University of Oulu

Utilizing vector network analyzer for measuring complex dielectric constant of indoor walls

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Author: Lopa, Fahmida1
Organizations: 1University of Oulu, Faculty of Information Technology and Electrical Engineering, Communications Engineering
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.4 MB)
Pages: 46
Persistent link: http://urn.fi/URN:NBN:fi:oulu-202005011585
Language: English
Published: Oulu : F. Lopa, 2020
Publish Date: 2020-05-04
Thesis type: Master's thesis
Tutor: Vuohtoniemi, Risto
Reviewer: Vuohtoniemi, Risto
Berg, Markus
Description:

Abstract

In this thesis, a two-port vector network analyzer (VNA) and double-ridged waveguide horn antennas (Rohde & Schwarz HF906) were utilized for assessing the complex relative permittivities of building materials. The measurements were done in two different frequency bands in the University main building in Linnanmaa, Oulu. Reflection coefficients of different walls were measured in the lecture room PR102. The measurement data were collected at lower frequency range of 1–9.5 GHz and at upper frequency range of 9.5–18 GHz.

An absorbing non-conductive material has a complex valued permittivity, whose quality can be assessed by fitting the theoretical reflection coefficient curve on the measured values over a large range of angles of incidence at parallel polarization. The reflection coefficients were estimated from the measured data taking into account the increased attenuation due a longer path length. After applying the path length compensation, coefficients falling within one degree from each other are averaged to give the data equal weighing over the abscissa. The dielectric constants were assessed for a brick wall with a smooth surface and a wall with a rougher surface. The value of complex dielectric constant in range of (3.7–4.22)–j(0.73–0.03) was found to be in accordance with results published by the International Telecommunications Union.

The measurement system was able to perform efficiently for the proposed objective of the study. Several improvements can be made in future to adopt a more accurate measurement system to study the reflection characteristics of building materials. The aim of this thesis is to effectively use a vector network analyzer for measuring material properties by inspecting the reflection of a parallel polarized electromagnetic wave from a flat surface of material samples.

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