Zuhani Ismail Khan

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.

Analysis of performance for multiple signal classification (MUSIC) in estimating direction of arrival

Array processing involves manipulation of signals induced on various antenna elements. Its capabilities of steering nulls to reduce co channel interferences and pointing independent beams toward various mobiles, as well as its ability to provide estimates of directions of radiating sources, make it attractive to a mobile communication system designer. In this paper MUSIC algorithm was implemented in Matlab to optimize the number of samples and number of elements with the presence of noise. The optimization was conducted in different configurations to improve the performance of the algorithm in estimating the direction of arrival (DOA) of the incident signals. The data captured was analysed in order to obtain the real performance of the algorithm by using statistical analysis.

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.

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.

Multilayer dual-mode dual-band bandpass filter

This paper presents a single ring resonator using multilayer technique for dual-band bandpass filter. The resonator is composed of two resonators with each one having a quarter-wavelength coupled-line connected in series to a transmission line. The two resonators are arranged in parallel to form a single ring dual-band bandpass filter topology. The controlling impedance parameters of this ring are Zr for the transmission line and even- and odd-mode characteristic impedances i.e. Zoe and Zoo for the coupled-lines. Observations on the controlling parameters are conducted to investigate the effect of each parameters in terms of bandwidth, matching level and the transmission zeros. For validation, the filter is realized using multilayer technique, designed at 2 GHz on FR-4 microstrip substrate. The results exhibited good isolation between the two passbands with centered transmission zero attenuated above 40 dB while the centered frequencies were found at 1.59 GHz in the first passband and 2.41 GHz in the second passband. The simulated and measured result is presented throughout this paper to validate the concept.

Dual-band dual-mode bandpass filter using seriescoupled ring resonators

This paper proposed a dual-band ring filter using two identical microstrip dual-mode ring resonators. The rings are cascaded in series side-by-side via a single quarter wavelength coupled-line forming two transmission poles which are distributed in each passband. Meanwhile, the coupled-line positioned in between the two rings help to create the center transmission zero which can be used to control the rejection level of the in-between isolation. The characteristics of the dual-band filter in terms of bandwidth, passband and out-of-band responses are controlled by the line impedances of the rings and the odd-and even-mode impedances of the coupled-line. Finally, to verify the concept, a prototype of a dual-band dual-mode filter is designed using EM simulator, fabricated on 1.63-mm-thick Tachonic substrate and measured. The resonant frequencies of the two passbands are found at 1.73 GHz and 2.37 GHz while the center transmission zero is found at 2.04 GHz.

Microwave ring resonator with a quarter-wavelength coupled-line integration

This paper proposes a novel topology of one-wavelength microstrip ring resonator which integrates a single quarter-wavelength parallel coupled-line as one of its input/output points. Such topology results in a single mode response with zero transmission at both sides of the bandpass. A complete simplified diagram of the proposed topology is developed and presented in this paper. An example of realization is performed using microstrip technology on FR4 epoxy glass substrate to verify the feasibility of the proposed idea. Measured results show good agreement with the ones from simulation.

Dual-band bandpass filter with rectangular shaped defective ground structure

A rectangular shaped defective ground structure (DGS) is proposed to enhance the response of an existing design of a dual-band bandpass filter topology. In this paper, the filter design is based on parallel-coupled lines connected to transmission lines. The filter consists of characteristics impedances of the transmission line represented by Zr, even-mode, Zre and odd-mode, Zro. The variation of the DGS positions and dimensions are realised and the effects on the response of the filter are analysed. It is found that an implementation of a rectangular shaped DGS in this topology improves the steepness of the response for both bands with centre frequencies at 1.22 GHz and 2.62 GHz. The optimised length and width of the DGS are 42 mm and 11.25 mm respectively, positioned at the upper and bottom centres of the ground plane. The simulated and measured results of the filter are compared where good agreement is achieved.

Reconfigurable ring filter with controllable frequency response.

Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GHz to 1.38 GHz spreading over 280 MHz frequency range. Both designs are found to be compact with acceptable insertion loss and high selectivity.Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GHz to 1.38 GHz spreading over 280 MHz frequency range. Both designs are found to be compact with acceptable insertion loss and high selectivity.

A dual-band microstrip filter topology based on quarter-wavelength coupled-lines inter-connections

A dual-band bandpass filter topology based on coupled-lines is presented. In the topology, two identical coupledlines are cascaded in series and duplicated in parallel. There are then ended with another two identical coupled-lines. The dual-path structure exhibits a 2nd order dual-band response with three transmission zeros that separate the passbands from each other, and from the rejection band. The odd- and even-mode impedances of the coupled-lines control the bandwidth, passband and out-of-band responses of the dual-band filter. Finally, to verify the concept, a prototype of a dual-band bandpass filter is designed using EM simulator, fabricated on 1.6-mm-thick FR-4 substrate and measured. The resonant frequencies of the two passbands are centered at 1.82 GHz and 2.38 GHz.