Improvement of signal‐to‐noise ratio in a combination of a linear and a nonlinear amplifier
Masanori Shinriki, Regular Member · Electronics and Communications in Japan (Part I Communications) · 1982
Abstract In general, when a signal with noise is applied to a nonlinear amplifier, the nonlinearity will suppress either the signal or the noise. This property is utilized in this paper; the input signal is applied to nonlinear and linear amplifiers and an output circuit forms their difference. It is found that such a circuit can markedly improve the signal‐to‐noise (S/N) ratio of an input signal containing strong noise. Simple saturation nonlinearity is produced by an element xν(ν 1 extension‐type nonlinearity characteristics result. A general type of noise is treated as a narrowband noise with a Weibull amplitude distribution. Analysis shows that when the Weibull coefficient is small, the use of the saturation characteristics of a nonlinear amplifier improves the S/N ratio considerably; when the Weibull coefficient is very large, neither extension‐ or saturation‐nonlinearity shows a marked difference. If the signal is contained in narrow‐band noise of constant amplitude, tests confirm the effectiveness of the theory.