In addition, an electrically small antenna (ESA) which can generate omnidirectional CP has been presented in Chapter 4. It is available for an antenna sensor application in WSNs. The antenna consists of a horizontal loop element enclosed by two U-shaped elements and a vertical element. The electrical size of the antenna is ka = 0.467 (i.e. < 0.5, where k is the wavenumber at the resonant frequency and a is the radius of a sphere surrounding the antenna), which satisfies the definition of ESA. The U-shaped elements also contribute to the generation of omnidirectional CP with the vertical element.
Throughout this thesis, the measured results of prototypes of the antennas show good agreements with respective simulated results. Each mechanism of all the proposed antennas has been analyzed by observing the electromagnetic field and current distribution.