Rizwan Khan

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 Dual-Band Multiple Input Multiple Output Frequency Agile Antenna for GPSL1/Wi-Fi/WLAN2400/LTE Applications

A novel dual-band, single element multiple input multiple output (MIMO) dielectric resonator antenna (DRA) with a modest frequency tuning ability is presented in this communication. The proposed antenna operates at GPS L1/Bluetooth/Wi-Fi/LTE2500/WLAN2400 frequency bands. A single dielectric resonator element is fed by two coaxial probes to excite the orthogonal modes. A couple of slots are introduced on the ground plane to improve the isolation between antenna ports. The slots also serve the purpose of reconfiguration in the lower band on placement of switches at optimized locations. The measured impedance bandwidth is 5.16% (1.41–1.49 GHz) in the lower band and 26% (2.2–2.85 GHz) in the higher band. The lower band reconfigures with an impedance bandwidth of 6.5% (1.55–1.65 GHz) when PIN diodes are switched ON. The gain, efficiency, correlation coefficient, and diversity gain of the MIMO DRA are presented with a close agreement between simulated and measured results.

A QUAD-BAND CPW FED SLOT ANTENNA ARRAY FOR LTE AND WIMAX APPLICATIONS

In this work, a quad-band omnidirectional slot antenna array is proposed. The structure consists of two closely-spaced radiating elements fed using coplanar waveguide (CPW) line. This combined structure is then integrated in a tapered slot etched on the antenna to enable operation in four frequency bands (0.8, 1.8, 2.6 and 3.45 GHz) for LTE and WiMAX applications with at least −10 dB of reflection coefficient. The antenna dimensional parameters are also studied to understand its behaviour and effects on its performance in facilitating the optimization process. Measurements of the fabricated antenna on a low-cost FR4 substrate validate its operation centred at 0.845 (from 0.77 to 0.92 GHz), 1.745 (from 1.59 to 1.9 GHz), 2.655 (2.59 to 2.72 GHz) and 3.49 GHz (from 3.28 to 3.7 GHz). Meanwhile, simulated and measured radiation patterns of the proposed antenna in all bands agree well and are omnidirectional, making is suitable for application in mobile terminals.

A reconfigurable dielectric resonator antenna with pattern diversity for DVB-H application

A stacked-dielectric resonator antenna (S-DRA) with frequency reconfigurability and radiation pattern diversity is presented for DVB-H application. Two metallic patches are used that can be connected by RF switches to extend the ground plane. By extending the ground plane, pattern diversity and reconfigurability is achieved. This antenna offers reconfigurability from 0.47 GHz to 0.89 GHz for return loss below -10 dB. Performance in terms of return loss, current distributions, peak gain, radiation pattern and total efficiency of the designed antenna is presented that covers UHF band IV and V, respectively.

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.