In this contribution internal calibration probes for circularly polarized patch antenna arrays are proposed. The probe network replicates the patch's natural mode of operation and thereby enables a precise calibration that incorporates finite array effects and mutual coupling. Furthermore, the approach allows for online monitoring which is of major importance for active arrays. The probes can be integrated with single feed circularly polarized microstrip antennas that use perturbations such as truncated corners. The feasibility of this calibration technique is demonstrated by measurements on a 4 by 1 array.
