Recently, OFDM systems have received wide interest, particularly in the field of terrestrial broadcasting of all digital television in the UHF/VHF bands. The use of TWT (Traveling Wave Tubes) is considered for the final amplification of the OFDM signal. The OFDM modulated signal is very close to a Gaussian random process. In this paper we revisit the most popular TWT models and recognize that they belong to a peculiar class of non-linearities, S×FSM, in which the output is the product of the incoming complex signal and a function of its modulus. For S×FSM nonlinearities, driven by a Gaussian input, output statistics can be evaluated in closed forms. We apply this analysis to the TWT non-linearity, deriving the power spectral density of the output signal as well as the probability density function, when the input is an OFDM signal
Nonlinear Model of TWT Revisited for OFDM Systems
VANGELISTA, LORENZO;
1996
Abstract
Recently, OFDM systems have received wide interest, particularly in the field of terrestrial broadcasting of all digital television in the UHF/VHF bands. The use of TWT (Traveling Wave Tubes) is considered for the final amplification of the OFDM signal. The OFDM modulated signal is very close to a Gaussian random process. In this paper we revisit the most popular TWT models and recognize that they belong to a peculiar class of non-linearities, S×FSM, in which the output is the product of the incoming complex signal and a function of its modulus. For S×FSM nonlinearities, driven by a Gaussian input, output statistics can be evaluated in closed forms. We apply this analysis to the TWT non-linearity, deriving the power spectral density of the output signal as well as the probability density function, when the input is an OFDM signal
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