Karim M. Nasr

A Reconfigurable Wideband and Multiband Antenna Using Dual-Patch Elements for Compact Wireless Devices

A reconfigurable wideband and multiband C-Slot patch antenna with dual-patch elements is proposed and studied. It occupies a compact volume of 50 × 50 × 1.57 (3925 mm3), including the ground plane. The antenna can operate in two dual-band modes and a wideband mode from 5 to 7 GHz. Two parallel C-Slots on the patch elements are employed to perturb the surface current paths for excitation of the dual-band and the wideband modes. Two switches, implemented using PIN diodes, are placed on the connecting lines of a simple feed network to the patch elements. Dual-band modes are achieved by switching “ON” either one of the two patch elements, while the wideband mode with an impedance bandwidth of 33.52% is obtained by switching “ON” both patch elements. The frequencies in the dual-band modes can be independently controlled using positions and dimensions of the C-Slots without affecting the wideband mode. The advantage of the proposed antenna is that two dual-band operations and one wideband operation can be achieved using the same dimensions. This overcomes the need for increasing the surface area normally incurred when designing wideband patch antennas. Simulation results are validated experimentally through prototypes. The measured radiation patterns and peak gains show stable responses and are in good agreements. Coupling between the two patch elements plays a major role for achieving the wide bandwidth and the effects of mutual coupling between the patch elements are also studied.

Compact Printed Multiband Antenna With Independent Setting Suitable for Fixed and Reconfigurable Wireless Communication Systems

This paper presents the design of a low-profile compact printed antenna for fixed frequency and reconfigurable frequency bands. The antenna consists of a main patch, four sub-patches, and a ground plane to generate five frequency bands, at 0.92, 1.73, 1.98, 2.4, and 2.9 GHz, for different wireless systems. For the fixed-frequency design, the five individual frequency bands can be adjusted and set independently over the wide ranges of 18.78%, 22.75%, 4.51%, 11%, and 8.21%, respectively, using just one parameter of the antenna. By putting a varactor (diode) at each of the sub-patch inputs, four of the frequency bands can be controlled independently over wide ranges and the antenna has a reconfigurable design. The tunability ranges for the four bands of 0.92, 1.73, 1.98, and 2.9 GHz are 23.5%, 10.30%, 13.5%, and 3%, respectively. The fixed and reconfigurable designs are studied using computer simulation. For verification of simulation results, the two designs are fabricated and the prototypes are measured. The results show a good agreement between simulated and measured results.

An application of smart antenna systems for archiving networks in TV studios

Data archiving networks and electronic media libraries for video and audio broadcasting have gained a large interest recently. This paper proposes the use of smart (adaptive) antennas for HIPERLAN/2 (HIgh PERformance Radio Local Area Network/2) in order to increase the data rate and user capacity targeting wired LAN replacement in modem TV broadcasting studio environments. Spatial channel models are necessary for the proper design, analysis and implementation of smart antenna systems. A simple 2D ray tracing indoor channel model for predicting propagation characteristics inside a room of arbitrary dimensions and wall properties is presented. The simulation model gives fast estimates of the power-delay profile (PDP) and direction of arrival (DOA) information based on the geometrical optics (GO) theory taking into account double reflections. The effects of the relative positions of the transmitter and the receiver, room dimensions as well as the number of transmitters are investigated.

A wall imperfection channel model for signal level prediction and its impact on smart antenna systems for indoor infrastructure WLAN

This paper presents a novel approach for the estimation of the local average signal level in an indoor environment based on a wall imperfection model. A ray-tracing tool based on the method of images with angular information, is first used to estimate the distribution of field strength (or coverage) in an arbitrary environment. The concept of spatial sampling is highlighted. The wall imperfection model is then introduced to study the sensitivity of the received signal level at an arbitrary location to imperfect wall positioning and electromagnetic material properties. An alternative approach to estimate the local mean signal level at a particular point is presented based on the wall imperfection model to reduce the computation time. The impact of the wall imperfection model on the patterns of a smart antenna system serving multiple users in an infrastructure WLAN is studied.

An optimum combiner for a smart antenna in an indoor infrastructure wireless local area network

The paper investigates the effect of the variation of the thermal noise level on the performance of an optimum combiner in an arbitrary indoor environment taking into account the multipath characteristics of the radio channel. An indoor infrastructure WLAN scenario with four users communicating with an access point is modeled using a deterministic 2D ray-tracing tool. A smart antenna optimum combiner is then developed for the case when the number of elements of a uniform linear antenna array is equal to the number of users, targeting capacity increase through space division multiple access (SDMA). The effect of the variation of thermal noise level (or SNR per antenna element) on the optimum combiner patterns as well on the obtained signal-to-interference-plus-noise ratio (SINR) values is investigated and compared for the multipath case as well as for the line of sight (LOS) only case.

A compact printed antenna for multiband wireless applications

This paper presents a design of a compact microstrip patch antenna with the ability of controlling the number of bands and the operating frequencies independently. The antenna comprises a main patch and four sub-patches fed by a 50Ω microstrip line. It is designed to generate up to five separate modes to cover the frequency range from 900 MHz to 3 GHz for the operation of wireless devices supporting multiple standards including Global System for Mobile communication (GSM900, 880–960 MHz), Digital Communication System (DCS1800, 1710–1880 MHz), Universal Mobile Telecommunication System (UMTS, 1920–2170 MHz), Wireless Local Area Network (WLAN, 2400–2483.5 MHz) and low band Worldwide Interoperability for Microwave Access (WIMAX, 2.5 to 2.8 GHz) The design verified through both numerical simulation and measurement of an experimental prototype.

Performance of different interpolation strategies for an OFDM/MMSE smart antenna system in an indoor WLAN

This paper assesses the performance of different interpolation strategies for an OFDM/MMSE smart antenna serving multiple users through space division multiple access (SDMA) in a wireless LAN following the IEEE 802.11a/e or HIPERLAN/2 standards. The frequency dependence of the channel transfer matrix and the weights is studied in indoor environments of different dimensions and for different coherence bandwidths using a ray-tracing tool. Interpolation is proposed to reduce the complexity of calculating the smart antenna weights at every OFDM subcarrier. The performance of different interpolation strategies is investigated in terms of complexity and signal to interference plus noise ratio (SINR) degradation relative to the case where the weights are calculated at every subcarrier. Simulation results agree with the expected behaviour showing that FFT based interpolation generally outperforms linear interpolation when the span between calculated subcarriers is less than 16. Channel transfer matrix based interpolation outperforms weight matrix based interpolation at the cost of increased complexity.

A downlink pattern optimisation algorithm for a smart antenna in an indoor infrastructure WLAN

This work presents a downlink pattern optimisation algorithm for a smart antenna optimum combiner operating in an infrastructure wireless local area network (WLAN) following the IEEE 802.11a or HIPERLAN/2 standards and serving the multiple users through space division multiple access (SDMA). An indoor infrastructure WLAN scenario with four users communicating with an access point is modeled using a deterministic ray-tracing tool. The performance of the smart antenna system is studied in both the uplink and downlink for the line of sight (LOS) and multipath cases to achieve optimum performance in terms of the maximisation of signal to interference plus noise ratio (SINR) for each user. It is shown that the proposed downlink optimisation algorithm achieves better SINR values for the worst case user compared to the case where uplink optimum weights are used for downlink and that the optimal downlink patterns are not necessary the same as the optimal uplink patterns.

A Field Measurement Campaign for a DVB-T/H System with Transmit Delay Diversity

This paper presents a field measurement campaign carried out by the IST PLUTO project to quantify the advantages that can be achieved practically if transmit delay diversity is applied to DVB-T/H systems. An extensive field trial was performed in Uxbridge (UK) to validate transmit diversity gain predictions obtained previously from theoretical modelling and laboratory measurements. DVB-T/H transmissions were performed in the 730 MHz frequency band. It is concluded that transmit delay diversity achieves significant improvement in the reception quality in difficult to reach areas without impacting the standard or increasing the complexity of receivers.

Average Signal Level Prediction in an Indoor WLAN Using Wall Imperfection Model

This paper presents a novel approach for the estimation of the local average signal level in an arbitrary indoor environment based on a wall imperfection model. A ray-tracing tool based on the method of images with angular information, is used to estimate the distribution of field strength (or coverage) in an arbitrary environment. The spatial sampling approach for signal level distribution prediction is studied. The wall imperfection model is then introduced to study the sensitivity of the received signal level at an arbitrary location to imperfect wall positioning and electromagnetic material properties. An alternative approach to estimate the local mean signal level at a particular point is proposed based on the introduced wall imperfection model to reduce the computation time compared to the spatial sampling approach