Chokes for alternating-phase fed single-layer slotted waveguide arrays

The alternating-phase fed array with the choke structure which dispenses with any contact between the slotted plate and the groove feed structure is discussed. It is demonstrated that the choke works very effectively to prevent the leakage in the feed waveguide and to keep the antenna efficiency high. A summary is included of the efficiency of various types of planar antennas as a function of antenna gain and frequency. The alternating-phase array achieves high-gain and high-efficiency performance in spite of the simple fabrication dispensing with any contacts.