SIW Horn Antenna with a Special Coplanar Transition and Dielectric Lens for Feeding a Leaky-Wave Antenna

The paper describes the main phases and features in designing a feeder for a leaky-wave antenna in the Ka-band. The problem of feeding can be effectively solved using a horn antenna SIW technology-based and single substrate-integrated with the radiating aperture of the leaky-wave antenna. Unlike most similar studies, where an aperture exciting from a closed-type structure is analyzed, in our work the open-type antenna feeder is synthesized.In the paper, we give a brief overview of the main achievements in designing traditional SIW-structures and present relations for their calculation. Basing on results of electromagnetic modeling, determine the influence of the substrate permittivity on the efficiency of SIW transmission line by the method of finite Weiland integrals. Consider the most popular types of the waveguide transitions to SIW, including micro-strip lines and grounded coplanar waveguides (GCPW). Depending on the required bandwidth and substrate dimensions specify conditions for selecting a design type of the waveguide transition.A special attention is paid to the non-standard coplanar transition with an elevated grounded surface (EGCPW), which is worth using if the substrates are thick. It was used as a basis for designing a new, more efficient EGCPW transition with the elevated grounded surface, which contains specially made slots (SEGCPW). Recommendations for its adjustment are given.The dependences of the gain on the aperture width for the H-plane SIW horn antenna, which are used to select its optimal size, are obtained basing on simulation. It was found that for matching the feeder with the leaky-wave antenna and decreasing the side lobes level, a dielectric lens with through holes worth using. Basing on the simulation of the unit cell of the lens the dependence of the effective permittivity on the diameter of the through hole is obtained. An influence of the non-uniformity degree of the lens with the holes of different diameters on the radiation efficiency of a horn antenna is determined. The complete design of the synthesized feeder and its radiation pattern is presented to prove the antenna efficiency in the wide frequency band.