Noise-switched tunnel diod amplifier on microwave
M.V. Davidovich
Saratov Technical University,
Saratov, Russia
The tunnel diod amplifier of small modulated signal switched by noise of big intensity was investigated in the microwave frequency range. As the tunnel diod have the cubic nonlinearity in the static current per voltage characteristic, noise switching over the two extremal points on this characteristic can cause the amplification of the small regular signal. This amplification and signal to noise ratio (SNR) increase when stochastic resonance (SR) occur or when the frequency of switching is equal to the main frequency of the modulated signal [1,2]. In this work the amplification of amplitude- modulated and frequency-modulated signals have explored for diod included in transmission line by use of two impedance transformers.
For the pass band of these tramsformers we can approximately use the following equation to describe the SR phenomenon:
where R is the transmission line wave impedance, C is the shunt diod
capacitance, L is the series inductance, J(U) is the current per
voltage diod characteristic function which can be taken by cubic
polynomial in the explored range of U, S(t) is the modulated signal
function and N(t) is the white noise. For solving (1) the procedure
based upon pertubation method for two follow from (1) integral
equations was elaborated. For each time realization of the solution
of equation (1) the spectrum have been computed by use the fast
Fourier integral tramsform based upon pulse-constant time
discreditation of this solution. The such transform for solitary
pulse between moments 
and 
with amplitude V and duration 
is
To compute the SNR the stochastic averaging by use the several tens of the spectral realizations have used.
The investigations show the following results: 1) there is strong (in order of several tens of decibel) wide band signal and noise amplification for frequencies more less then own resonant frequency; 2) the pass band without perceptible signal distortion is about 20%; 3) the SNR increase when SR occur and decrease with frequency.