Power detector utilizing bias voltage divider for precision control of an amplifier
First Claim
1. A controlled-output radio-frequency (RF) amplifier circuit wherein the output power level can be maintained at a number of predetermined levels over a range of operating temperatures, the amplifier circuit receiving an input RF signal and providing an output RF signal, the amplifier circuit comprising:
- A. an RF amplifier stage having an input connected to receive the input RF signal, an output connected to provide the output RF signal, and a gain control input;
B. a power level detector responsive to the output RF signal, and connected to provide a gain control signal to the gain control input of the amplifier stage, the power level detector further comprising;
i. a detector diode, having an anode connected to be responsive to the output RF signal, and a cathode connected to provide the gain control signal;
ii. means for providing a bias voltage and a ground reference voltage; and
iii. voltage divider means, connected to the detector diode, the voltage divider means comprising;
a. a first resistor, connected between the bias voltage and the anode of the diode; and
b. a second resistor, connected between the cathode of the diode and the ground reference voltage, with the second resistor having a resistance much less than the first resistor.
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Accused Products
Abstract
A controlled-output amplifier circuit whose output power may be maintained at a number of predetermined levels over a wide ambient temperature range. The amplifier includes a controllable gain amplifier stage, and a power level detector consisting of a detector diode and a linear voltage divider. The linear voltage divider is preferably composed of two resistors, with a first resistor being connected in series between a direct current (DC) voltage and the anode of the diode, and a second resistor connected between the cathode of the diode and a ground reference point. Preferably, the resistance of the first resistor is much greater than that of the second resistor. This insures that the detector bias voltage is sufficiently small so that any effects of variation in temperature are attenuated to an acceptably small level. Additionally, the first and second resistors have temperature coefficients such that the effect of the rate of change of the forward voltage drop of the detector diode with respect to temperature is reduced by the ratio of the resistance of the second resistor to that of the first resistor.
44 Citations
13 Claims
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1. A controlled-output radio-frequency (RF) amplifier circuit wherein the output power level can be maintained at a number of predetermined levels over a range of operating temperatures, the amplifier circuit receiving an input RF signal and providing an output RF signal, the amplifier circuit comprising:
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A. an RF amplifier stage having an input connected to receive the input RF signal, an output connected to provide the output RF signal, and a gain control input; B. a power level detector responsive to the output RF signal, and connected to provide a gain control signal to the gain control input of the amplifier stage, the power level detector further comprising; i. a detector diode, having an anode connected to be responsive to the output RF signal, and a cathode connected to provide the gain control signal; ii. means for providing a bias voltage and a ground reference voltage; and iii. voltage divider means, connected to the detector diode, the voltage divider means comprising; a. a first resistor, connected between the bias voltage and the anode of the diode; and b. a second resistor, connected between the cathode of the diode and the ground reference voltage, with the second resistor having a resistance much less than the first resistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A controlled-output radio-frequency (RF) amplifier circuit wherein the output power level can be maintained at one of a number of predetermined output power levels over a range of operating temperatures, the amplifier circuit receiving an input RF signal and providing an output RF signal, the amplifier circuit comprising:
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A. an RF amplifier stage having an input connected to receive the input RF signal, an output connected to provide the output RF signal, and a gain control input; B. means, connected to receive the output RF signal, for providing a sample of the RF output signal; C. a detector diode, having an anode connected to receive the sample of the output RF signal, and a cathode connected to provide a detector output signal; D. means for providing a direct current bias voltage and a ground reference voltage; E. a first resistor, connected between the direct current bias voltage and the anode of the diode; F. a second resistor, connected between the cathode of the diode and the ground reference voltage, with the resistance of the second resistor being much less than the resistance of the first resistor; G. means for providing a reference voltage indicative of one of the predetermined output power levels; H. a comparator, connected to receive the reference voltage and the detector output signal, and to provide an error voltage indicative of their difference; and I. means for receiving the error voltage and providing a gain control signal to the gain control input of the RF amplifier stage in response thereto. - View Dependent Claims (10)
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11. A controlled-output amplifier having an input and an output, said input for receiving an input signal, said output for producing an output signal having a substantially constant predetermined magnitude, said amplifier comprising:
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controllable-gain amplifier means having first and second inputs and an output, said first input adapted to receive said input signal, said second input adapted to receive gain control signal, said output providing the output signal of said controlled-output amplifier; rectifier means having an input and an output, said input coupled to the output of said controllable-gain amplifier means, said rectifier means producing at said output a signal indicative of the magnitude of the output signal of said controlled-output amplifier; linear voltage dividing means, coupled to the input and output of said rectifier means, for providing a bias voltage and for linearly voltage-dividing the bias voltage, and thereby reducing the range of voltages over which the rectifier means must operate, the linear voltage dividing means including a first and second resistor, with the first resistor connected between the input of the rectifier means and the bias voltage, and the second resistor connected between the output of the rectifier means and a ground reference voltage, with the resistance of the second resistor being much less than the resistance of the first resistor; comparison means having first and second inputs and an output, said first input coupled to the output of said rectifier means, said second input adapted to receive a reference signal, said comparison means providing a signal at said output which is indicative of the difference in magnitude of the reference signal and the signal produced at the output of said rectifier means; and control signal generator means having an input and an output, said input coupled to the output of said comparison means, said output coupled to the second input of the controllable-gain amplifier means, said generator means producing the gain control signal in response to the signal produced at the output of the comparison means, whereby the gain of the controllable-gain amplifier means is adjusted so as to maintain the output signal of the controlled-output amplifier at the predetermined magnitude.
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12. Circuitry for controlling the magnitude of a radio frequency (RF) signal in response to control signals, comprising:
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means, having variable output, for amplifying the RF signal to an output magnitude and for obtaining a sample of said amplified RF signal; means, coupled to said means for amplifying-and-obtaining-a-sample, for linearly voltage-dividing said sample of said amplified RF signal; means for rectifying said voltage-divided sample to generate a power magnitude signal having a magnitude related to said RF signal output magnitude; means, for adjusting said power magnitude signal by an adjustment factor selected by the control signals; means, responsive to said adjusted power magnitude signal, for varying said variable output amplifying means to produce a corresponding RF signal output magnitude; and wherein said means for linearly voltage-dividing further includes a first and second resistor, with the first resistor connected between the means-for-obtaining-a-sample and a bias voltage, and the second resistor connected between an output of the means for rectifying and a ground reference voltage, with the resistance of the second resistor being much less than that of the first resistor.
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13. Control circuitry for maintaining the magnitude of a radio frequency (RF) signal from an RF signal amplifier at one of a plurality of levels selected by level control signals from a signal source, said control circuitry comprising:
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means coupled to the RF signal amplifier for generating an output power signal having a magnitude that is related to the magnitude of the RF signal from the RF signal amplifier; means coupled to the generating means for linearly voltage dividing the output power signal; means coupled to the level control signals for adjusting the output power signal by an adjustment factor selected in response to the level control signals; and wherein said means for linearly voltage dividing further includes a first and second resistor, with the first resistor connected between the generating means and a bias voltage, and the second resistor connected between an output of the generating means and a ground reference voltage, with the resistance of the second resistor being much less than that of the first resistor.
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Specification