Tan-Phu Vuong

UWB Antennas: Systems With Transfer Function and Impulse Response

The conventional ultra-wide-band (UWB) antenna model is reviewed and assessed. A new UWB system vision is proposed and analyzed with analytic expressions. It is shown that this approach presents several practical advantages. Especially the models of the TX and RX antennas are independently separated from the propagation channel. The proposed method is illustrated with an example

A Time/Frequency Model of Ultrawideband Antennas

A new approach to model ultrawideband (UWB) antennas is proposed. A mathematical analysis of transmission through an UWB system in terms of transfer function and impulse response is proposed. The analysis allows the separation of the transmitting and receiving antenna characteristics, using a consistent treatment with other UWB and earlier narrowband analysis techniques. A parametric modeling is added to provide efficient directional time-frequency models of UWB antennas. The technique is demonstrated through simulation and experiment.

Antennas for RFID tags

This communication covers the design and optimization of antennas for RFID tags at UHF and microwave frequencies. Such design will focus on the specific characteristics of RFID applications such as back-scattering mode, variability of substrates and low cost constraints. The introduction includes a short history of RFID development. The second part will address the main characteristics of RFID antennas. The third part introduces the material characterization. Current developments of RFID antennas that meet the objectives of low-cost and size reduction are presented in part four. Design of antennas on plastic substrate using conductive inks will be shown as an example of low-cost approach. Advanced design techniques for size reduction, such as fractal techniques will be introduced and some design examples will be discussed. The fifth part concerns antenna modeling from the system point of view and examples of system simulation of an RFID communication will be shown.

Miniaturized patch antenna for the Radio Frequency Identification of metallic objects

The growing interest in the Radio Frequency Identification (RFID) technology is giving rise to new applications, in particular for the identification of metallic objects. This interest has initiated the development of new designs for RFID tag antenna. This paper presents a UHF miniaturized patch antenna aimed at this application. The patch antenna is fed by a balanced feed to avoid a cross-layered construction and matched with a stub. Its miniaturization is achieved by inserting a u-shaped slot in the radiating patch.

New design antenna for RFID UHF tags

A novel printed antenna is proposed for radio frequency identification. The antenna has a much wider bandwidth than known printed antenna, mostly planar antennas. The antenna geometry is much smaller than a printed dipole antenna at the same frequency band. The method of design and realization with experimental results is shown. The introduction includes basic concepts of RFID systems. The second part addresses the main characteristics of the proposed RFID tag antenna. The third part introduces a comparison between measurements and simulations. Few advantages of the proposed RFID tag that meets the objectives of low-cost and size reduction are presented in part four

Design and measurements of antennas for RFID, made by conductive ink on plastics

Embedded communication systems are composed of digital, analogue and RF parts with specific characteristics for each one. Antennas are fundamental elements in communication systems. The objective of our work is the design of low-cost integrated antennas in the ISM band, and more specifically for RFID applications. This implies material selection. Plastics and conductive ink seem to be good candidates as the antennas substrate and radiating patch, respectively. However, the dielectric and conductive properties of these low-cost materials are quasi-unknown in the ISM band. This communication addresses the experimental determination and the use of these parameters.

Determination of measurement uncertainties applied to the RCS and the differential RCS of UHF passive RFID tags

Measurement methodology and theoretical equations to RCS and ΔRCS determination are recalled and the measurement uncertainties are evaluated in this paper. Even if measurement uncertainties are generally not required for RFID, it is important to understand and to be able to determine the measurement uncertainty. Currently, manufacturers and testing laboratories present some results of RFID measurements but never show the associated uncertainty. Yet, seeing the values of the uncertainties, it is clear that they are not negligible.

Realistic modeling of antennas for ultra wide band systems

This paper presents a new approach for realistic modeling of antenna. The presented method is applied for UWB antenna. The objective is to derive an equivalent and complete model of the antenna which can be straightaway integrated into a simulation system. The developed model is a parametric one and takes into account the complex gain (amplitude and phase) of the antenna. Its determination can be obtained from measurements or from full wave electromagnetic simulation

Efficient compact dual-band antennas for GSM and Wi-Fi energy harvesting

Since the demand for autonomous wireless sensors increases, there is an important interest in battery-less systems that use radiofrequency (RF) energy harvesters. The key element on the receiving side of an energy harvesting system is the rectenna (rectifier + antenna) which receives electromagnetic power and converts it into electric continuous power. With the development of multiple frequency bands in todays wireless communication systems, the multi-band rectennas would be useful. Among various entities of rectenna, antenna is one of the important elements which is responsible for collecting the incoming RF signals of various frequencies. We present in this paper two efficient compact dual-band antennas for RF energy harvesters: a Printed-IFA for GSM bands with 1.3 dBi at 900 MHz band and 3.2 dBi at 1800 MHz band; and a quasi-Yagi for Wi-Fi bands with 5.7 dBi at 2.45 GHz band and 5.9 dBi at 5.3 GHz band. Also simulation and measurement results will be presented.

A new quasi - isotropic antenna for ultra - wideband application

In this paper, we propose a new compact antenna design for applications where an ultra-wideband (UWB) frequency range is needed. The main features of the proposed antenna is the capability of generate a quasi-isotropic radiation pattern. For this case, the proposed antenna is designed to operate from 2.17 GHz to 2.68 GHz. The construction details of the conceived antenna are presented and discussed. The measurements of reflection coefficient and radiation pattern were made in UFCG/LEMAs laboratory. The experimental results have good agreement with the simulated one. The simulation was made using the CST - Microwave Studio. The antenna is of easy construction and has application in wireless system and network sensors, field measurement or electromagnetic compatibility (EMC).