For the lower microwave frequency bands such as the Ku-band operation, the design of efficient dielectric waveguide antennas is still a major challenge due to several factors such as unavailability of commercial substrates of adequate thickness, bulky feeding networks, and the requirement of large radiating length. The high permittivity substrates have generally been used in the past to reduce the thickness of the radiating structure, but it results into performance degradation due to high dielectric losses, dispersive propagation, and poor impedance matching at the radiating aperture. To overcome these challenges, the concept of a novel substrate integrated travelling wave antenna using the low-index core dielectric waveguide (LICDW) for operation in the Ku-band is proposed in this work. The LICDW structure here consists of a three-layer dielectric waveguide with a relatively lower refractive index core layer sandwiched between two outer cladding layers, which basically confines the electromagnetic energy within the central core enabling lowloss, less-dispersive wave propagation. The proposed antenna is excited by a grounded coplanar waveguide-fed-substrate integrated waveguide (GCPW-fed-SIW) based magneto electric dipole array feeding network to enhance the overall radiation performance. A comprehensive parametric study and the detailed field analysis including numerical simulation is carried out to optimize various parameters of the structure. The optimized structure is fabricated and tested to validate the proposed design methodology. Experimental results confirm the superior performance of the proposed radiating structure compared to the existing Ku-band travelling wave antennas, thereby showcasing its potential for integration into compact, planar RF modules in small satellite systems.

In this work, a new approach to analyse and design the rectangular shaped low index core dielectric waveguide (LICDW) structure is proposed, which is based on derivation of the generic transcendental characteristic equations for the corresponding geometry using the effective dielectric constant method. The proposed method is not based on the image theory, and hence the derived characteristic equations can effectively be utilized to compute all possible modes of the LICDW structure quite accurately. The propagation constant of the LICDW structure is computed here as a function of the core-cladding parameters using the proposed characteristic equations. The reflection coefficient at the core-cladding interface of the structure in the specified frequency band is also computed to show the effect of the total reflection along the LICDW. The LICDW structure is fed using a newly proposed fully planar transition, which is realized by the SIW based magneto-electric dipole array feeding technique. For validating the proposed approach, a prototype structure comprising the LICDW along with the transition in the Ku-band is designed, fabricated, and tested. The proposed LICDW structure can be integrated with the corresponding dielectric radiator for the miniaturization of conventional Ku-band VSAT network.