Techniques for harmonic tuning in microstrip active integrated antennas

In this chapter design strategies are reviewed and presented for harmonic-tuned active integrated antennas based on the use of microstrip patches and compact electromagnetic band-gap filters. The synthesis of optimal values for the antenna input impedance at the fundamental, second, and third harmonic frequencies can be achieved by perturbing either the geometry of the antenna or the geometry of the filter. In particular, assuming a periodic configuration, a full-wave moment-method approach is employed to characterize the dispersive behavior of a representative class of electromagnetic band-gap microstrip lines, acting as band-stop filters in wide frequency ranges. Numerical simulations of input impedance and radiation properties are provided on specific examples of antennas to validate the proposed approaches.