N.M. Ashimov, I.V. Grachev

Reception and demodulation of signals of frequency telegraphy (FT) by means of the frequency detector is considered. Work is carried out for the purpose of definition of the relation a signal/noise (s/n) on an exit of the frequency detector and probability of correct reception of a symbol of the binary combination, necessary for an estimation of a noise stability of system. Demodulation FT of a signal in AM a range is carried out by means of widely known scheme named also the scheme of optimum not coherent reception FT of a signal, it includes two co-ordinated or kvazioptimal the strip filter, adjusted on frequencies FT of the signal, two detectors bending around and the subtracting device. At work in VHF a range stability of frequency of a signal in the given scheme appears insufficient. In this case for demodulation FT of a signal the frequency detector can be used. In work the new scheme of the frequency detector in which FT the signal on an exit of the filter of intermediate frequency (IF) passes through the phase shifter on 90 degrees is offered and the contour which has been adjusted on average frequency FT of a signal arrives on single oscillatory. Target signals of filter PCH and an oscillatory contour arrive further on an input перемножителя to which exit the filter of the bottom frequencies which exit is connected to the filter of the bottom frequencies is connected. It is supposed, that on a scheme input sum FT of a signal and white noise, and on an exit of filter PCH with almost rectangular form AFH - sum FT of a signal and narrow-band noise operates. The remultiplier of signals is the nonlinear device, on its exit three components are formed: - СС a component caused by interaction of a signal with self; - СХ a component caused by interaction of a signal with a hindrance; - XX a component caused by interaction of a hindrance with by itself. In work we define capacity СС of a component of process (capacity of a signal) and autocorrelation function СХ and XX of making process on filter FNCH exit. Further under Wiener-Hinchin's formula spectral density of capacity of these components on an input of the digital filter co-ordinated with an element of video signal and connected to an exit of filter FNCH are defined, and also capacities of these components in a strip of the co-ordinated filter and the relation a signal/noise are defined. As the pass-band of the co-ordinated filter is many times less than pass-band of filter PCH and oscillatory contour at passage through the co-ordinated filter noise process is normalised, that allows to define compact analytical expression for probability of correct reception of element FT of a signal in its dependence on the relation a signal/noise in filter GTCH strip. The compact expression presented through integral of probability by Laplas.