We consider a single Chua's circuit and a system of a unidirectionally coupled n-Chua's circuits driven by a biharmonic signal with two widely different frequencies ω and Ω, where Ω ω. We show experimental evidence for vibrational resonance in the single Chua's circuit and undamped signal propagation of a low-frequency signal in the system of n-coupled Chua's circuits where only the first circuit is driven by the biharmonic signal. In the single circuit, we illustrate the mechanism of vibrational resonance and the influence of the biharmonic signal parameters on the resonance. In the n(= 75)-coupled Chua's circuits enhanced propagation of low-frequency signal is found to occur for a wide range of values of the amplitude of the high-frequency input signal and coupling parameter. The response amplitude of the ith circuit increases with i and attains a saturation. Moreover, the unidirectional coupling is found to act as a low-pass filter.
We investigate the resonance behaviour in a system composed by n-coupled Duffing oscillators where only the first oscillator is driven by a periodic force, assuming a nearest neighbour coupling. We have derived the frequency-response equations for a system composed of two-coupled oscillators by using a theoretical approach. Interestingly, the frequency-response curve displays two resonance peaks and one anti-resonance. A theoretical prediction of the response amplitudes of two oscillators closely match with the numerically computed amplitudes. We analyse the effect of the coupling strength on the resonance and anti-resonance frequencies and the response amplitudes at these frequencies. For the ncoupled oscillators system, in general, there are n-resonant peaks and (n − 1) anti-resonant peaks. For large values of n, except for the first resonance, other resonant peaks are weak due to linear damping. The resonance behaviours observed in the n-coupled Duffing oscillators are also realized in an electronic analog circuit simulation of the equations. Understand- ing the role of coupling and system size has the potential applications in music, structural engineering, power systems, biological networks, electrical and electronic systems.
In this paper, we report an improved implementation of an inductorless third order autonomous canonical Chua's circuit. The active elements as well as the synthetic inductor employed in this circuit are designed using current feedback operational amplifiers (CFOAs). The reason for employing CFOAs is that they have better features such as high slew rate, high speed of operation, etc., which enable the circuit to operate at higher frequency ranges, when compared to the circuits designed using voltage operational amplifiers. In addition to this, the inclusion of CFOAs provide a buffered output which directly represent a state variable of the system. The Multisim simulations in the time and frequency domains confirm the theoretical estimates of the performance of the proposed circuit at high frequencies. It is also confirmed through hardware experiments.
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