UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

Science Mission Directorate TechPort Records for 2019 STI-DAA Release

The role of the Science Mission Directorate (SMD) is to enable NASA to achieve its science goals in the context of the Nation's science agenda. SMD's strategic decisions regarding future missions and scientific pursuits are guided by Agency goals, input from the science community including the recommendations set forth in the National Research Council (NRC) decadal surveys and a commitment to preserve a balanced program across the major science disciplines. Toward this end, each of the four SMD science divisions -- Heliophysics, Earth Science, Planetary Science, and Astrophysics -- develops fundamental science questions upon which to base future research and mission programs

High Efficiency Microwave Amplifiers and SiC Varactors Optimized for Dynamic Load Modulation

The increasing use of mobile networks as the main source of internet connectivity is creating challenges in the infrastructure. Customer demand is a moving target and continuous hardware developments are necessary to supply higher data rates in an environmentally sustainable and cost effective way. This thesis reviews and advances the status of realizing wideband and high efficiency power amplifiers, which will facilitate improvements in network capacity and energy efficiency. Several demonstrator PAs are proposed, analyzed, designed, and characterized: First, resistive loading at higher harmonics in wideband power amplifier design suitable for envelope tracking (ET) is proposed. A 40 dBm decade bandwidth 0.4–4.1 GHz PA is designed, with 10–15 dB gain and 40–62% drain efficiency. Its versatility is demonstrated by digital pre-distortion (DPD) linearized measurements resulting in adjacent channel leakage ratios (ACLR) lower than −46 dBc for various downlink signals (WCDMA, LTE, WiMAX). Second, a theory for class-J microwave frequency dynamic load modulation (DLM) PAs is derived. This connects transistor technology and load network requirements to enable power-scalable and bandwidth conscious designs. A 38 dBm PA is designed at 2.08 GHz, maintaining efficiencies >45% over 8 dB of output power back-off (OPBO) dynamic range. From this pre-study a fully packaged 86-W peak power version at 2.14 GHz is designed. ACLR after DPD is −46 dBc at a drain efficiency of 34%. For DLM PAs there is a need for varactors with large effective tuning range and high breakdown voltage. For this purpose, SiC Schottky diode varactors are developed with an effective tuning range of 6:1 and supporting a 3:1 tuning ratio at 36 V of RF swing. Nonlinear characterization to enable Q-factor extraction in the presence of distortion is proposed and demonstrated by multi-harmonic active source- and load-pull, offering insights to tunable network design. Third, a method to evaluate and optimize dual-RF input PAs, while catering to higher harmonic conditions and transistor parasitics, is proposed. The method is validated by a PA design having a peak power of 44 +/- 0.9 dBm and 6 dB OPBO PAE exceeding 45% over a 1–3 GHz bandwidth. The results in this thesis contribute with a novel device and analysis of high efficiency and wideband PAs, aiding in the design of key components for future energy efficient and high capacity wireless systems

GaN Technologies for Microwave Heating and Broadband Receiver Applications

This thesis entitled, "GaN Technologies for Microwave Heating and Broadband Receiver Applications," consists of two parts. Part I discusses galium nitride (GaN) for high-power transmitters used in a solid-state microwave waste-to-fuel reactor. As the global population is producing and consuming more, there is a worldwide need for more efficient methods of reducing, reusing, recycling, and upcycling produced waste. Pyrolysis for municipal solid waste is investigated through a scalable solid-state microwave heating cavity. The detailed analysis of different power combining methods at 2.45 GHz was covered in the comprehensive exam and will be briefly summarized in this defense. In Part II, the high-power handling and linearity of GaN is examined for use in RF receivers. Broadband receivers are susceptible to interference and a large interfering signal can saturate multiple systems including the low noise amplifier, mixer, and analog to digital converter. Interference suppression circuits using GaN tunable delay lines are explored for suppressing out-of-band interfering signals. Multiple hybrid 2-4 GHz tunable notch boards were designed, fabricated, and characterized for this study. This defense will focus on analog interference suppression circuit design and performance.</p

Terahertz Technology for Defense and Security-Related Applications

This thesis deals with chosen aspects of terahertz (THz) technology that have potential in defense and security-related applications. A novel method for simultaneous data acquisition in time-resolved THz spectroscopy experiments is developed. This technique is demonstrated by extracting the sheet conductivity of photoexcited charge carriers in semi-insulating gallium arsenide. Comparison with results obtained using a standard data acquisition scheme shows that the new method minimizes errors originating from fluctuations in the laser system out-put and timing errors in the THz pulse detection. Furthermore, a new organic material, BNA, is proved to be a strong and broadband THz emitter which enables spectroscopy with a bandwidth twice as large as conventional spectroscopy in the field. To access electric fields allowing exploration of THz nonlinear phenomena, field enhancement properties of tapered parallel plate waveguide

Solid-state technology for domestic microwave heating applications

The use of solid-state power for microwave heating, first proposed in the late 1960’s and early 1970’s, is now an area of growing interest and research for a number of stakekholders; semiconductor device manufacturers, domestic and commercial microwave oven manufacturers, large-scale heating industry and consumers. The traditional way of generating power for these applications has been through the use of a high power magnetron source, the power is then coupled into the cavity via a waveguide. Although cost effective, the magnetron source is limited in that it has a relatively small bandwidth (20MHz) which means that only a small number of modes are excited. The different ingredients in a meal often have different dielctric properties and require multi-mode excitations over the entire (2.4-2.5GHz) band to distribute heat evenly and prevent uneven heating of the load. Its other limitations include no direct means of quantifying forward and reflected powers, the transit time becoming an appreciable portion of the signal cycle which decreases efficiency has been well documented. The recent advances and developments in semiconductor device technology (LDMOS, HVLDMOS and GaN-on-Si) has alleviated some of the earlier obstacles relating to lowpower and poor-efficiency. However, concerns remain about cost, device reliability and output power levels. For example the relatively recent, sufficiently high power levels from a single transistor (300W, CW), and the use of new power combining techniques are factors that are increasing the viability of solid-state power in microwave heating. This thesis focuses on a proposed application that involves the use of RF generated power from a solid-state amplifier, at the heart of the SSPA is the “power transistor”, which generates power to heat the loads (e.g. food) in resonant cavities. From an energy consumption perspective, the solid-state source is a key element that must be designed to satisfy stringent efficiency requirements. Device and circuit related efficiencies are required to maintain an efficient transfer of power into the cavity under variable loading conditions which poses an even greater challenge. The delivery of power into a cavity iii under variable loading conditions usually leads to impedance mismatch, highly reflective states and associated heating inefficiency. Addressing this set of unique challenges has led to continuous research to improve the efficiency and reliability of power transistors. For example, new power transistor technologies (GaN, SiC) offer increased performance compared to traditional silicon components. These transistors can operate at higher power levels, frequencies and temperatures with an improved energy efficiency with respect to that guaranteed by previous generation. From a solid-state heating perspective most of this research has focused on high power and high efficiency PA architectures and device reliability, there is little literature addressing the importance of a coupling structures and the potential performance enhancements they may offer in solid-state implementations. The coupling structure plays an important role in transferring available SSPA power into the cavity to heat the load. The novel work presented in this thesis includes capturing cavity impedance behaviour of different cavity geometries under variable loading conditions and introduces a coupling architecture through which these changes are identified and optimally matched to maintain system and heating efficiency. Following extensive research into means of transferring SSPA power into the cavity efficiently, maintaining device reliability and realizing the goal of homogeneous heating, the study has led to the development of a novel coupling structure. This structure ensures an optimised match under variable loading conditions by incorporating harmonic tuning elements for improved efficiency. The novel research introduced in this work shows how device reliability and efficiency can be improved along with improving heating uniformity