Mohammed S. Bin-Melha

A Frequency Tunable PIFA Design for Handset Applications.

A frequency tunable planar inverted F antenna (PIFA) is presented for use in the following bands: DCS, PCS, and UMTS. Initially, the tuning was achieved by placing a lumped capacitor, with values in the range of 1.5 to 4 pF, along the slot of the radiator. The final tuning circuit uses a varactor diode, and discrete lumped elements are fully integrated with the antenna. The antenna prototype is tunable over from 1850 MHz to 2200 MHz, with an associated volume of 21×13.5×5 mm3, making it suitable for potential integration in a commercial handset or mobile user terminal.

Improved multi-antenna system capacity using beamformer weights

Beamforming is used to achieve diversity gain. It is a technique in diversity to remedy power penalty due to channel fading. The beam-weights for multi-antenna system are evaluated for two different approaches. These weights are then used to weight the signal beams of each transmit antenna branch. Results reveal that by exploiting the transmit channel substructures exposed by the singular vector decomposition algorithm, the capacity of a multi-antenna system can be enhanced.

MIMO Wavelet Transform using Optimized Successive Interference Cancellation

This research introduces a physical layer technique to enhance the capability of MIMO wavelet systems by using successive interference cancellation which enables the receiver to decode simultaneous data packets. The received power of the data packet was introduced to further optimize the receiver’s decision capability. Results show that a Discrete Wavelet Transform-based MIMO system with interference cancellation provides a performance gain as compared to a theoretical 2x2 MIMO channel in terms of BER vs. SNR performance. The performances of two different techniques have been evaluated in this work using interference cancellation both with and without consideration of received signal power.

Effects of Transmit Diversity on a Discrete Wavelet Transform and Wavelet Packet Transform-based Multicarrier Systems

This paper proposes a MIMO-WPT-based multicarrier system with feedback from the receiver to the transmitter carrying the channel state information (CSI), whereby a steering matrix can be defined to enhance robust performance against multipath fading effects at the receiver. This relies on the time-scale localization of wavelet bases, and is demonstrated in terms of bit error rate performance. In contrast to sinusoidal carriers WP have very narrow side lobes, with most energy contained in the main lobe; this makes the proposed system less susceptible to inter-carrier interference. The main contribution of this work is the evaluation of system parameters using different wavelet families, order of filters and number of elements to balance overall performance and cost of the system, and to provide a reliable system with a high data-rate.

Liquid level monitoring using passive RFID tags

Tank flooding have become major causes of pollution both in residential and industrial areas majorly caused by overflows of water(mostly residential) and volatile poisonous industrial liquids from the storage tanks. An effective way of avoiding this problem will be by deploying some mechanism to monitor liquid level at each point in time and escalating unusual liquid levelsto a pump control circuit or to the relevant authorities for prompt action to avoid a flooding occurrence. This paper presents a low cost power efficient liquid level monitoring technique. Passive RFID tags are designed modelled and deployed, the signal variation from the Alien Reader Software are used to effectively estimate the level of liquid in any surface or underground tank. The experimental set up is presented and an expository presentation is made of the passive tag design, modelled and simulated and adopted for same application.

Two Miniaturized Printed Dual-Band Spiral Antenna Designs for Satellite Communication Systems

Two novel reduced-size, printed spiral antennas are proposed for use in personal communications mobile terminals exploiting the “big low earth orbit” (Big-LEO) satellite system (uplink 1.61–1.63 GHz; downlink 2.48–2.5 GHz). The two proposed antenna give 3.12―6.25% bandwidth at lower resonant mode of 1600MHz, while at the higher resonant mode of 2450MHz a bandwidth of around 6% is obtained. The experimental and simulated return losses of the proposed antennas show good agreement. The computed and measured gains, and axial ratios are presented, showing that the performance of the proposed two antennas meets typical specifications for the intended applications.

On the Wavelet Families for OFDM System - Comparisons over AWGN and Rayleigh Channels

In the study of OFDM systems, discrete wavelet transforms have been reported to perform better than Fast Fourier Transform in multicarrier systems (MCS) - in terms of spectral efficiency because they can operate without a cyclic prefix, have reduced side-lobes and improved BER. However all of the wavelet families do not perform alike. This study has investigated various wavelet families such as Daubechies, Symlet, Haar (or db1), biorthogonal, reverse-biorthogonal and Coiflets for OFDM system design over an AWGN and multipath channels. Results show that Daubechies, Symlet, Haar and Coiflet wavelet families perform considerably better than other families considered, thus these families could be better in OFDM.