM performance are discussed. The available device technologies for HSM and PA implementations are also delineated, and implementation challenges of an integrated ET-PA system are summarized. Finally, a Current-Mode with Dynamic Hysteresis HSM is proposed, designed, and implemented. With the proposed technique, the HSM is able to track LTE signals up to 100 MHz bandwidth. Switching at a peak frequency of 40 MHz, the design is able to track a 1 Vpp sinusoidal signal with high fidelity, has an output voltage ripple around 54 mV, and achieves a peak static and dynamic efficiency of 92.2% and 82.29%, respectively, at the maximum output. The HSM is capable of delivering a maximum output power of 425 mW and occupies a small die area of 1.6mm2. Overall, the proposed HSM promises competitive performance compared to state-of-the-art works.
ContributorsBHARDWAJ, SUMIT (Author) / Kitchen, Jennifer (Thesis advisor) / Ozev, Sule (Committee member) / Bakkaloglu, Bertan (Committee member) / Singh, Shrikant (Committee member) / Arizona State University (Publisher)
Created2024