Characteristics of WLAN Transmission in an Indoor Environment

This thesis describes the study of a deterministic model for WLAN system in indoor environment. The measurement system consists of a spectrum analyzer and a log-periodic antenna. A computer program has been developed to acquire measured field strength data from the spectrum analyzer by using Agilent VEE and analyzed the data by using MATLAB software. Both line-of-sight (LOS) propagation (empty room or corridor) and non-line-of-sight (NLOS) propagation (furnished room) have been investigated. The measured path losses have been compared with deterministic model, namely Geometrical Optics (GO) and Uniform Theory of Diffraction (UTD) with the aid of image theory. The predicted results show good agreement with measurement data for the NLOS environment with absolute mean error ranging between 1.61 dB and 3.07 dB. However, the multiple reflections (third order of multiple reflections estimated the highest order in all cases) and direct ray condition which estimated significant in Instrumentation Laboratory (periodical structural ground) gave poor result when compared with the measured path losses. A typical mean relative error and absolute mean error of direct ray model was found to be within 55.04 % and 7.47 dB, but was further reduced to less than 7.43 % and 0.69 dB after optimization

Amplitude-only measurements of a dual open ended coaxial sensor system for determination of complex permittivity of materials

This paper describes a novel permittivity measurement technique using dual open ended coaxial sensors. The magnitudes of the reflection coefficient from two open ended coaxial sensors were used to determine complex reflection coefficients and permittivity of a sample under test

In-situ Noise Measurement and Analysis for the Motorcycle Muffler

Noise from the vehicles is one of the noise pollution to the environment. The noises emitted by the vehicles have to obey the requirement of regulation of maximum sound pressure level permitted for respective vehicles. In this study, the aim is to reduce the noise emitted from the motorcycle muffler. The noise emitted from the motorcycle muffler is analyzed and measured using a sound level meter. The average sound pressure level of the motorcycle muffler is determined in certain conditions. The sound pressure level is obtained from original motorcycle muffler, when it is under constant speed (10 km/hr, 20 km/hr, 30 km/hr) and under acceleration (in the scope of 0 km/hr to 30 km/hr). The study is continued by using a modified motorcycle muffler which contains sound absorptive materials. The absorptive materials chosen are glass wool, cotton and Styrofoam and they are taking turn to be placed into the motorcycle muffler to reduce the sound pressure level. Then the experiment is repeated. It is found that Styrofoam does not perform significantly in absorbing sound or noise in this study. Glass wool demonstrates relatively better sound energy absorption compared with cotton. In general, soft and porous materials are considered good performance in sound absorption. Denser materials are better at soundproofing or sound blocking. Therefore, glass wool with relatively higher density among the investigated absorptive materials in this study has the greatest sound absorption performance

Modeling and measuring dielectric constants for very thin materials using a coaxial probe

This paper is focused on the non-destructive measurement of the dielectric constants (relative permittivities) of thin dielectric material (0.1-0.5 mm) using an open-ended coaxial probe with an outer diameter of 4.1 mm. Normalized de-embedding and network error calibration procedures were applied to the coaxial probe. The measured reflection coefficients for the thin samples were taken with a vector network analyzer up to 7 GHz, and the calibrated reflection coefficients were converted to relative dielectric constants using an empirical reflection coefficient model. The empirical model was created using the regression method and expressed as a polynomial model, and the coefficients of the model were obtained by fitting the data using the Finite Element Method (FEM)

Ultra-wideband and off-optimised five-port reflectometer using power splitters

This paper presents an ultra-wideband (UWB) and off-optimised Five-Port Reflectometer (FPR) configured by power splitters. The proposed non-multi-state FPR is characterised and realised for complex reflection coefficient determinations. The measurement system can be easily setup using commercial power splitters, three detectors and a microwave source. The transmission lines method is used as calibration standard for FPR measurement system. Both the FPR setup and the transmission lines are characterised with a Vector Network Analyser prior to be used for the off-optimised measurement system. The results show good agreement between actual and calculated reflection coefficient for frequency range of 0.1 to 40 GHz. This novel FPR setup provides a simple, cost effective and accurate alternative in measuring broadband complex reflection coefficient

Determination of Moisture Content in Oil Palm Fruits Using a Five-Port Reflectometer

This paper presents the development of a PC-based microwave five-port reflectometer for the determination of moisture content in oil palm fruits. The reflectometer was designed to measure both the magnitude and phase of the reflection coefficient of any passive microwave device. The stand-alone reflectometer consists of a PC, a microwave source, diode detectors and an analog to digital converter. All the measurement and data acquisition were done using Agilent VEE graphical programming software. The relectometer can be used with any reflection based microwave sensor. In this work, the application of the reflectometer as a useful instrument to determine the moisture content in oil palm fruits using monopole and coaxial sensors was demonstrated. Calibration equations between reflection coefficients and moisture content have been established for both sensors. The equation based on phase measurement of monopole sensor was found to be accurate within 5% in predicting moisture content in the fruits when compared to the conventional oven drying method

Optical properties of ultraphosphate glasses containing mixed divalent zinc and magnesium ions

Ternary zinc magnesium ultraphosphate glasses corresponding to (ZnO)x(MgO)30−x(P2O5)70 were prepared by melt quenching technique in the range of 5 ⩽ x ⩽ 20 mol%. The optical absorption spectra of the glasses were measured at room temperature in the wavelength range between 190 and 1100 nm, and the refractive indices of the glasses were measured at room temperature at a wavelength of 632.8 nm. The optical absorption spectra indicated that the electronic transition was indirect and associated with the phonon-assisted transition. From the absorption spectra, the optical energy band gap (Eopt) and Urbach energy (EU) values for all of the glass samples were calculated from their ultraviolet edges. The values of Eopt and EU were found to be in the range of 3.54–3.81 eV and 0.27–0.45 eV, respectively, both of which vary in a non-linear manner, with a turning point at 15 mol% of ZnO. The composition-dependence of these values has been suggested and analyzed in the light of switching role of Mg2+ based on its anomalous natural behavior from network builder to modifier depending upon its concentration. The values of refractive index ranged from 1.513 to 1.534. Variations in these optical parameters, as well as variations in density and molar volume are discussed and correlated with the structural changes within the glassy matrix

Dielectric spectroscopy on mixture of rice husk, rice husk ash and rice bran from 4 Hz to 1 MHz

In this study, mixtures of rice husk/rice husk ashes (RHA) with RB on different ratios were prepared. Dielectric permittivity (ε'), loss factor (ε") and AC conductivity (σ') were measured in the frequency range of 4 Hz to 1 MHz in ambient temperature. Results for mixture of RHA and RB indicate that a dipolar relaxation occurring between 103 - 105 Hz and the peak is depressed and shifted to lower frequency as the RB content increases in the mixture. Moreover, AC conductivity decreases as the RB content increase. This may attributed to production of natural oil content from RB. In contrast, a dielectric characteristic for RH is generally not affected by the RB contents. This study explore dielectric characteristic of mixture between RH/RHA and RB in low frequency range because lack of literature is reported on low frequency response. Additionally, the potential application of RH/RHA and RB could be explored in effort to diminish waste disposal and enhance environmental protection

Development of five port reflectometer for reflection based sensing system

Five-Port Reflectometer is a microwave passivedevice where it implements the six-port algorithm to measure the complex reflection coefficient of material under test (MUT) through reflection on interface between MUT and microwave sensor. Initially, the Six-Port Reflectometer (SPR) was introduced by Engen in 1977 and major component used insix-port technique was designed in many types. When Riblet and Hanssonproposed ring junction with 5 ports only on 1981. Six ports ring junction has been reduced to five ports. In this paper, a dual frequency five ports ring junction circuit was designed, simulated and fabricated for reflection based sensing system. The fabricated five port ring junction is operating at frequencies of 0.64 GHz and 2.42 GHz. The measured result had good agreement with the simulated results for dual frequencies in terms of magnitude and phase

S-band five-port ring reflectometer-probe system for in vitro breast tumor detection

A five-port ring reflectometer-probe system was developed to measure relative permittivity of normal and tumorous breast tissues in frequency range from 1.6 to 2.75 GHz. The calibration procedures of the study reflectometer and the coaxial probe were described in detail. In this study, the synthetic breast tissues have been used, which are the Triton TX-100-water mixture at different ratios that mimic dielectric properties of normal and tumor breast tissue samples. The comparative studies of reflection coefficient and dielectric properties of the synthetic mixture samples were conducted using study reflectometer-probe system and commercial vector network analyzer with Keysight (formerly Agilent) 85070E dielectric probe. Maximum mean errors of the linear magnitude, phase, dielectric, and loss factor measurements were recorded to be 0.02, 6.1°, 2.21, and 1.60, respectively. These measurements were significantly distinguishable for normal and tumorous breast tissues