On the Dual-Frequency Behavior of Stacked Microstrip Patches

The dual-frequency behavior of stacked rectangular microstrip patches fabricated on a two-layered substrate is investigated. In the case where the top patch is longer than the bottom one, computations show that the lower resonance is very close to the resonant frequency of the isolated top patch and the upper resonance is determined primarily by the size of the bottom patch. In the opposite case, the investigation shows also that the lower resonance is very close to the resonant frequency of the isolated bottom patch and the upper resonance is highly dependent on the top patch size. Other results also indicate that substrate dielectric anisotropy has a more pronounced effect on the lower resonance than on the upper resonance.