FMCW Signals for Radar Imaging and Channel Sounding

A linear / stepped frequency modulated continuous wave (FMCW) signal has for a long time been used in radar and channel sounding. A novel FMCW waveform known as “Gated FMCW” signal is proposed in this thesis for the suppression of strong undesired signals in microwave radar applications, such as: through-the-wall, ground penetrating, and medical imaging radar. In these applications the crosstalk signal between antennas and the reflections form the early interface (wall, ground surface, or skin respectively) are much stronger in magnitude compared to the backscattered signal from the target. Consequently, if not suppressed they overshadow the target’s return making detection a difficult task. Moreover, these strong unwanted reflections limit the radar’s dynamic range and might saturate or block the receiver causing the reflection from actual targets (especially targets with low radar cross section) to appear as noise. The effectiveness of the proposed waveform as a suppression technique was investigated in various radar scenarios, through numerical simulations and experiments. Comparisons of the radar images obtained for the radar system operating with the standard linear FMCW signal and with the proposed Gated FMCW waveform are also made. In addition to the radar work the application of FMCW signals to radio propagation measurements and channel characterisation in the 60 GHz and 2-6 GHz frequency bands in indoor and outdoor environments is described. The data are used to predict the bit error rate performance of the in-house built measurement based channel simulator and the results are compared with the theoretical multipath channel simulator available in Matlab

Energy efficient 5G networks

For a greener tomorrow, an important step today will be the energy efficient designs in any aspect. The 5G networks which is most awaited by all, though proposes better data rates, but also speaks about the energy efficiency in its agenda. A broad study of different techniques for energy efficiency reveals that beamforming plays a crucial role. Thus leading to this thesis mainly concentrating on the aspects of beamforming. Beamforming though has been into existence for more than over a decade, continuous improvements in the methodology keeps it ahead of many other technologies used for the common goal. This thesis work is done with the concept called multi-beam beamforming. An interesting concept of amplitude tapering is tailed to keep a check on the magnitude of power supplied at the antenna terminals. Using these, the thesis compares the gain values of both the desired and undesired users which will aid in estimating the amount of power required for covering a set of users using different tapering methods. This works also includes the effect of increasing number of antennas and the users and the effect on the gain values for both desired and undesired users. This develops a scope to introduce a new metric called “potential power improvement” for different tapering methods. Also, a framework has been developed to expand and evaluate the cases mentioned above to a multi-cell scenario in both general antenna configuration and Massive MIMO configuration

Composite Right-Left Handed Stripline Structures for Antenna Array Feed Networks

In this dissertation composite right/left-handed striplines are proposed as viable key structures in antenna array applications, enabling reduction of the overall feed network sizes as well as allowing integration opportunities and possible reduction of radiating beam pattern distortions. A via-less composite right/left-handed stripline unit cell is introduced as an option to attain right/left-handed performance in stripline with a via-less fabrication process that is not sensitive to drill positioning errors and is amenable to academic settings. An analysis of the passbands of this structure based on the distributed transmission line circuit theory is provided as well as a description of the method utilized to tune the performance. Three different application scenarios are explored using variations of the via-less composite right/left-handed stripline in the feed networks. The first application is a linear frequency scanning antenna array in which arbitrary radiating elements may be used. The second application is in a 2D planar frequency scanning array that has the capability of steering radiated beams over most of a hemisphere. The last one is in a wideband phase shifting network that can be used to excite a circularly polarized antenna array. Comparisons to the traditional unit cell with vias are provided when appropriate, as well as comparisons to non composite right/left-handed approaches traditionally used for each application. This practical research is supported by extensive 3D electromagnetic simulations and, for the via-less solutions, validated through scattering parameters and radiation pattern measurements of fabricated prototypes. The fabrication process is described in detail with emphasis on aspects that have the most significant effect on overall performance. The measured results presented are in good agreement with simulated predictions, bolstering the case for the use of composite right/left-handed striplines in antenna array feed networks

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

Beamforming management and beam training in 5G system

Massive multiple-input-multiple-output (MIMO) antenna system with beamforming technique is an integral part of upcoming 5G new radio (NR) system. For the upcoming deployment of 5G NR system in both stand-alone (SA) and non-stand-alone (NSA) structure, beamforming plays an important role to achieve its key features and meet the estimated requirement. To be employed with massive MIMO antenna structure, beamforming will allow 5G system to serve several users at a time with better throughput and spectral usage. Beamforming will also minimize the path loss due to high susceptibility of millimetre wave and provide beamforming gain. For a wide range of benefit scheme, beamforming is currently a hot topic regarding the deployment of 5G. With the advantage of both analog and digital beamforming, hybrid beamforming structure can provide better system benchmark performance in terms of cost and flexibility. Switched beam training and adaptive beam training approaches and algorithms are developed in order to reduce training time, signalling overhead and misdetection probability. Some of the approaches and algorithm are addressed in this thesis. Beamforming management ensures the initiation and sustainability of the established link between transmitter and receiver through different processes. Beam tracking helps to keep track of the receiver devices during mobility. As beamforming is related to antenna configuration, near-field spherical wave front incident problem was ignored, and all the references and examples presented in this topic was obtained with a far-field propagation perspective. To avoid mutual coupling between antenna elements and grating lobe problems in antenna radiation pattern, each element is separated by half of the wavelength. This thesis paper aims to provide a broader view into beamforming scenario, starting from the basics of beamforming to training the beams and management aspects in the hardware part of 5G structure. Another goal is to present the necessity of beamforming in a 5G system by stating different benefits scheme such as spatial diversity, interference suppression, energy efficiency, spectral efficiency and so on. These benefits are justified by evaluating various research paper and MATLAB simulations

Circularly Polarized Antennas for GNSS Applications

Global navigation satellite system (GNSS) is developing rapidly. Modern GNSS technology is facing challenges for researchers to explore. One hot topic is the multi-system GNSS device. The motivation for the antenna designers is to miniaturize the size of the antenna and meanwhile keep its standard performance. It is a challenging task for an antenna array design to achieve a wide bandwidth, high gain, small size, good coverage, and simple fabrication technique all at the same time. This thesis develops several different novel compacts, high gain, and wide bandwidth circularly polarized (CP) antenna capable of providing wide coverage for GNSS frequency bands from 1.16 GHz to 1.6 GHz to cover the GPS L1-L5 bands, GLONASS G1, G2 and G3 as well as the Galileo E5a, E5b, E6, and E1bands

Mutual Coupling in Phased Arrays: A Review

The mutual coupling between antenna elements affects the antenna parameters like terminal impedances, reflection coefficients and hence the antenna array performance in terms of radiation characteristics, output signal-to-interference noise ratio (SINR), and radar cross section (RCS). This coupling effect is also known to directly or indirectly influence the steady state and transient response, the resolution capability, interference rejection, and direction-of-arrival (DOA) estimation competence of the array. Researchers have proposed several techniques and designs for optimal performance of phased array in a given signal environment, counteracting the coupling effect. This paper presents a comprehensive review of the methods that model and mitigate the mutual coupling effect for different types of arrays. The parameters that get affected due to the presence of coupling thereby degrading the array performance are discussed. The techniques for optimization of the antenna characteristics in the presence of coupling are also included

Advanced Radio Frequency Antennas for Modern Communication and Medical Systems

The main objective of this book is to present novel radio frequency (RF) antennas for 5G, IOT, and medical applications. The book is divided into four sections that present the main topics of radio frequency antennas. The rapid growth in development of cellular wireless communication systems over the last twenty years has resulted in most of world population owning smartphones, smart watches, I-pads, and other RF communication devices. Efficient compact wideband antennas are crucial in RF communication devices. This book presents information on planar antennas, cavity antennas, Vivaldi antennas, phased arrays, MIMO antennas, beamforming phased array reconfigurable Pabry-Perot cavity antennas, and time modulated linear array

Improving the Performance of Medium Access Control Protocols for Mobile Adhoc Network with Smart Antennas

Requirements for high quality links and great demand for high throughput in Wireless LAN especially Mobile Ad-hoc Network has motivated new enhancements and work in Wireless communications such as Smart Antenna Systems. Smart (adaptive) Antennas enable spatial reuse, increase throughput and they increase the communication range because of the increase directivity of the antenna array. These enhancements quantified for the physical layer may not be efficiently utilized, unless the Media Access Control (MAC) layer is designed accordingly. This thesis implements the behaviours of two MAC protocols, ANMAC and MMAC protocols in OPNET simulator. This method is known as the Physical-MAC layer simulation model. The entire physical layer is written in MATLAB, and MATLAB is integrated into OPNET to perform the necessary stochastic physical layer simulations. The aim is to investigate the performance improvement in throughput and delay of the selected MAC Protocols when using Smart Antennas in a mobile environment. Analytical methods were used to analyze the average throughput and delay performance of the selected MAC Protocols with Adaptive Antenna Arrays in MANET when using spatial diversity. Comparison study has been done between the MAC protocols when using Switched beam antenna and when using the proposed scheme. It has been concluded that the throughput and delay performance of the selected protocols have been improved by the use of Adaptive Antenna Arrays. The throughput and delay performance of ANMAC-SW and ANMAC-AA protocols was evaluated in details against regular Omni 802.11 stations. Our results promise significantly enhancement over Omni 802.11, with a throughput of 25% for ANMAC-SW and 90% for ANMC-AA. ANMAC-AA outperforms ANMAC-SW protocol by 60%. Simulation experiments indicate that by using the proposed scheme with 4 Adaptive Antenna Array per a node, the average throughput in the network can be improved up to 2 to 2.5 times over that obtained by using Switched beam Antennas. The proposed scheme improves the performances of both ANMAC and MMAC protocols but ANMAC outperforms MMAC by 30%