Amplifier bias adjustment circuit to maintain high-output third-order intermodulation distortion performance
AssigneeAnadigics, Inc.
InventorDouglas Matthew Johnson
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Abstract
An circuit and method are provided for amplifying RF input signal to produce RF output signals with third-order intermodulation distortion products. The circuit and method use a feedback signal to control the bias voltage of the amplifier, such that the output third-order intermodulation distortion product increases monotonically with the RF input signal power. Specifically, the third-order intermodulation distortion product responds over a predetermined output power range by increasing three decibels in response to each one-decibel increase in input power.
Claims6
A circuit for amplifying an input RF signal comprising:
- (a) an RE amplifier having an input port that receives such input RF signal and an output port, wherein said RE amplifier produces at said output port an amplified RE signal comprising a third-order intermodulation distortion product signal;
- (b) a power divider that is connected to said output port of said RE amplifier to divide said amplified RF signal into an output RE signal and a feedback signal;
- and
- (c) a feedback circuit connected to said power divider to detect said feedback signal and to produce a DC voltage that is proportional to the power of said feedback signal and that is used to bias said RF amplifier circuit;
- wherein said DC voltage causes said third-order intermodulation distortion product signal to increase in response to an increase in the level of said input RF signal over a predetermined range of power of said output RF signal.
A method for amplifying an input RF signal comprising the steps of:
- (a) amplifying said input RF signal in an amplifier to produce an amplified signal;
- (b) dividing said amplified signal into an output RF signal and a feedback signal, said output RF signal comprising a third-order intermodulation distortion product signal;
- (c) generating a DC signal with a DC voltage proportional to the power of said feedback signal;
- and
- (d) biasing said amplifier based on said DC signal;
- wherein the DC voltage causes said third-order intermodulation distortion product signal to increase in response to an increase in the level of said input RF signal over a predetermined range of power of said output RF signal.
Dependencies are inferred from the claim text.