A Differentially Excited Coupled Half-Width Microstrip Leaky ${\rm EH}_{1}$ Mode Antenna

This paper presents a coupled half-width leaky-wave antenna driven differentially. The guided-wave structure of coupled half-width microstrip lines are proposed and investigated, showing two leaky modes in the form of even- and odd-symmetry, respectively. Rigorous studies show that the odd-leaky-mode outperforms the even-mode approach in radiation patterns and bandwidth. Following the rigorous investigation of the modal characteristics of the coupled half-width EH₁ mode guided structure, this paper reports a differentially fed, coupled, odd-leaky-mode, half-width, antenna of size 1λ₀ by 3.6λ₀ (including the feed), showing measured maximum antenna gain of 11.6 dBi, 15% fractional bandwidth, gain flatness of 2.4-dB variation, and input return loss greater than 10 dB. (λ₀ is the free space wavelength at the maximum gain frequency of 10.1 GHz). Both full-wave simulated results and measured data show good agreements for the proposed antenna structure. The measured leaky-wave antenna performance is compared to the recently published results, demonstrating a good compromise among all major performance metrics.