K-band planar antenna array fed through loop transitions

A microstrip patch antenna array is designed and tested at K-band. Two efficient end launched waveguide to coaxial loop to microstrip transitions (loop A and loop B) are designed to feed the antenna array. The loops achieve a simulated 2:1 VSWR from 22 to 25.4 GHz for loop A and from 21.4 to 26.7 GHz for loop B. The corresponding insertion loss is less than 0.4 dB for both loops over the band. The microstrip patch antenna array broadside gain is 23.6 dB using loop A at the design frequency of 24.125 GHz. The array measured return loss is less than 9.54 dB from 24 to 24.4 GHz with loop A.