Abstract
A detailed analysis of wireless-coupled oscillator systems under the effect of an injection-locking signal is presented. The injection source of high spectral purity is introduced at a single node and enables a reduction of the phase-noise spectral density. Under this injection source, the behavior of the coupled system is qualitatively different from the one obtained in free-running conditions. Two cases are considered: bilateral synchronization, in which an independent source is connected to a particular system oscillator, coupled to the other oscillator elements, and unilateral synchronization, in which one of these elements is replaced by an independent source that cannot be influenced by the rest. The two cases are illustrated through the analysis of a wireless-coupled system with a star topology, such that the injection signal is introduced at the central node. The investigation involves an insightful analytical calculation of the coexisting steady-state solutions, as well as a determination of their stability and bifurcation properties and phase noise. The injection signal stabilizes the system in a large and continuous distance interval, enabling a more robust operation than in autonomous (noninjected) conditions. A coupled system operating at 2.45 GHz has been manufactured and experimentally characterized, obtaining a very good agreement between simulations and measurements.
Highlights
SYNCHRONIZATION is an essential requirement in sensor networks, multiple-input multiple output (MIMO) antenna systems, measurement systems, and other [1]-[10]
Note that the analysis above is immediately extended to a globally-coupled oscillator system with a symmetric topology, having the injection-locked oscillator symmetrically located with respect to the rest
In a general topology, having an independent source that is not symmetrically located with respect to the system oscillators, these oscillators will be subject to the influence of both the independent source and the coupling signals
Summary
SYNCHRONIZATION is an essential requirement in sensor networks, multiple-input multiple output (MIMO) antenna systems, measurement systems, and other [1]-[10]. The formulation in [14]-[15] is based on a realistic description of the coupled system, such that the oscillator elements are represented with accurate models, extracted from harmonic-balance (HB) and the coupling effects are thoroughly described in terms of the operation frequency, distance and antenna gain. As the source amplitude increases, a value is reached, such that stable operation is obtained for all the distance values up to a certain maximum This is a fundamental difference with respect to the behavior in freerunning conditions [15], i.e., in the absence of the synchronizing source [14]-[15], in which stable and unstable intervals alternate.
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