Bøger af Taimoor Khan

Miniaturization of planar microwave components and antennas has become important for applications where physical space is constrained. Modern wireless communication terminals require small planar microwave elements integrated into compact and light-weight systems. As we concern about small elements in an integrated system, the design of the antenna is a significant issue of any wireless system. Antenna designs play a significant role in the development of modern wireless communication devices. However, the design of conventional antennas encounters severe practical limitations such as narrow bandwidth and poor radiation characteristics. Thus, many design efforts on antenna designs have been focused on enhancing bandwidth and shaping of the radiation pattern. One exciting breakthrough is the use of electromagnetic band gap structures (EBG) technology in antenna designs. A great research effort on EBG structures to be compatible with antenna designs over a wide range of applications have attracted in this book.

The present era of communication indicates the frequency range of interest for many systems has progressively grown upward. From application point of view, the frequency beyond the usual microwave band and near the millimeter-wave region are often required. Most of the currently used microwave antennas cannot be easily scaled in frequency. The basic problem in scaling can be attributed to conduction losses in any metal portion of the radiating structure/element, which mostly changes post scaling, and, as a result, these losses may affect the required efficiency of the system. On the other hand, the placement one low Q-factor dielectric resonator (DR) on a conducting ground plane led the power/energy to lost in to the free space/radiated fields and act as an antenna. Indeed, this idea of using DR as an antenna had been firstly accepted in the mid of 1983. DR antennas have numerous interesting facts/advantages like; smaller in size, large power handling capacity, less dissipation loss, high efficiency compatible to any 3-D shape, etc. which make them more popular than those traditional antennas.