Power system overvoltages due to switching, lightning and other disturbances are the main problem for designers of the power transformers. Once some frequencies of the incoming surges match with some of the natural frequencies of transformer winding, the resonance phenomenon is expected in transformer winding. The resonant overvoltages may destroy the insulation between turns and cause to insul...

This article briefly reviews broadband design techniques in dielectric resonator antennas (DRAs). The attentions focus on a type of DRAs that can offer multi-resonant frequencies and these frequencies can be mergered into a broad band. Index Terms dielectric resonator antenna, broadband, multi-frequencies.1

The design of a compact, varactor controlled, electronically reconfigurable dual frequency microstrip antenna is presented in this paper. Dual frequency operation is realized by embedding a hexagonal slot with extended slot arms within a square patch. Varactor diodes integrated with the slot arms are used to tune the operating frequencies considerably, by applying reverse bias voltage. Tuning r...