1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Antennas as Precise Sensors for GNSS Reference Stations and High-Performance PNT Applications on Earth and in Space

Satellite navigation is more and more important in a plethora of very different application fields, ranging from bank transactions to shipping, from autonomous driving to aerial applications, such as commercial avionics as well as Unmanned Aerial Vehicles (UAVs) . In very precise Positioning, Navigation and Timing (PNT) applications, such as in reference stations and precise timing stations, it is important to characterize all errors present in the system, in order to possibly account for them or calibrate them out. Antennas play an important role in this respect: they are indeed the “sensor” that captures the signal in space from Global Navigation Satellite Systems (GNSS) satellites and thereby strongly contribute to the overall achievable performance. This paper reviews the currently available antenna technologies, targeting specifically reference stations as well as precise GNSS antennas for space applications, and, after introducing performance indicators, summarizes the today achievable performance. Finally, open research issues are identified and possible approaches to solve them are discussed

Модель системи придушення спуфінгу глобальними навігаційними системами

Робота публікується згідно наказу Ректора НАУ від 27.05.2021 р.№311/од "Про розміщення кваліфікаційних робіт здобувачів вищої освіти в репозиторії університету" Керівник проекту: д.т.н., професор кафедри аеронавігаційних систем, Конін Валерій ВікторовичВ першому розділі дипломної роботи був проведений аналітичний огляд проблеми втручання до навігаційної апаратури за допомогою радіоперешкод, наведені характеристики сигналів GNSS і методи впливу на них. У другому розділі розглянуто принцип роботи адаптивної антеної решітки, описана модель придушення спуфінгу на базу адаптивної антеної системи. У третьому розділі відображено блок-схему програмної частини роботи у середовищі Matlab, описано функціонування кожного блоку моделі. У четвертому розділі коротко описаний приймач OEM719, розглянуто інтерфейс програми Novatel Connect 2.3.2, описаний принцип формування вхідних даних. У цьому ж розділі показані та проаналізовані отримані результати дослідженн

Economically sustainable public security and emergency network exploiting a broadband communications satellite

The research contributes to work in Rapid Deployment of a National Public Security and Emergency Communications Network using Communication Satellite Broadband. Although studies in Public Security Communication networks have examined the use of communications satellite as an integral part of the Communication Infrastructure, there has not been an in-depth design analysis of an optimized regional broadband-based communication satellite in relation to the envisaged service coverage area, with little or no terrestrial last-mile telecommunications infrastructure for delivery of satellite solutions, applications and services. As such, the research provides a case study of a Nigerian Public Safety Security Communications Pilot project deployed in regions of the African continent with inadequate terrestrial last mile infrastructure and thus requiring a robust regional Communications Satellite complemented with variants of terrestrial wireless technologies to bridge the digital hiatus as a short and medium term measure apart from other strategic needs. The research not only addresses the pivotal role of a secured integrated communications Public safety network for security agencies and emergency service organizations with its potential to foster efficient information symmetry amongst their operations including during emergency and crisis management in a timely manner but demonstrates a working model of how analogue spectrum meant for Push-to-Talk (PTT) services can be re-farmed and digitalized as a “dedicated” broadband-based public communications system. The network’s sustainability can be secured by using excess capacity for the strategic commercial telecommunication needs of the state and its citizens. Utilization of scarce spectrum has been deployed for Nigeria’s Cashless policy pilot project for financial and digital inclusion. This effectively drives the universal access goals, without exclusivity, in a continent, which still remains the least wired in the world

Towards a more efficient spectrum usage: spectrum sensing and cognitive radio techniques

The traditional approach of dealing with spectrum management in wireless communications has been through the definition on a license user granted exclusive exploitation rights for a specific frequency.Peer ReviewedPostprint (published version

Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications

A Bibliography of NPS Space Systems Related Student Research, 2013-2022

Dudley Knox Library, Naval Postgraduate School.Approved for Public Release; distribution is unlimite

Satellite Communications

This study is motivated by the need to give the reader a broad view of the developments, key concepts, and technologies related to information society evolution, with a focus on the wireless communications and geoinformation technologies and their role in the environment. Giving perspective, it aims at assisting people active in the industry, the public sector, and Earth science fields as well, by providing a base for their continued work and thinking

Science Mission Directorate TechPort Records for 2019 STI-DAA Release

The role of the Science Mission Directorate (SMD) is to enable NASA to achieve its science goals in the context of the Nation's science agenda. SMD's strategic decisions regarding future missions and scientific pursuits are guided by Agency goals, input from the science community including the recommendations set forth in the National Research Council (NRC) decadal surveys and a commitment to preserve a balanced program across the major science disciplines. Toward this end, each of the four SMD science divisions -- Heliophysics, Earth Science, Planetary Science, and Astrophysics -- develops fundamental science questions upon which to base future research and mission programs