Distributed antenna system | EPFL Graph Search

A distributed antenna system, or DAS, is a network of spatially separated antenna nodes connected to a common source via a transport medium that provides wireless service within a geographic area or structure. DAS antenna elevations are generally at or below the clutter level, and node installations are compact. A distributed antenna system may be deployed indoors (an iDAS) or outdoors (an oDAS). Concept As illustrated in the figure, the idea is to split the transmitted power among several antenna elements, separated in space so as to provide coverage over the same area as a single antenna but with reduced total power and improved reliability. A single antenna radiating at high power (a) is replaced by a group of low-power antennas to cover the same area (b). The idea was described in a paper by Saleh et al. in 1987. These antennas have recently been employed by several service providers in many areas around the United States. DAS is often used in scenarios where altern

Analysis and Design of Ultra-Wideband Antennas in the Spectral and Temporal Domains

Gabriela Quintero Diaz De Leon

Formal research on Ultra-wideband (UWB) technology started in the U.S. in 2002; where its definition was formulated and the frequency allocation in that country established. However, the first ultra-wideband transmission was done during the confirmation of Maxwell's equations by Heinrich Hertz in 1886, the first ever reported radio transmission. Sparks or very short pulses were sent and received at a distance away from its source. UWB antennas have existed since those times, but technology has been mostly focused on the transmission of continuous wave narrowband signals. The largest problematic encountered in today's UWB antennas is that characterization methods were, since the beginning, meant to describe narrowband antennas. The frequency characteristics of these antennas are constant over their operational bandwidth, hence they can be fully characterized in the frequency domain. UWB antennas, on the other hand, are meant to transmit pulsed signals. Analyzing them only in the frequency domain is not enough to fully evaluate their performance, as pulse distortion is an important parameter that should be controlled. An extended literature review is included in the first part of this thesis, where the available UWB antenna characterization methods are evaluated. Many limitations were encountered, showing that the available techniques do not analyze simultaneously the most important parameters of an UWB antenna. A new characterization method is proposed: the System Fidelity Factor (SFF). Its main purpose is to incorporate frequency, time and space characteristics of a two-antennas system to compare UWB antennas in an efficient way. This is achieved with the correlation between the received and the input pulses, quantifying the distortion produced by the system. The SFF is an interesting tool because both simulations and measurements can be done in a simple and straight-forward manner, using tools that are commonly available in any antenna lab. Any combination of antennas can be analyzed and the free-space channel can be easily replaced with any other environment. Several UWB antennas were designed and used to prove the efficiency of the SFF. A good agreement between the proposed simulation techniques and the measurements was achieved. The antennas are novel designs specially developed for UWB applications under the American or European regulations. The last part of the thesis presents these antennas and analyzes them using the SFF to compare their performance.

EPFL2010

Analysis of UWB antennas for carrier-based UWB impulse radio

Gabriela Quintero Diaz De Leon, Anja Skrivervik Favre

A Carrier-based UWB pulse is compared with the commonly used Gaussian pulse. Two antenna systems are simulated and measured in frequency domain. The impulse response and the Power Spectral Density (PSD) of both studied pulses are obtained. The effect of each antenna system on each pulse is analyzed in frequency and time domain.

2007

Omnidirectional Pulse Dispersion of Planar Circular Monopoles

Gabriela Quintero Diaz De Leon, Anja Skrivervik Favre

Three antenna systems, composed of circular monopoles with different ground plane sizes, are studied. The transmission of an UWB pulse between two identical monopoles is analyzed. The omnidirectional properties of the UWB antennas are measured and simulated in frequency and time. The System Fidelity Factor of each system is obtained, quantifying the distortion of the received pulses in the azimuth plane. Results show that. the size of the ground plane affects the efficiency of a monopole system when transmitting an UWB pulse.

IEEE Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

Analysis and Design of Ultra-Wideband Antennas in the Spectral and Temporal Domains

Gabriela Quintero Diaz De Leon

EPFL2010