ETD system

Electronic theses and dissertations repository


Tesi etd-07202007-175405

Thesis type
Tesi di dottorato di ricerca
Serra, Andrea Antonio Ignazio
Analysis and design of efficient techniques for modern mobile communication systems
Settore scientifico disciplinare
Corso di studi
Relatore Prof. Nepa, Paolo
Relatore Prof. Manara, Giuliano
Parole chiave
  • Smart Antennas
  • PIFA
  • Diversity
  • Array
Data inizio appello
Data di rilascio
Riassunto analitico
The thesis regards the analysis and the design of new efficient antenna systems and the implementation of modern techniques to improve their performances. In the first part, the design of a smart antenna array panel of 16 dual polarized stacked patches is described. The designed array operates in the frequency range between 1.92 GHz and 2.69 GHz for the UMTS, WLAN and UMTS II wireless communication systems. The UMTS II system has been recently standardized as an extension of the UMTS and it will be available from January 2008. The antenna has been designed by using Ansoft HFSS. A prototype has been realized and measurements have been carried out to determine Return Loss and radiation patterns.
In the second part, the attention has been focused on antennas for mobile terminals. After a preliminary investigation about the integration issues of an antenna in a portable device, two multi-band PIFAs (Planar Inverted F-Antennas) for IEEE 802. 11 a,b,g and HIPERLAN 2 have been designed and a number of prototypes have been realized. Parametric studies on the position of the antennas on the laptop display have been conducted to evaluate the isolation, the Return Loss and the radiation patterns. New feeding techniques have been implemented to increase the antenna impedance bandwidth. Using two of the above PIFAs, a diversity scheme for laptop has been implemented. Spatial, polarization and pattern diversity schemes have been studied as a function of the distance between the two receiving antennas. Different combining techniques have been used to calculate the system performance and results are evaluated in terms of diversity gain, power imbalance and correlation coefficients. Measurements have been carried out in a reverberation chamber where Rayleigh fading has been reproduced.
The last part of the work is concerned about the analysis of systems for on-body communications. A diversity scheme has been implemented to verify the feasibility of such a system and good promising results have been obtained. A series of postures and antenna placements have been identified as the most significant and representative of how and where an on-body device can be installed or carried. A receiving system of two monopole antennas was mounted in five significant placements on the body and a single transmitting monopole was fixed in the waist proximity. Collected power samples have been combined by resorting to Selection, Equal Gain and Maximum Ratio combining techniques and Cumulative Distribution functions have been calculated to evaluate the statistics and the diversity performances. Results have been analyzed in terms of diversity gain and correlation between branches.