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US 6,587,257 B1Granted
Non-linear subcarrier predistortion and upconversion system
AssigneeTelecommunications Research Laboratories
InventorRobert James Davies
Life of this patent
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AssigneeTelecommunications Research Laboratories
InventorRobert James Davies
Estimating the term…
A method and apparatus for harmonically upconverting a phase and/or amplitude modulated subcarrier signal to a higher frequency through a non-linear optical link is disclosed. The method requires that a bandpass signal, with a carrier frequency at a submultiple of the desired radio transmission frequency, be frequency translated in a non-linear two-port device. To avoid the inherent distortion inflicted on the information signal in harmonic upconversion, a predistortion technique is outlined. This consists of phase compression in the case of a phase modulated signal, amplitude scaling in the case of amplitude only and combined phase-amplitude predistortion for QAM type signals. With predistortion on the subcarrier signal input to the non-linear two-port, the resulting upconverted signal may be transmitted in a standard form suitable for demodulation at the signal destination without special equipment.
A method of subcarrier harmonic modulation of an information signal, the method comprising the steps of:
A subcarrier harmonic modulation system comprising:
A phase predistortion method in which the original phase portion of a quadrature information signal is predistorted such that when the predistorted phase is modulated onto a radio carrier so as to produce a bandpass signal and the bandpass signal is subsequently translated in frequency through a harmonic upconversion device, causing the phase of the bandpass signal to be further altered by the upconversion process, the phase of the upconverted bandpass signal returns to the original phase state.
An amplitude predistortion method in which the original amplitude portion of a quadrature information signal is altered such that when the altered amplitude signal is modulated onto a radio carrier so as to produce a bandpass signal and the bandpass signal is subsequently translated in frequency through a harmonic upconversion device, causing the amplitude of the bandpass signal to be farther altered by the upconversion process, the amplitude of the upconverted bandpass signal returns to the original amplitude state.
Dependencies are inferred from the claim text.