Spatial power combining of circularly polarized active antennas

Much attention has been paid to spatial power combining using active antenna arrays to obtain high power solid-state millimeter-wave sources. An active antenna is obtained by mounting an active device such as GaAs FET and Gunn diode on or near a microstrip antenna, and it operates as an oscillator or an amplifier. Active antenna arrays can be small-sized sources in the millimeter-wave region, and power losses in conventional power combining circuits can be avoided in spatial power combining. Linearly polarized active antennas and power combining arrays have been reported so far. The authors do not know of reports on spatial power combining of circularly polarized active antennas. The design of circularly polarized active patch antennas and the result of a spatial power combining experiment using two such active antennas are presented.