High linearity satellite payload using solid state power amplifiers
A solid state power amplifier uses a Doherty power amplifier that can be implemented as a monolithic microwave integrated circuit. By adjusting the DC bias of the amplifying stages in each branch of the Doherty amplifier, the output power, linearity, and DC power can be adjusted to provide a specified output, where the specification for the output can include the maintaining of desired DC power and linearity. The Doherty power amplifier can be used in a satellite payload or other application utilizing solid state power amplifiers, while providing the proper amount of RF output power and DC power. A single amplifier can have its bias levels adjusted for different output levels, helping to minimize the number of designs that are required for a given satellite payload, reducing the variety of parts in a satellite payload.
1. A solid state amplifier, comprising:
an input
port; an
output
port;
a main arm connected between the input port and the output port, including a first main amplifier stage configured to generate a first output signal from an input signal received from the input port;
an auxiliary arm connected in parallel with the main arm between the input port and the output port, including a first auxiliary amplifier stage configured to generate a second output signal by amplifying portions of the input signal received the input port having an amplitude above a threshold level;
an input splitter configured to receive the input signal and provide it to the main arm and the auxiliary arm;
a combining circuit configured to receive the first output signal and the second output signal, generate therefrom a combined output signal and provide the combined output signal to the output port;
a first bias control circuit connected to the first main amplifier stage and configured to bias the first main amplifier stage according to a corresponding first set of control signals;
a second bias control circuit connected to the first auxiliary amplifier stage and configured to bias the first auxiliary amplifier stage according to a corresponding second set of control signals; and
a control circuit configured to generate the corresponding first set of control signals and the corresponding second sets of control signals, the first set of controls signals configured to generate the first output signal to have a specified response over a first output range when the input signal has an amplitude below the threshold level, and the corresponding second set of control signals configured relative to the corresponding first set of control signals to generate the combined output signal to have the specified response over a second output range when the input signal has an amplitude above the threshold level.
2. The solid state amplifier of claim 1 , wherein:
the main arm comprises a plurality of N serially connected main amplifier stages, including the first main amplifier stage, connected to the input port and configured to generate the first output signal from the input signal;
the auxiliary arm comprises a plurality of N serially connected auxiliary amplifier stages, including the first auxiliary amplifier stage, connected to the input port and configured to generate the second output signal from the input signal;
the first bias control circuit is connected to the N main amplifier stages and configured to individually bias the N main amplifier stages according to the corresponding first set of control signals; and
the second bias control circuit connected to the N auxiliary amplifier stages and configured to individually bias the N auxiliary amplifier stages according to the corresponding second set of control signals.
3. The solid state amplifier of claim 1 , wherein the control circuit is configured to change the corresponding first set of control signals and the corresponding second set of control signals in response to the specified response being changed.
4. The solid state amplifier of claim 3 , wherein the changed corresponding first set of control signals and the corresponding second set of control signals change the threshold level.
5. The solid state amplifier of claim 1 , further composing:
a memory, where the control circuit determines the corresponding first set of control signals and the corresponding second set of control signals corresponding to the specified response from values stored in the memory.
6. The solid state amplifier of claim 1 , wherein the control circuit determines the corresponding first set of control signals and the corresponding second set of
control signals corresponding to the specified response by monitoring the combined output signal.
7. The solid state amplifier of claim 1 , wherein the specified response includes an output power level.
8. The solid state amplifier of claim 1 , wherein the first main amplifier stage and the first auxiliary amplifier stage are amplifiers of differing classes.
9. The solid state amplifier of claim 1 , wherein the main arm, the auxiliary arm, the input splitter, the combining circuit, first bias control circuit, second bias control circuit and control circuit are formed on a common integrated circuit.
10. The solid state amplifier of claim 1 , wherein the input splitter
comprises:
a quadrature generator connected to the input port and configured receive the input signal, generate form the input signal a first quadrature signal and a second quadrature signal, and to provide the input signal to the main arm and the auxiliary arm respectively
as the first quadrature signal and second quadrature signal.