Robiatun A. Awang

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.

Meta-atom microfluidic sensor for measurement of dielectric properties of liquids

High sensitivity microwave frequency microfluidic sensing is gaining popularity in chemical and biosensing applications for evaluating the dielectric properties of liquid samples. Here, we show that a tiny microfluidic channel positioned in the gaps of a dual-gap meta-atom split-ring resonator can exploit the electric field sensitivity to predict the dielectric properties of liquid samples. Employing an empirical relation between resonant characteristics of the fabricated sensor and the complex permittivity of water-ethanol or water-methanol mixtures produces good congruence to standardized values from the literature. This microfluidic sensor offers a potential lab-on-chip solution for liquid dielectric characterization without external electrical connections.

Mechanically tolerant fluidic split ring resonators

Flexible resonators are crucial elements for non-planar, conformal and curved or movable surfaces in flexible high frequency electronic environments. Here, we demonstrate a stretchable, bendable, twistable and reversibly deformable split ring resonator (SRR) operating at ~3 GHz. The mechanical and electrical performance of the SRR was achieved by encapsulating liquid metal (galinstan) in a microfluidic channel of highly elastic polydimethylsiloxane. Applying mechanical deformation (bending, stretching and twisting) to the SRR results in minimal deviation of the transmission response. This offers a stable and predictable response for flexible electronic applications where mechanical deformation or conformity is inherent.

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.

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.

Elastomeric composites for flexible microwave substrates

Manipulating dielectric properties of polydimethylsiloxane(PDMS) is an important consideration for flexible, low-loss device design. This paper presents a method for reducing dielectric loss (tan δ) by forming PDMScomposites loaded with various concentrations of either alumina (Al2O3) or polytetrafluoroethylene (PTFE) particles. The structural, mechanical, and electrical properties of the composites are investigated. Theoretical mixing models were used to predict the relative permittivity (er) of PDMScomposites, and good similarity with the measured er was observed. The incorporation of either low dielectric loss filler in the PDMS matrix (up to 50 wt. % filler loading) is shown to reduce the dielectric loss while maintaining the flexibility of the host matrix. The fillers can also control the permittivity of the composite, either increasing or decreasing relative permittivity from that of PDMS. Interestingly, a strain of ∼500% can be applied to 15 wt. % PDMS/PTFE composites, compared with ∼350% for pure PDMS.

3D simulation and measurements of free space characterization for silicon wafers at K-band

This paper describes the 3D simulation and measurements of free space characterization for the complex permittivity of p-type and n-type doped silicon wafers at K-band. The component of this free space measurement system (FSMM) consists of Millitech series GOA Gaussian optics lens antennas, vector network analyzer (VNA) and a high performance workstation. The antennas were modeled and simulated using Computer Simulation Technology (CST) software. The thru, reflect and line (TRL) calibration technique were used to eliminate the effect of undesirable multiple reflections. The simulation and measurement results are presented where good agreements are observed.

Pneumatically tuned microfluidic meta-atom SRR

A fluidic split ring resonator (SRR) is proposed to achieve frequency tunability. An integrated microfluidic channel is employed in between the gaps of the fluidic SRR to harness pneumatic tuning by air injection/suction. An experimental investigation demonstrates that a frequency tuning of 3% can be achieved using air as the manipulating force to induce a small deflection in the SRR gap.

Polymeric microfluidic meta-atoms

High frequency components for flexible circuit applications require tolerance to mechanical variation to maintain stable performance. A polymeric SRR meta-atom with a wide gap in its liquid metal conductor is proven to exhibit frequency stability when subjected to mechanical strain. Additionally, a dual gap SRR meta-atom with a microfluidic channel integrated into its polymer structure is shown to have an electromagnetic response sensitive to a range of dielectric fluids.