High field strength in a large volume: the extended double ridged guide vs. the biconical and log-periodic antenna

International civil standards require the generation of a reasonable constant field strength over a large area. In this paper it is shown that the dipole-like biconical and log-periodic antennas are less favourable compared to double ridged guide antennas. Due to the near field antenna pattern of the dipole-like antennas, considerable power is radiated to the floor and walls of a shielded enclosure. Although the floor and walls are covered by absorbing material, these absorbers are not performing well in the near field of antennas resulting in a high standing wave ratio of the antenna. Due to the high standing wave ratio the antennas present a low efficiency and poor quality of the field. A double ridged guide antenna has less sidelobes, higher gain and is less influenced by the floor and walls of a shielded enclosure. An extended double ridged guide antenna, extending the frequency range of classic double ridged guide antennas (200 MHz-1 GHz) to 80 MHz up to 1 GHz, has been developed and presented in this paper. The theoretical background and practically obtained results are shown