Broadband Dual-Beam Elliptical Waveguide Leaky Wave Antenna Based on Four-Transverse-Slot Unit

In this article, a novel broadband dual-beam elliptical waveguide (EWG) leaky wave antenna (LWA) with beam scanning is proposed and fabricated. The antenna works on two spatial harmonic waves (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${u}~\in $ </tex-math></inline-formula> [0, −1]) simultaneously to generate two radiation beams, respectively. Through the detailed theoretical analysis of radiation E -field and reflection coefficient of the multislot unit on the EWG, the radiation frequency range of harmonics and the frequency of open stopband (OSB) can be derived and accurately calculated. By adopting the proposed four-transverse-slot unit with reasonable spacing, both two groups of designated higher order harmonics and OSBs of the slots can be suppressed effectively to achieve wide operation bandwidth for both transmission and dual-beam radiation, and the beam scanning range can be greatly expanded. Based on the analysis of multislot radiation above, the dual-beam gains of the proposed EWG LWA can be improved significantly. To achieve large single-mode bandwidth for ensuring the wideband operation of the LWA, it is fed by the broadband coaxial-to-EWG transition, which can suppress two high-order transmission modes (TE<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {s11}}$ </tex-math></inline-formula> and TE<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {c21}}$ </tex-math></inline-formula>) of the EWG. For verification, an EWG LWA with seven four-transverse-slot units centered at 6.1 GHz is designed and measured. The measured impedance bandwidth with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert $ </tex-math></inline-formula>S<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {11}} \vert \lt -10$ </tex-math></inline-formula> dB is over 61%. Good agreement between the simulated and measured results can be observed.