Study of the Characteristics of Second-Order Underdamped Unsaturated Stochastic Resonance System Driven by OFDM Signals

Aiming at the issue of suboptimal demodulation performance in OFDM signal enhancement processes due to slow response speeds in first-order overdamped stochastic resonance systems, this paper designs an OFDM signal enhancement and demodulation system based on second-order underdamped unsaturated bistable stochastic resonance (SUUBSR). Firstly, a nonsaturated bistable potential function model is constructed by combining a traditional monostable potential function with a Gaussian potential function, and a damping coefficient is introduced simultaneously to build the SUUBSR system. Subsequently, the transient and steady-state output response analytical expressions of the SUUBSR system under OFDM signal excitation are derived, the energy loss of OFDM symbol waveforms caused by the transient response of the system is discussed, and the relationship between the damping coefficient and the steady-state output response of the system is explored. Finally, simulations are conducted to evaluate the enhancement and demodulation process of OFDM signals using the SUUBSR system. The simulation results show that at an input signal–noise ratio of 2 dB, compared to the first-order unsaturated bistable stochastic resonance (FUBSR) system, the proposed system reduces the system response time by 3.956% of a symbol period and decreases the demodulation bit error rate for OFDM signals by approximately 35%.