Potential immunity of radio control lines

Abstract

In the work, a methodology for assessing the potential noise immunity of radio control lines operating with binary FT signals is presented when using both element-by-element signal processing and signal processing in toto. The calculation method is based on the criterion adopted in radio control lines. According to the proposed technique, calculation shows that potential noise immunity with element-by-element signal processing is achieved with coherent reception of the FT signal under conditions of an unlimited increase in the code width, therefore, the frequency band occupied by the signal is expands indefinitely. In this case processing a binary signal in toto is realized by transferring the clipper from the video channel to the input signal receiving circuit. The transition from element-by-element signal processing to processing it in toto accompanied by an increase in the maximum possible value of the noise immunity coefficient by a factor of / 2 . Such an effect, in comparison with the circuit of the model of the radio control line with element-by-element processing of the FT signal, is achieved due to the transfer of the clipper, which plays the role of a decisive element in the circuit when receiving a symbol, into the input circuit. As a result, a filter-clipper-filter system is formed together with bandpass F1 and F2 filters. Therein F1 filter is still tuned to the frequency of the FT signal and matched to its symbol, and the passband of F2 is much higher than the bandwidth of the matched filter so that only the first harmonic of the signal spectrum is isolated without distortion practically. In this case, the clipper (O) ensures that the probability of false reception Pl is independent of the level of input noise, and at the s-n ratio q≤1 the clipper behaves like a linear device, while it is a classical nonlinear device when it is operating in the video signal channel (fig. 2) where there is signal suppression by interference which leads to a certain decrease in the potential radio link noise immunity during signal processing in element-by-element type.