Study On High-gain Omni-directional Antenna

Base on the application of Distance Measuring Equipment(DME) in the navigation system, this paper mainly researches on the properties of omnidirectional antenna to realize high gain and wide frequency band. Traditionally, the high-gain omnidirectional antenna is a series feed configuration, and sometimes a series-parallel feed one. However, in some applications, in order to make one antenna be worked in a wide band with high gain or to realize a steady radiation pattern, the parallel feed style is presented and invoked.At the beginning of this paper, it concisely introduces several kinds of high-gain omnidirectional antenna and gives their advantages and disadvantages. Based on these properties, a printed series-fed high-gain omnidirectional antenna is presented, with a dipole element and parallel wire feedline. This antenna is operated in certain application with some properties to be improved and we give effective ways to achieve them. Then, in the second part, two wideband antennas, which can be used as the elements in a lengthwise array, are designed based on the bicone antenna and dipole respectively. The radiation properties and the input impedance are detailedly discussed in this part, related to which the antenna array is design then. Finally, at the end part of the paper, an8-elemented array composed of the wideband dipole is designed. The novel feed network guarantees a good omnidirectional radiation pattern. The distance between the two adjacent elements has dramatic effect on the radiation pattern. A proper distance is chosen based on the discussion on the affection. In order to reduce the mutual coupling between the adjacent elements and to improve the radiation pattern in the higher frequency band, a quarter-wavelength choking cup is introduced between the two adjacent elememts. At the basis of all the conclusions above, the main lobe of the radiation pattern having an altitude angle of4°is obtained by adjusting the phase of the elements in the array. And then, we manufacture and measure the antenna. The measured results have a good agreement with the simulated resulted.