Linear amplifier arrangement

A linear power amplifier arrangement comprising a high power amplifier, a pre-distortion circuit and a feedback circuit;

• wherein an input is operable to receive radio frequency (RF) input signals and is connected to the power amplifier via a directional coupler, a first delay line, an RF amplitude modulator and an RF phase modulator;
• wherein the feedback circuit comprises a directional coupler operable to sample an output of the amplifier and provide a signal to an amplitude and phase error detector;
• wherein the pre-distortion circuit comprises a coupled line from the input directional coupler, a power gplitter, the outputs of which are connected to a second delay line and an adaptive pre-distortion subsystem;
• wherein the second delay line is operable to provide a signal to the amplitude and phase error detector;
• and
• wherein the pre-distortion subsystem is operable to receive signals from the power splitter via an RF envelope detector and signals relating to gain error and amplitude error from the phase and amplitude error detector and to provide a gain correction signal to a control port of the amplitude modulator;
• and a phase correction signal to a control port of the phase modulator,
• wherein the adaptive pre-distorter is operable to generate the correction signals as functions of a tapped RF input signal in such a way that the modulated delayed RF input signal on passing through the high power amplifier emerges with reduced distortion.

A linear power amplifier arrangement comprising a high power amplifier, a pre-distortion circuit and a feedback circuit;

• wherein an input is operable to receive radio frequency (RF) input signals and is connected to the power amplifier via an input directional coupler, a first delay line, a first RF amplitude modulator, a first RF phase modulator, a second RF amplitude modulator and a second RF phase modulator;
• wherein the feedback circuit comprises a directional coupler operable to sample an output of the amplifier and provide a signal to an amplitude and phase error detector, baseband processing elements;
• and second amplitude and phase modulators;
• wherein the pre-distortion circuit comprises a coupled line from the input directional coupler, a power splitter, the outputs of which are connected to a second delay line and an adaptive pre-distortion subsystem;
• wherein the second delay line is operable to provide a signal to the amplitude and phase error detector;
• and
• wherein the pre-distortion subsystem is operable to receive signals from the power splitter via an RF envelope detector and signals relating to gain error and amplitude error from the phase and amplitude error detector and to provide, with reference to a look-up table, a gain correction signal to a control port of the first amplitude modulator;
• and a phase correction signal to a control port of the first phase modulator;
• the baseband processing elements comprise feedback loops operable in the gain and phase domains in order to centre the operation of the pre-distorter;
• wherein the adaptive pre-distorter is operable to generate the correction signals as functions of a tapped RF input signal in such a way that the modulated delayed RF input signal on passing through the high power amplifier emerges with reduced distortion.

A method of operating a linear power amplifier arrangement comprising a high power amplifier, a pre-distortion circuit and a feedback circuit;

• comprising the following steps:
• receiving RF input signals at an input connected to the power amplifier via a directional coupler, a first delay line, an RF amplitude modulator and an RF phase modulator;
• in the feedback circuit:
• coupling output signals from an output of the amplifier employing a directional coupler operable to sample an output of the amplifier and to provide signals to an amplitude and phase error detector;
• in the pre-distortion circuit:
• coupling a sample of the RF input signal employing a directional coupler, splitting the signal via a power splitter, feeding a first output of which to an amplitude and phase error detector via a second delay line and a second output of which to an adaptive pre-distortion sub-system via an RF envelope detector;
• at the pre-distorter sub-system:
• receiving sampled RF input signals from the RF envelope detector and signals relating to gain error and amplitude error from the phase and amplitude error detector and providing a gain correction signal to a control port of the RF amplitude modulator;
• and a phase correction signal to a control port of the RF phase modulator;
• wherein the adaptive pre-distorter is operable to generate the correction signals as functions of a tapped RF input signal in such a way that the modulated delayed RF input signal on passing through the high power amplifier emerges with reduced distortion.

A method of operating a linear power amplifier arrangement comprising a high power amplifier, a pre-distortion circuit and a feedback circuit;

• comprising the following steps:
• receiving input signals at an input connected to the power amplifier via a directional coupler, a first delay line, a first amplitude modulator, a first phase modulator, a second amplitude modulator and a second phase modulator;
• in the feedback circuit:
• coupling output signals from an output of the amplifier employing a directional coupler operable to sample an output of the amplifier and to provide signals to an amplitude and phase error detector and to second amplitude and phase modulators via baseband processing elements which baseband processing elements comprise feedback loops operable in the gain and phase domains and which centre the operation of the pre-distorter;
• in the pre-distortion circuit:
• coupling a sample of the input signal employing a directional coupler, splitting the signal via a power splitter, feeding a first output of which to an amplitude and phase error detector via a second delay line and a second output of which to an adaptive pre-distortion sub-system via an envelope detector;
• at the pre-distorter sub-system:
• receiving sampled input signals from the envelope detector and signals relating to gain error and amplitude error from the phase and amplitude error detector and providing a gain correction signal to a control port of the first amplitude modulator;
• and a phase correction signal to a control port of the first phase modulator,
• wherein the adaptive pre-distorter is operable to generate the correction signals as functions of a tapped input signal in such a way that the modulated delayed input signal on passing through the high power amplifier emerges with reduced distortion.

A linear power amplifier arrangement comprising a high power amplifier, a pre-distortion circuit and a feedback circuit;

• wherein an input is operable to receive radio frequency (RF) input signals and is connected to the power amplifier via a directional coupler, a first delay line, an RF amplitude modulator and an RF phase modulator;
• wherein the feedback circuit comprises a directional coupler operable to sample an output of the amplifier and provide a signal to an amplitude and phase error detector;
• wherein the pre-distortion circuit comprises a coupled line from the input directional coupler, a power splitter, the outputs of which are connected to a second delay line and an adaptive pre-distortion subsystem;
• wherein the second delay line is operable to provide a signal to the amplitude and phase error detector;
• and
• wherein the adaptive pre-distortion subsystem comprises an input operable to receive a time-varying output from the power splitter proportional to the varying amplitude envelope of the RF input signal from an RF envelope detector, inputs operable to receive signals relating to gain error and amplitude error from the phase and amplitude error detector, an anti-alias filter and analogue-to-digital converter (ADC) signal digitiser, a lookup table (LUT) to determine gain and phase correction coefficients;
• digital-to-analogue converters (DACs) and anti-alias filters operable to convert these gain and phase correction coefficients to the analogue domain and to provide a continuous-time gain correction signal to a control port of the amplitude modulator;
• and a continuous-time phage correction signal to a control port of the phase modulator,
• wherein the adaptive pre-distorter subsystem is operable to generate the continuous-time correction signals as functions of a tapped RF input signal in such a way that the modulated delayed RF input signal on passing through the high power amplifier emerges with reduced distortion.

A linear power amplifier arrangement comprising a high power amplifier, a pre-distortion circuit and a feedback circuit;

• wherein an input is operable to receive radio frequency (RF) input signals and is connected to the power amplifier via an input directional coupler, a first delay line, a first RF amplitude modulator, a first RF phase modulator, a second RF amplitude modulator and a second RF phase modulator;
• wherein the feedback circuit comprises a directional coupler operable to sample an output of the amplifier and provide a signal to an amplitude and phase error detector;
• baseband processing elements;
• and second amplitude and phase modulators;
• wherein the pre-distortion circuit comprises a coupled line from the input directional coupler, a power splitter, the outputs of which are connected to a second delay line and an adaptive pre-distortion subsystem;
• wherein the second delay line is operable to provide a signal to the amplitude and phase error detector;
• and
• wherein the adaptive pre-distortion subsystem comprises an input operable to receive a time-varying output from the power splitter proportional to the varying amplitude envelope of the RF input signal from an RF envelope detector, inputs operable to receive signals relating to gain error and amplitude error from the phase and amplitude error detector, an anti-alias filter and analogue-to-digital converter (ADC) signal digitiser, a lookup table (LUT) to determine gain and phase correction coefficients;
• digital-to-analogue converters (DACs) and anti-alias filters operable to convert these gain and phase correction coefficients to the analogue domain and to provide a continuous-time gain correction signal to a control port of the first amplitude modulator;
• and a continuous-time phase correction signal to a control port of the first phase modulator,
• the baseband processing elements comprise feedback loops operable in the gain and phase domains in order to centre the operation of the pre-distorter;
• wherein the adaptive pre-distorter subsystem is operable to generate the continuous-time correction signals as functions of a tapped RF input signal in such a way that the modulated delayed RF input signal on passing through the high power amplifier emerges with reduced distortion.

A method of operating a linear power amplifier arrangement comprising a high power amplifier, a pre-distortion circuit and a feedback circuit;

• comprising the following steps:
• receiving RF input signals at an input connected to the power amplifier via a directional coupler, a first delay line, an RF amplitude modulator and an RF phase modulator;
• in the feedback circuit:
• coupling output signals from an output of the amplifier employing a directional coupler operable to sample an output of the amplifier and to provide signals to an amplitude and phase error detector;
• in the pre-distortion circuit:
• coupling a sample of the RF input signal employing a directional coupler, splitting the signal via a power splitter, feeding a first output of which to an amplitude and phase error detector via a second delay line and a second output of which to an adaptive pre-distortion sub-system via an RF envelope detector;
• at the adaptive pre-distorter sub-system:
• receiving a time-varying sampled RF signal proportional to the varying amplitude envelope of the RF input signal from the envelope detector, digitising this signal by an anti-alias filter and analogue-to-digital converter (ADC), receiving signals relating to gain error and amplitude error from the phase and amplitude error detector, determining gain and phase correction coefficients in a lookup table (LUT);
• converting these gain and phase correction coefficients to the analogue domain by digital-to-analogue converters (DACs) and anti-alias filters, and providing a continuous-time gain correction signal to a control port of the RF amplitude modulator;
• and a continuous-time phase correction signal to a control port of the RF phase modulator;
• wherein the adaptive pre-distorter subsystem is operable to generate the continuous-time correction signals as functions of a tapped RF input signal in such a way that the modulated delayed RF input signal on passing through the high power amplifier emerges with reduced distortion.