Envelope tracking amplifier for a transmitter having a voltage mapping linearly related to the square of the amplitude of the baseband signal

A transceiver comprising:

• a receiver for receiving signals from a receive antenna;
• and
• a transmitter configured to transmit, via a transmit antenna, an RF signal derived from baseband samples, the transmitter comprising:
• a modulator for modulating information derived from the baseband samples onto a RF carrier;
• an amplifier for amplifying the modulated signal for application to the transmit antenna;
• processing circuitry for deriving an amplitude signal indicative of an instantaneous amplitude of a square of the baseband samples, the processing circuitry configured to apply a voltage mapping, provided to the amplifier, to the amplitude signal to provide a resultant signal;
• and
• an envelope modulator for using the resultant signal to control the voltage applied to the amplifier, wherein the voltage mapping provided to the amplifier is a linear function of the square of the amplitude of the baseband samples;
• wherein the processing circuitry is further configured to determine a power mapping signal representative of a mapping giving optimal amplifier power efficiency, form the voltage mapping to be tangential to the power mapping signal, and select a point on the power mapping signal at which the voltage mapping signal is tangential to the power mapping signal,
• wherein the point is a point corresponding to a square of the average signal amplitude or the point is in a range between 0.75 times a square of the average signal amplitude and 3 times the square of the average signal amplitude.

A transceiver comprising:

• a receiver for receiving signals from a receive antenna;
• and
• a transmitter configured to transmit, via a transmit antenna, an RF signal derived from baseband samples, the transmitter comprising:
• a modulator for modulating information derived from the baseband samples onto a RF carrier;
• an amplifier for amplifying the modulated signal for application to the transmit antenna;
• processing circuitry for deriving an amplitude signal indicative of an instantaneous amplitude of a square of the baseband samples, the processing circuitry configured to apply a voltage mapping, provided to the amplifier, to the amplitude signal to provide a resultant signal;
• and
• an envelope modulator for using the resultant signal to control the voltage applied to the amplifier, wherein the voltage mapping provided to the amplifier is a linear function of the square of the amplitude of the baseband samples;
• wherein the processing circuitry is further configured to determine a power mapping signal representative of a mapping giving optimal amplifier power efficiency, form the voltage mapping to be tangential to the power mapping signal, and select a point on the power mapping signal at which the voltage mapping signal is tangential to the power mapping signal and based upon out-of-band noise.

A method of transmitting an RF signal derived from baseband samples, comprising:

• modulating information derived from the baseband samples onto a RF carrier, and amplifying the modulated signal in an amplifier,
• wherein the amplifying comprises applying a voltage mapping, provided to the amplifier, to an amplitude of the baseband samples to control the amplifier supply, wherein the voltage mapping provided to the amplifier is a linear function of a square of the amplitude of the baseband samples,
• determining a power mapping signal representative of a mapping giving optimal amplifier power efficiency,
• forming the voltage mapping to be tangential to the power mapping signal, and
• selecting a point on the power mapping signal at which the voltage mapping signal is tangential to the power mapping signal and based upon out-of-band noise.