Muhammad Khan

A tri-band H-shaped microstrip patch antenna for DCS and WLAN applications

In this paper, a tri-band H-shaped microstrip patch antenna is presented for DCS and WLAN (IEEE 802.11a/b/g) applications. The proposed antenna has symmetrical properties and has been designed by etching H-shape structure on FR-4 substrate with coaxially fed input. It radiates for DCS (1.79-1.81 GHz) and WLAN (2.43-2.47 GHz, 5.11-5.27 GHz) frequency bands. It is demonstrated that the fabricated antenna offers improved values of S11 and VSWR. The noted gain at 1.8 GHz, 2.45 GHz and 5.2 GHz are 1.6 dBi, 1.9 dBi and 2.1 dBi, respectively. The return loss S11 of the fabricated antenna was simulated using Ansoft HFSS which was in good agreement with experimental data.

Multiband Microstrip Patch Antenna for Microwave Applications

In this paper, we present a fractal shape slot based patch antenna for multiband operations. The fractal shape slot is designed on the rectangular patch and the antenna is fed through a microstrip line. The proposed design and feeding technique allows the antenna to operate at multiple frequencies in the range of 120 GHz. It is demonstrated through simulation that the Return Loss (RL) values occurred at 1.33 GHz, 4.16 GHz, 7 GHz, 9.8 GHz, 12.7 GHz, 15.5 GHz and 18.3 GHz, respectively, having VSWR ≤ 2. It is also observed that the gain of proposed design is higher than the conventional patch antenna. Parametric study is also included to give an overview for the performance of proposed design.

Polymorphic Extensions to Object-Z Specifications

Inheritance and polymorphism are powerful constructs of object-oriented paradigm, which are supported by almost all object-oriented programming languages. However, majority of existing formal specification languages lack concrete support for polymorphism. For this reason, we propose polymorphic extensions to object-Z, a formal specification language commonly used for object-oriented systems, by defining several novel notations specific to polymorphism. We also define a schema policy that determines the actual late binding of the object with the corresponding reference. We then demonstrate the usability of these extensions by applying them on an example