Noor Hasimah Baba

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.

Circular patch antenna on metamaterial

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 2.4 and the gain directivity was increased from 4.17 dBi in conventional design on Flame Retardant 4 (FR-4) to 5.66 dBi in the new approach. A better return loss was obtained from the metamaterial antenna which is −24.2 dB compared to −22.08 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.

Performance analysis for Estimation of signal Parameters via Rotational Invariance Technique (ESPRIT) in estimating Direction of Arrival for linear array antenna

Smart antenna refers to any type of antenna arrays combined with signal processor components which can adjust its own beam pattern in order to emphasize on the signal of interest and minimizing the interference signal. The accurate estimation of direction of interest which is also known as direction of arrival (DOA) of the incident signals is very significant to produce beam from antenna. There are several algorithms those have the ability in calculating the DOA of the incidents signals. In this paper an adaptive antenna is applied by using the most frequent used algorithm, estimation of signal parameters via rotational invariance technique (ESPRIT) to obtain the direction of arrival (DOA) of any incident signals. The exact number of samples and elements used is the most important parameter in the algorithms in order to sustain the accuracy of the direction of arrival of the incident signals. The optimization was done by running the program in cellular mobile environments. The data from the optimization was evaluated using SPSS in evaluating the performance of the algorithm.

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.

A free-space method for measurement of complex permittivity of silicon wafers at microwave frequencies

A non-destructive, non-contact technique has been developed to characterize p-type and n-type silicon semiconductor wafers at microwave frequencies. The measurement system consists of a pair of spot-focusing horn lens antennas, mode transitions, coaxial cables and a vector network analyser (VNA). In this paper, the free-space reflection and transmission coefficients, S/sub 11/ and S/sub 21/, for a normally incident plane wave, are measured for a silicon wafer sandwiched between two teflon plates which are quarter-wavelength at midband. The actual reflection and transmission coefficient, S/sub 11/ and S/sub 21/, of the silicon wafers are calculated from the measured S/sub 11/ and S/sub 21/ of the teflon plate-silicon wafer-teflon plate assembly in which the complex permittivity and thickness of the teflon plates are known. From the complex permittivity, the resistivity and conductivity can be obtained. Results are reported in the frequency range of 11-12.5 GHz. The values of the dielectric constant obtained were close to published values for silicon wafers.

Earthquake prediction technique based on GPS dual frequency system in equatorial region

The ionospheric Total Electron Content (TEC) measurements were investigated at Universiti Teknologi Malaysia, UTMJ on 20 February - 20 March 2007. The observation was made 14 days before earthquake and 14 days after earthquake. TEC is extracted using GPS dual frequency data which in RINEX format that supplied by JUPEM (Jabatan Ukur dan Pemetaaan Malaysia). In order to reveal possible earthquake precursor through the changes variation of TEC reading, Southern Sumatra Indonesia earthquake that happened on 6th March 2007 is chosen as a study case. The results show that satellite facilities may detect earthquake precursors in ionosphere 5-11 days or a few hours before main shock and various grounds based or satellite observation have shown strong perturbation of the ionosphere after earthquake. The results show a good agreement with other researchers who studied other earthquakes.

Microwave Characterization of Silicon Wafer Using Rectangular Dielectric Waveguide

A non-destructive and easy to use method is presented to characterize p-type and n-type silicon semiconductor wafers using a rectangular dielectric waveguide measurement (RDWG) system. The measurement system consists of a vector network analyzer (VNA), a pair of coaxial cable, coaxial to waveguide adapter and dielectric-filled standard gain horn antenna. In this method, the reflection and transmission coefficients, S11 and S21 were measured for silicon wafer sandwiched between the two Teflon, the dielectric that filled the standard gain horn antenna. It was observed that, the dielectric constant of the silicon wafers are relatively constant, varying slightly over the frequency range of 9 to 12 GHz. The loss factor, loss tangent and conductivity of the doped wafers are higher than the undoped type

Microwave non-destructive testing of semiconductor wafers in the frequency range 8-12.5 GHz

Microwave non-destructive testing (MNDT) using free-space microwave measurement (FSMM) system involve measurement of reflection (S/sub 11/) and transmission (S/sub 21/) coefficients in free-space. The measurement system consists of a pair of spot-focusing horn lens antenna, mode transitions, coaxial cables and a vector network analyzer (VNA). The inaccuracies in free-space measurements are due to two main sources of errors. 1) Diffraction effects at the edges of the material specimen. 2) Multiple reflection between horn lens antennas and mode transitions via the surface of the sample. The spot-focusing antennas are used for minimizing diffraction effects and free-space LRL (line, reflect, line) calibration method implemented on VNA eliminates errors due to multiple reflections. The time domain gating or smoothing feature of VNA is used to reduce post calibration errors in reflection and transmission measurements. In this paper, complex reflection coefficients were measured using FSMM system for silicon wafers backed by a metal plate. It was observed that the dielectric constants of the silicon wafers are higher than the values reported for intrinsic silicon wafers which maybe due to the presence of highly conductive epitaxial layer doped on the wafers. Results are reported in the frequency range of 8.0-12.5 GHz.

Design of hairpin band pass filters for K-Band application

This paper presents Chebyshev three and four poles microstrip hairpin filter for radar applications. The filters are operated at K-band frequency segment of 20-20.3 GHz. The filters were designed using Genesys software and implemented on Roger 5870 substrate. The results from simulation and measurement show that both filters were operating at the desired specification. Based on the experimental analysis, it was observed that the filter with four elements better than the three which was quite agree to other researchers.

A free-space measurement of complex permittivity of doped silicon wafers using transmission coefficient at microwave frequencies

A contactless and non-destructive method is presented to characterize p-type and n-type silicon semiconductor wafers using a spot-focused free-space measurement system. In this method, the free-space reflection and transmission coefficients, S11 and S21, are measured for silicon wafer sandwiched between two teflon plates which are quarter-wavelength at mid-band. The actual reflection and transmission coefficient, S11 and S21 of the silicon wafers are then calculated from the measured S11 and S21 by using ABCD matrix transformation in which the complex permittivity and thickness of the teflon plates are known. Complex permittivity are computed using only the transmission coefficient, S21. From the complex permittivity, the resistivity and conductivity can be obtained. Results are reported in the frequency range of 9–12.5 GHz. The dielectric constant obtained were close to published values for silicon wafers and the resistivities agree well with that measured by other conventional method.