FDTD study of dispersion characteristics of leaky modes in microstrip leaky wave antennas

Due to the simplicity of fabrication, microstrip leaky wave antennas (MLWA) are well suited for millimeter wave applications. They also demonstrate high gain and possess frequency beam scanning capability in the elevation plane. These attributes make MLWAs prospective devices for application in low cost radar systems, such as side-looking sensors in automotive anti-collision equipment. The present work shows how the FDTD method can be used to study the dispersion characteristics of the first higher order mode in the radiating lines of MLWAs. The results of other studies (see Lin, Y.-D. and Sheen, J.-W., IEEE Trans. Microwave Theory Tech., vol.45, no.10, p.1672-80, 1997; Wang, C.-J. et al., Electronics Lett., vol.36, no.7, p.596-7, 2000; Yau, D. et al., IEEE Proc. Microwave Antennas Propag., vol.146, no.5, p.324-8, 1999; Sheen, J.-W. et al., IEEE MTT-S Digest, p.175-8, 1999) do not agree well with each other and have not been verified experimentally. In contrast, the FDTD method does not employ any artificial assumptions in modeling the wave processes; consequently, the results of the FDTD simulations are usually in excellent agreement with experimental data (see Qian, Y., IEEE MTT-S Digest, vol.4, p.1419-22, 1999).