In a conventional phased-array, a constant phase progression is established using electronically-controlled phase shifters at each element. This approach is conceptually simple, but can be complicated in practice, especially in recent efforts to develop monolithic T/R modules where it is difficult to integrate the phase shifter circuitry, RF distribution network, control signals and DC bias lines along with the planar antenna. However, an attractive feature of injection locking techniques is the ability to manipulate the phase distribution without phase-shifting circuitry, suggesting a potential for low cost beam scanning systems.
We propose a new technique for electronic beam scanning without phase shifter circuitry. A constant phase progression which is independent of both the number of oscillators and the locking range is accomplished by controlling the coupling phase of the outmost coupling circuits only, while that of the innermost coupling circuits is zero and all free-running frequencies of the oscillators are same. A constant phase progression is a piecewise linear function of coupling phases only and is not arcsine nonlinear function of free-running frequency. This technique is tested using an experiment of a four-element oscillator array. The radiation pattern of patch antenna attached to innermost two-element oscillators could be continuously steered over a range of angles from -17° to 18° off broadside. This scan range is very close to the theoretically achievable scan range.
One apparent limitation of the injection-locked or coupled oscillator topologies is the limited range of phase progression that can be synthesized. A coupled oscillator array at fundamental frequency produces a phase shift up to 180° when free-running frequency is pulled across the locking bandwidth.
In this dissertation, enhanced beam scanning range is achieved by using frequency doubler circuit and control technique of coupling angle. The full scan range is measured to be -22...