Kim Yee Lee

THE USE OF DIELECTRIC MIXTURE EQUATIONS TO ANALYZE THE DIELECTRIC PROPERTIES OF A MIXTURE OF RUBBER TIRE DUST AND RICE HUSKS IN A MICROWAVE ABSORBER

A change in the relative proportions of a mixture of rubber tire dust and rice husks will cause a change in the mixtures electrical permittivity and its ability to absorb electromagnetic energy. An open- ended coaxial probe was used in conjunction with three dielectric mixture equations (the Kraszewski equation, the Landau equation and the Lichtenecker equation) to obtain the dielectric properties of a mixture of rubber tire dust and rice husks (RTDRH) over the frequency range of 7GHz to 13GHz. Lichteneckers equation for dielectrics proved to be a useful practical formulation for determining the efiective permittivity of homogeneous dielectric mixtures. The efiectiveness of these dielectric mixture equations in determining the efiective permittivity of RTDRH was investigated in this study. A newly developed mixture equation was derived based on these dielectric

Determination of Moisture Content in Mortar at Near Relaxation Frequency 17 GHz

Determination of Moisture Content in Mortar at Near Relaxation Frequency 17 GHz The knowledge of moisture content in cement based material is important especially for the safety in field work. In this paper, a non-destructive and contactless free space method is used for measurement of moisture content in cement based materials (mortar) at microwave frequencies. The measurement system consists of a 17 GHz dielectric resonator oscillator (DRO) as a microwave source, a Power Meter as the detector, and a pair of lens horn antennas to transmit and receive the microwave signal. An empirical formula of moisture content was obtained by using a relationship between attenuation and moisture content. This model is best for prediction of moisture content greater than 2% with percentage mean error of 3%.

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 re∞ection coe-cient from two open ended coaxial sensors were used to determine complex re∞ection coe-cients and permittivity of a sample under test.

Improved Path Loss Simulation Incorporating Three-Dimensional Terrain Model Using Parallel Coprocessors

Current network simulators abstract out wireless propagation models due to the high computation requirements for realistic modeling. As such, there is still a large gap between the results obtained from simulators and real world scenario. In this paper, we present a framework for improved path loss simulation built on top of an existing network simulation software, NS-3. Different from the conventional disk model, the proposed simulation also considers the diffraction loss computed using Epstein and Peterson’s model through the use of actual terrain elevation data to give an accurate estimate of path loss between a transmitter and a receiver. The drawback of high computation requirements is relaxed by offloading the computationally intensive components onto an inexpensive off-the-shelf parallel coprocessor, which is a NVIDIA GPU. Experiments are performed using actual terrain elevation data provided from United States Geological Survey. As compared to the conventional CPU architecture, the experimental result shows that a speedup of 20x to 42x is achieved by exploiting the parallel processing of GPU to compute the path loss between two nodes using terrain elevation data. The result shows that the path losses between two nodes are greatly affected by the terrain profile between these two nodes. Besides this, the result also suggests that the common strategy to place the transmitter in the highest position may not always work.

Study of Dual Open Ended Coaxial Sensor System for Calculation of Phase Using Two Magnitudes

A dual open ended coaxial sensor system to determine complex permittivity was studied in detail. This paper focuses on determination of a reflection coefficient phase from two magnitudes using modified capacitance model from 300 kHz to 8 GHz. The phase information can then be used for calculation of the samples complex permittivity. Factors such as range and limitation of the model, samples permittivity, operating frequency, and size of sensor were investigated. Sensitivity of calculated phase with respect to small changes in measured magnitude was carried out.

L - Probe Transmitarrays for X - Band Mobile Communications

Abstract—Two novel wire transmitarrays, which are designed using a pair of co-joined L-shaped probes, have been developed for X-band mobile communications. By adjusting the orientation of the L probes, the polarization of the transmitting wave can be easily made either vertical or horizontal. Floquet method has been used for characterizing the transmission responses, and both transmitarray unit cells are found to have achieved a phase range of greater than 380◦ and a linear phase sensitivity of 44.5◦/mm. Wide −1 dB gain bandwidth larger than 10% is achievable in both the vertically and horizontally polarized full-fledged transmitarrays, with radiation efficiency of ∼ 90%. The proposed transmitarrays have low radar cross section, which can be used for military applications.

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.

Broadrange L-probe reflectarray

A new reflectarray is designed using two co-joined L-shaped probes. In this case, the horizontal lengths of the two L-shaped probes are functioning as the phase-shifters. The unit element is simulated using the Floquet cell, and simulation shows that the unit element is able to provide a linear phase range of 454.2°. A full-fledge reflectarray consisting of 121 elements is designed, fabricated, and measured. The proposed reflectarray is able to achieve an antenna gain of 20.43dBi and a −1dB gain bandwidth of 15.38%.

Analysis on monopole antenna for moisture determination in oil palm fruit using finite difference method

Finite difference analysis were applied to study the principle operation of monopole antenna for moisture determination in oil palm fruit at 2 GHz. The electromagnetic field interact with oil palm fruit on the interface between the antenna and oil palm fruit and cause a reflection. The reflection measurement is based on mismatch impedance or dielectric properties between two media. Reflection coefficient is used to quantify the level of reflection. The monopole antenna was made of RG405/U semi-rigid coaxial cable with an inner and outer diameter of 0.45 mm and 1.50 mm, respectively with 2.23 mm length of protruding conductor over 5.66 cm length of monopole antenna. This monopole antenna for moisture detection was compared with induced EMF method in terms of reflection coefficient at 2 GHz. The results show that the complex reflection coefficient measured using monopole antenna provides significant results to predict moisture content in oil palm fruit.

REFLECTION AND DIELECTRIC MEASUREMENT FOR SALINITY OF WATER USING MICROSTRIP LOOP ANTENNA AND DIELECTRIC PROBE

This study was conducted to investigate the feasibility of loop antenna in gauging level of salinity of water via electromagnetic wave reflection. High salinity cause adverse effect to environment. When high levels salinity of water diffuse into soil, it declines values of land for human and animal consumption. These impacts can cause tremendous monetary lost because the restoration of impairments is extremely costly. Therefore, a reliable salinity detection system of water source is crucial. In this work, reflection measurement was conducted using loop antenna in conjunction with network analyser for water salinity detection. Dielectric probe will be then used for dielectric characterization due to different water salinity. It comes to learn that the different level of salinity of water exhibit different dielectric properties through reflection measurement. The increment of salinity leads to increment and decrement of dielectric constant and loss factor, respectively. Similar observation can be found in reflection coefficient.