International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, Nevada / A major factor in the performance of a Telemetry System over the sea is the effect of multipath. The reflected signal from the surface of the sea may, in general, add to or subtract from the direct signal, and may therefore lead to severe fading and possible loss of useful signal. The multipath is a function of the sea state and the polarization of the signal. In order to reduce the effect of multipath on performance, a dual polarization diversity system is being built for the Airborne Telemetry Relay System for the Gulf Range. An analysis of the performance of the dual polarization diversity system in the presence of multipath for different sea states, different reflection angles, and different initial polarization angles is presented. For comparison, a similar analysis is presented for a circular polarization receiving antenna system.

Recent days, antennas play an important role in wireless communication system. Microstrip patch antennas are well known to have positive features for cost-effective, low profile and broadband. This type of antenna can be used in wide range of applications such as in wireless communications, radar systems, and satellites. Inhibiting characteristics of single patch antenna with low gain and narrow band leads to the research area to have array configuration. Beam steering antennas are the ideal solution for various systems such as traffic control and collision avoidance radar systems. The goal of this work is to design and implement a dual-linear polarization stacked microstrip patch phased array antenna. Single stacked microstrip patch antenna fed by microstrip line was designed to have approximately 3 GHz bandwidth in X-band with another ground plane to form a stripline-fed. Stripline-fed design protects feed lines from any outside effects. The array configuration was adapted to design in order to accomplish beam scan angle of /- 30 degrees by /- 15 degrees. Binomial power distribution of 3x2 array structure was used in order to reduce grating lobes, and changing length of feed lines was implemented for phase shifting. Bowtie cross shape aperture and dual-offset microstrip feedline was used to feed radiating patches. For the feed network, T-split power divider was implemented and optimized to achieve low loss. The length of microstrip line was adjusted to meet desired phase shift that in wideband application, the length of the line had to be long enough to have similar wavelength response over broad frequency range. The antenna array was designed using standard equations and simulated by electromagnetic analysis software called Zealand's IE3D which is method-of-moments based simulator. The resulting measured impedance bandwidth and gain of both microstrip and stripline-fed single antenna are 43 percent and 5 to 10 dBi with low cross polarizations for all frequencies. The array antenna was measured to have 29 to 60 percent impedance bandwidths depending on the different types of beam scan angles. The gain of the array antenna is 8 to 13 dBi, and the beams are directed as required with /- 3 degrees beam scan angle tolerance. The array antenna had a small offset as compared with simulated results because of the fabrication process such as alignment, distorted feed lines while etching, and etc, but the bandwidths and array patterns were acceptable.

Several novel designs of printed monopole antennas are proposed and experimentally studied. These antennas have the advantages of low profile, light weight and easy construction and can be printed on dielectric substrates and integrated with associated circuitry on the same substrates, which not only reduces the manufacturing cost but also decreases the required size of the complete system. This dissertation mainly consists of four sections and several novel designs are introduced in each section. First, a novel dual-band antenna with two stacked inverted-F strips and a CPW-fed folded inverted-F strip antenna are proposed. Second, a novel printed dual-band double-T monopole antenna, comprising two stacked T-shaped monopoles, is discussed. Third, three diversity antenna designs obtained by protruding a ground plane with optimal dimensions between two printed monopoles for WLAN communication applications in the 2.4 GHz and 5.2 GHz bands are presented. Good dual-polarized radiation with an enhanced port decoupling (isolation less than ¡V27 dB) for the two feeding ports is obtained. Finally, a novel printed ultra-wideband diversity monopole antenna is shown. The operating bandwidth of the ultra-wideband antenna reaches about 5.4 GHz, covering the WLAN bands at 2.4, 5.2 and 5.8 GHz, and the antenna can provide spatial diversity to combat the multipath fading problem.

Yes / A planar dual-polarized phased array is proposed for 5G cellular communications. The array has the properties of dual-polarization, wideband and quasi end-fire radiation, which is printed on one side of a single-layer substrate. The design contains two 8-element sub-arrays including horizontally polarized end-fire dipole antennas and vertically polarized end-fire periodic slot antennas, employed on the PCB ground plane of the 5G mobile platform. Both sub-arrays provide wide bandwidth to cover 28 and 38 GHz (promising 5G candidate bands). The -10 dB impedance bandwidth of the proposed CPW-fed dipole and slot antennas are 26.5-39.5 GHz and 27.1-45.5 GHz, respectively. Moreover, for -6 dB impedance bandwidth, these values could be more than 20 GHz (24.4-46.4 GHz for the dipole antenna) and 70 GHz (22.3-95 GHz for the slot antenna). The fundamental characteristics of the proposed dual-polarized 5G antenna array in terms of the impedance bandwidth, realized gain, polarization, radiation pattern, and beam steering are investigated and good results are obtained. The clearance of the proposed dual-polarized 5G antenna array is less than 4.5 mm which is sufficient for cellular applications. / This work is partially supported by the InnovationsFonden project of Reconfigurable Arrays for Next Generation Efficiency (RANGE), AAU Young Talent Program, and European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016SECRET-722424.

Broadband wireless communications require wideband antennas to support large number of users and higher data rates. Desirable features of a wideband antenna are low-profile, dual-polarization and wide bandwidth in a compact size. Many existing wideband antennas are large in size and some have only circular polarization. On the other hand low-profile, dual-polarized antennas frequently have limited bandwidth. This dissertation reports on results from original research into several new wideband antennas. All are compact and planar, and many are low-profile and dual-polarized. Since 1994, Virginia Tech Antenna Group (VTAG) has performed research on the wideband, low-profile and dual-polarized antennas of compact size. This research resulted in the following antenna innovations: the Fourpoint, Fourtear, PICA (Planar Inverted Cone Antenna), diPICA (dipole PICA) and LPdiPICA (Low-Profile diPICA) antennas. They are all planar in geometry so one can easily construct them in a compact size. The antennas were characterized and investigated with extensive simulations and measurements. The computed and measured data demonstrates that some of the antennas appear to have the characteristics of the self-complementary antenna and most of the proposed antennas provide more than a 10:1 impedance bandwidth for a VSWR < 2. Patterns, however, are degraded at the high end of the frequency. Several tapered ground planes were proposed to improve the radiation pattern characteristics without degrading the impedance performance. A simulation result proposed a possibility of another antenna inventions providing 10:1 pattern bandwidth with the 10:1 impedance bandwidth. Research into wideband antennas demonstrated that the newly invented antennas are closely related each other and are evolved from a primitive element, PICA. Not only the comprehensive investigation but also a practical antenna design has been done for commercial base-station array antennas and to phased array antennas for government applications. This dissertation presents results of comprehensive investigation of new planar wideband antennas and its usefulness to the broadband wireless communications. / Ph. D.

Over the last two decades, dual-polarimetric weather radar has proven to be a valuable instrument providing critical precipitation information through remote sensing of the atmosphere. Modern weather radar systems operate with high sampling rates and long dwell times on targets. Often only limited target information is desired, leading to a pertinent question: could lesser samples have been acquired in the first place? Recently, a revolutionary sampling paradigm – compressed sensing (CS) – has emerged, which asserts that it is possible to recover signals from fewer samples or measurements than traditional methods require without degrading the accuracy of target information. CS methods have recently been applied to point target radars and imaging radars, resulting in hardware simplification advantages, enhanced resolution, and reduction in data processing overheads. But CS applications for volumetric radar targets such as precipitation remain relatively unexamined. This research investigates the potential applications of CS to radar remote sensing of precipitation. In general, weather echoes may not be sparse in space-time or frequency domain. Therefore, CS techniques developed for point targets, such as in aircraft surveillance radar, are not directly applicable to weather radars. However, precipitation samples are highly correlated both spatially and temporally. We, therefore, adopt latest advances in matrix completion algorithms to demonstrate the sparse sensing of weather echoes. Several extensions of this approach are then considered to develop a more general CS-based weather radar processing algorithms in presence of noise, ground clutter and dual-polarimetric data. Finally, a super-resolution approach is presented for the spectral recovery of an undersampled signal when certain frequency information is known.

Novel designs of planar antennas including the feed network for improving the antenna performance improvement (CP axial-ratio bandwidth, XPL, port decoupling for dual-polarized operation, and harmonic control) or achieving dual-band operation are presented. This thesis, comprises five sections. Firstly, for obtaining broadband CP designs, the Wilkinson power divider and branch-line coupler are used. The 3-dB axial ratio CP bandwidths of all proposed antennas are larger than 30%. Secondly, the dual broadband patch antennas including a stopband network are proposed. Thirdly, the dual-polarized patch antenna with high XPL and isolation between two ports by using a Wilkinson power divider with a 180¢X phase shift between its two ports is proposed. Fourthly, the dual-band and dual-polarized patch antenna suitable for base-station antenna applications for mobile communications systems is studied. Finally, the harmonic control study of a square microstrip antenna is presented.

Several broadband dual-polarized patch antenna designs are presented and studied. Good isolation (< ¡V30 dB) between the two feeding ports of the proposed broadband dual-polarized patch antenna has been obtained. This dissertation reports four different innovative designs. Firstly, a new design of the aperture-coupled patch antenna with modified H-shaped coupling slots for achieving dual-polarized radiation with high isolation over a wide bandwidth is studied. Secondly, Optimized feeding of the dual-polarized aperture-coupled patch antenna with H-shaped coupling slots for achieving highly decoupled feeding ports is experimentally investigated. Thirdly, an aperture-coupled patch antenna with a cross slot for compact dual-polarized operation in the 1800-MHz band suitable for applications in personal communication system is presented. Finally, new designs of the broadband dual-polarized patch antenna with hybrid feeds suitable for DCS base-station application are proposed.

This paper have investigated the dual polarization oscillations (DPO) and associated dynamical behaviors in laser-diode-pumped microchip Nd:GdVO4 laser. Some optical properties of Nd:YAG, Nd:YVO4, and Nd:GdVO4 laser materials are compared. The higher thermal conductivity of Nd:YAG makes it suitable for higher-power applications. The larger stimulated-emission coefficient of Nd:YVO4 material makes it favorable for increasing light-light conversion efficiency. However, Nd:GdVO4 material has high thermal conductivity and large stimulated-emission coefficient. Many experiments done to study Nd:GdVO4 crystal¡¦s properties focused on the efficiency of high power generation. Orthogonal linearly-polarized emissions could be obtained in fluorescence spectrum of Nd:GdVO4, but DPO did not be observed in Nd:GdVO4 laser possessing a large fluorescence anisotropy with laser-diode pumping. In this paper, DPO on different transitions in laser-diode-pumped microchip Nd:GdVO4 are obtained for the first time. Furthermore, more effective generation of dual polarization oscillations is affected by the pumping conditions associated with different temperature gradient than different pumping power density. The results imply that DPO can be generated without having to use additional optical elements and Nd:GdVO4 material is suitable for the construction of compact DPO lasers. Laser properties including oscillation spectra, input-output characteristics, pump-dependent pattern formations and noise power spectra are studied experimentally. A poor mode matching between the pump beam and lasing beam results in the generation of high order transverse modes. The observed anti-phase dynamics have been explained in terms of the reduced three-dimensional cross-saturation of population inversions among orthogonally-polarized modes. The study of dynamics of microchip Nd:GdVO4 lasers under pump modulation has also been reported in this paper. Different phase correlations among laser modes are obtained by tuning the modulation frequency and amplitude. The observed dynamical states are reproduced theoretically by rate equations of multimode class-B lasers including the cross-saturation among individual modes and the pump modulation.

Current marine navigation radars are capable of high-resolution imagery of marine ice but are not able to classify the marine ice. Classifying marine ice means identifying the ice as first-year ice, multi-year ice or glacier ice. The latter two ice types are as hard as concrete and capable of damaging even ice hardened vessels such as icebreakers. The Canadian Coast Guard has identified the ability of marine navigation radars to classify marine ice as the single greatest improvement to be made in the safety of Arctic navigation. This thesis presents new research that improves our understanding of electromagnetic backscatter from marine ice. The goal of this work was two-fold: to demonstrate the feasibility of using commercial computational electromagnetic modelling software to simulate real-world marine ice targets, and to identify an optimum frequency or range of frequencies at which the marine ice targets can be definitively classified. Engineering models for scattering from electrically large objects made of a highly variable, complex, heterogenous, three-phase mixture of ice, air and brine are developed. To do so, an extensive literature review of the Arctic environment, and the physical and electrical properties of marine ice, is conducted to distill the required geophysical parameters of the three marine ice types of interest in this work. Using well-established dielectric mixing theory, these parameters are applied to homogenize the marine ice and model the target (in the presence of a flat sea halfspace) using a surface integral equation formulation. To reduce the computational resources required to numerically solve the integral equation models using the method of moments, computational electromagnetic modelling studies are conducted to select a suitable seawater halfspace representation and determine if the properties of larger objects can be inferred from scaled down models of the object. A case study is presented for backscatter from marine ice from 6 to 10 GHz, which explores the effects of frequency on the co- and cross-polarized backscatter intensity (and hence the apparent radar cross-section) of the three marine ice types of interest. Good agreement is found between the co- and cross-polarized backscatter intensity responses found from the engineering model computations and some existing experimental data from real-world marine ice targets. This work: (a) proves the feasibility of using computational electromagnetic modelling to simulate real-world marine ice targets, providing a new, cost-effective method for the study of backscatter from marine ice; (b) confirms the viability of using cross-polarization as a method of classification; and (c) identifies 10 to 16 GHz as a potential optimal frequency range for the classification of marine ice using dual-polarization radar.