Jawad Saleem

Reconfigurable UWB monopole antenna for cognitive radio applications

A compact frequency reconfigurable UWB antenna for cognitive radio application is presented in this paper. The proposed structure has a simple design and easy construction. The antenna is made reconfigurable, by enabling or disabling the parasitic element coplanar to the main radiator. The resonance frequency of the proposed antenna operates in two configurations which is achieved by employing three ideal switches. This antenna is operational in the practically whole UWB spectrum. Antenna parameters in terms of current distribution, return loss and radiation pattern are also presented. Experimental results successfully validate the proposed design methodology in this work. The simulations were carried out in the Agilent Advance Design System (ADS).

Design of a Dual-Band MIMO Dielectric Resonator Antenna with Pattern Diversity for WiMAX and WLAN Applications

In this paper, a dual-band multiple-input multiple-output dielectric resonator antenna (DRA) with pattern diversity is presented. L-shape of the DRA produces patterns diversity at the lower band whereas, at the upper band, it is caused by exciting TEx 121/TEy 211 mode in the DRA. Two copper strips are pasted at the corner of the dielectric radiator to improve matching at both the bands. A cylindrical air-gap introduced in the radiator improves isolation up to 25 dB and 20 dB at lower and upper frequency bands, respectively. The MIMO system possesses pattern diversity and isolation without applying any special decoupling technique. The design covers the WiMAX and WLAN bands at 3.6 and 5.2GHz, respectively. Simulated and measured reflection coefficients, envelope correlation, diversity gain and mean effective gain, are in good agreement.

A Compact Frequency Reconfigurable Hybrid DRA for LTE/Wimax Applications

A compact hybrid antenna structure with frequency reconfiguration capabilities is presented in this article. The proposed design employs a combination of a rectangular DR element and a coupling slot on the structure’s ground plane (GP). The slot shifts the fundamental DRA mode by introducing a slow wave effect and its resonant behavior helps to achieve an omnidirectional pattern at low frequencies. The slot is loaded with a series of PIN diode switches whose ON/OFF combinations alter the effective slot length. Slot loading with PIN diodes results in frequency reconfiguration of the proposed structure with a large tuning range of 76.2% (between 1.73 and 3.86 GHz). A parametric analysis was performed to investigate the effects of slot length, width, and position on the reflection coefficients of the proposed structure. A prototype of the proposed design was fabricated and results were measured. The measured results show a close agreement with the simulated ones. The proposed design is suitable for DCS 1800 MHz, PCS 1900 MHZ, UMTS, LTE 2500–2700 MHz, and Wimax 3.5 GHz.

Corrigendum to “A Compact Frequency Reconfigurable Hybrid DRA for LTE/Wimax Applications”

A compact hybrid antenna structure with frequency reconfiguration capabilities is presented in this article. The proposed design employs a combination of a rectangular DR element and a coupling slot on the structure’s ground plane (GP). The slot shifts the fundamental DRAmode by introducing a slow wave effect and its resonant behavior helps to achieve an omnidirectional pattern at low frequencies. The slot is loaded with a series of PIN diode switches whose ON/OFF combinations alter the effective slot length. Slot loading with PIN diodes results in frequency reconfiguration of the proposed structure with a large tuning range of 76.2% (between 1.73 and 3.86GHz). A parametric analysis was performed to investigate the effects of slot length, width, and position on the reflection coefficients of the proposed structure. A prototype of the proposed design was fabricated and results were measured. The measured results show a close agreement with the simulated ones. The proposed design is suitable for DCS 1800MHz, PCS 1900MHZ, UMTS, LTE 2500–2700MHz, and Wimax 3.5GHz.

Analysis of the high gain five port converter with ultra capacitor, battery, and asymmetric bipolar outputs for microgrid/HEV applications

This paper presents a five port converter with generation source, ultra capacitor, battery and asymmetric bipolar output for microgrid and hybrid electric vehicles applications. Proposed converter has two asymmetric bipolar outputs. This makes it suitable for interfacing with multilevel inverter in hybrid microgrid applications. On the basis of power sharing between ports, charged and discharged of the battery and ultra capacitor, three operating modes are defined. Proposed structure uses a three winding coupled inductor with high gain. Operation and analysis, simulation, and design consideration of the proposed structure is presented. To validate the simulation and theoretical analysis a laboratory prototype of 450 W by using DS1104 dSPACE is presented.

Statistical modeling of optical attenuation measurements in continental fog conditions

Abstract. Free-space optics is an innovative technology that uses atmosphere as a propagation medium to provide higher data rates. These links are heavily affected by atmospheric channel mainly because of fog and clouds that act to scatter and even block the modulated beam of light from reaching the receiver end, hence imposing severe attenuation. A comprehensive statistical study of the fog effects and deep physical understanding of the fog phenomena are very important for suggesting improvements (reliability and efficiency) in such communication systems. In this regard, 6-months real-time measured fog attenuation data are considered and statistically investigated. A detailed statistical analysis related to each fog event for that period is presented; the best probability density functions are selected on the basis of Akaike information criterion, while the estimates of unknown parameters are computed by maximum likelihood estimation technique. The results show that most fog attenuation events follow normal mixture distribution and some follow the Weibull distribution.

High gain bidirectional multiport DC to DC converter for DC microgrid

Generally, operating voltage of photovoltaic (PV) arrays are low. To interface such systems with high voltage DC bus, a high gain converter is needed. Moreover, power generated by the PV systems is non-uniform most of the time. Therefore, for this purpose, a battery port is mandatory. Hence, for this application a high gain multi port converter is suitable candidate that increases conversion efficiency with a reduced cost. In this work, a high gain multi port bidirectional DC to DC converter for the DC microgrid application is proposed. Proposed converter has three ports. One for the power source, the second for the battery, the third for the high voltage DC Bus. Converter is analyzed in boost/battery discharging and buck/battery charging mode. Detailed theoretical analysis and operation of the converter is presented. The proposed converter has inter source and bidirectional power flow capability. A gain comparison is performed with its previous counterpart converters. A 744 W converter is simulated in the Matlab to validate the theoretical and operational analysis of the converter. Experimental results are performed using the developed prototype converter and dSPACE (DS-1104) controller.

Comparative analysis of performance for seven and five levels inverter

Multilevel inverter has numerous features for high and medium voltage applications. The size and complexity of multilevel inverter topologies limits its applications. In this paper performance comparison of seven and five levels inverter is presented. For both inverters cascaded H-bridge and reduced switched topologies are used. Performance of the inverters is compared topological and by reduction in total harmonics distortion (THD) using the sinusoidal pulse width modulation (SPWM) control techniques. These techniques are phase disposition (PD), phase opposition disposition (POD), alternate phase opposition disposition (APOD), phase shift (PS) and hybrid PWM. Models are implemented in Matlab Simulink environment and results are compared. In reduced switch topologies increasing the output voltage level by minimizing the number of switching devices produce significant reduction in total harmonic distortion. Thus the conventional topology can be replaced with proposed reduced switched structure with the benefit of reducing losses, size and cost.

A Pattern Reconfigurable Dielectric Resonator Antenna for Wireless Fidelity Applications

A pattern reconfigurable dielectric resonator antenna for wireless fidelity (2.4 GHz) band is presented in this communication. A rectangular dielectric resonator antenna which is fed by a microstrip line serves as the main radiating element. The pattern reconfigurability is achieved by the introduction of slots on the ground plane. The switch placement on the slots redistributes the surface currents and results in pattern reconfigurability. Six useful configurations are obtained by the ON/OFF combination of the switches with a diverse pattern and almost same resonant frequency.