System for set-up of transmitters in high capacity digital radio links
First Claim
1. A method for initializing a transmitter used in a high capacity digital radio link in which multilevel QAM digital signals are sent on a carrier wave, said initializing being accomplished by:
- (a) generating a test signal which simulates the digital signal to be transmitted, said test signal being generated by selectively summing four sinusoidal signals amplitude-modulated by a square wave with a variable duty cycle and amplitude, said test signal being adjusted to obtain a signal having a ratio of peak power/mean power which is equal to that of the digital signal to be transmitted,(b) sending said test signal through the transmitter, said transmitter including a power amplifier which has a nonlinear behavior and distorts signals passing therethrough, and(c) adding pre-distortion signals to the digital signals sent through the power amplifier to compensate for the distortion caused by the non-linearities in the power amplifier of the transmitter.
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Accused Products
Abstract
The invention relates to a system for initializing transmitters in high capacity digital radio links, in which a digital signal with QAM (Quadrature Amplitude Modulation) modulation is transmitted over a radio frequency carrier wave. The initialization of the transmitter is accomplished by generating a plurality of sinusoidal signals (tones), adding those tones together to simulate a digital singal to be transmitted, sending the simulated digital signal through the transmitter, and adjusting the transmitter to compensate for the intermodulation odd order products developed as a result of the nonlinearity of the power amplifier in the transmitter.
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Citations
3 Claims
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1. A method for initializing a transmitter used in a high capacity digital radio link in which multilevel QAM digital signals are sent on a carrier wave, said initializing being accomplished by:
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(a) generating a test signal which simulates the digital signal to be transmitted, said test signal being generated by selectively summing four sinusoidal signals amplitude-modulated by a square wave with a variable duty cycle and amplitude, said test signal being adjusted to obtain a signal having a ratio of peak power/mean power which is equal to that of the digital signal to be transmitted, (b) sending said test signal through the transmitter, said transmitter including a power amplifier which has a nonlinear behavior and distorts signals passing therethrough, and (c) adding pre-distortion signals to the digital signals sent through the power amplifier to compensate for the distortion caused by the non-linearities in the power amplifier of the transmitter. - View Dependent Claims (2)
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3. A device for initializing a transmitter used in a high capacity data link in which digital signals are sent on a carrier wave, comprising:
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(a) a test signal generator for generating a test signal, said test signal generator comprising four oscillators for producing said sinusoidal signals, a summator for summing said sinusoidal signals, an amplitude modulator for modulating the summed sinusoidal signals and a square wave generator adjustable in amplitude and duration for adjusting said amplitude modulator, and (b) a pre-distorter signal generator for adding distortion to the digital signals to be transmitted which compensates for distortion introduced by a power amplifier in the transmitter.
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Specification