A low-cost patch antenna phased array with analog beam steering using mutual coupling and reactive loading

In this letter, a low-cost patch antenna phased array is demonstrated with analog beam steering without using phase shifters. This novel technique can greatly reduce the cost of a phased-array system and will enable the wide-scale deployment of phased arrays in low-end commercial products. In the presented three-element phased array, the center (driven) antenna is fed by an RF source and the two neighboring (passive) antennas are excited through the mutual coupling from the center antenna. The phase shifts between the antenna elements are achieved by changing the reactance of the capacitors loading the two passive antennas. A phased array using this novel technique is designed, fabricated, and measured at 3 GHz with a bandwidth of 1.8%. This phased array is shown to be able to steer the antenna beam from 20 to 20 degrees in an analog fashion. The measured radiation patterns of this phased array closely match the theoretical calculation and full-wave simulation results.