Application of mutually coupled oscillators on beam-scanning and polarization-agile antenna array

With the tunable relative phases, one-dimensional mutually coupled oscillator arrays have been used for the application of beam-scanning antenna arrays. In this paper, a two-dimensional mutually coupled oscillator array is studied for the application of a beam-scanning and polarization-agile antenna array. In the antenna array design, the polarization-agility is considered as one of the two dimensions (or y-direction) with the other dimension (or x-direction) for beam scanning of a two-dimensional oscillator array in x-y plane. By properly tuning the free-running frequencies of the oscillators, the array radiation direction can be scanned for the selected polarization states including linearly polarized, left-hand and right-hand circularly polarized states. The maximal phase difference of /spl plusmn/180/spl deg/C between coupled oscillating signals is acquired by using frequency doubling circuits. This then gives well-defined phase differences among oscillators for beam scanning in addition to the required quadrature phase difference for circular polarization. The performances of polarization agility and beam scanning for a four-element antenna array are verified experimentally.