Dissertation (Ph.D.)--Worcester Polytechnic Institute. / Keywords: cooperative communication; optimum energy allocation; game theory. Includes bibliographical references (leaves 132-145).

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

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Astronomy constantly pushes the limits of technology in order to decipher the workings of the Universe. There is a constant need for higher resolution observations across a wide range of wavelengths, at preferably a minimal cost. The terahertz regime (lambda=100 um to lambda=1000 um) covers a region of the electromagnetic spectrum that is blocked by Earth's atmosphere, which limits observations to high altitude plane and balloon telescopes and space telescopes. These current options limit the resolution achievable due to the size of telescopes that can be launched. This dissertation investigates a new approach, the Large Balloon Reflector (LBR), where a 20 meter diameter spherical balloon can be inflated and used as a 10 meter telescope inside a larger carrier balloon. Detailed in this dissertation are design considerations for the terahertz regime and a series of scaled versions of this balloon concept where I work to develop on-axis spherical corrector designs. Chapters 1 through 6 focus on the LBR designs and their variants, including investigations for a 3 meter rooftop proof of concept model, a 5 meter test flight model, and the final 20 meter LBR. The successful modeling and proof of concepts from the LBR studies then prompted an investigation into a Terahertz Space Telescope (TST), a proposed 20 meter inflatable telescope adapted from the LBR technology. Starting with Chapter7, this dissertation explores the application of using 1 meter diameter inflatable balloons as rapidly deployable communications satellites from standard CubeSats. The concept, design and test results of an electronically steerable line feed antenna array are presented which allows for instantaneous, non mechanical pointing of a 10 GHz signal within a 500 km ground footprint. Alternative uses of the 1 meter inflatable balloon CubeSat are also discussed, such as low cost astronomical galactic plane surveys.

Electromagnetic wave propagation is a well-known phenomenon in the scientific world and when the first telescope was built method of sensing objects excelled afterwords. Research in optical system and infrared is growing day by day but radar system still dominates the world in object sensing. One of the benefits of using electromagnetic waves in a Radar system is that they can create images of areas which cannot be observed with optical light. Radars work on the basic phenomena of an extremely short burst of radio energy which transmit energy that reflects from the object as an echo. This principle is also known as ECHO Principal [13]. This thesis presents a Coffee Can radar system which gives detection of a stationary and moving object. Objects detection is performed on the oscilloscope using a triangular wave transmitted from an antenna, that gets reflected from an object and received on the second antenna. The prototype consists of two antennas one of which is used for transmitting signal and other is used for receiving signal. Voltage control oscillator is used to generate the RF frequency signal and power amplifiers are used before transmitting and receiving the RF signal. The signals are down-converted using a mixer the output of which is observed on an oscilloscope. Detection of the reflected signal can be performed using Doppler shift which can be determined from the velocity of electromagnetic radiation and angular displacement of the reflected waves. The wavelength of the Doppler shift is then used to indicate the detection and ranging of the object. Coffee Can radar operates at 2.4GHz with the output power of 10mW. Triangular wave signal is generated with the help of a wave generator. The radar prototype built in this thesis is used for detection and ranging of two different types of materials. First, is a metal sheet and secondly an aluminum foil.  The detection process is completed by noting the Vpp values reflected from these sheets. Vpp values are measured on the oscilloscope when the signal reflected from aluminum sheet. With the help of a commercial software, aluminum foil presence is detected under the snow. For the future work if the video amplifier is built then the aluminum foil presence can be detected on MATLAB without the help of any commercial software. In future Coffee Can Radar can also be used for surveillance purposes like smart homes, autonomous vehicles and as a jammer. This Radar system can also be used as a data logging system.

Radio Frequency Identification (RFID) is a short range radio technology for communication between two objects namely, a reader and a tag. Design of an RFID tag with the best range is always the motive of an RFID designer. In this thesis two RFID tags were simulated, designed and manufactured. The first one is a semi-passive RFID tag, which also serves as a discrete prototype tag for the research group to master RFID tag designs. The user can program and further extend the use of this tag according to the requirements. This RFID tag is provided with JTAG interface to program and debug. The read range of this prototype tag is found to be 1m with reader EIRP of 30dBm. The second design is a passive tag which can be commercialized. It achieves a competitive read range of 2.9m for reader EIRP of 21dBm. The read range when measured in a practical implementation inside a building corridor was 15m.

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As the world continues to adopt the next generation of mobile technology, dual-band 5G wireless communications are becoming increasingly significant. 5G technology operates on two different frequency bands, the sub-6 GHz Frequency Range (FR1) and the millimeter wave (MMW) Frequency Range (FR2). The special features in each band enable 5G dual-band communication to provide better coverage and capacity than previous generations of wireless networks. This is especially essential for applications that need high-bandwidth and low-latency connections, such as virtual and augmented reality, autonomous vehicles, and industrial automation. Furthermore, dual-band 5G can help alleviate network congestion in urban areas by redirecting traffic to the MMW band, which has considerably greater capacity. As a result, dual-band 5G is expected to play a critical role in facilitating the next wave of technological innovation and revolutionizing the way we live and work. A dual-band antenna with a large frequency ratio (FR) is required due to the significant difference between each frequency band in 5G. Research on dual-band antennas is facing challenges such as low FR and a lack of a specific design methodology. Despite attempts to develop dual-band antennas with large FRs, there are still issues with low performance and limited bandwidth. This study introduces a novel approach for designing a dual-band antenna with a large FR. The proposed solution draws inspiration from a hybrid design of a dual-band antenna to achieve a large FR, and from the parabolic reflector antenna design to significantly enhance gain in the upper band. The lower band antenna in this design serves as both a radiator for the lower band and a reflector to align the beam in the upper band. This approach can be used to design dual-band antennas for various frequencies. In this thesis, we present a comprehensive model and framework for designing an antenna integrated reflector that offers a large FR. The proposed model is capable of producing an antenna that meets the requirements of the targeted application, namely 5G. This antenna exhibits wideband characteristics and high gain. Two different antenna integrated reflectors, named AIR-I and AIR-II, were designed based on the proposed model. AIR-I has a FR of 10.1. As for AIR-II, due to the presence of dual-band upper antennas, it has a lower band at 1.35 GHz and two upper bands at 13 GHz and 24 GHz thus, a FR of 9.5 and 18, respectively. The above design followed a specific purpose. It uses a 24 GHz/1.35 GHz frequency ratio of 18 to showcase the antenna performance in the context of dual-band 5G. However, the measurement facilities being limited to 20 GHz, a frequency ratio of 9.5 at 13 GHz/1.35 GHz was measured for the AIR-II, as proof of concept. Then, two prototypes were fabricated from AIR-II namely, Prototype-I and Prototype-II. While it would have been possible to demonstrate a proof of concept from a single prototype, it has been decided to produce and test two samples to enable a more exhaustive examination of the subject and obtain additional data that would lend greater support to the model outlined in this thesis. Prototype-I had the same structure as AIR-II and had an operational bandwidth of 0.69 GHz-1.74 GHz / 6 GHz-18 GHz and a FR of 9.9. On the other hand, Prototype-II had an operational bandwidth of 0.69 GHz-1.74 GHz / 13 GHz-18 GHz and a FR of 12.8. These prototypes exhibited maximum bandwidths of 100% and 86%, respectively. Furthermore, at the upper band, Prototype-I achieved a peak gain improvement of 12.6 dB, while Prototype-II achieved an improvement of 8.7 dB. These results demonstrated the significant advantages of our proposed methodology in dual-band antenna design.

No / A novel printed diversity monopole antenna is presented for WiFi/WiMAX applications. The antenna comprises two crescent shaped radiators placed symmetrically with respect to a defected ground plane and a wideband zigzag neutralization line is connected between them to achieve good impedance matching and low mutual coupling. Theoretical and experimental characteristics are illustrated for this antenna, which achieves an impedance bandwidth of 54.5% (over 2.4 – 4.2 GHz), at a reflection coefficient < −10 dB, mutual coupling < −16 dB. An acceptable agreement is obtained for the computed and measured gain, radiation patterns, and envelope correlation coefficient. These characteristics demonstrate that the proposed antenna is an attractive candidate for the multiple input multiple output (MIMO) portable mobile devices.

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