Eduardo B. Lima

Compact Beam-Steerable Lens Antenna for 60-GHz Wireless Communications

This paper presents a new concept of steerable beam antenna composed by a dielectric lens which pivots in front of a single stationary moderate gain feed. The lens not only allows steering mechanically the beam in elevation and full azimuth, but further increases the gain up to 21 dBi. The solution is broadband, including the entire international unlicensed spectrum from 57 GHz to 66 GHz. A fabricated prototype shows the possibility of tilting the beam from - 45deg to + 45deg for all azimuths with gain scan loss below 1.1 dB and radiation efficiency above 95%. The arrangement is very simple, it does not require rotary joints, it is low cost and compact, lens plus feed volume being of the order of 3 times 3 times 3 cm3 with lens weight less than 10 g.

Wideband Slot Antenna for WLAN Access Points

This letter presents a new printed slot antenna with cavity back for wireless local area network (WLAN) access points (base stations) providing wideband operation bandwidth at least from 2.5 to 4.8 GHz. The design is based upon an ultrawideband (UWB) antenna configuration modified with the inclusion of a cavity back in order to produce stable unidirectional radiation pattern. The new configuration also ensures a stable linear polarization with cross-polarization level below -20 dB. Results are confirmed with measurements. Not disregarding other applications, the new design is especially adequate for multiple-input-multiple-output (MIMO) space and polarization diversity arrangements, presenting low cross polarization and very low coupling to adjacent elements.

Evaluation of a New Wideband Slot Array for MIMO Performance Enhancement in Indoor WLANs

A new wideband compact slot antenna array for indoor WLAN access points (AP) is described, covering several wireless communication services from 2.4 to 4.8 GHz, that is especially designed to enhance MIMO system capacity. The array topology provides both spatial and polarization diversity. Despite very close packing of the array elements, these exhibit very low mutual coupling and low cross-polarization, greatly favoring MIMO diversity gain. A detailed MIMO performance comparison is conducted against a common array of patches in indoor environment, based both on simulation and indoor measurements: the new antenna shows a clear improvement in terms of channel capacity.

ILASH - Software tool for the design of integrated lens antennas

This paper presents the new software tool - ILASH - that was developed at IT under contract for ESA-ESTEC. The set of powerful tools for double-shell lens design, analysis, optimization and diagnosis along with its Windows-based user-friendly interface make the ILASH tool unique. ILASH software tool proved to be reliable, accurate and very versatile. It not only enables the lens design, but the wide range of possible analysis and diagnosis tools allows a complete insight on the lens properties and limitations.

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

A new integrated shaped lens antenna configuration is described with frequency stable radiation pattern and phase center position across a broad 1:3 frequency band, which can be used for focal plane reflector feeding in quasi-optical radio telescope systems. The lens is compatible with the integration of ultrawideband uniplanar printed feeds at its base and equally broadband mixing devices, like the Hot Electron Bolometer (HEB), although these are not used in the present work. Measurements on a scaled mm-wave lab prototype have confirmed stable performance versus frequency, with only dB directivity variation, and better than 94% Gaussicity, thanks to the possibility to impose a predefined output radiation pattern template. Simulations were performed to test the illumination of an off-set parabolic reflector by the lens radiation pattern, which confirmed reasonably constant aperture efficiency in the order of 78% across the 100% bandwidth.

Circular Polarization Wide-Angle Beam Steering at Ka-Band by In-Plane Translation of a Plate Lens Antenna

A simple mechanical beam steering antenna concept is proposed for ground mobile terminals of Ka-band satellite and high altitude platform (HAP) providing broadband access services. The wide-angle elevation beam steering is achieved by in-plane translation of a thin offset flat lens in front of a stationary primary feed while full azimuth coverage is obtained by simple 360° rotation of the lens. A new strategy is also proposed to reduce the effective F/D of the focusing system and consequently the total antenna height without increasing beam distortion: a second small flat lens is added on top of the primary feed to create a virtual focus located well below the feed phase center. The challenge is to conciliate high gain both with wide beam scanning and reduced antenna height. Design rules are presented for this antenna concept along with a 27.3-dBi gain fabricated example for the up-link Ka-band (29.5-30 GHz), with circular polarization, 0° to 50° elevation scan, better than 2.8-dB scan loss and an effective F/D of only 0.55. Both lenses are 3.35-mm thick, formed by a suitable assembly of phase shifting unit cells with less than 0.4 dB of transmission loss in simulation. The main lens dimensions are 195 mm × 145 mm and its weight is 215 g. Total antenna height, including the feed is 84 mm.

Tx-Rx Lens-Based Satellite-on-the-Move Ka-Band Antenna

A simple low-cost mobile ground terminal antenna for Ka-band satellite communications is presented. The antenna is composed of a shaped dielectric lens which tilts and rotates in front of a feed to direct the beam. The wideband feed system is composed of a quad-ridged horn with a 45° slant aperture and a coaxial-to-quad-ridged circular waveguide transition. The lens allows simple mechanical beam steering from 0 ° to 65 ° in relation to the zenith and 360 ° in azimuth by rotating both the lens and the feed slanted aperture. Performance measurements of a manufactured prototype prove the beam tilting capabilities in elevation with a maximum gain of 22 dBi and scan loss below 3 dB at 20 GHz and 24 dBi gain with less than 4.5 dB scan loss at 30 GHz.

Ball Grid Array-Module With Integrated Shaped Lens for WiGig Applications in Eyewear Devices

A ball grid array-module (BGA-module) incorporating a low-cost shaped dielectric lens is proposed for wireless communications in the 60-GHz WiGig band between a smart eyewear, where it is integrated and facing a laptop or TV. The module, which is codesigned with a 60-GHz transceiver, consists of two separate identical antennas for transmitting (Tx) and receiving (Rx). The in-plane separation of these elements is 6.9 mm both being offset from the lens focus. This poses a challenge to the lens design to ensure coincident beam pointing directions for Rx and Tx. The shaped lens is further required to narrow the angular coverage in the elevation plane and broaden it in the horizontal plane. A 3-D-printed eyewear frame with an integrated lens and a recess for proper BGA-module integration is fabricated in ABS-plastic material. Measurements show a reflection coefficient below -12 dB in the 57-66 GHz band. A maximum gain of 11 dBi is obtained at 60 GHz, with 24° and 96° beamwidth at 5-dBi gain, respectively, in the vertical and horizontal planes. The radiation exposure is evaluated for a homogeneous SAM head phantom and a heterogeneous visible human head. The simulated power density values for both models are found to be lower than the existing standards.

A 120 GHz 3D-printed plastic elliptical lens antenna with an IPD patch antenna source

In this paper, we investigate the performance of a 3D-printed plastic lens operating in the 120 GHz frequency band. An Integrated Passive Device module with built-in linearly polarized patch antenna is used as the source of the lens. The profile of the lens is based on elliptical shape. It is first optimized with Geometrical Optics (GO) and Physical Optics (PO) methods. Then, full-wave simulations are conducted to fine tune the overall antenna-structure. Using a lens height of 10 mm, the overall antenna has a simulated realized gain higher than 15 dBi from 120 GHz to 130 GHz. The lens and the patch antenna have just been manufactured and measurements will be presented in the final paper.

Antenna phase center determination from amplitude measurements using a focusing lens

One critical performance parameter associated with feed systems for reflectors or other focused antennas is the feed phase center position. Maximum aperture efficiency is obtained when the feed phase center is positioned at the reflector focal point. Although horn antennas are the most common feeds for reflectors, lens antennas with bolometer detectors integrated at its base are the most common configuration [1] at millimeter and, especially, at sub-millimeter waves imaging and radiometric applications. Unlike horns, where the phase center position is normally located close to the aperture plane, the phase center of integrated lenses is very dependent upon the lens shape and may even be far out from the lens body. However, when bolometers or other detectors are used at the lens under test, only amplitude measurements can be obtained, preventing the usual phase center calculation from radiation pattern phase information. In this communication an alternative procedure based on power measurements is proposed and evaluated. Corresponding results obtained for a double-shell dielectric lens are compared to those obtained for the same lens with the usual method based on measured phase pattern. The alternative method uses an auxiliary collimated lens and can be used in small anechoic chambers.