An electrically-small annular slot operating in the ´DC´ mode

This paper considers the operation of an the annular slot antenna operating in the ´DC´ mode. This stripline-fed antenna includes a shorting pin between the central resonating element and ground that causes an additional resonant mode (the ´DC´ mode) to be excited well below the first natural resonance of the structure (i.e. the slot being one wavelength long). Operation at this ´DC´ mode´s resonant frequency results in an electrically small element that radiates in the same fashion as a wire monopole above a ground plane. To illustrate the performance of this antenna, a thorough comparison against the performance of a wire monopole is given, with the following parameters being considered; input response, full 3D radiation pattern, gain, directivity and efficiency. It is shown that the radiation potential of the annular slot in the ´DC´ mode is only slightly less efficient than the wire monopole, but in all other aspects the behaviour is identical.