Polarization isolation limit for dual-polarized phased array systems

Polarization isolation in dual polarized phased arrays is studied as an expansion of the unit cell behavior. It concludes that a fundamental polarization isolation limit exists in the diagonal far-field planes, while the principal planes exhibit no polarization limit. The diagonal plane polarization isolation limit is scan dependent, reaching a 0 dB maximum at 90°, or end-fire scan. While aperture design features may approach this limit, and manufacturing tolerances modulate it, it apparently is not exceeded in phased array test results. Polarization compensation circuits may improve on the aperture polarization isolation, but are also fundamentally limited by it.