Leaky-wave characteristics from double periodic composite right-/left-handed transmission lines

A double periodically loaded leaky-wave antenna (LWA) based on composite right-/left-handed transmission lines is proposed. Dispersion characteristics and the radiation efficiency are investigated with the help of a singular perturbation procedure, and the radiation efficiency is numerically estimated as a function of the antenna length. In addition to the left-handed (LH) characteristic of the structure, a novel leaky-wave radiation is obtained below the LH passband with narrow bandwidth, and this point is focused on the leaky-wave phenomenon because of space harmonics of the Bragg reflection from double periodically loaded inductances and/or series interdigital capacitances. Compact LWAs are designed using microstrip lines with double/single periodically loaded inductances and/or capacitances. Radiation characteristics are measured for the investigated compact antenna, and the results demonstrate the expected novel leaky-wave behaviour.