Hardware architectures for compact microwave and millimeter wave cameras

Millimeter wave SAR imaging has shown promise as an inspection tool for human skin for characterizing burns and skin cancers. However, the current state-of-the-art in microwave camera technology is not yet suited for developing a millimeter wave camera for human skin inspection. Consequently, the objective of this dissertation has been to build the necessary foundation of research to achieve such a millimeter wave camera. First, frequency uncertainty in signals generated by a practical microwave source, which is prone to drift in output frequency, was studied to determine its effect on SAR-generated images. A direct relationship was found between the level of image distortions caused by frequency uncertainty and the product of frequency uncertainty and distance between the imaging measurement grid and sample under test. The second investigation involved the development of a millimeter wave imaging system that forms the basic building block for a millimeter wave camera. The imaging system, composed of two system-on-chip transmitters and receivers and an antipodal Vivaldi-style antenna, operated in the 58-64 GHz frequency range and employed the ω-k SAR algorithm. Imaging tests on burnt pigskin showed its potential for imaging and characterizing flaws in skin. The final investigation involved the development of a new microwave imaging methodology, named Chaotic Excitation Synthetic Aperture Radar (CESAR), for designing microwave and millimeter wave cameras at a fraction of the size and hardware complexity of previous systems. CESAR is based on transmitting and receiving from all antennas in a planar array simultaneously. A small microwave camera operating in the 23-25 GHz frequency was designed and fabricated based on CESAR. Imaging results with the camera showed it was capable of basic feature detection for various applications --Abstract, page iv

Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

Through Wall Imaging Radar Antenna with a Focus on Opening New Research Avenues

This review paper is an effort to develop insight into the development in antennas for through wall imaging radar application. Review on literature on antennas for use in through wall imaging radar, fulfilling one or more requirements/specifications such as ultrawide bandwidth, stable and high gain, stable unidirectional radiation pattern, wide scanning angle, compactness ensuring portability and facilitating real-time efficient and simple imaging is presented. The review covers variants of Vivaldi, Bow tie, Horn, Spiral, Patch and Magneto-electric dipole antennas demonstrated as suitable antennas for the through wall imaging radar application. With an aim to open new research avenues for making better through wall imaging radar antenna, review on relevant compressive reflector antennas, surface integrated waveguide antennas, plasma antennas, metamaterial antennas and single frequency dynamically configurable meta-surface antennas are incorporated. The review paper brings out possibilities of designing an optimum through wall imaging radar antenna and prospects of future research on the antenna to improve radiation pattern and facilitate overall simple and efficient imaging by the through wall imaging radar

Design of a microwave imaging system for rapid wideband imaging

An imaging system composed of two linear arrays of antennas is designed through full-wave simulation and fabricated for use in synthetic aperture radar imaging. The arrays electronically scan along their antenna elements and are mechanically moved along a second orthogonal direction for scanning large two-dimensional areas quickly. Each linear array is printed on a circuit board where the antenna elements are integrated into the edge of the board as tapered slot-line antennas operating at 22 to 27 GHz. A multiplexer circuit is printed onto each linear array to transmit wideband signals to each antenna in the array. Receivers are printed onto the radiating end of the antennas on the edge of the circuit board. These receivers are less complex than traditional microwave receivers, and they require no phase calibration for synthetic aperture radar processing. A controller board is designed and fabricated to facilitate electronic scanning along the arrays and route measurement data to a PC for storage. The linear arrays and controller board are mounted on a small mechanical scanning table for moving the arrays along one direction. All receivers are calibrated for variations in voltage outputs among the elements by scanning a known target and applying an equalization matrix. Several targets are scanned by the final imaging system, and the resulting images show the ability of the system to detect dielectric contrast under the surface of dielectric materials. The tapered slot-line antenna is redesigned and improved for -10 dB reflection coefficient across the operating frequency band and higher voltage output of the receivers with respect to the original antenna design. Imaging results of the redesigned antenna show how refabricating the imaging system with the improved antenna will improve overall image quality of the system--Abstract, page iii

Multiband reconfigurable antennas for future wireless communication systems

Evolution in wireless technology has resulted in remarkable capabilities, but ever increasing user demand and limited bandwidth spectrum has always instigated the researchers to think of new techniques that can improve network efficiency in terms of size, power and bandwidth consumption. Antenna designing is one of the key factors in achieving this goal and as a result plethora of research work has been conducted in past for crafting sustainable reconfigurable multiband antennas for different wireless services. The concept of combining the wideband-narrowband reconfiguration functionality into a single antenna has created an effective solution for optimizing antenna size and enhancing flexibility in antenna designing. Moreover; this combination has offered the advantage of pre-filtering, which has helped in mitigating the level of interference at the receiver end and has provided an edge over the fixed or non-reconfigurable transceivers. This paper has presented a detailed outlook about reconfigurable antennas and the various techniques involved in attaining reconfigurability in antenna design. The review has been supported by some antenna designs and simulation results that have provided an insight into reconfiguration features. Some new technologies employed in antenna design have also been briefly presented

Multiband reconfigurable antennas for future wireless communication systems

79-97Evolution in wireless technology has resulted in remarkable capabilities, but ever increasing user demand and limited bandwidth spectrum has always instigated the researchers to think of new techniques that can improve network efficiency in terms of size, power and bandwidth consumption. Antenna designing is one of the key factors in achieving this goal and as a result plethora of research work has been conducted in past for crafting sustainable reconfigurable multiband antennas for different wireless services. The concept of combining the wideband-narrowband reconfiguration functionality into a single antenna has created an effective solution for optimizing antenna size and enhancing flexibility in antenna designing. Moreover; this combination has offered the advantage of pre-filtering, which has helped in mitigating the level of interference at the receiver end and has provided an edge over the fixed or non-reconfigurable transceivers. This paper has presented a detailed outlook about reconfigurable antennas and the various techniques involved in attaining reconfigurability in antenna design. The review has been supported by some antenna designs and simulation results that have provided an insight into reconfiguration features. Some new technologies employed in antenna design have also been briefly presented

The Study of Reconfigurable Antennas and Associated Circuitry

This research focuses on the design of pattern reconfigurable antennas and the associated circuitry. The proposed pattern reconfigurable antenna designs benefit from advantages such as maximum pattern diversity and optimum switching circuits to realise 5G reconfigurable antennas. Whereas MIMO based solutions can provide increased channel capacity, they demand high computational capability and power consumption due to multiple channel processing. This prevents their use in many applications most notably in the Internet of Things where power consumption is of key importance. A switched-beam diversity allows an energy-efficient solution improving the link budget even for small low-cost battery operated IoT/sensor network applications. The main focus of the antenna reconfiguration in this work is for switched-beam diversity. The fundamental switching elements are discussed including basic PIN diode circuits. Techniques to switch the antenna element in the feed or shorting the antenna element to the ground plane are presented. A back-to-back microstrip patch antenna with two hemispherical switchable patterns is proposed. The patch elements on a common ground plane, are switched with a single-pole double-throw PIN diode circuit. Switching the feed selects either of two identical oppositely oriented radiation patterns for maximum diversity in one plane. The identical design of the antenna elements provides similar performance control of frequency and radiation pattern in different states. This antenna provides a simple solution to cross-layer PIN diode circuit designs. A mirrored structure study provides an understanding of performance control for different switching states. A printed inverted-F antenna is presented for monopole reconfigurable antenna design. The proposed low-profile antenna consists of one main radiator and one parasitic element. By shorting the parasitic element to the ground plane using only one PIN diode, the antenna is capable of switching both the pattern and polarisation across the full bandwidth. The switched orthogonal pattern provides the maximum spatial pattern diversity and is realised using a simple structure. Then, a dual-stub coplanar Vivaldi antenna with a parasitic element is presented for the 5G mm-Wave band. The use of a dual-stub coupled between the parasitic element and two tapered slots is researched. The parasitic element shape and size is optimised to increase the realised gain. A bandpass coupled line filter is used for frequency selective features. The use of slits on the outer edge of the ground plane provides a greater maximum gain. This integrated filtenna offers lower insertion loss than the commercial DC blocks. The UWB antenna with an integrated filter can be used for harmonic suppression. The influence of the integrated filter circuit close to the antenna geometry informs the design of PIN diode circuit switching and power supply in the 5G band. Based on the filter design in the mm-Wave band, a method of designing a feasible DC power supply for the PIN diode in the mm-Wave band is studied. A printed Yagi-Uda antenna array is integrated with switching circuitry to realise a switched 180° hemispheres radiation pattern. The antenna realises a maximum diversity in one plane. The study offers the possibility to use PIN diodes in the mm-Wave band for reconfigurable antenna designs. For the presented antennas, key geometric parameters are discussed for improved understanding of the trade-offs in radiation pattern/beamwidth and gain control for reconfigurable antenna applications

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

Antenna Designs for 5G/IoT and Space Applications

This book is intended to shed some light on recent advances in antenna design for these new emerging applications and identify further research areas in this exciting field of communications technologies. Considering the specificity of the operational environment, e.g., huge distance, moving support (satellite), huge temperature drift, small dimension with respect to the distance, etc, antennas, are the fundamental device allowing to maintain a constant interoperability between ground station and satellite, or different satellites. High gain, stable (in temperature, and time) performances, long lifecycle are some of the requirements that necessitates special attention with respect to standard designs. The chapters of this book discuss various aspects of the above-mentioned list presenting the view of the authors. Some of the contributors are working strictly in the field (space), so they have a very targeted view on the subjects, while others with a more academic background, proposes futuristic solutions. We hope that interested reader, will find a fertile source of information, that combined with their interest/background will allow efficiently exploiting the combination of these two perspectives

Design And Practical Implementation Of Harmonic-Transponder Sensors

Harmonic radar is a nonlinear detection technology that transmits and receives radio-frequency (RF) signals at orthogonal frequencies, so as to suppress the undesired clutters, echoes and electromagnetic interreferences due to multipath scattering. Its implementation generally comprises a nonlinear tag (i.e, a harmonic transponder), which picks the interrogation signal at specific fundamental frequency (f0) and converts it into a high/sub-harmonic signal (nf0). Such a technology has been successfully applied to tracking small insects and detection of electrically-small objects in the rich-scattering environment. Similarly, a harmonic sensor is used to interrogate electrically-small and passive sensors, of which the magnitude and peak frequency of output harmonics (e.g., second harmonic) are functions of the parameter to be sensed. A harmonic tag or sensor comprises one or multiple antennas, a frequency modulator, a sensor, a microchip and matching networks. Here, we propose and experimentally validate compact, low-cost, low-profile, and conformal hybrid-fed microstrip antennas for the harmonics-based radar and sensor systems. The proposed 98 microstrip antennas are based on a simple single-layered and hybrid-feed structure. By optimizing the feed position and the geometry of microstrip patch, the fundamental mode and particular higher-order modes can be excited at the fundamental frequency and the second harmonic. We have derived the analytical expressions for calculating the antennas’ resonant frequencies, which have been verified with numerical simulations and measurements. Our results show that the proposed hybrid-feed, single-layered microstrip antennas, although having a compact size and a low profile, can achieve descent realized gain (1.2 – 3.5 dB), good impedance matching (return loss \u3c -15 dB), high isolation (\u3c-20 dB), and favorable co/cross-polarization properties. The proposed microstrip antennas may benefit various size-restricted harmonic transponders used for harmonic radars, harmonic sensors, medical implants, passive radio-frequency identification (RFID), and internet-of-things (IoT) applications