A clamped-mode, log-periodic loop antenna with an omnidirectional, E-plane pattern

Omni-directional, log-periodic antennas are relatively uncommon, but nevertheless some implementations have previously been described. Also, so-called clamped-mode, log-periodic structures which provide greater bore-sight gain by employing linear elements substantially longer than one-half wavelength have been described in the patent literature. Here we show how an omni-directional, clamped-mode log-periodic antenna can be derived from its conventional (directional) counterpart. We demonstrate that the clamped-mode antenna satisfies the rigorous definition of a log-periodic structure. The operation of the antenna is described in detail using a numerical model. The antenna has two rather diverse applications, the first being as an HF broadcast antenna and the second as an isotropic (in the E-plane) source for over-the-air wireless measurements where it serves as a broadband counterpart to the so-called center-fed, Alford, or cloverleaf loop. Finally, we show that the approach termed clamping is actually the combination of two separate procedures: clamping (discrimination against the fundamental mode) and also elision (removal of part of the structure).