Ban-Leong Ooi

Novel design of broad-band stacked patch antenna

A novel broadband stacked E-shaped patch antenna is proposed in this paper. The proposed antenna has an input impedance bandwidth of about 38.41%, better than the conventional E-shaped microstrip patch antenna, which has an input impedance bandwidth of 33.8%. Through the use of the washer on the probe of the stacked patch antenna, the input impedance bandwidth is improved further to 44.9%. The radiation patterns are found to be relatively constant throughout the whole band. Comparisons of these antennas are presented in this paper.

A miniaturized dual-mode ring bandpass filter with a new perturbation

A miniaturized dual-mode ring bandpass filter at 1.45 GHz with a bandwidth of 6% is demonstrated. The perturbation of the dual modes is realized by a pair of local ground defects. The miniaturization is achieved by loading the peripheral of the ring with the butterfly radial stub structure. A 41% loading factor has been achieved using this method. The simulated and measured results are in good agreement.

A modified microstrip circular patch resonator filter

Circular holes are etched off a microstrip disk resonator. This results in a size reduction of 30%. By offsetting the positions of some of these holes, a degenerate orthogonal mode is excited, resulting in a split-mode bandpass filter. This filter can be considered as a lattice-type structure. A filter with a bandwidth of 8% centered at 2.0 GHz was designed. The measured insertion loss is 0.6 dB.

A compact wideband hybrid dielectric resonator antenna

A novel wideband hybrid dielectric resonator antenna structure comprises a rectangular dielectric resonator (DR) and a coplanar waveguide (CPW) inductive slot is proposed. In this configuration, the CPW inductive slot simultaneously acts as an effective radiator and the feeding structure of the DR. Dual resonances of the two radiators are merged to extend the antennas bandwidth. A parametric study is performed to optimize the antenna performance and a prototype for 5-GHz WLAN application has been built and tested.

An improved prediction of series resistance in spiral inductor modeling with eddy-current effect

Based on an earlier study by Kuhn and Ibrahim (see IEEE J. Trans. Microwave Theory Tech., vol. 49, no. 1, p. 31-38, 2001) on current crowding, an improved expression incorporating the skin effect for the prediction of series resistance in spiral inductor modeling has been derived. A modified model for the spiral inductor, which accounts for the eddy-current effect, is thus proposed. Relatively good agreements between the measured data and the results generated from the model are obtained.

Design of 60- and 77-GHz Narrow-Bandpass Filters in CMOS Technology

This paper investigates the design and implementation of millimeter-wave narrow-bandpass filters in a standard 0.18- m CMOS technology. Filters with a measured 10% 3-dB bandwidth at 60 and 77 GHz are realized in a thin-film microstrip structure by using the lowest metallization layer as a ground plane. The impact of dissipation losses of the filters is also examined. It is found that the metallization losses in the coupled-line filter as well as the ground plane are the main reasons for the insertion loss.

A novel approach for determining the GaAs MESFET small-signal equivalent-circuit elements

A simple way of extracting the small-signal equivalent circuit of a MESFET is proposed. The intrinsic elements and one of the extrinsic parameters are described as functions of the remaining extrinsic parameters. This drastically reduces the search space and the number of unknowns for optimization. It provides an important new insight into the correlation between the various extrinsic and intrinsic parameters. The method also reveals that there are two sets of solution for the parameters R/sub s/ and L/sub s/ which can fully satisfy the global solution. A numerical comparison in terms of both accuracy and speed between the proposed method and some conventional methods on a 400-/spl mu/m gatewidth GaAs MESFET is presented.

Experimental Characterization of the Effect of Metal Dummy Fills on Spiral Inductors

In modern CMOS technologies, metal dummy fills are required to maintain metal density uniformity and to planarize the layers. As frequency increases, the effect of the metal dummy fills on the CMOS integrated circuits or components should be taken into account. This work presents experimental results of the effect of metal dummy fills on the microwave behavior of spiral inductors fabricated in a standard 0.18-mum CMOS technology. The influences on the equivalent model parameters and the Q-factor are characterized based on measured S-parameters of inductors with and without metal dummy fills.

A modified contour Integral analysis for Sierpinski fractal carpet antennas with and without electromagnetic band gap ground plane

A modified contour integral method coupled with segmentation method has been used, for the first time, to analyze both the Sierpinski fractal carpet (SFC) antennas of different orders and an SFC antenna with electromagnetic band gap (EBG) ground plane. The close agreement between the calculated and measured results for resonant frequencies and input return losses indicates that this technique can be used to accurately predict the impedance characteristic. A novel stacked microstrip Sierpinski carpet fractal antenna using the EBG ground plane is also presented. Comparing to an ordinary microstrip fractal antenna, which has a maximum bandwidth of approximately 2%, the proposed antenna has a higher input impedance bandwidth of nearly 9%. The radiation patterns of the proposed antenna are improved due to the removal of unwanted radiation caused by the surface wave. The experimental measurement results of the proposed antenna are presented in this paper.

Compact EBG in-phase hybrid-ring equal power divider

A novel electromagnetic-bandgap (EBG) in-phase hybrid-ring equal power divider is described. Coupled with the closed-form analytical expressions for the EBG structure, a systematic technique of design is presented for the first time. Compared to the conventional hybrid-ring equal power divider, based on the 15-dB return-loss criteria, an increase in both the input and output impedance bandwidth of approximately 10% from a starting frequency of 2.5 GHz, and a phase error of 0.006/spl deg/ within the passband have been achieved for the proposed structure. The proposed in-phase hybrid-ring equal power divider, besides providing a much broader bandwidth and occupying a smaller estate area, also possesses good harmonic suppression characteristic.