A Photonic-Doping-Inspired SIW Antenna With Length-Invariant Operating Frequency

This article presents a novel substrate-integrated waveguide (SIW) antenna with a designable broadside pattern at a length-irrelevant operating frequency, which is inspired from the concept of photonic doping, i.e., embedding a dielectric impurity into the epsilon-near-zero (ENZ) medium. In our design, a section of SIW operating around its cutoff frequency imitates the ENZ host, while a high-permittivity dielectric block is “doped” into the SIW to control the overall field distributions, achieving a sharp 180° phase shift of electric field at the predesigned half- wavelength resonance. Owing to the infinite wavelength in the ENZ medium, the operating frequency of the proposed antenna is irrelevant to its length. In this way, the broadside radiation of the proposed antenna allows to be configured at the same frequency via simply altering the length of the SIW, i.e., the spacing between two radiating apertures. Systematic studies show that the directivity of the proposed antenna can be manipulated over a range from around 6 dBi to almost 10 dBi, along with the half-power beamwidth reduced from 110° to 20°, for the length of the antenna varying from $0.2\lambda _{0}$ ($\lambda _{0}$ is the wavelength in free space at 5.5 GHz) to $1.2\lambda _{0}$ .