Broadband circularly polarized moxon based antennae for RFID and GPS

Abstract-Novel circularly polarized (CP) VHF SATCOM antenna which was based on Moxon antenna (bent dipole element over a ground plane) has been extended for RFID and GPS applications. A sequence of topologies starting from a single vertical element to two vertical elements of the Moxon arms, then widened strip arm elements were investigated to understand the effects on impedance match over the widened bandwidth. The logic in this evolution was to obtain maximized gain based on Fano-Chu limits, which suggests that more metallization in the radiating configuration that fill the volume would yield higher gain for electrically small antenna. Extending the width of the strip of the equivalent dipole elements lead to a wider bandwidth and improved cross-polarization ratio. Furthermore, splitting the tapered bow tie elements increased the volume filled with radiating elements leading to improved overall performance. Ultimately extended bends at the tip of the tapered sections parallel to the ground plane helped to improve overall performance. In overall, the antenna presented here produced lower physical height, higher gain, wider bandwidth, better crosspolarization and lower back lobe radiation compared to commercial counterparts such as an eggbeater currently used in SATCOM practice as well as similar antennas in RFID and GPS applications. Here, the concept is extended to cover RFID (850-1050 MHz) and GPS (centered at 1227 and 1575 MHz) bands leading to new applications at a significant cost and size reductions and much improved performance. Prototype antennas were built based on HFSS simulations yielded better than -25 dB return loss. During simulations attention was paid to identify the effects of individual antenna elements as an optimization parameter on the overall input impedance matching over the extended bandwidth. Simulated and measured results yielded higher than industrial counterpart antenna gain, bandwidth and cross-polarization for much reduced physical dimensions

Moxon based RFID tag reader and GPS antenna

Modern communication applications at UHF frequencies require antennas with wide band, high forward gain, low backward radiation, high cross-polarization, small size and low manufacture cost. The Moxon antenna based on a two element Yagi-Uda antenna over the ground reflector is one of the most favorite antennas for HAM operators which can produce outstanding front to back ratio of radiated power, good match over the desired band and relatively low elevation height. A sequence of topologies has been proposed from a single vertical element to two vertical elements of the Moxon arms, until the lately patented Broadband Circularly Polarized Moxon Based Antennas for UHF satellite communications (SATCOM). The logic was to obtain the best possible performance based on Fano-Chu limits for electrically small antenna with maximum radiating elements in a given volume. This dissertation is an extension of this configuration to cover Radio Frequency IDentification (RFID) (850 MHz-1050 MHz) and Global Positioning System (GPS) (centered at 1227 MHz and 1575 MHz) bands. Prototype antennas are built based on HFSS-11 simulations and experimental measurements yielded satisfactory results. Various design parameters of the proposed complex antenna are optimized to obtain a significant size reduction and much improved performance than the commercial counterpart antennas

The 29th Aerospace Mechanisms Symposium

The proceedings of the 29th Aerospace Mechanisms Symposium, which was hosted by NASA Johnson Space Center and held at the South Shore Harbour Conference Facility on May 17-19, 1995, are reported. Technological areas covered include actuators, aerospace mechanism applications for ground support equipment, lubricants, pointing mechanisms joints, bearings, release devices, booms, robotic mechanisms, and other mechanisms for spacecraft

The Second Conference on Lunar Bases and Space Activities of the 21st Century, volume 1

These papers comprise a peer-review selection of presentations by authors from NASA, LPI industry, and academia at the Second Conference (April 1988) on Lunar Bases and Space Activities of the 21st Century, sponsored by the NASA Office of Exploration and the Lunar Planetary Institute. These papers go into more technical depth than did those published from the first NASA-sponsored symposium on the topic, held in 1984. Session topics covered by this volume include (1) design and operation of transportation systems to, in orbit around, and on the Moon, (2) lunar base site selection, (3) design, architecture, construction, and operation of lunar bases and human habitats, and (4) lunar-based scientific research and experimentation in astronomy, exobiology, and lunar geology

Proceedings of the 6th Annual Summer Conference: NASA/USRA University Advanced Design Program

The NASA/USRA University Advanced Design Program is a unique program that brings together NASA engineers, students, and faculty from United States engineering schools by integrating current and future NASA space/aeronautics engineering design projects into the university curriculum. The Program was conceived in the fall of 1984 as a pilot project to foster engineering design education in the universities and to supplement NASA's in-house efforts in advanced planning for space and aeronautics design. Nine universities and five NASA centers participated in the first year of the pilot project. The study topics cover a broad range of potential space and aeronautics projects that could be undertaken during a 20 to 30 year period beginning with the deployment of the Space Station Freedom scheduled for the mid-1990s. Both manned and unmanned endeavors are embraced, and the systems approach to the design problem is emphasized

Bowdoin Orient v.131, no.1-24 (1999-2000)

https://digitalcommons.bowdoin.edu/bowdoinorient-2000s/1000/thumbnail.jp

History of Construction Cultures Volume 1

History of Construction Cultures Volume 1 contains papers presented at the 7ICCH – Seventh International Congress on Construction History, held at the Lisbon School of Architecture, Portugal, from 12 to 16 July, 2021. The conference has been organized by the Lisbon School of Architecture (FAUL), NOVA School of Social Sciences and Humanities, the Portuguese Society for Construction History Studies and the University of the Azores. The contributions cover the wide interdisciplinary spectrum of Construction History and consist on the most recent advances in theory and practical case studies analysis, following themes such as: - epistemological issues; - building actors; - building materials; - building machines, tools and equipment; - construction processes; - building services and techniques ; -structural theory and analysis ; - political, social and economic aspects; - knowledge transfer and cultural translation of construction cultures. Furthermore, papers presented at thematic sessions aim at covering important problematics, historical periods and different regions of the globe, opening new directions for Construction History research. We are what we build and how we build; thus, the study of Construction History is now more than ever at the centre of current debates as to the shape of a sustainable future for humankind. Therefore, History of Construction Cultures is a critical and indispensable work to expand our understanding of the ways in which everyday building activities have been perceived and experienced in different cultures, from ancient times to our century and all over the world

1995 BRAC Commission

Long Beach Naval Shipyard, CA-Commission Working Papers-Staff Assessment of DoD Recommendation II. (Box 263

Bowdoin Orient v.135, no.1-25 (2005-2006)

https://digitalcommons.bowdoin.edu/bowdoinorient-2000s/1006/thumbnail.jp