Abstract: A transmit power control system includes: an output power estimator for estimating a transmit power of a transmitter; and a transmit power controller responsive to the output power estimator and to compare this with a requested power in order to calculate a target power which takes account of errors within the transmit power control system, and to vary a gain of an amplifier in a transmit signal path so as to reduce an error between the transmit power of the amplifier and the requested power.

Abstract: A switching circuit comprising: first and second steering switches operable to make or break a path between first and second terminals thereof, and each steering switch further having a control terminal for controlling the switch, the first and second steering switches having their control terminals driven by first and second switching signals, the first and second switching signals having a first frequency and the second switching signal being in anti-phase with the first switching signal and a first chopping switch operable to make or break a path between first and second terminals thereof and being connected in series with at least one of the first and second steering switches and receiving at its first terminal an input to be modulated, wherein the control terminal of the chopping switch is driven by a first switching control signal such that the chopping switch is non-conducting while the first and second steering switches are changing between being conducting and being non-conducting.

Abstract: A transmit power control system includes: an output power estimator for estimating a transmit power of a transmitter; and a transmit power controller responsive to the output power estimator and to compare this with a requested power in order to calculate a target power which takes account of errors within the transmit power control system, and to vary a gain of an amplifier in a transmit signal path so as to reduce an error between the transmit power of the amplifier and the requested power.

Abstract: A low drop out voltage regulator, comprising first and second field effect transistors arranged in series between a regulator input and a regulator output; a third field effect transistor co-operating with the first field effect transistor to form a first current mirror; a fourth field effect transistor co-operating with the second field effect transistor to form a second current mirror; first and second control transistors, which advantageously are bipolar transistors connected in series with the third and fourth field effect transistors respectively so as to control the current flowing therein; and a controller for providing a control signal to the first and second bipolar transistor as a function of a voltage at the regulator output.

Abstract: A signal processing system has a first, digitally controlled, gain element, a second, analogue controlled, gain element and a gain control unit configured to receive a gain request signal and to generate a first gain control signal to be input to the first gain element and a second gain control signal to be input to the second gain element such that the gain provided by the signal processing system corresponds to the gain request signal.

Abstract: A frequency agile voltage controlled oscillator is provided in which amplitude control is performed by digitally controlling the current supplied to the oscillator from a current source (10). The use of digital control means that phase noise performance of the oscillator is not degraded by the introduction of noise from the current source controller.

Abstract: An RC equivalent filter is provided in which the resistor is replaced by a voltage source (40) and a capacative divider. With suitable control the voltage occurring across a capacitor (44) in the divider can reproduce that which would occur across at the output of the original RC filter, but with much lower noise.