Wide angle phase-shifterless beam scanning in unilaterally coupled active antenna arrays

In coupled oscillator arrays, it is possible to control the inter-element p hase shift up to 180 degrees by free-running frequency distribution based o n injection-locking phenomenon. In this paper, a new technique to control t he inter-element phase shift electronically up to the maximum extent of 360 degrees is reported. Oscillators are unilaterally coupled to the preceding oscillator through one of the two paths, which differ from each other 180 degrees in electrical length and each includes an amplifier. Turning on the desired amplifier one can control the phase shift either -180 degrees to 0 degrees or 0 degrees to 180 degrees. The technique was applied in a three- element oscillator array each coupled to a patch antenna via a round apertu re. The radiation beam of the array could be scanned 47 degrees in total.