Designs and Experiments of a Novel Radial Line Slot Antenna for High-Power Microwave Application

A radial line slot antenna (RLSA) is a nonresonant multimode waveguide slotted array. To improve the power handing capacity, we design a radial line slow wave structure which replaces a traditional dielectric sheet. At the same time, the structure of the radiator unit is redesigned and optimised. This high-power microwave (HPM) RLSA is fed from a double-layered radial line waveguide to realize the directional radiation of high-power microwave. However, the slots spirally arrayed for circular polarization give rise to serious reflection in higher order modes, which disturbs the normal antenna operation. A reflection cancelling slot is added to the conventional one and the antenna return-loss is effectively improved. An antenna operating at 9.42 GHz was designed with a length of 15 cm and an aperture radius of 27 cm. Numerical simulation results show that the calculated aperture efficiency reaches 44.8%, the reflectance is less than -20 dB, the radiation efficiency is more than 99%. Experimental measurements are accomplished for the prototype. In the range of 9.30-9.45 GHz, the reflection of the antenna is below -10 dB. The antenna gain reaches 29.0 dBi, and the axial ratio is below 1.6 dB. In addition, the high-power experiment proves that this antenna has a power-handing capacity of more than 1 GW.