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.