Differential feeding technique for mm‐wave series‐fed antenna‐array

A differential feeding technique for a broadband planar antenna‐array is presented. The antenna structure is composed of four parallel linear series‐fed arrays of four microstrip patches. To cancel the beam tilt versus frequency, one side of the array is fed with in‐phase signal, whereas the same out‐of‐phase signal feeds the opposite side of the array. A rat‐race balun is especially designed to generate those two signals. In comparison with other feeding techniques, there is no need for a resistive load which is actually a problem at millimeter (mm)‐wave frequencies. To validate the concept, a 60 GHz prototype etched on the TacLamPlus substrate is designed and measured.