| With the development of the high-power microwave(HPM) technology, more attentions have been progressively paid to the function of HPM antenna. As the terminal of HPM system, the performance of HPM antenna directly decides that of the whole HPM system. Due to particularities of HPM, HPM antenna shall meet some special requirements as high-power capacity on the premise of ensuring favorable radiation. Therefore, many researches have been made by researchers at home and abroad, and such HPM antennas as mode converter with radiant horn, Vlasov antenna, mode-transducing antenna (like COBRA antenna and radial line array antenna etc. have been put forward. Although they are subject to some disadvantages more or less, they can not perfectly meet the requirements of HPM system that become greater. Radial line array antenna has its particular advantage which can probably solve many problems exist in HPM radiation.High-power radial line helical array antenna adopts short helical antenna which radiates circularly-polarized wave at its axial direction as radiation unit, uses radial line as feeding waveguide, applies new-type coupled probe to feed energy from radial line to unit antenna. Scheduled excitation magnitude and radiation phase can be reached by adjusting the coupling factor of the probes and rotating the radiation units, and in which way, directional radiation of microwave can be achieved. The whole antenna avoids occurrence of medium and it is contained in a random placed upon the helical antennas to make it stay in vacuum and reach comparatively high power-handling capacity.Mutual coupling between units is an inevitable effect of the array antenna. It will affect the radiation performance of the array antenna. Therefore, mutual coupling should be reduced when an array antenna is proposed. The helicone which is composed of a helical antenna and a conical horn can reduce the sidelobe of the helical antenna. The mutual coupling between two helicones is less than that between two helical antennas when they used as units of an array antenna. The helicone is composed of the long helical antenna in the past investigatioins. It is long at its axial direction which makes it cannot be used as a unit of array antennas. To use the advantage of the helicone to reduce mutual coupling and to reduce the size at its axial direction, short helicone can be considered composed of the short helical antenna and conical horn to which can meet the request of the high power microwave area.High power microwave antennas must have high power capacity. To improve the power capacity of the HPM antenna, generally, antenna should be made stay in the vacuum. The short helical array antenna is airproofed using the antenna cover, so when the aperture of the antenna is large, it is difficult to do airproof the antenna. When use the short helicone as the unit of a radial line array antenna, it is convenient to airproof the unit antenna because of the presence of the conical horn. Therefore it is important to investigate the short helicone which can meet the request of the high power array antenna.In this paper, a short helicone antenna is proposed which can be used as a unit of high power array antenna. Mutual coupling of two short helicone antennas at different distances is simulated using the numberical simulation software. By comparing with mutual coupling of two short halical antennas in the same situation, restriction to be followed is determined to reduce the mutual coupling between two short helicone antennas. Based on the restriction, a short helicone antenna is proposed which can be used in array antenna. At the centre frenquency, the directivity of this antenna is increased by ldB, the sidelobe is 8dB lower than that of a short helical antenna. The mutual coupling between two of these antennas is 3dB smaller than that of two short helical antennas in the same situation.A 2-circle 18-unit high power array antenna fed from single-layered radial waveguide is designed using the proposed antenna as units. It is shown from the simulation result that the antenna has a reflection coefficient of 0.05, an axial ratio of 0.96, a gain of 22.16dB, an aperture efficiency of 67.8% at the centre frequency. Compared with the helical array antenna in the same situation, the gain is improved by 1.3dB, aperture efficiency is increased by 16.6%. At last, the power capacity of this array antenna is analysed theoretically. Simulation result of power capacity of the array antenna is analysed as well. |
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