Method and apparatus for controlling gain of a power amplifier
First Claim
1. A gain controller for controlling gain of a power amplifier, said power amplifier having an input for receiving a first radio frequency signal at a first power level, an output for outputting a second radio frequency signal at a second power level, whereby a difference between said first and second power levels is controlled by controlling said power amplifier gain according to a DC level of a control signal coupled to a gain control input of said power amplifier, comprising:
- an attenuator having an input coupled to said power amplifier output for attenuating said second radio frequency signal from said second power level to an attenuated second power level;
a signal power detector coupled alternatively via a radio frequency switch to said power amplifier input and an output of said attenuator, said detector detecting said first radio frequency signal at said first power level and said second radio frequency signal at said attenuated second power level, and producing via a DC signal switch a first and a second signal each having an average DC level corresponding to said first and attenuated second power levels; and
an operational amplifier, configured for closed loop operation, having a positive input, a negative input and an output, said first and second signals coupled respectively to said positive and negative inputs, and said output producing said control signal according to said operational amplifier closed loop operation and said first and second signals average DC level.
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Accused Products
Abstract
A method and apparatus for controlling the gain of a power amplifier wherein the method includes the steps of attenuating, detecting, and comparing. An attenuator (108) attenuates an amplified version of a radio frequency signal to an attenuated level. A single detector (109) alternatively detects the radio frequency signal power level at a power amplifier (101) input and the attenuated version of the amplified radio frequency signal. The detector (109) produces a first and a second signal each having a DC level representing the detected power levels. An operation amplifier configured for closed loop operation compares the DC levels of the first and second signals to produce a control signal (102) for controlling power amplifier (101) gain. Filters (119) and (120) filter the first and second signals before the comparing step.
37 Citations
11 Claims
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1. A gain controller for controlling gain of a power amplifier, said power amplifier having an input for receiving a first radio frequency signal at a first power level, an output for outputting a second radio frequency signal at a second power level, whereby a difference between said first and second power levels is controlled by controlling said power amplifier gain according to a DC level of a control signal coupled to a gain control input of said power amplifier, comprising:
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an attenuator having an input coupled to said power amplifier output for attenuating said second radio frequency signal from said second power level to an attenuated second power level; a signal power detector coupled alternatively via a radio frequency switch to said power amplifier input and an output of said attenuator, said detector detecting said first radio frequency signal at said first power level and said second radio frequency signal at said attenuated second power level, and producing via a DC signal switch a first and a second signal each having an average DC level corresponding to said first and attenuated second power levels; and an operational amplifier, configured for closed loop operation, having a positive input, a negative input and an output, said first and second signals coupled respectively to said positive and negative inputs, and said output producing said control signal according to said operational amplifier closed loop operation and said first and second signals average DC level. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of controlling gain of a power amplifier, comprising the steps of:
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attenuating an amplified version of a radio frequency signal to produce an attenuated version, said amplified version of said radio frequency signal being amplified through a power amplifier having a gain controlled by a control signal; switching alternatively, to a power detector, said attenuated version of said radio frequency signal and said radio frequency signal at said power amplifier input; detecting alternatively at said power detector said attenuated version power level and a power level of said radio frequency signal at said power amplifier input and producing respectively therefrom a first and a second signal, each of said first and second signal having a DC level corresponding to said detected power levels; and comparing said first and second signals DC levels to produce said control signal. - View Dependent Claims (8, 9, 10, 11)
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Specification