Radar Receiver Correction of Polarization

In radar meteorology, it is desired to have various forms of polarization diversity in transmission and reception. In this paper, we consider a phased array radar whose radiating elements are crossed dipoles or equivalent such that relative phase and amplitude will create any form of transmitter polarization. The crossed dipoles are associated with transmit/receive (TR) modules where phase/amplitude control provides beam steering and desired polarization. We consider the construction such that the receive paths from the orthogonal dipoles are separated from the transmit paths (by RF switches or circulators). Errors in transmission can be corrected in the receive paths where power levels are low. Errors in polarization can be corrected upon reception where power levels are low, reducing demands on transmitter specifications.

With reception of orthogonal polarization components, these can be appropriately phase and amplitude controlled to produce the effect of having transmitted and received any form and received any form and combination of polarizations. All of the receiver correction may be done at coherent base band (I + j Q) with digital signal processing and all of the desired polarization combinations may be achieved simultaneously from the same pair of transmitted orthogonal components. Any transmitter errors can be corrected digitally in the receive paths.

Calibration will be needed over many steering angles in the field of view and requires a calibration sphere or its' equivalent in the far field. The relationships for correcting amplitudes and phases are presented in the paper and are easily accomplished with digital processing.