Design of a balanced-fed patch-excited horn antenna at millimeter-wave frequencies

In this paper, a patch-excited horn antenna with a center frequency of 79 GHz is introduced. Its plane of polarization can be rotated by 45° relative to the balanced feed, which is useful for multi-element array radar applications with digital beam forming (DBF) capabilities, where easy planar integration with transceiver chips is essential. The stacked conical horn is responsible for the high gain radiation pattern while maintaining the planar nature of the patch element. The non rotated but matched antenna has a measured gain of more than 8 dBi in boresight direction, while the sideway radiation is always 20 dB lower than the main beam, reducing mutual coupling and crosstalk. Radiation characteristics are enhanced with a substrate integrated cavity. This design achieves a relative bandwidth of 18 % by using an aperture coupled patch element. Simulation and measurement are in good agreement. After an introduction, the design of three antenna variants is presented, including some simulation results. The paper will be concluded by the measurement setup and measurements of the radiation pattern and return loss.