Analysis of Strong Coupling in Coupled Oscillator Arrays

Significant improvement in the mutual injection locking range (MILR) and phase noise can be obtained by strengthening the coupling between the oscillator elements in a coupled oscillator array (COA). An analysis of the array properties in the strongly coupled regime is provided in this paper. Previous analyses of COAs have employed a so-called broadband condition that substantially simplifies analysis. The broadband condition is observed to break down in the strongly coupled regime, a feature that is central in the understanding of the behavior of strongly coupled arrays. The observed improvement in the phase noise performance can be attributed to the highly resonant nature of the coupling network in the strongly coupled regime. The theory is verified using a five-element linear COA operating at 3.75 GHz. Significant improvements in the MILR and phase noise is reported. The beam steering capabilities of strongly coupled arrays are also presented.