Variable filter systems and methods for enhanced data rate communication systems
AssigneeAnalog Devices, Inc.
InventorsRobert J. McMorrow, Roxann Blanchard
Life of this patent
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Abstract
A radio frequency output power control system is disclosed for use in communication systems that use a modulation scheme having a non-constant amplitude envelope. The system includes a power amplifier having a radio frequency input node for receiving a radio frequency input signal, a power control node for receiving a filtered power control signal, and an output for providing an amplified output signal. The system also includes a variable filter that receives a power control signal at a power control input and a receives a trigger signal at a trigger input, and provides a filtered power control signal to the power control node of the power amplifier responsive to the power control signal and the trigger signal.
Claims25
A radio frequency output power control system for use in communication systems that use a modulation scheme having a non-constant amplitude envelope, the system comprising:
- a power amplifier comprising a radio frequency input node for receiving a radio frequency input signal, a power control node for receiving a power control signal, and an output for providing an amplified output signal;
- an envelope detection unit that receives the radio frequency input signal and provides a positive current output and a negative current output in accordance therewith;
- a differential variable filter that converts the positive current output to a positive voltage output, converts the negative current output to a negative voltage output, filters the positive and negative voltage outputs, and provides a filtered power signal while allowing the envelope of the power signal to pass;
- and
- a comparison unit that compares the filtered power signal to a power level of the amplified output signal and provides the error signal to the power control node of the power amplifier to cancel amplitude modulation from the amplified output signal,
- wherein the variable filter has a first time constant for providing a fast transient response to changes in a power level of the input signal and a second time constant for filtering the input signal.
A radio frequency output power control system comprising:
- a power amplifier for amplifying an input signal and for providing an amplified output signal, the power amplifier comprising a control node for receiving a control signal for correcting distortion in the amplified output signal;
- an input power detector for detecting a power level of the input signal and for providing an input voltage level signal, the input power detector comprising a differential variable filter having a first time constant for providing a fast transient response to changes in the power level of the input signal and a second time constant for filtering the input signal, the differential variable filter comprising a differential current-to-voltage converter for converting a received differential current into a differential voltage and a differential filter element for filtering the differential voltage;
- an output power level detector for detecting a power level of the amplified output signal and providing an output voltage level signal;
- and
- a comparison unit for comparing the input voltage level signal to the output voltage level signal and for generating the control signal based on the comparison.
A method for amplifying a radio frequency output signal comprising:
- receiving an input signal at a power amplifier, the power amplifier configured to provide an amplified output signal;
- sensing an input power level of the input signal with an input power detector, the input power detector comprising a log amp for providing a differential current signal representing the input power level and a variable filter for converting the differential current signal to a differential voltage signal and for filtering the differential voltage signal;
- assigning a first time constant to the variable filter in response to a change in a power level of the input signal, the first time constant having a fast transient response to the change in the power level;
- thereafter assigning a second time constant to the variable filter, the second time constant selected for filtering the input signal;
- sensing an output power level of the amplified output signal with an output power detector;
- comparing the input power level to the output power level;
- and
- adjusting the power amplifier, based on the result of the comparison, to linearize the amplified output signal.
Dependencies are inferred from the claim text.