Doctor of Philosophy, The Ohio State University, 2003, Electrical Engineering

For the past years, great efforts have been made to implement a single chip transceiver for a target wireless system. More over, world-wide massivetransportations necessitate global communication methods. However, lots of different standards exist nowadays and a mobile unit for a certain standard can not be used for different standards. In order to cover various wireless systems, unless a new unified global communication standard is adopted, conventional systems need to be merged and evolve into a more complicated communication system called a "multi-standard'' transceiver. In a typical receiver architecture, incoming RF signals are multiplied by a local oscillator(LO) signal to obtain desired signals that might be either intermediate frequency(IF) signals or baseband signals. The local oscillator is practically an output signal of a frequency synthesizer. Conventional synthesizers can provide channel selection over a limited band due to limited division ratios of prescalers and voltage-controlled oscillator(VCO) operating frequency ranges. In this dissertation, a frequency synthesizer for multi-standard applications is presented. Based on a phase-locked loop, the synthesizer can provide various channel selection in order to comply with a designer's own frequency plan to cover multiple wireless standards. A fully programmable dual-modulus frequency divider is proposed with a new frequency division method to avoid division ratios that contain a decimal point. Newly developed PLL sub-blocks are presented. A new method to analyze and suppress effects of VCO pushing is introduced. Due to the difficulty in building a wide-band/multi-band LC-tank oscillator, a 900MHz band and tri-band single-ended voltage controlled oscillator(SE-VCRO) are built for the purpose of multi-band test even though they exhibit inferior phase noise performance to their LC-tank counterparts. A phase noise equation for a voltage-controlled oscillator is derived by modifying a phase noise equation (open full item for complete abstract)

Committee: Mohammed Ismail (Advisor) Subjects:

Doctor of Philosophy, University of Toledo, 2015, Electrical Engineering

The ever-growing demand toward designing microwave front-end components with enhanced access to the radio spectrum (e.g., multi-/wideband functionality) and improved physical features (e.g., miniaturized circuitry, ease and cost of fabrication) is becoming more paramount than ever before. This dissertation proposes new design methodologies, simulations, and experimental validations of passive front-ends (i.e., antennas, couplers, dividers) at microwave frequencies. The presented design concepts optimize both electrical and physical characteristics without degrading the intended performance. The developed designs are essential to the upcoming wireless technologies. The first proposed component is a compact ultra-wideband (UWB) Wilkinson power divider (WPD). The design procedure is accomplished by replacing the uniform transmission lines in each arm of the conventional single-frequency divider with impedance-varying profiles governed by a truncated Fourier series. While such non-uniform transmission lines (NTLs) are obtained through the even-mode analysis, three isolation resistors are optimized in the odd-mode circuit to achieve proper isolation and output ports matching over the frequency range of interest. The proposed design methodology is systematic, and results in single-layered and compact structures. For verification purposes, an equal split WPD is designed, simulated, and measured. The obtained results show that the input and output ports matching as well as the isolation between the output ports are below –10 dB; whereas the transmission parameters vary between –3.2 dB and –5 dB across the 3.1–10.6 GHz band. The designed divider is expected to find applications in UWB antenna diversity, multiple-input-multiple-output (MIMO) schemes, and antenna arrays feeding networks. The second proposed component is a wideband multi-way Bagley power divider (BPD). Wideband functionality is achieved by replacing the single-frequency matching uniform microstrip lines (open full item for complete abstract)

Committee: Vijaya Devabhaktuni (Committee Chair); Mansoor Alam (Committee Member); Junghwan Kim (Committee Member); Daniel Georgiev (Committee Member); Douglas Nims (Committee Member); Mohammad Almalkawi (Committee Member); Abdelrazik Sebak (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2010, Electrical Engineering

A Voltage Controlled Oscillator (VCO) is essentially a tunable frequency generator. A VCO is used as a part in PLL system which is a system that generates a stable oscillating signal. As the digital electronic industry demands an ever increasing performance in speed, VCO's are required to create higher frequency signals. However, the phase noise performance of a VCO decreases as the operating frequency gets higher. The LC VCO is developed in this thesis to be used in with a tunable frequency divider as a part of a PLL system. The LC VCO structure design takes the advantage of a current source in the LC tank to provide an operational condition while lowering the overall tank size for a higher oscillation. The variable frequency divider structure uses the low voltage swing current mode and two CML latch configurations. The dividing constant of the frequency divider is varied by adjusting the load resistance of the CML latches. The resulting combined circuit structure yields a maximum operating frequency of 43.23GHz with the divided frequency of 296MHz. The phase noise of the VCO at maximum operating frequency is - 80dBc/Hz at 1MHz offset.

Committee: Saiyu Ren PhD (Advisor); Raymond Siferd PhD (Committee Member); Kefu Xue PhD (Committee Member); Marian Kazimierczuk PhD (Committee Member) Subjects: Electrical Engineering