Differential excitation of a hybrid antenna for a 75 GHz antenna array implemented on a multilayer PC board

If, for practical reasons, there is a need to bend a differential waveguide, the bend has to be compensated to avoid mode conversion into the common mode which can lead to unwanted resonance effects. This paper deals with two possible compensating structures for a 45° bend in a differential waveguide exciting a hybrid antenna. The hybrid antenna in turn is part of a large array used in a security scanner for people screening. Simulations show antenna behavior with and without compensation with respect to matching, mode conversion, gain, and suppression of the cross polarization.