A tactical broadband omnidirectional antenna

In this paper, a vertically polarized broadband antenna with an adjustable shape for specific applications in the VHF and UHF bands is proposed. This antenna is a compact monopole with a pseudo-conical shape set on a rectangular ground plane, partially made of wire netting. A part of the radiating element is made of metallic pipes which are bent to minimize the height of the shape without deteriorating the impedance matching. The bent pipes and the wire netting of the ground plane can be removed in order to dramatically reduce the size of the antenna for applications in high-frequency range. As a result, two compact structures relatively to the wavelength are obtained with a vertical size of respectively lambda_LF/6.25 for the low-frequency mode (100-500 MHz) and lambda_LF/7.2 for the high-frequency mode (415-915 MHz) (lambda_LF is the wavelength associated to the lowest frequency of the covered bandwidth). The structures operate with good gain and radiation patterns in both E- planes and H-planes.