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| High frequency pulse amplifier |
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| Low distortion operational amplifier |
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| Protection circuit for RF power amplifiers |
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| Portable radio communication equipment |
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| Temperature insensitive piezoelectric crystal mounting arrangement |
| OF THE PREFERRED EMBODIMENT FIG. 3A illustrates a simplified top view of the crystal mounting ... |
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| Impulse generator for use with phosphor energizable lamps |
| OF A PREFERRED EMBODIMENT Referring now in more detail and by reference characters to the drawings ... |
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| Starting and operating circuit for gaseous discharge lamps |
| What I claim as new and desire to secure by Letters Patent of the United States is: 1. A starting ... |
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| Varible frequency current control device for discharge lamps |
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| Gas distribution system for sputtering cathodes |
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Automatic electrical power control circuit
| Details |
Inventors: Hotta, Toshinori; Yamamoto, Osamu;
Assignee: NEC Corporation (JP)
Primary Examiner: Mullins; James B.
Assistant Examiner:
Attorney, Agent or Firm: Laff, Whitesel, Conte & Saret
A power control circuit comprises a signal input, a controllable attenuator, an amplifier, an output, a power detector, a reference circuit, a comparator, an external control input, an error detector, and a controller. The comparator, error detector, and controller are digital circuits realized by a microprocessor. The attenuator is between the signal input and the input to the amplifier to regulate the amplifier's output. The power detector couples to the amplifier output to generate a measurement signal representing the power at the output. The reference circuit generates a reference signal representing a predetermined minimum output when the signal input is nonzero. The comparator compares the measurement and reference signals and generates a decision signal indicating if the signal input is nonzero. The external control input receives an external control signal. The error detector is coupled to the power detector and the external control input and computes the difference between the external control signal and the measurement signal. When the measurement signal is at or above the minimum power, the controller provides an integral of the computed difference to control the variable attenuator. When the measurement signal is below the minimum power, the controller keeps the attenuator at a prior constant value. |
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DETAILED DESCRIPTION A control circuit is provided for regulating the power amplification of communication signals.
The circuit comprises an amplifying transmission path including a power amplifier, a controllable variable attenuator, an external power control input, an output power level detector, a threshold reference circuit, a threshold power comparator, an error detector, and an attenuator controller.
The threshold power comparator, error detector, and attenuator controller are designed as digital circuits and therefore can be conveniently realized by a programed microcomputer, such as a microprocessor on a chip with onboard program and scratchpad memory.
The amplifying transmission path has an input for a communication signal and an output for the amplified version of the signal.
The controllable attenuator is a variable attenuation circuit which regulates the signal input to the power amplifier, thereby controlling the signal power of the amplified communication signal at the amplifier's output.
The power level detector has a directional coupler coupled to the transmission path for generating a measurement signal representing the power of the amplified communication signal at the output.
The threshold reference circuit is adapted to generate a predetermined threshold reference signal which represents a predetermined minimum signal power of the amplified communication signal at the output when a nonzero communication signal is fed to the input.
The threshold power comparator is for comparing the measurement and threshold reference signals, and generating a decision signal which indicates whether the measurement signal is at or above the minimum power.
The external power control input is for inputting an external power control signal.
The error detector is a subtractor circuit coupled to the power level detector and the external power control input.
It determines the difference between the external power control signal and the measurement signal for use by the attenuator controller in computing a negative feedback correction signal
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Audio Signal Processing 
