Telefonaktiebolaget Lm Ericsson (Publ)

Karl-Gosta Sahlman

Radio transmissions to multiple radio terminals are improved using scheduled backoff of a multi-signal power amplifier. A radio channel quality associated with each of the radio terminals is determined. First signals for first radio terminals associated with a better channel quality are amplified by a power amplifier during a first time period resulting in a first composite output signal. Second signals for second radio terminals associated with a lower channel quality are amplified by the power amplifier during a second time period resulting in a second composite output signal. Transmission during the first time period occurs at a first power level, e.g., mean power, that is associated with a lower probability of clipping the first composite output signal. During the second time period, the second composite signal is transmitted at a second power level, e.g., mean power, higher than the first power level which improves reception at the second terminals.

Radio communications using scheduled power amplifier backoff

In the present invention a completely different approach for modeling of non-linear devices or processes is used. A cascade of blocks each depending on a non-linearity parameter are utilized both in non-linear modeling and a pre-distorter design. The new non-linear model description can be used for characterization of a non-linear system or for linearizing a non-linear system. Application to a Communications System Multi-carrier Amplifier is shown as an application example. Also for other application areas of the new mathematical method is feasible echo-canceling, non-linear communications channels etc. Parameter extractions and tables for the new model do not give multiple dimensional mathematical solutions for parameter extractions as in prior art.

Non-linear modeling method

A transmitter subsystem is disclosed whereby the output frequency spectrum of a DDS device, for use in the transmitter subsystem, is frequency multiplied to achieve greater frequency coverage at the RF bands. In one embodiment of the present invention, a DDS device is structured in such a way that the DDS output signal spectra can be multiplied directly for direct conversion to RF or IF bands. As such, the requirements placed on the DACs in the DDS device are lessened, because the DACs require much lower sampling frequencies than those used in the existing technology. Also, the requirements placed on the implemented bandpass filters used for image rejection in the applied upconverters are lessened, because of the larger frequency difference created between the desired output and the image frequency band. In a second embodiment of the present invention, a DDS device is also structured in such a way that multiplication of the baseband spectra can be accomplished at the IF. Consequently, in accordance with the present invention, less complex or costly DACs can be used for generating wideband signals at higher frequencies, but relatively high linearity signals can still be attained.

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Sollentuna, Sweden

Karl-Gosta Sahlman