Thesis (Ph. D.)--Ohio University, August, 1981. / Title from PDF t.p.

Radio Frequency Identification (RFID) systems use electromagnetic signals to wirelessly identify and track RFID-tagged objects. A reader transmits a carrier wave request signal to an RFID tag, which then transmits a unique identification signal back to the reader. Applications include supply chain inventory management, automated toll booth fee systems, sports event timing, restricted access control, pet monitoring and retail theft prevention. An RFID tag includes an antenna connected to a Radio Frequency Integrated Circuit (RFIC). RFID tags in the ultra-high frequency (UHF), industrial, scientific and medical (ISM) 902-928MHz band and global Electronic Product Code (EPC) 860‑960MHz band are powered passively (power extracted from carrier wave) and cost less than 15 cents per tag. Low cost UHF ISM RFID tags are an effective solution for tracking large inventories. UHF ISM tag antennas are typically planar dipoles printed onto a plastic dielectric substrate (inlay). Power exchange and transmit range is maximized when a tag antenna’s input impedance is conjugate matched to the RFIC input impedance. Since RFIC input impedance includes capacitive reactance, optimized antenna input impedance includes compensating inductive reactance. The T-match network adds inductive matching microstrips to conjugate match the RFIC. Narrowband (±1.5% of center frequency) and broadband (±5% of center frequency) lumped element designs also use inductive matching strips. Narrowband, lumped element design is accomplished through Smith Chart matching assuming lumped antenna elements. The broadband lumped element design is accomplished through a circuit transformation to an equivalent network and tuning the transformed circuit to resonate from 865MHz to 955MHz, with a center frequency of 910MHz. This thesis demonstrates a start-to-finish design process for narrow (±1.5% of center frequency) and broadband (±5% of center frequency) RFID tag antennas [3]. Furthermore, antenna matching element geometries are parametrically swept to characterize input impedance frequency response. Thesis accomplishments include (a) narrow and broadband antenna designs, (b) Keysight’s Advanced Design System (ADS) Momentum simulations, (c) antenna fabrication, and (d) differential probe impedance setup and antenna impedance measurements. Additional items include (e) impedance adjustments (f) tag range testing and (g) narrow vs. broadband matching technique comparisons. Antennas were fabricated in Cal Poly’s Graphic Communication Department by silk-screening silver conductive ink onto DuPont Melinix Polyethylene Terephthalate (PET) plastic. Impedance simulations are compared to fabricated antenna impedance measurements and range testing results.

Tunability and adaptability for radio frequency (RF) front-ends are highly desirable because they not only enhance functionality and performance but also reduce the circuit size and cost. This thesis presents a number of novel design strategies in DC-DC converters, impedance networks and adaptive algorithms for tunable and adaptable RF based mobile telecommunication systems. Specifically, the studies are divided into three major directions: (a) high voltage switch controller based DC-DC converters for RF switch actuation; (b) impedance network designs for impedance transformation of RF switches; and (c) adaptive algorithms for determining the required impedance states at the RF switches. In the first stage, two-phase step-up switched-capacitor (SC) DC-DC converters are explored. The SC converter has a simple control method and a reduced physical volume. The research investigations started with the linear and the non-linear voltage gain topologies. The non-linear voltage gain topology provides a higher voltage gain in a smaller number of stages compared to the linear voltage gain topology. Amongst the non-linear voltage gain topologies, a Fibonacci SC converter has been identified as having lower losses and a higher conversion ratio compared to other topologies. However, the implementation of a high voltage (HV) gain Fibonacci SC converter is complex due to the requirement of widely different gate voltages for the transistors in the Fibonacci converter. Gate driving strategies have been proposed that only require a few auxiliary transistors in order to provide the required boosted voltages for switching the transistors on and off. This technique reduces the design complexity and increases the reliability of the HV Fibonacci SC converter. For the linear voltage gain topology, a high performance complementary-metaloxide- semiconductor (CMOS) based SC DC-DC converter has been proposed in this work. The HV SC DC-DC converter has been designed in low voltage (LV) transistors technology in order to achieve higher voltage gain. Adaptive biasing circuits have been proposed to eliminate the leakage current, hence avoiding latch-up which normally occurs with low voltage transistors when they are used in a high voltage design. Thus, the SC DC-DC converter achieves more than 25% higher boosted voltage compared to converters that use HV transistors. The proposed design provides a 40% power reduction through the charge recycling circuit that reduces the effect of non-ideality in integrated HV capacitors. Moreover, the SC DC-DC converter achieves a 45% smaller area than the conventional converter through optimising the design parameters. In the second stage, the impedance network designs for transforming the impedance of RF switches to the maximum achievable impedance tuning region are investigated. The maximum achievable tuning region is bounded by the fundamental properties of the selected impedance network topology and by the tunable values of the RF switches that are variable over a limited range. A novel design technique has been proposed in order to achieve the maximum impedance tuning region, through identifying the optimum electrical distance between the RF switches at the impedance network. By varying the electrical distance between the RF switches, high impedance tuning regions are achieved across multi frequency standards. This technique reduces the cost and the insertion loss of an impedance network as the required number of RF switches is reduced. The prototype demonstrates high impedance coverages at LTE (700MHz), GSM (900MHz) and GPS (1575MHz). Integration of a tunable impedance network with an antenna for frequency-agility at the RF front-end has also been discussed in this work. The integrated system enlarges the bandwidth of a patch antenna by four times the original bandwidth and also improves the antenna return loss. The prototype achieves frequency-agility from 700MHz to 3GHz. This work demonstrates that a single transceiver with multi frequency standards can be realised by using a tunable impedance network. In the final stage, improvement to an adaptive algorithm for determining the impedance states at the RF switches has been proposed. The work has resulted in one more novel design techniques which reduce the search time in the algorithm, thus minimising the risk of data loss during the impedance tuning process. The approach reduces the search time by more than an order of magnitude by exploiting the relationships among the mass spring’s coefficient values derived from the impedance network parameters, thereby significantly reducing the convergence time of the algorithm. The algorithm with the proposed technique converges in less than half of the computational time compared to the conventional approach, hence significantly improving the search time of the algorithm. The design strategies proposed in this work contribute towards the realisation of tunable and adaptable RF based mobile telecommunication systems.

"In the design of any antenna radiator, single or multi-element, a significant amount of time and resources is spent on impedance matching. There are broadly two approaches to impedance matching; the first is the distributed impedance matching approach which leads to modifying the antenna geometry itself by identifying appropriate degrees of freedom within the structure. The second option is the lumped element approach to impedance matching. In this approach instead of modifying the antenna geometry a passive network attempts to equalize the impedance mismatch between the source and the antenna load. This thesis introduces a new technique of impedance matching using lumped circuits (passive, lossless) for electrically small (short) non-resonant dipole/monopole antennas. A closed form upper-bound on the achievable transducer gain (and therefore the reflection coefficient) is derived starting with the Bode-Fano criterion. A 5 element equalizer is proposed which can equalize all dipole/monopole like antennas. Simulation and experimental results confirm our hypothesis. The second contribution of this thesis is in the design of broadband, small size, modular arrays (2, 4, 8 or 16 elements) using the distributed approach to impedance matching. The design of arrays comprising a small number of elements cannot follow the infinite array design paradigm. Instead, the central idea is to find a single optimized radiator (unit cell) which if used to build the 2x1, 4x1, 2x2 arrays, etc. (up to a 4x4 array) will provide at least the 2:1 bandwidth with a VSWR of 2:1 and stable directive gain (not greater than 3 dB variation) in each configuration. Simulation and experimental results for a solution to the 2x1, 4x1 and 2x2 array configurations is presented. "

R.M. Fano. / "January 2, 1948." / Bibliography: p. 34. / Army Signal Corps Contract W-36-039 sc-32037.

Thin-film theorems are well developed and so are the fabrication processes. Yet under some special conditions, traditional methods (such as the ABCD matrix and the transmission matrix methods) will lead to a serious numerical error. In this thesis, we propose a new method called Couple E/H field formulation, which will overcome this numerical problem in simulating characteristics of complex multi-layered structures. We have verified both the algorithm and its results with the traditional techniques. By extending the impedance matching principle, we came out with a multi-layer anti-reflection coating design optimized for a time-harmonic plane wave incidence with any incident angle. Such a design allows for more plane waves with adjacent angles to pass through the coating layers with minimal reflection. Furthermore, we apply this AR coating design to facets of semiconductor lasers. Our calculation shows that multi-layer coating does a better job than a single layer coating. The reflectivity of a laser diode from single layer coating 0.085% to 5 layer coating 0.056%, which is a 33% improvement.

The proposed energy harvesting system intends to harvest vibrational energy via an electromagnetic generator (EMG). The proposed circuit intends to extract maximum power from the EMG by utilizing the maximum power transfer theorem which states that maximum power is transferred to the load when the source resistance equals the load resistance. The proposed circuit is a synchronous split-capacitor boost converter operating in boundary conduction mode (BCM) to achieve impedance matching and therefore maximum power transferred to the load. The circuit topology combines the rectifier and power stage to reduce power loss of the power management integrated circuit (PMIC). The proposed circuit is designed and fabricated in 130 nm BiCMOS technology. The circuit is validated through schematic level simulations and post-layout simulations. The results conclude the proposed circuit and control operates in a manner to achieve BCM. / Master of Science / Tracking and monitoring systems and products has become more prevalent in our society. Consumers want to know when a package they ordered will arrive. Grocery stores would like to track a produce from harvest to the shelves, ensuring their produce is safe to eat. Produce should be kept around 0 °C and if it exceeds that anywhere during the supply chain, the store should be alerted. Wireless sensor nodes (WSNs) are such devices that would be able to monitor the temperature of produce or the location of a package. These devices must be small, reliable, long-life and cost efficient. Using a battery to power WSNs is an inconvenience as the battery must be replaced often. The proposed circuit enables a self-sufficient WSN that is compact, dependable, long-lasting and economical when deployed at large scale. The proposed circuit has been designed, fabricated and proven through simulations.

Without noise, a wireless system would be able to transmit and receive signals over an arbitrary long-distance. However, practical wireless systems are not noise-free, leading to a limited communication range. Thus, the design of low-noise devices (such as antennas, amplifiers, and filters) is essential to increase the communication range. Also, it is well known that the noise performance of a receiving radio is primarily determined by the frontend including the antenna, filter, and a low-noise amplifier. In our first design, we intend to reduce the noise level of the receiving system by integrating a parametric amplifier into the slot antenna. The parametric amplifier utilizes nonlinear and/or time-variant properties of reactive elements (capacitors and/or inductors) to amplify radio frequency signals. Also, the parametric amplifier offers superior noise performance due to its reactive nature. We utilize the parametric amplifier to design a low-noise active matching circuit for electrically small antennas in our second design. Using Chu's limit and the Bode-Fano bound, we show a trade-off between the noise and bandwidth of the electrically small antennas. In particular, to make the small antenna wideband, one needs to introduce a mismatch between the antenna and the amplifier. Due to the mismatch, the effect of the low-noise amplifier becomes even more critical and that is why we choose the parametric amplifier as a natural candidate. As a realized design, a loop antenna is configured as a receiver, and the up-converter parametric amplifier is connected to it leading to a low-noise and wideband active matching circuit. The structure is simulated using a hybrid simulation technique and its noise performance is compared to the transistor counterpart. Our simulation and measurement results show more than 20 times bandwidth improvement at the expense of a 2 dB increase in the noise figure compared to the passive antenna counterpart. / Doctor of Philosophy / Nowadays, there is a high demand for compact and high-speed electronic devices such as cellphones, tablets, laptops, etc. It is therefore essential to design a miniaturized wideband antenna. Unfortunately, a trade-off exists between the bandwidth and gain of small antennas. The trade-off is based on some fundamental limits and extends to all small and passive antennas, regardless of their shape or structure. By using an active component such as an amplifier, the gain-bandwidth trade-off can be improved. However, we show that the active component adds noise to the receiving system leading to a new trade-off between noise and bandwidth in the receiving structures. In other words, utilizing the active component does not solve the problem and just replaces the gain-bandwidth trade-off with the noise-bandwidth trade-off. To improve the noise-bandwidth trade-off, we propose a new receiving structure in which we use the parametric amplifier instead of a commercially available transistor amplifier. The noise performance of the parametric amplifier is extremely better than the transistor amplifier leading to lower noise for the specified bandwidth. In particular, we improved the noise performance of the receiving system by 3 dB leading to doubling the communication distance.

Yes / In this paper a metamaterial-inspired T-matching network is directly imbedded inside the feedline of a microstrip antenna to realize optimum power transfer between the front-end of an RF wireless transceiver and the antenna. The proposed T-matching network, which is composed of an arrangement of series capacitor, shunt inductor, series capacitor, exhibits left-handed metamaterial characteristics. The matching network is first theoretically modelled to gain insight of its limitations. It was then implemented directly in the 50-Ω feedline to a standard circular patch antenna, which is an unconventional methodology. The antenna’s performance was verified through measurements. With the proposed technique there is 2.7 dBi improvement in the antenna’s radiation gain and 12% increase in the efficiency at the center frequency, and this is achieved over a significantly wider frequency range by a factor of approximately twenty. Moreover, there is good correlation between the theoretical model, method of moments simulation, and the measurement results.

Yes / This paper presents an approach to implement an automatically tuning antenna for optimising power transfer suitable for software defined radio (SDR). Automatic tuning is accomplished using a closed loop impedance tuning network comprising of an impedance sensor and control unit. The sensor provides the control unit with data on the transmit or receive power, and the algorithm is used to impedance of a T-network of LC components to optimize the antenna impedance to maximise power transmission or reception. The effectiveness of the proposed tuning algorithm in relation to impedance matching and convergence on the optimum matching network goal is shown to be superior compared with the conventional tuning algorithm. / This work is partially supported by innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1