Nonlinear Responses of Microwave Oscillators to External Illumination Predicted by an Equation-Based Collective Approach

Abstract

This paper provides a comprehensive study on and a collective prediction approach to the responses of a microstrip microwave oscillator illuminated by an external plane wave. The field-induced responses are complicated and can be divided into periodic, quasi-periodic, and chaotic regimes. These responses can be effectively simulated by a harmonic-balance simulator based on the newly proposed approach. The main effort of this approach is to incorporate the equation-based equivalent sources with an auxiliary source embedded in the circuit schematic, which is then solved by the circuit simulator. The equivalent sources stand for the plane-wave incidence while the auxiliary source is added to search for the nontrivial solutions. Also based on this approach, the stability property of the obtained solutions can be confirmed, and the predictions of the phase-noise degradation and the demarcation of the chaotic response are provided. A 2.5-GHz oscillator is created and simulated by this approach, and the measurement performed inside a standardized anechoic chamber is compared to the simulation with good agreement. Indeed, the oscillator is observed to have the periodic, quasi-periodic, and chaotic responses. In the periodic regime, the oscillation may be locked or blocked by the external incidence. In the quasi-periodic regime, the oscillation frequency shifts and the phase noise varies. In the chaotic regime, the output spectrum is continuous.