Noor Hasimah Baba

Bio: Noor Hasimah Baba is an academic researcher from Universiti Teknologi MARA. The author has contributed to research in topics: Microstrip antenna & Dielectric. The author has an hindex of 8, co-authored 34 publications receiving 210 citations.

A Free-Space Method for Complex Permittivity Measurement of Bulk and Thin Film Dielectrics at Microwave Frequencies

Abstract: 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.

Circular patch antenna on metamaterial

Abstract: This paper recommends a compact circular antenna on metamaterial substrate for C-band applications The antenna has been designed to improve the performance of gain directivity, return loss and size The size of the new metamaterial antenna has been reduced by a factor of 24 and the gain directivity was increased from 417 dBi in conventional design on Flame Retardant 4 (FR-4) to 566 dBi in the new approach A better return loss was obtained from the metamaterial antenna which is −242 dB compared to −2208 from the conventional antenna By analyzing the radiation pattern, the metamaterial antenna has a sharp focus to the targeted direction The compact antenna is expected to improve the cost of production due to the size reduction in a mess production

Rectangular microstrip patch antenna with EBG structure

Abstract: This paper presents a rectangular microstrip patch antenna with EBG structure. The combination of the rectangular microstrip patch antenna fabricated on the top of the substrate Rogers RO3003 with Electromagnetic Band Gap (EBG) structures at the ground plane is proposed to investigate the metamaterial characteristics in antenna design for satellite application. The patch antenna along with the EBG structure is designed to resonate at 7.3 GHz. Simulations and measurements have been carried out to verify the performance of EBG structures in patch antenna. All the simulation and measurement work is done by using Computer Simulation Technology Microwave Studio (CST-MWS) and Vector Network Analyzer (VNA) respectively. Metamaterial characteristics which exhibit negative permittivity and permeability of the proposed EBG structures have been verified using Nicolson-Ross-Weir (NRW) method. As a result of combining the rectangular patch with EBG structure, the bandwidth of the antenna has been increased by 39.63% and the size of the antenna reduced by 22.38% compared to the antenna without EBG. The return loss also met the specification of −10 dB cut off.

Design and Application of the CSRR-Based Planar Sensor for Noninvasive Measurement of Complex Permittivity

Abstract: A novel microwave noninvasive planar sensor based on the complementary split ring resonator (CSRR) is proposed for an accurate measurement of the complex permittivity of materials. The CSRR is etched in the ground plane of the planar microstrip line. Two CSRRs of rectangular and circular cross-sections are chosen for the sensitivity analysis, where the later is found to possess higher sensitivity and hence appears to be more appropriate for the sensor design. At resonance, the electric field induced along the plane of CSRR is found to be quite sensitive for the characterization of specimen kept in contact with the sensor. A numerical model is developed here for the calculation of the complex permittivity as a function of resonant frequency and the quality factor data using the electromagnetic simulator, the Computer Simulation Technology. For practical applications, a detailed air gap analysis is carried out to consider the effect of any air gap present between the test sample and the CSRR. The designed sensor is fabricated and tested, and accordingly the numerically established relations are experimentally verified for various reference samples e.g., teflon, polyvinyl chloride, plexiglas, polyethylene, rubber, and wood. Experimentally, it is found that the permittivity measurement using the proposed sensor is possible with a typical error of 3%.

Analysis of the Nicolson-Ross-Weir Method for Characterizing the Electromagnetic Properties of Engineered Materials

Abstract: A method for predicting the behavior of the permittivity and permeability of an engineered material by examining the measured S-parameters of a material sample is devised, assuming that the sample is lossless and symmetric. The S-parameter conditions under which the material parameters extracted using the Nicolson-Ross-Weir method may be associated with a lossless homogeneous material are described. Also, the relationship between the signs of the real and imaginary parts of the permittivity and permeability are determined, both when the extracted material parameters are real and when they are complex. In particular, the conditions under which metamaterials exhibit double-negative properties may be predicted from the S-parameters of a metamaterial sample. The relationships between material characteristics and the S-parameters should prove useful when synthesizing materials to have certain desired properties. Examples, both from experiment and simulation, demonstrate that the relationships may be used to understand the behavior of several different categories of engineered materials, even when the materials have appreciable loss.

Multi-Band RF Planar Sensor Using Complementary Split Ring Resonator for Testing of Dielectric Materials

Abstract: In this paper, an attractive multi-band RF planar sensor, suitable for non-destructive testing of dispersive materials, is proposed. The proposed sensor is based on a number of complementary split ring resonator (CSRR) unit cells etched in the ground plane of the microstrip line. Each CSRR unit cell can be represented by a narrow band reject filter with its center frequency corresponding to the resonant frequency of the respective CSRR cell. The proposed technique is used to design the two, three and four band microwave sensors operating at 1.5 GHz, 2.45 GHz, 3.8 GHz, and 5.8 GHz. The distance between the two adjoining CSRRs is minimized for each case without appreciably increasing the inter-cell coupling effect. The transcendental equations required for determining the complex permittivity of the material under test in terms of the resonant frequency are derived from the numerical data obtained using the electromagnetic solver, the CST studio. These numerical equations are then used to obtain the dielectric properties of various test samples, which are measured using the vector network analyzer. The detailed air gap analysis is also performed for checking the accuracy of the designed planar sensor under the real situation. The proposed sensors are fabricated on 0.8 mm thick FR4 substrates using the standard photolithography technique. A number of standard samples are tested using the fabricated sensors in multiple frequency bands, and a good agreement between the obtained results and the data available in literature shows the applicability of the proposed scheme.

Earthquakes magnitude predication using artificial neural network in northern Red Sea area

Abstract: Since early ages, people tried to predicate earthquakes using simple observations such as strange or atypical animal behavior. In this paper, we study data collected from past earthquakes to give better forecasting for coming earthquakes. We propose the application of artificial intelligent predication system based on artificial neural network which can be used to predicate the magnitude of future earthquakes in northern Red Sea area including the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez. We present performance evaluation for different configurations and neural network structures that show prediction accuracy compared to other methods. The proposed scheme is built based on feed forward neural network model with multi-hidden layers. The model consists of four phases: data acquisition, pre-processing, feature extraction and neural network training and testing. In this study the neural network model provides higher forecast accuracy than other proposed methods. Neural network model is at least 32% better than other methods. This is due to that neural network is capable to capture non-linear relationship than statistical methods and other proposed methods.

Buried Object Characterization Using Ultra-Wideband Ground Penetrating Radar

Abstract: In this paper, a method to characterize buried nonmagnetic objects in ground using ultra-wideband (UWB) ground penetrating radar (GPR) is proposed. In this method, UWB pulses are radiated by the radar, while scattered signals from the ground with the buried object are received. The received signals are then post-processed to estimate the depth, thickness, and electrical properties of the buried object. A constant depth and thickness is enforced at all frequencies while the signals are processed to extract the buried object characteristics, resulting in more accurate estimations and reduced processing time. In addition, path loss due to the close proximity of the radar to the ground is compensated analytically. The applicability of the proposed method is validated with several planar objects and a boulder that we typically encounter in the construction industry. The proposed method can achieve sufficient reliability in estimating the permittivity of buried objects for the purpose of material identification. Incorporating the proposed method into the GPRs enhances their existing imaging ability by adding material identification capability.