Analytical Study of Dirac Type Dispersion in Simple Periodic Waveguide Structures for Leaky-Wave Applications

Abstract

In this work, we present a study on the existence of Dirac type dispersion in the simplest of periodic metallic waveguide structures. It is shown that periodic repetitions of two dissimilar waveguides (WGs) can be properly designed to lead to a Dirac type dispersion. A simple theory using circuit modeling is presented to find the condition for Dirac point operation. In addition, mode-matching followed by full-wave simulations validate that the band structure matches that of the theory and shows that a Dirac dispersion can be realized. A Dirac Leaky-Wave Antenna (DLWA) is then implemented using this simple arrangement in substrate-integrated-waveguide (SIW) technology. This DLWA has the closed broadside stopband feature, leading to continuous frequency beam scanning through broadside and a simple feeding network. Phase and leakage constants are adjusted to yield a directive fan-beam featuring continuous scanning in a wide range of angles. The presented DLWA has a wide impedance bandwidth with high efficiency and operates with peak gains of about 12.5 dBi without any significant gain variation throughout the frequency range from 13.5 GHz to 16.5 GHz. Measured results show excellent agreement with the simulated results, validating the proposed concepts.

Keywords

• Dirac leaky-wave antenna
• mode-matching technique
• broadside radiation
• frequency scanning antenna
• substrate integrated waveguide (SIW)
• microwave applications