Carlos A. Fernandes

Performance of lens antennas in wireless indoor millimeter-wave applications

Dielectric lens antennas can be designed to produce highly shaped beams that significantly improve the system performance in emerging wireless indoor millimeter-wave systems. A lens configuration is analyzed in this paper that produces a circularly symmetric cell with uniform spatial power distribution, fairly sharp boundaries, and scalable cell radius. The last characteristic is used to control the reflections at sidewalls. A hemispherical coverage lens antenna is designed for the mobile terminal (MT) to ensure relatively free movement. The impact of these antennas is analyzed in terms of cell coverage and channel time dispersion, considering the effect of cell radius scaling, and MT antenna tilting. Measurements and simulations show that the proposed lens antennas outperform common solutions based on pyramidal horns or biconics.

Performance of a Crossed Exponentially Tapered Slot Antenna for UWB Systems

A compact printed antenna is described that exhibits adequate transient performance for ultrawideband (UWB) applications and it is further adequate for polarization diversity schemes. The antenna is based on an original combination of two crossed exponentially tapered slots plus a star-shaped slot to produce a stable radiation pattern with very stable polarization over the 3.1-10.6 GHz FCC assigned band. Results are confirmed with measurements. Figures of merit like output pulse fidelity and time window containing 90% of the transmitted energy are analyzed over the entire solid angle and showed to remain quite stable, in line with envisaged UWB system requirements. Compact dual-antenna arrangements are also analyzed in view of potential use for UWB multiple-input-multiple-output implementations.

Additional boundary condition for a wire medium connected to a metallic surface

In this work, we demonstrate that the interaction of electromagnetic waves with a microstructured material formed by metallic wires connected to a metallic surface can be described using homogenization methods provided an additional boundary condition (ABC) is considered. The ABC is derived by taking into account the specific microstructure of the wire medium. To illustrate the application of the result, we characterize a substrate formed by an array of tilted metallic wires connected to a ground plane, demonstrating that in such a configuration the wire medium behaves essentially as a material with extreme optical anisotropy and that in some circumstances the substrate can be seen as an impedance surface.

Hybrid UHF/UWB Antenna for Passive Indoor Identification and Localization Systems

There is a growing interest for simultaneous identification and centimetre-resolution localization of multiple targets in indoor environments. A hybrid passive UHF/UWB RFID concept has been recently proposed that conciliates the potential from high resolution UWB impulse radio with the typical range from UHF-RFID identification systems. This paper proposes a new planar antenna for hybrid passive tag systems, which operates both in the UHF-RFID band and in the FCC UWB band. The co-designed UHF and UWB antenna elements are printed back-to-back on each side of a common substrate with appropriate topology for future integration with a single UHF-UWB RFID chip. Experimental tests have shown that both UHF-RFID and UWB performance of the hybrid antenna are comparable to available commercial solutions that work just on a single band. The antenna is adequate for low-cost mass production of hybrid passive tags. It aims at low-cost passive RFID systems combining the ability of item identification with precise tracking in indoor environments.

A Broadband Implantable and a Dual-Band On-Body Repeater Antenna: Design and Transmission Performance

The design of a new miniature broadband implantable antenna and a dual-band on-body antenna are presented along with the transmission performance between the two. The former and latter antennas are intended for integration into implantable medical devices (IMDs) and on-body repeaters, respectively. The on-body repeater antenna favors the use of very low power IMDs. The on-body repeater receives low power data from an IMD (MedRadio band, 401-406 MHz) and retransmits it to remote devices placed further apart (ISM band, 2400-2480 MHz ). The MedRadio implantable antenna maintains miniature size (399 mm3), and exhibits two close resonances which increase the -10 dB bandwidth inside muscle tissue (87 MHz). The on-body antenna is relatively small (6720 mm3), and exhibits dual resonances in the MedRadio and ISM bands. Assuming a typical arm implantation scenario and an on-body receiver sensitivity of -75 dBm, the proposed configuration is found to enable reduction of the IMD power by a factor of 100. Patient safety and tolerance to electromagnetic interference are, thus, preserved, and lifetime of the IMD is increased. The setup is, finally, shown to be robust to antenna misalignment and polarization rotation.

3D printed plastic 60 GHz lens: Enabling innovative millimeter wave antenna solution and system

During the past years, various research teams developed 60 GHz chipset solutions, using both advanced CMOS [1] and BiCMOS [2] technologies. But for the 60 GHz market to flourish not only low cost RFICs are required, low cost antennas and packages are also key elements. Recently, low cost High Density Interconnect (HDI) organic technology has been evaluated [3, 4] to develop 60 GHz module using antenna-in-package approach. Measured gain is in the order of 4 dBi but there is still a need to achieve higher gain in order to increase the transmit/receive range of the system. The use of a lens is an appealing solution since it enables to customize the system performances while using existing chipset solution. In this paper, we investigate the performances achievable by a plastic (ABS-M30) lens manufactured using low cost and rapid manufacturing 3D printing technology. Material properties at 60 GHz are reviewed, a preliminary 60 GHz lens design is detailed and the full system is validated using a WiGig wireless link (demonstrating a 10 dB improvement in the link budget in comparison with the system without lens).

Broadband UHF RFID Passive Tag Antenna for Near-Body Applications

One challenge for UHF RFID passive tag design is to obtain a low-profile antenna that minimizes the influence of near-body or attached objects without sacrificing both read range and universal UHF RFID band interoperability. A new improved design of a RFID passive tag antenna is presented that performs well near problematic surfaces (human body, liquids, metals) across most of the universal UHF RFID (840-960 MHz) band. The antenna is based on a low-profile printed configuration with slots, and it is evaluated through extensive simulations and experimental tests.

Superlens made of a metamaterial with extreme effective parameters

We propose a superlens formed by an ultra-dense array of crossed metallic wires. It is demonstrated that due to the anomalous interaction between crossed wires, the structured substrate is characterized by an anomalously high index of refraction and supports strongly confined guided modes with very short propagation wavelengths. It is theoretically proven that a planar slab of such structured material makes a superlens that may compensate for the attenuation introduced by free-space propagation and restore the subwavelength details of the source. The bandwidth of the proposed device can be quite significant since the response of the structured substrate is non-resonant. The theoretical results are fully supported by numerical simulations.

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.

Review of lens antenna design and technologies for mm-wave shaped-beam applications

Design procedures (analysis, synthesis and optimization), technologies (materials and fabrication issues) and applications of millimetre-wave dielectric lens antennas are reviewed. In particular a detailed state of the art of mm-wave shaped-beam applications is given. Future trends are also proposed.