Zaiki Awang

EXPERIMENTAL BREAST TUMOR DETECTION USING NN-BASED UWB IMAGING

This paper presents a system with experimental comple-ment to a simulation work for early breast tumor detection. The ex-periments are conducted using commercial Ultrawide-Band (UWB) transceivers, Neural Network (NN) based Pattern Recognition (PR) software for imaging and proposed breast phantoms for homogenous and heterogeneous tissues. The proposed breast phantoms (homoge-neous and heterogeneous) and tumor are constructed using available low cost materials and their mixtures with minimal e®ort. A speci¯c glass is used as skin. All the materials and their mixtures are con-sidered according to the ratio of the dielectric properties of the breast tissues. Experiments to detect tumor are performed in regular noisy room environment. The UWB signals are transmitted from one side of the breast phantom (for both cases) and received from opposite side diagonally repeatedly. Using discrete cosine transform (DCT) of these received signals, a Neural Network (NN) module is developed, trained and tested. The tumor existence, size and location detection rates for both cases are highly satisfactory, which are approximately: (i) 100%,95.8% and 94.3% for homogeneous and (ii) 100%, 93.4% and 93.1% for heterogeneous cases respectively. This gives assurance of early de- tection and the practical usefulness of the developed system in near future.

3d experimental detection and discrimination of malignant and benign breast tumor using nn-based uwb imaging system

This paper presents both simulation and experimental study to detect and locate breast tumors along with their classification as malignant and/or benign in three dimensional (3D) breast model. The contrast between the dielectric properties of these two tumor types is the main key. These dielectric properties are mainly controlled by the water and blood content of tumors. For simulation, electromagnetic simulator software is used. The experiment is conducted using commercial Ultrawide-Band (UWB) transceivers, Neural Network (NN) based Pattern Recognition (PR) software for imaging and homogenous breast phantom. The 3D homogeneous breast phantom and tumors are fabricated using pure petroleum jelly and a mixture of wheat flour and water respectively. The simulation and experimental setups are performed by transmitting the UWB signals from one side of the breast model and receiving from opposite side diagonally. Using discrete cosine transform (DCT) of received signals, we have trained and tested the developed experimental Neural Network model. In 3D breast model, the achieved detection accuracy of tumor existence is around 100%, while the locating accuracy in terms of (x, y, z) position of a tumor within the breast reached approximately 89.2% and 86.6% in simulation and experimental works respectively. For classification, the permittivity and conductivity detection accuracy are 98.0% and 99.1% in simulation, and 98.6% and 99.5% in experimental works respectively. Tumor detection and type specification 3D may lead to successful clinical implementation followed by saving of precious human lives in the near future.

A FREE-SPACE METHOD FOR COMPLEX PERMITTIVITY MEASUREMENT OF BULK AND THIN FILM DIELECTRICS AT MICROWAVE FREQUENCIES

A free-space, non-destructive method for measuring the complex permittivity of a double-layer bulk dielectrics and thin fllm oxide layers at microwave frequencies have been developed. The method utilizes a spot-focusing antenna system in conjunction with a vector network analyzer in the range of 18{26GHz. The bulk dielectric was measured using the Transmission Method and Metal-Backed Method, while the Metal-Backed Method was used to investigate the thin fllms. Both types of samples were sandwiched between two quarter-wavelength Te∞on plates to improve the mismatch at the frequencies of measurement. The thin fllm sample arrangement was backed by an additional metal plate. The double-layer bulk dielectric samples were Te∞on-PVC and Plexiglas-PVC, while the thin fllm samples consisted of SiO2 layers of difierent thicknesses grown on doped and undoped Si wafer substrates. The relative permittivity obtained for PVC ranged between 2.62 to 2.93, while those for Plexiglas exhibited values between 2.45 to 2.63. The relative permittivity of SiO2 deposited on these wafers was between 3.5 to 4.5. All these values are in good agreement with published data. The advantage of the method is its ability to measure the dielectric properties of the fllms at the mid- frequency band irrespective of the substrate type used. Simulations of the measurement setup were carried out using CST Microwave Studio and the simulation results agreed closely with the measurements.

A free-space method for measurement of complex permittivity of double-layer dielectric materials at microwave frequencies

Two methods for the calculation of complex permittivity of double-layer dielectric materials measured by a spot-focusing free-space measurement system have been developed. Standard materials have been used to test these methods and further works will be carried out on SiO2 wafer. The dielectric constants obtained were close to the published values. The two methods developed are Transmission Method and Metal-Backed Method. The S11, S21, and S22 are measured for Transmission Method, while only S11 is measured for Metal-Backed Method. In both methods, the samples are sandwiched between two Teflon plates which are quarter wavelength at mid-band frequency. Results are reported in the frequency range of 18–26GHz.

Cross polarization ratio analysis of circular polarized patch antenna

Cross polarization ratio (CPR) analysis can be used to determine the quality of circular polarization of an antenna as compared to the commonly used axial ratio (AR) analysis. The analysis is independent of E-field left and right polarity measurement which requires two circular polarized reference antennas of left and right. Through CPR, the quality of circular polarization of an antenna can be measured from a reference linear polarity antenna. A low complexity 2.4 GHz circular polarized truncated corner patch antenna is designed and fabricated on printed circuit board (PCB) to show the simple process to analyse circular polarization quality of the antenna. Simulation result is compared to the theoretical considerations and measurement of ratio and E-field results.

Fabrication and Characterization of PZT Thin Film Capacitors for MMIC Applications

This paper reports on the use of thin lead zirconate titanate (PZT) films for monolithic microwave integrated circuit (MMIC) capacitors to replace existing materials for better size-reduction. The films were sputtered on Pt/Ti/SiO2 coated, undoped silicon wafers. Square Pt electrodes with sides ranging from 10 mum to 50 mum were patterned on the PZT layers to form the capacitors. Results of this study show that PZT thin films can be utilized for efficient size reduction in MMIC. The linewidth obtained for a 50 Omega transmission line is merely 300 nm - this results in a size reduction of approximately five times compared to conventional MMIC. For a 50 times 50 mum electrode area, capacitance values ranging from 5 to 20 pF were obtained at frequencies up to 20 GHz. Suitable de-embedding of S parameters using Cascade microwave probes revealed films with relative permittivities of the order of 100 to 500

Synthesis of a single side access ring resonator for higher order bandpass filters

A single-side-access ring resonator topology is presented. It employs a single quarter-wavelength coupled-line that couples to a one-wavelength ring to exhibit a single-mode resonance with transmission zeros. A global synthesis is presented, in order to control the transmission zeros in its response. As the transmission zeros of the ring resonator maintains their positions when multiple identical rings are used, the global synthesis can further be used for the design of higher order fllters with multiple rings. Furthermore, since only one coupled-line is used in the resonator topology, only one section of line is present in the ring, other than the coupled-line. Hence, there will be no second section of the ring that needs to be adjusted to obtain the symmetrical response during its realization, as compared to other types of ring topologies. To show the advantage of the synthesis, it is applied in the design of higher order ring-based bandpass fllters, which also involve extra quarter-wavelength coupled-lines to create additional poles. Five bandpass ring fllters up to 5th-order were realized using microstrip technology, and measured to validate the proposed concept. Measurement results showing good agreement with those from the simulation are also presented throughout the paper.

Modeling and simulation of sol-gel thin films for monolithic microwave integrated circuit applications

This paper reports on the feasibility study of using sol gel lead zirconate titanate for monolithic microwave integrated circuit (MMIC) thin film capacitors. The films were modeled as thin film microstrip lines (TFMS) and their microwave behaviour was simulated using a commercially available electromagnetic simulator Sonnet. The capacitances were calculated for film thicknesses ranging from 0.1 - 0.3 /spl mu/m and with dielectric constant from 100 - 1000 over the frequency range of 1 to 100 GHz. In addition, the characteristic impedances of various TFMS lines were also calculated for different line widths. For a 500 dielectric constant/1 /spl mu/m film thickness structure, the width obtained for a 50 /spl Omega/ is less than 1 /spl mu/m. Results of this study show that the proposed sol-gel material can be used for efficient size reduction in MMIC.

Preliminary studies on the use of natural rubber in the design of flexible microstrip antennas

In this paper, we report the first attempt to use natural rubber as a substrate in the design of flexible microstrip patch antennas. The effects of dielectric properties of rubber on the performance of microstrip patch antennas are presented. The patch geometry has been designed and optimized at a frequency of 10 GHz. It has been found that for a fixed substrate thickness, the antenna directivity and return loss decrease with increasing relative permittivity. However for a given permittivity, increasing the substrate thickness will result in lower return loss but higher directivity. Hence, some trade-off must be made between these parameters in order to obtain an optimum design.

Microwave non-destructing testing of rubber at X-band

In this paper, the measurement of complex dielectric constant of natural rubber at microwave frequencies is reported. A free space, non-destructive technique was used to measure the parameter for several rubber samples at X band. The samples were prepared using different amounts of carbon filler to alter the dielectric properties so that the relation between filler content and ε_r can be investigated. Our studies show that ε_r and tan δ increase with the filler content. In addition, ε_r showed a decreasing trend, while tan δ increased with frequency.