Solid state power amplifier with dynamically adjusted operating point

Claim 2

The closed-loop power amplifier circuit of Claim 1 wherein the solid state power amplifier comprises: an input amplifier stage adapted to receive the RF input from the input sampling device; a PIN attenuator having one input connected to the input amplifier stage and having another input adapted to receive operating point settings; a first isolator connected to the output of the PIN attenuator, in which reflected signals are dissipated in a resistive termination; a pre-driver amplifier having its input connected to the output of the first isolator; a driver amplifier having its input connected to the output of the pre-driver amplifier; a second isolator connected to the output of the driver amplifier, in which reflected signals are dissipated in a resistive termination; and a solid state hybrid power amplifier stage connected to the second isolator, comprised of multiple solid state power amplifiers, wherein the DC bias voltages of each solid state power amplifier is dynamically variable and controllable; and wherein said closed-loop power amplifier circuit further comprises a third isolator connected to the output of the output sampling device, in which reflected signals are dissipated in a resistive termination.

Claim 3

The closed-loop power amplifier circuit of Claim 2 wherein the power supply comprises: a switching power supply coupled to the comparator / integrator means, which accepts the difference signal from the comparator / integrator means, wherein the switching power supply is adapted to supply varying bias voltages to each amplifier of the solid state hybrid power amplifier stage via electrical conductors, feed back control voltages, to dynamically change the applied voltages to the overall closed-loop hybrid power amplifier circuit, such that a constant operating point resulting in constant gain, linearity and efficiency is maintained for a range of input and output power variations.

Claim 4

A closed-loop hybrid power amplifier circuit having a RF input, RF output and an operating point, comprising: an input sampling device electrically coupled to the RF input for electrically sampling the RF input signal power; an input power detector connected to the input sampling device for detecting and measuring the electrical power intensity of the RF input signal; an input amplifier stage for receiving the RF input from the input sampling device; a PIN attenuator having one input connected to the input amplifier stage and having another input adapted to receive operating point settings; a first isolator connected to the output of the PIN attenuator; a pre-driver amplifier having an input connected to the output of the first isolator; a driver amplifier having an input connected to an output of the pre-driver amplifier; a second isolator connected to the output of the driver amplifier; a solid state hybrid power amplifier stage connected to the second isolator, comprised of multiple solid state power amplifiers, wherein the DC bias voltages of each solid state power amplifier is dynamically variable and controllable; an output sampling device electrically coupled to the output of the solid state power amplifier stage for electrically sampling the RF output signal; an output power detector connected to the output sampling device and matched in electrical characteristics to the input power detector; a third isolator connected to the output sampling device; comparator / integrator means coupled to the input and output detectors for accepting the outputs from the input and output detectors and comparing them, for generating a difference signal as a measure of the gain, and for filtering the difference signals; and a switching power supply coupled to the comparator / integrator means, which accepts the difference signal from the comparator / integrator means, for supplying varying bias voltages to each amplifier of the solid state hybrid power amplifier stage via electrical conductors, feeding back control voltages, and for dynamically changing the applied voltages to the overall closed-loop hybrid power amplifier circuit, such that a constant operating point resulting in constant gain, linearity and efficiency is maintained for a range of input and output power variations.

Claim 5

A hybrid matrix power amplifier system for RF communication satellites comprising: a beam forming network accepting a plurality of input electromagnetic wave beams and generating a plurality of corresponding RF output signals; an input hybrid distribution matrix adapted to receive the output signals from the beam forming network; a set of closed loop hybrid power amplifier circuits adapted to receive the RF signals from the input hybrid distribution matrix, wherein the DC bias voltages of each solid state power amplifier is under closed loop dynamic control, and wherein the solid state power amplifiers are matched in gain and phase at the system operating point; an output hybrid distribution matrix adapted to receive the output signals from the closed loop solid state power amplifier circuits, and adapted to refocus the RF signals to a corresponding output; and an antenna feed distribution network connected to the output of the output hybrid distribution matrix, which provides a signal distribution function for transmitting antennas.

Claim 6

The hybrid matrix power amplifier system recited in claim 5, in which the input hybrid matrix, the set of closed-loop solid state power amplifier circuits, and the output hybrid matrix are each repeated in tandem, and placed in between the beam forming network and the antenna feed distribution network.

Claim 7

A solid state power amplifier with dynamically maintained operating point comprising: a solid state amplifier having an operating point that varies as a function of applied DC and RF bias and having RF input and output terminals; a switching type power supply coupled to said solid state amplifier for applying DC bias thereto and having a sense input terminal; two matched square law detectors each individually coupled to the RF input and output terminals of said solid state amplifier; and a comparator / integrator having two differential inputs each individually to the output of one of said detectors and having an output coupled to the sense input terminal of said switching type power supply; whereby the power gain of the solid state amplifier is continually measured and used to dynamically adjust the DC bias applied to the solid state amplifier so as to maintain constant gain, linearity and efficiency for a range of output power variations.

Claim 8

A dynamic control circuit for automatically adjusting the operating point of a solid state power amplifier comprising: a solid state power amplifier having RF devices for amplifying RF signals in the region of 1500 MHz, said power amplifier having an input and an output; means for sampling and measuring RF power at the input and output of said power amplifier comprising a pair of directional couplers and a pair of matched square law detectors; a DC operational amplifier having differential inputs each individually coupled to the output of said detectors for comparing and filtering the outputs thereof to produce a resulting difference signal; and a switching type power supply for converting a DC input voltage to a plurality of positive and negative supply voltages supplied to the RF devices in the solid state power amplifier, said power supply having a control input coupled to the difference signal produced by said operational amplifier; whereby the supply voltages are varied in accordance with the power gain of the power amplifier to maintain constant gain, efficiency, and linearity therefor such that a constant compressed operating point is maintained along with acceptable linearity.