Search Results (2 total)

We identify a method for optimizing the stochastic resonance (SR) in a symmetric bithreshold device: by varying the coherence of the added noise series. To show SR enhancement via this method, we compare the performance of the system using noise sources with different coherence at normalized amplitude. The normalization of the noise amplitude is based on the mean threshold crossing rate of the Gaussian white noise, which is considered as the standard noise in SR studies, at optimal variance. The amplitude for optimal performance of the Gaussian white noise is determined using a signal-to-noise ratio (Q). The Q measure is also used to compare and examine the system performance for different noise cases. This measure is used because it is particularly sensitive to the effects of coherence on the quality of the output power spectrum.

The detection threshold B of a sinusoid-crossing (SC) detector is improved using a new dithering technique. In a real SC detector, B is always greater than zero because the crossings could be located only with finite accuracy. Dithering is employed to determine the frequency f_s and the amplitude A_s of the subthreshold oscillation s(t)=A_s cos(2πf_st), where A_s<B. The data representation of an analog input signal of bandlimit W, consists of locations {t₁,t₂,…,t_2M}={t_i} where the signal intersects with the reference sinusoid r(t)=A cos(2πf_rt). A crossing exists within each interval Δ=1/2 f_r=T/2M, where T is the sampling period. If W/2<~f_r, and the signal amplitude is less than A for all t values within T, then SC sampling satisfies the Nyquist sampling theorem. The unknown f_s value is determined from the power spectrum of the crossing locations of [s(t)+n_σ(t)], where n_σ(t) is the noise of variance σ². The A_s value is approximated from the signal-to-noise ratio (R) vs σ plot. The performance of the technique is studied from the R plots for different A_s, f_s, and T values.