Nonreciprocity and scan blindness in phased arrays using balanced-fed radiators

It is shown that scanning an array of balanced wire or patch type radiators in their -plane can destroy the radiators\´ dual probe symmetry. This loss of symmetry can cause the radiator\´s unit cell "scattering matrix" to be nonreciprocal, where in this scattering matrix each of the radiator\´s dual probes is now considered as a separate input port. This breaking of radiator symmetry can result in scan blindness when the radiator is fed by a reactive power divider balun. This effect is illustrated by a numerical example using balanced-fed patch radiators.