Theory of an active transmit/reflect array of patch antennas operating as a spatial power combiner

A theory exploring the Friis transmission formula and scattering parameters of cascaded two-ports is presented to analyze the operation of a spatial power combiner formed by either a transmitarray or reflectarray of microstrip patch antennas. This theory is applied to investigate insertion losses when the elements of the transmitarray or the reflectarray are phased to focus the re-transmitted wave onto a receiving sub-array. Comparison with experiment and a fullwave analysis confirms the validity of the developed theory.