Automatic power control apparatus for linear modulation
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorAkira Andoh
Life of this patent
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Abstract
An automatic power control apparatus has a level control circuit for adjusting the power level of a linearly modulated signal prior to amplification by a power amplifier, and a coupler for extracting part of the amplified signal. An envelope detector detects the envelope of the extracted signal. A dc component detecting means detects the dc component of the envelope signal. An error amplifier amplifies the difference between this dc component and a reference voltage, and a loop filter filters the amplified difference to produce a control voltage that controls the level control circuit, thus controlling the power of the amplified signal without being affected by ac components of the signal envelope.
Claims3
An automatic power control apparatus for a linearly modulated signal, comprising:
- level control means for receiving the modulated signal and adjusting the power level thereof in response to a control voltage;
- power amplifying means connected to said level control means, for receiving the adjusted modulated signal from said level control means and amplifying said adjusted modulated signal to produce an amplified signal;
- coupling means connected to said power amplifying means, for extracting part of the power of said amplified signal, thereby producing an extracted signal;
- envelope detecting means connected to said coupling means, for detecting an envelope of said extracted signal, thereby generating an envelope signal;
- dc component detecting means connected to said envelope detecting means, for detecting a dc component of said envelope signal, including
- a dc blocking circuit connected to said envelope detecting means, for receiving said envelope signal and rejecting dc components therein, thus producing an ac component;
- an inverting circuit connected to said dc blocking circuit, for inverting said ac component, thus producing an inverted ac component;
- and
- a voltage adding circuit connected to said envelope detecting means and said inverting circuit, for summing said envelope signal and said inverted ac component, thus producing said dc component;
- reference voltage selecting means for selecting a reference voltage;
- error amplifying means connected to said dc component detecting means and said reference voltage selecting means, for amplifying a difference between said dc component and said reference voltage, thereby producing an error signal;
- and
- loop filter means connected to said level control means and said error amplifying means, for filtering said error signal, thereby producing said control voltage.
Dependencies are inferred from the claim text.