A.A. Sudakov, A.V. Zaitsev

Signal, which goes through propagation channel, has linear frequency distortions. For example, first Maxwell equation told that radiated field is first derivative of antenna current. Differentiation of continuous wave signals changes only phase of the signal. Differentiation of ultra-wideband signals changes shape of pulse so it is impossible to use optimal processing in receiver. Thus during estimation of noise immunity of ultra-wideband signals it is necessary to consider additional factors. For solving this task it is necessary to present transmitting channel as four-port network which includes - transmitting apparatus - transmitting antenna - propagation channel - receiving antenna - receiving apparatus?. Transmitting and receiving apparatus includes transfer functions all blocks (amplifiers, limiters, filters etc.) which signal goes before transmitting and after receiving. For non-distortion transfer of signal through four-port network the signal must be matching with four-port network transfer function. At this amplitude-frequency characteristic of matching signal must be correspond to amplitude-frequency characteristic of four-port network and phase-frequency characteristic of matching signal must be correspond to and phase-frequency characteristic of four-port network. Thus knowledge of four-port network transfer function allow to synthesize signal which match with transmitting channel as inverse Fourier transform from four-port network transfer function. After getting matching signal estimation of noise immunity of well-known ultra-wide band signals is calculated. Losses for given transmitting channel (for BER 10-6) for zero order Gauss, Hermit and modified Hermit pulses are within 6.39-7.21 dB. Theses losses are caused by present of constant component in signal spectrum. For Gauss, Hermit and modified Hermit pulses with older orders and for radio pulse are vary from 6.39 dB till 30.6 dB. Theses losses are caused by unmatching amplitude-frequency characteristic of signal and transmitting channel. Less losses has signal which spectrum matched with frequency channel mask. This signal has losses within 0.06-0.43 dB. Value of losses depends of matched signal duration. Also matched signal has the best spectral efficiency 86.62-97.05%. At the same time for other signals spectral efficiency no more than 55.23%. The method of present transmitting channel as - transmitting apparatus - transmitting antenna - propagation channel - receiving antenna - receiving apparatus - allow to get ultra-wideband signal which match with transmitting channel (or choose signal or signal parameters from well-known signals) and has the lowest linear frequency distortions (the best noise immunity) for given channel.