Abstract: An IQ-modulator pre-distorter includes an iteratively updated digital filter (gQ0, gQ1) for filtering one of the branches of an IQ-signal to compensate for IQ-modulator generated amplitude errors. An iteratively updated digital filter (cQI0, cQI1), cross-connected from one of the branches to the other branch, filters one of the components of an IQ-signal to compensate for IQ-modulator generated inter-modulation between the branches. Iteratively updated compensators (dcI, dcQ) counteract IQ-modulator generated offset errors.

Abstract: A method for compensating signal distortions in multiple transmitting branches (3, 5; 43, 45, 46) entering a composite amplifier (1; 1?). According to the invention the method comprises the steps of: —providing (S1) one or more input signals (x) to the composite amplifier, —observing (S2) an output signal (z) from the composite amplifier ( 1; 1?) for each provided input signal; —deriving (S5) an error in each output signal (z) by comparing the output signal with an ideal output signal, said error being caused by said signal distortions; —deriving (S11) the individual contribution from each transmitting branch (3, 5; 43,45,46) to the error by utilising a composite amplifier model, said composite amplifier model comprising information about the contribution from each constituent amplifier (23, 25; 103a,103b,103c) to the output signal for each provided input signal: —compensating the signal distortions in the transmitting branches (3, 5; 43,45,46) accordingly.

Abstract: An IQ-modulator pre-distorter includes an iteratively updated digital filter (gQ0, gQ1) for filtering one of the branches of an IQ-signal to compensate for IQ-modulator generated amplitude errors. An iteratively updated digital filter (cQI0, cQI1), cross-connected from one of the branches to the other branch, filters one of the components of an IQ-signal to compensate for IQ-modulator generated inter-modulation between the branches. Iteratively updated compensators (dcI, dcQ) counteract IQ-modulator generated offset errors.

Abstract: A power amplifier pre-distorter is formed by a FIR filter structure which includes an individual look-up table for each filter tap, where each look-up table represents a sample polynomial in a variable representing signal amplitude, and means for selecting, from each filter tap look-up table, a filter coefficient that depends on the amplitude of corresponding complex signal value to be multiplied by the filter tap. A training method for such a pre-distorter sets (S1) the entries of table T0 and T1 to predetermined values. Then it measures and stores (S2) a batch of input signals x and feedback signals y. New estimates of T0 and T1 are determined (S3) using an iteration of a least mean square based iterative procedure. Then it is tested (S4) whether the tables have converged. If the tables have converged, the current estimates are provided as the final tables. Otherwise another iteration (S2-S4) of the least mean square procedure is performed.

Abstract: A power amplifier pre-distorter is formed by a FIR filter structure which includes an individual look-up table for each filter tap, where each look-up table represents a sample polynomial in a variable representing signal amplitude, and means for selecting, from each filter tap look-up table, a filter coefficient that depends on the amplitude of corresponding complex signal value to be multiplied by the filter tap. A training method for such a pre-distorter sets (S1) the entries of table T0 and T1 to predetermined values. Then it measures and stores (S2) a batch of input signals x and feedback signals y. New estimates of T0 and T1 are determined (S3) using an iteration of a least mean square based iterative procedure. Then it is tested (S4) whether the tables have converged. If the tables have converged, the current estimates are provided as the final tables. Otherwise another iteration (S2-S4) of the least mean square procedure is performed.

Abstract: To generate a high-power modulated radio frequency signal SOUT from an input low or medium frequency information signal SIN, the information signal is pulse-shaped in a quantifier to form a digital signal SD having discrete signal values. The digital signal is processed in a switching unit comprising switches for each signal value, in radio frequency wave generators for each switch generating carrier waves of radio frequency, and in control circuits for each switch to control the opening and closing thereof. When a switch is closed, its associated generator is connected to the output line of the switching unit, and when it is opened, the generator is disconnected therefrom. In the switching unit, a switched radio frequency signal SSW carrying the information of the input signal is formed by opening and closing the switches when the digital signal adopts or does not adopt, respectively, the signal value associated with the respective switch.