Stacked microstrip patch antennas with dissimilar substrates, non-aligned patches or unequal patch sizes

Stacked microstrip patch antennas are capable of dual-frequency operation. Various forms of these antennas have emerged and some of their characteristics have been reported in the literature. The authors focus on the behaviours of stacked rectangular patch antennas with dissimilar substrates, nonaligned patches or with unequal patch sizes. For these structures little or no coherent information is available in the literature. The work presented is mainly theoretical, but where possible the theory is checked against the measurement