Radiation by a probe through a substrate

Radiation by a probe through a grounded substrate layer is considered. The reaction concept is adopted and the coaxial line aperture effects are taken into account. Image theory is invoked to simplify the evaluation of the involved Sommerfeld type integrals. These integrals are computed through a real axis integration which combines numerical and analytical techniques. An interpolation method is introduced which eliminates repetitive calculation of reaction quantities. The properties of the probe such as input, mutual impedance, radiation pattern and radiation efficiency are examined as functions of substrate parameters such as thickness and dielectric constant. The probe length may be chosen to be smaller than, equal to or greater than the substrate thickness. The effect of substrate transverse magnetic (TM) surface wave modes is analyzed and it is found that at each mode cutoff omnidirectional radiation is obtained in the -plane with maximum radiation along the horizon. The effect of small substrate loss on the probe parameters is also considered.