Method and circuit for adaptive control of the bandwidth of a carrier recovery loop in radio transmission systems
AssigneeAlcatel
InventorsRoberto Valtolina, Massimo Brioschi
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Abstract
A method for adaptively controlling bandwidth of a carrier recovery loop in radio transmission systems, wherein the phase error in a PLL is adjusted to a minimum level by means of a loop filter incorporated in said PLL. The phase noise value in the local oscillator is determined and the value of the additive white gaussian noise in the PLL is estimated. Next these values are applied in a predetermined mathematical relationship indicative of the phase error in said PLL in such a manner that the desired wavelength of the PLL can be determined by corresponding to a minimum value of the phase error.
Claims4
A method for adaptive control of bandwidth of a carrier recovery loop in a radio transmission system, said system comprising a local oscillator and a phase locked loop (PLL) for tracking a carrier phase, the PLL having a transfer function, characterized in that a phase error in the PLL is adjusted to an optimum level by means of a loop filter incorporated in said PLL, said optimization of the phase error in the PLL comprising, at every symbol time, the steps of:
- determining a first value relative to phase noise in the local oscillator;
- estimating a second value relative to additive white Gaussian noise in the PLL;
- applying the said first and second values in a predetermined mathematical relationship representing the phase error variance σe2 as a function of a transfer function L(f) of said PLL, and as a function of said phase noise and of said additive Gaussian noise;
- and
- calculating a value of said PLL transfer function L(f) corresponding to an optimum phase error variance σe2 according to said predetermined mathematical relationship.
Dependencies are inferred from the claim text.