Improving the scan performance of probe-fed microstrip patch arrays on high dielectric constant substrates

This paper presents a thorough investigation into the use of E-plane parasitic elements to remove scan blindness in probe-fed microstrip patch phased arrays using a rigorous full-wave analysis. It is shown that the addition of an E-plane parasitic element in the unit cell of the array can enhance the impedance scanning range; however, the parasitic element must be resonating. As a consequence of this, the method of scan blindness removal is only suited to microstrip patch arrays mounted on high dielectric constant material. A novel configuration incorporating a varactor diode to reduce the significant reactive nature of the input impedance at large scan angles is introduced which further improves the scanning potential of the parasitic element array. A further modification to the unit cell is proposed which allows the array to operate over a broad frequency range. For all the configurations considered, comparisons of active reflection coefficient, scan impedance behavior, efficiency, and cross-polarization levels are presented