A leaky-wave antenna using an artificial dielectric medium

A narrow-beam antenna using an artificial dielectric medium with effective permittivity less than unity has been investigated theoretically and experimentally. Complex propagation constant for a wave propagating along the structure is evaluated by solving the dispersion relation. The analysis indicates the presence of a leaky-wave mode. The radiation pattern is calculated by using Kirchhoff-Huygens integration method. Experimental results for an antenna of this type designed for operation at X band are reported and compared with theoretical calculations. Beam position varies from 17 to 47 when the frequency is changed from 8. 6 to 11. 5 GHz. Over this frequency range the half-power beamwidth varies from 5. 6 to 4. 8. An expression for the half-power beamwidth of a leakywave antenna of finite length has been derived and discussed in the Appendix.