Realistic implementation of ellipsoidal reflector antennas to produce near‐field focused patterns

Abstract

[1] The radiation characteristics of ellipsoidal reflector antennas in the near zone of antenna aperture are investigated using Physical Optics (PO) approximations. This antenna has potential applications in the near-field communications because its radiation focuses in the near zone. Analytical formulations to predict the radiation efficiency and exhibit field phenomena are developed. Its applications as a RFID reader antenna at 2.4 GHz are demonstrated by numerical simulations and measurements over a realistic implementation of offset reflector fed by a microstrip patch antenna. Both numerical and experimental studies are performed to validate this antenna design.

Technologies for Near-Field Focused Microwave Antennas

“…The circular reflectarray has a diameter of 80 cm and allows getting a focal spot size of around 20 cm on a transverse plane at 90 cm far from the reflectarray center. In [41], the NF performance of the above microstrip reflectarray is compared against that of a planar microstrip [5] array and an ellipsoidal reflector [42]. All above NFF antennas are for 2.4 GHz RFID readers, exhibit the same transversal size (80 cm), and are designed to get a maximum field amplitude at around 90 cm from the antenna aperture.…”

Changing Landscapes in Documentation Efforts: Civil Society Documentation of Serious Human Rights Violations

“…In an effort to verify their material, they try to get at least three other corroborating sources. 49 A well-known example of an individual placing himself at great risk to document abuses in Syria has been code-named 'Caesar'. Caesar was an official forensic photographer for the military police and had personally photographed and archived photos of bodies of dead detainees.…”

Dome-Shaped Ellipsoidal Reflector Antenna for UHF-RFID Readers With Confined Near-Field Detection Region

“…5. Indeed, due to the propagation spreading factor [2], [5], the NF distribution along the reflector axis (z-axis) shows a peak value at a distance from the feed location that is smaller than the distance from the feed location of the second focus 2 F . By properly modifying the ellipsoid sizes, it is possible to recover the above focal shift in such a way that the field peak occurs at the assigned point.…”

“…In this context, near field focused antennas (NFFAs) [2], [3] have been proposed to assure the tag detection in a confined area, with a minimal radiation outside of the area of interest. Since most of NFFAs are electrically large in size [4] to guarantee an effective focusing effect, this paper presents an alternative design concept for RFID reader antennas, which is based on an ellipsoidal reflector structure [5] that can be integrated into environmental structures such as in buildings with a dome-shaped entry area for gate access control. This type of building architecture is quite popular in modern public buildings, as theaters and malls ( Fig.…”