Differential RF front-end components provide greater immunity to ground noise and distortion by suppressing external interference. Recent advancements in differential RF front-end components offer high dynamic range, high input linearity, and low noise in the transceiver chain. However, differential phased arrays are not inherently ultra-wideband (UWB). To create a wideband differentially fed array, a novel approach is introduced by building on the well-established UWB Tightly Coupled Dipole Array (TCDA). This differential TCDA (D-TCDA) is proposed for S-Ku band (3-18 GHz) communications with emphasis on dual-linear polarization and wide-angle scanning. The array achieves 6:1 bandwidth for VSWR

In addition to the FSS superstrate, a modified version of the stripline-based folded Marchand balun is presented. As usual the balun serves to match the 50-Ohm coaxial cable to the high input impedance (~200-Ohm) at the terminals of array elements. Doing so, earlier Wilkinson power dividers, which degrade efficiency during E-plane scanning, are eliminated. To verify the proposed array concept, 12x12 TCDA prototype was fabricated using the modified balun and the new FSS superstrate layer. The design and experimental data showed an impedance bandwidth of 6.1:1 with VSWR

Abstract: In this thesis the focus was on the design, fabrication, and tests of the feeding networks individually and within an array system. The array feeding network is a corporate-fed type utilizing equal-split, stepped-multiple sections of the conventional Wilkinson power divider in microstrip form with a unique topology. The feeding network was specifically designed for a broadside relatively small linearly-polarized wideband UHF non-scanning array for directed power applications that uses an array radiator with a new volumetric ribcage dipole configuration. The array has a large impedance bandwidth and consistent front lobe gain over the wide frequency band. Theoretical and experimental results describing the performance of the array feeding network and the array are presented and discussed.

This book focuses on determination of scattering of parallel-fed planar dipole arrays in terms of reflection and transmission coefficients at different levels of the array system. In aerospace vehicles, the phased arrays are often in planar configuration. The radar cross section (RCS) of the vehicle is mainly due to its structure and the antennas mounted over it. There can be situation when the signatures due to antennas dominate over the structural RCS of the platform. This necessitates the study towards the reduction and control of antenna/ array RCS. The planar dipole array is considered as a stacked linear dipole array. A systematic, step-by-step approach is used to determine the RCS pattern including the finite dimensions of dipole antenna elements. The mutual impedance between the dipole elements for planar configuration is determined. The scattering till second-level of couplers in parallel feed network is taken into account. The phase shifters are modelled as delay line. All the couplers in the feed network are assumed to be four port devices. It is shown that the array RCS can be reduced considerably for a low observable platform by an optimization of array design parameters even in the presence of mutual coupling. This book presents a systematic step-by-step analytical formulation for RCS of planar half-wavelength centre-fed dipole arrays through various schematics and illustrations. The analytical description and analysis provided in this book should be useful for students, researchers, and design engineers of phased arrays.

Furthermore, we co-designed the feeding network with the phased array antenna to achieve lower loss and higher compactness. Up to date, researchers have focused either on phased array design or on feeding network design. They have never addressed the whole system as a single design; therefore, any possible chance of collaboration or simplification between the feeding network and array antenna is diminished. In this work, we reduce the size and loss of phased array co-designing the arrays with the feeding network. Firstly, we adapted optimum beam forming architecture. This architecture utilizes phase shifter at each unit cell and true time delay at the sub array level. Secondly, we propose to integrate compact phase shifters into each array element of the TCDA using low-loss, low-profile micro-electro mechanical systems (MEMS) technology. This approach is effective in integrating the beam former into the radiating aperture without changing the overall thickness of the array. The phase shifter is designed by using circuit simulation tools such as microwave office and ADS. Subsequently, a full wave simulation of the phase shifter is performed by using Ansoft HFSS. The fabrication challenges that arise due to the smaller features for Ka-band operation, such as the minimum trace width, and the size of the feeding cables and connectors, are addressed by performing the beamforming at the unit cell level, while combining several unit cells through the same connector and feeding cable. The performance of the unit cell with the integrated phase shifter is examined using the full wave simulator Ansoft HFSS. Finally, minimum cost requirements are addressed through the design simplicity, in which, vias, and multi-layer structures are avoided, while the minimum requirements of the affordable PCB fabrication technique are satisfied. The proposed Ka-band TCDA array with integrated MEMS phase shifters is 4.4mm in overall height and covers 18-40GHz continuously with ±45 degrees scan capability.

This book presents the detailed analytical formulation for the RCS of parallel-fed linear dipole array in the presence of mutual coupling. The radar cross section (RCS) of an object represents its electromagnetic (EM) scattering properties for a given incident wave. The analysis of scattered field is critical in military and defence arenas, especially while designing low-observable platforms. It is well-known that the presence of an antenna/array on the target influences its echo area significantly. The primary cause for such scattering of the incident signals is reflection that occurs within the antenna aperture and its feed network. In this book, the RCS estimation is done based on the signal path within the antenna system. The scattered field is expressed in terms of array design parameters including the reflection and transmission coefficients. The computed results show the variation in the RCS pattern with and without mutual coupling. The effect of finite dipole-length, inter-element spacing, scan angle, array configuration, amplitude distribution and terminating load impedance on the RCS pattern is studied. It is shown that the array RCS can be controlled by choosing optimum design parameters, including terminating impedance and geometric configuration. This book explains each step of the RCS estimation and analysis of dipole array with detailed schematics, tables and illustrations. Moreover, it includes parametric analysis of RCS estimation and control. This book provides an insight into the phenomenon of scattering within the phased array system.

Introduces timed arrays and design approaches to meet the newhigh performance standards The author concentrates on any aspect of an antenna array thatmust be viewed from a time perspective. The first chapters brieflyintroduce antenna arrays and explain the difference between phasedand timed arrays. Since timed arrays are designed for realistictime-varying signals and scenarios, the book also reviews widebandsignals, baseband and passband RF signals, polarization and signalbandwidth. Other topics covered include time domain, mutualcoupling, wideband elements, and dispersion. The author alsopresents a number of analog and digital beamforming networks forcreating and manipulating beams. The book concludes with anoverview of the methods to integrate time delay into the arraydesign and of several other adaptive arrays that prove useful inmany different systems. Examines RF signal concepts such as polarization and signalbandwidth and their applications to timed antenna arrays Covers arrays of point source, elements in timed antennaarrays, active electronically scanned array technology, and timedelay in corporate fed arrays Includes complete design examples for placing time delay inarrays Timed Arrays: Wideband and Time Varying Antenna Arrays iswritten for practicing engineers and scientists in wirelesscommunication, radar, and remote sensing as well as graduatestudents and professors interested in advanced antenna topics.

Ultrawideband (UWB) phased antenna arrays are critical to the success of future multi-functional communication, sensing, and countermeasure systems, which will utilize a few UWB phased arrays in place of multiple antennas on a platform. The success of this new systems approach relies in part on the ability to manufacture and assemble low-cost UWB phased arrays with excellent radiation characteristics. This dissertation presents the theory and design of a new class of UWB arrays that is based on unbalanced fed tightly-coupled horizontal dipoles over a ground plane. Practical implementation of this concept leads to two inexpensive wideband array topologies, the Banyan Tree Antenna (BTA) Array, and the Planar Ultrawideband Modular Antenna (PUMA) Array. The key challenge in designing unbalanced-fed tightly-coupled dipole arrays lies in the control of a common mode resonance that destroys UWB performance. This work introduces a novel feeding strategy that eliminates this resonance and results in wideband, wide-angle radiation. More importantly, the new feeding scheme is simple and intuitive, and can be implemented at low-cost in both vertically and planarly-integrated phased array architectures. Another desirable byproduct of this topology is the electrical and mechanical modularity of the aperture, which enables easy manufacturability and assembly. A theoretical framework is presented for the new phased array topologies, which is then applied to the design of innite BTA and PUMA arrays that achieve 4:1 and 5:1 bandwidths, respectively. A practical application of this technology is demonstrated through the full design, fabrication, and measurement of a 7.25-21GHz 16x16 dual-pol PUMA array prototype for SATCOM applications.

The report describes the activities and accomplishments associated with the two major technical tasks on this project. The first task is the development of a linearly polarized two-dimensional phased array which is well matched simultaneously over a large scan angle range and over an octave bandwidth. The second task is to extend the impedance matching of the linearly polarized element to an arbitrarily polarized element for wide-angle scanning and wide tunable bandwidth.

This book presents a detailed and systematic analytical treatment of scattering by an arbitrary dipole array configuration with unequal-length dipoles, different inter-element spacing and load impedance. It provides a physical interpretation of the scattering phenomena within the phased array system. The antenna radar cross section (RCS) depends on the field scattered by the antenna towards the receiver. It has two components, viz. structural RCS and antenna mode RCS. The latter component dominates the former, especially if the antenna is mounted on a low observable platform. The reduction in the scattering due to the presence of antennas on the surface is one of the concerns towards stealth technology. In order to achieve this objective, a detailed and accurate analysis of antenna mode scattering is required. In practical phased array, one cannot ignore the finite dimensions of antenna elements, coupling effect and the role of feed network while estimating the antenna RCS. This book presents the RCS estimation of an array with unequal-length dipoles. The signal reflections within the antenna system and the mutual coupling effect are considered to arrive at the total RCS for series and parallel feed. The computations are valid for any arbitrary array configurations, including side-by-side arrangement, parallel-in-echelon, etc.