Continuous Beam-Steering Leaky-Wave Antenna based on Substrate Integrated Waveguide

In contrast to previously realised leaky-wave antennas, in which the composite left-handed/right-handed transmission line (CRLH TL) theory [1][4] is more or less directly implemented by realising the corresponding lumped equivalent circuit elements, for the antenna in this work a substrate integrated waveguide is employed. The waveguide is opened to allow leakage or rather radiation to take place and its analysis and design starts from the well-known equivalent circuit model of the H₁₀ rectangular hollow waveguide mode. In comparison to the CRLH equivalent circuit model, only the lacking series capacitor needs to be added. Since the etching of transverse slots in the upper major side would not result in sufficient series capacitance, introduced metal plates in a plane slightly below the upper level serve as enhancement. The so created overlapping areas generate a very large capacitance such that the unit cell length can be made very short in comparison to the wavelength. Tuning the design for balanced operation can be implemented as a one-dimensional optimization process because the dimensions of the shunt elements of the equivalent circuit are already fixed by the geometry of the waveguide. Achieving the adaptation of the shunt and of the series resonance, the antenna reveals broadside radiation. By scanning the frequency, the beam moves from close to backfire to close to endfire with a maximum gain up to 10.15 dBi and a maximum efficiency of 0.69 at 3.8 GHz.