S. E. Barbin

Reconfigurable Antennas: Design and Applications

The advancement in wireless communications requires the integration of multiple radios into a single platform to maximize connectivity. In this paper, the design process of reconfigurable antennas is discussed. Reconfigurable antennas are proposed to cover different wireless services that operate over a wide frequency range. They show significant promise in addressing new system requirements. They exhibit the ability to modify their geometries and behavior to adapt to changes in surrounding conditions. Reconfigurable antennas can deliver the same throughput as a multiantenna system. They use dynamically variable and adaptable single-antenna geometry without increasing the real estate required to accommodate multiple antennas. The optimization of reconfigurable antenna design and operation by removing unnecessary redundant switches to alleviate biasing issues and improve the systems performance is discussed. Controlling the antenna reconfiguration by software, using Field Programmable Gate Arrays (FPGAs) or microcontrollers is introduced herein. The use of Neural Networks and its integration with graph models on programmable platforms and its effect on the operation of reconfigurable antennas is presented. Finally, the applications of reconfigurable antennas for cognitive radio, Multiple Input Multiple Output (MIMO) channels, and space applications are highlighted.

Planar Monopole Antenna With Attached Sleeves

The analysis of a new printed antenna is presented and discussed. This antenna consists of a printed monopole, with one or two sleeves on each side, fed by a coplanar waveguide (CPW) line. Switches are used to control the length of the monopole and the sleeves and to tune the resonant frequencies of the antenna. In the case of the double-sleeved antenna, the switch is used to connect or disconnect a second sleeve in the cactus antenna. Measurement results show that the cactus antenna maintains the dipole-like radiation patterns for all the different resonant frequencies

Introduction to the Software-defined Radio Approach

Telecommunications have been in constant evolution during past decades. Among the technological innovations, the use of digital technologies is very relevant. Digital communication systems have proven their efficiency and brought a new element in the chain of signal transmitting and receiving, the digital processor. This device offers to new radio equipments the flexibility of a programmable system. Nowadays, the behavior of a communication system can be modified by simply changing its software. This gave rising to a new radio model called Software Defined Radio (or Software-Defined Radio - SDR). In this new model, one moves to the software the task to set radio behavior, leaving to hardware only the implementation of RF front-end. Thus, the radio is no longer static, defined by their circuits and becomes a dynamic element, which may change their operating characteristics, such as bandwidth, modulation, coding rate, even modified during runtime according to software configuration. This article aims to present the use of GNU Radio software, an open-source solution for SDR specific applications, as a tool for development configurable digital radio.

A new reconfigurable multi band patch antenna

A new reconfigurable multi band microstrip antenna is presented in this paper. The patch has the shape of a 6 armed star printed on a hexagonal substrate. The reconfigurability of the antenna is obtained by inserting small switches on rectangular slots cut in the patch. Different switch configurations were investigated and different functionalities of the antenna were obtained. The antenna has many practical applications, like in GSM, wireless LAN, WIMAX and many other systems, as illustrated in detail herein. The antenna changes its application according to which switches are activated.

Signal classification with an SVM-FFT approach for feature extraction in cognitive radio

The estimation of the spectrum usage from the point of view of number of users and modulation types is addressed in this paper. The techniques used here are based on Support Vector Machines (SVM). SVMs are machine learning strategies which use a robust cost function alternative to the widely used Least Squares function and that apply a regularization which provides control of the complexity of the resulting estimators. As a result, estimators are robust against interferences and nongaussian noise and present excellent generalization properties where the number of data available for the estimation is small. The structure presented here has a feature extraction part that, instead of using an FFT approach, uses the SVM criterion for spectrum estimation, feature extraction and modulation classification.

Detecting failure of antenna array elements using machine learning optimization

A Multi-class support vector classifier (SVC) is proposed for planar array failure diagnosis. Extracted feature information from the far field intensity of the array is used to train and test the multi-class SVC, so one can detect the location of failed elements in an array and also the level of failure.

Optimization and Complexity Reduction of Switch-Reconfigured Antennas Using Graph Models

This letter addresses the optimization and complexity reduction of switch-reconfigured antennas. A new optimization technique based on graph models is investigated. This technique is used to minimize the redundancy in a reconfigurable antenna structure and reduce its complexity. A graph modeling rule for switch-reconfigured antennas is proposed, and examples are presented.

A novel antenna array based on quasi-Yagi element for adaptive wireless system applications

This work presents the design and performance characteristics of a novel antenna array structure. The prototype is composed by three equal quasi-Yagi antennas 120/spl deg/ shifted, due to this new layout to allow the configuration of the radiation pattern, forming directional patterns with high directivity, and keeping the same performance as the isolated element has in band terms. The array was designed for working at 2.4 GHz and optimized to include 1.9 GHz, GSM-USA standard. The simulation and design optimization were done by a commercial software using MoM (moment method). There is an acceptable agreement between the simulation and measured results of return loss of the array.

Analyzing the Complexity and Reliability of Switch-Frequency-Reconfigurable Antennas Using Graph Models

This paper addresses the functional reliability and the complexity of reconfigurable antennas using graph models. The correlation between complexity and reliability for any given reconfigurable antenna is defined. Two methods are proposed to reduce failures and improve the reliability of reconfigurable antennas. The failures are caused by the reconfiguration technique or by the surrounding environment. These failure reduction methods proposed are tested and examples are given which verify these methods.

A new approach for vehicle access control using active RFID tags

Radio frequency identification (RFID) is an emerging technology with many different applications. In this paper, results obtained from the use of an active RFID system for trucks access control will be presented. Using a directive antenna with a reader and a middleware with RSSI feature, it is possible to make the system much more accurate than in conventional approaches, avoiding most reading problems and making the system more robust. A comparison between the system with and without these resources is shown in the text.