Trimode Leaky Wave Antenna Based on Hansen–Woodyard Condition Using DSPSL Structure

A trimode leaky wave antenna (LWA) based on Hansen–Woodyard condition using double-sided parallel stripline (DSPSL) structure is presented in this communication. The minimum permittivity of substrate is found out to exclude the interference from higher order space harmonics. Grooves are added within the unit cells (UCs) to suppress the open stopband (OSB). The full-space scanning mode radiated from
${n}$
= −1 space harmonic is achieved. To improve the radiations and expand the bandwidths in the backfire and endfire direction, the optimum formula of period length and number of UCs is derived based on the Hansen–Woodyard condition. The structure is further modified to maximize the gains in the backfire mode and endfire mode. A prototype of the trimode LWA is simulated, fabricated, and measured. In the backfire mode of 2.85–3.2 GHz, the main beam points to the exact backfire direction. In the full-space scanning mode of 3.2–8 GHz, the antenna scans seamlessly from −90° to +90° with suppressed OSB. In the endfire mode from 8 to 8.8 GHz, the antenna offers stable endfire radiation. The realized maximum gains are 11.34, 15.88, and 15.75 dBi in the three modes, and the size of the antenna is only
$4.58\lambda _{0} \times 0.17\lambda _{0}$
.