Predistortion in radio frequency transmitter
AssigneeSkyworks Solutions, Inc.
InventorsHamid R. Amir Firouzkouhi, Bipul Agarwal, Hasan Akyol
Life of this patent
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Abstract
A power amplifier circuit includes an amplifier MOSFET and a predistorter MOSFET. The predistorter MOSFET source and drain are connected together, and the predistorter MOSFET is connected between the gate of the amplifier MOSFET and a second bias voltage signal. This biasing of the predistorter MOSFET causes it to provide a nonlinear capacitance at the gate of the amplifier MOSFET. The combined non-linear capacitances of the amplifier MOSFET and predistorter MOSFET provide predistortion that promotes cancellation of the distortion or nonlinearity contributed by the amplifier MOSFET alone.
Claims20
A method for amplifying a radio frequency voltage signal in a radio frequency transmitter, the method comprising:
- coupling, via a linear capacitance, the radio frequency voltage signal to a gate terminal of an amplifier metal oxide semiconductor field-effect transistor;
- providing a first bias voltage signal to the gate terminal of the amplifier metal oxide semiconductor field-effect transistor;
- and
- predistorting a voltage between the gate terminal and a source terminal of the amplifier metal oxide semiconductor field-effect transistor using a predistorter metal oxide semiconductor field-effect transistor electrically connected between the gate terminal of the amplifier metal oxide semiconductor field-effect transistor and a second bias voltage signal, the source terminal of the predistorter metal oxide semiconductor field-effect transistor being connected to a drain terminal of the predistorter metal oxide semiconductor field-effect transistor, and a combination of a size of the predistorter metal oxide semiconductor field-effect transistor and a voltage level of the second bias voltage signal defining a first nonlinear capacitance similar to a second nonlinear capacitance of the amplifier metal oxide semiconductor field-effect transistor.
A method for amplifying a radio frequency signal in a radio frequency transmitter, the method comprising:
- providing a radio frequency input voltage signal to a gate of an amplifier field effect transistor via a linear capacitance;
- predistorting a voltage between the gate and a source of the amplifier field effect transistor using a predistorter field effect transistor electrically connected between the gate of the amplifier field effect transistor and a bias voltage signal, a combination of a size of the predistorter field effect transistor and a voltage level of the bias voltage signal defining a nonlinear capacitance behaving inversely to an input capacitance of the amplifier field effect transistor;
- and
- amplifying the radio frequency input voltage signal using the amplifier field effect transistor.
A radio frequency transmitter comprising:
- an amplifier field effect transistor having a gate configured to receive a radio frequency input voltage signal, the amplifier field effect transistor also being configured to provide a radio frequency output current;
- a linear capacitance configured to provide the radio frequency input voltage signal to the gate of the amplifier field effect transistor;
- and
- a predistorter field effect transistor electrically coupled to the gate of the amplifier field effect transistor, the predistorter field effect transistor being configured to receive a bias voltage, the predistorter field effect transistor being arranged such that a combination of a size of the predistorter field effect transistor and a voltage level of the bias voltage define a nonlinear capacitance that behaves inversely to an input capacitance of the amplifier field effect transistor.
Dependencies are inferred from the claim text.