Abstract: A digital predistorter comprises a module (J) for producing a counteracting signal Vm1 for combination with the input signal of a power amplifier to correct the output of the amplifier for distorting memory effects within the amplifier. The module (J) produces the counteracting signal Vm1 by convolving (see FIG. 6) non-linear functions of the input signal with impulse response characteristics related to the memory effects being corrected.

Abstract: A digital predistorter comprises a module J for producing a counteracting signal Vm1 for combination with the input signal of a power amplifier to correct the output of the amplifier for distorting memory effects within the amplifier. The module J produces the contracting signal Vm1 by convolving (see FIG. 6) functions of the input signal with impulse response characteristics related to the memory effects being corrected. The counteracting signal Vm1 is produced by a function fm and parameters in that function are adjusted to minimise any residual distortion in the amplifier output.

Abstract: A frequency upconverter using mixers operating on one or more signals and inverted versions thereof and a subtractor, such as a balun, for subtractively combining the mixer outputs to produce an upconverted signal.

Abstract: The control scheme uses the input and output signals of an amplifier (10) to control a lineariser (24) operating on the amplifier (10). The input and output signals are sensed and used to develop assay signals that have ideal inter-relationships when the amplifier is operating as desired. The control scheme modifies the operation of the lineariser to account for any departures observed in the relationships.

Abstract: A method of controlling an amplifier, the method comprising a sampling step of using a sampler to obtain digital samples of both an output signal of said amplifier and a reference signal, a derivation step of obtaining from said samples values of a first parameter and associated values of a second parameter, an averaging step of averaging the first parameter values over ranges of the second parameter such that, for each range, an average of the first parameter is obtained by averaging the first parameter values whose associated second parameter values lie in the range, a generation step of generating a control signal for said amplifier from said averages, a suppression step of using said samples of said reference signal to inhibit the effect upon said control signal of errors in the operation of said sampler and a control step of applying the control signal to said amplifier to direct the operation of said amplifier. The invention also relates to apparatus involved in carrying out the method.