On the effect of substrate thickness and permittivity on printed circuit dipole properties

The effect of substrate thickness and relative permittivity on the radiation properties of printed circuit dipoles (PCD\´s) is investigated. A trade-off between substrate thickness and resonant input resistance, bandwidth, and radiation efficiency is presented for a polytetrafluorethylene (PTFE) glass random fiber substrate. It is found that for a fixed substrate thickness , the resonant length and directivity decrease with increasing relative dielectric constant . The - and -plane normalized power pattern is also examined as a function of and . It is shown that even for thin substrates, multiple-beam radiation can result for certain values of by the excitation of surface waves. Multiple-beam patterns can also be obtained with increasing for a given . In fact as increases it is determined that the resonant length, bandwidth, and resonant resistance approach the apparent value of a PCD on a dielectric halfspace.