Baseband predistortion method for multicarrier transmitters
AssigneeNokia Corporation
InventorTommi Ylamurto
Life of this patent
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Abstract
A multicarrier transmitter is shown having an embodiment of the invention. Sampling of modulated and amplified signals is done to obtain energy values for four or more symbols. Combining the energy values with the baseband in-phase and quadrature signals of the multiple carriers may result in a set of imbalance parameters, which are subsequently stored. Later baseband in phase and quadrature signals are predistorted or compensated by applying the stored imbalance parameters to produce new compensated baseband in-phase and compensated baseband quadrature signals, which are suitable for input to an inverse fast fourrier transform (IFFT) block.
Claims6
A method for providing a first quadrature compensated data symbol (FQCDS), a second quadrature compensated data symbol (SQCDS), a first in-phase compensated data symbol (FICDS) and a second in-phase compensated data symbol (SICDS) to an inverse fast fourrier transform (IFFT) of a multicarrier quadrature modulator having an amplifier, wherein at least four transmitted symbols are available from the amplifier and at least four data symbols and a next data symbol are available from a mapper, comprising the steps of:
- a) calculating the energy of the at least four transmitted symbols;
- b) calculating an alpha, an epsilon and a gain based on the energy of the at least four transmitted symbols and the at least four data symbols, wherein the alpha, epsilon and gain are imbalance parameters;
- c) storing the alpha, epsilon and gain;
- d) first quadrature compensating the next data symbol of a first quadrature subcarrier based on the alpha, epsilon and gain to produce the FQCDS;
- e) second quadrature compensating the next data symbol of a second quadrature subcarrier based on the alpha, epsilon and gain to produce the SQCDS;
- f) first in-phase compensating the next data symbol of a first in-phase subcarrier based on the alpha, epsilon and gain to produce the FICDS;
- g) second in-phase compensating the next data symbol of a second in-phase subcarrier based on the alpha, epsilon and gain to produce the SICDS;
- h) repeating steps a, b and c wherein the at least four transmitted symbols include a next transmitted data symbol and the at least four data symbols include the next data symbol.
An apparatus for providing a first quadrature compensated data symbol (FQCDS), a second quadrature compensated data symbol (SQCDS), a first in-phase compensated data symbol (FICDS) and a second in-phase compensated data symbol (SICDS) to an inverse fast fourrier transform (IFFT) of a multicarrier quadrature modulator having an amplifier, wherein at least four transmitted symbols are available from the amplifier and at least four data symbols and a next data symbol are available from a mapper comprising:
- a) means for calculating the energy of the at least four transmitted symbols;
- b) means for calculating an alpha, an epsilon and a gain based on the energy of the at least four transmitted symbols and the at least four data symbols, wherein the alpha, epsilon and gain are imbalance parameters;
- c) means for storing the alpha, epsilon and gain;
- d) means for first quadrature compensating the next data symbol of a first quadrature subcarrier based on the alpha, epsilon and gain to produce the FQCDS;
- e) means for second quadrature compensating the next data symbol of a second quadrature subcarrier based on the alpha, epsilon and gain to produce the SQCDS;
- f) means for first in-phase compensating the next data symbol of a first in-phase subcarrier based on the alpha, epsilon and gain to produce the FICDS;
- g) means for second in-phase compensating the next data symbol of a second in-phase subcarrier based on the alpha, epsilon and gain to produce the SICDS;
- h) means for repeating implementation of a, b and c wherein the at least four transmitted symbols include a next transmitted data symbol and the at least four data symbols include the next data symbol.
Dependencies are inferred from the claim text.