Method and apparatus for improved output power level control in an amplifier circuit

• US 6,803,818 B2
• Filed: 11/26/2002
• Issued: 10/12/2004
• Est. Priority Date: 11/26/2002
• Status: Active Grant

• Current Assignee: Broadcom International Pte Ltd. (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: van Amerom, Johannes Herman Maurits
• Primary Examiner(s): Choe, Henry
• Application Number:
  US10/304,648
• Publication Number:
  US 20040100325A1
• Time in Patent Office: 686 Days
• Field of Search: 330/144, 330/284, 330/279, 330/129, 330/136, 330/207.P, 330/298, 327/307
• US Class Current: 330/144
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

An amplifier circuit having a controllable output power level comprises an attenuator configurable for receiving an input signal and operative to control an attenuation thereof, and an amplifier coupled to the attenuator, the amplifier receiving the attenuated input signal and generating an amplified output signal. The amplifier circuit further includes at least one power detector configurable to independently detect at least a portion of an incidental wave and a reflected wave corresponding to the amplified output signal and to generate first and second signals representative of the detected incidental and reflected waves, respectively. A controller is coupled between the power detector and the attenuator in a feedback configuration, the controller controlling the attenuation of the input signal and/or an amplification of the input signal as a function of the first and second signals from the power detector. In this manner, the output signal of the amplifier circuit is substantially maintained at a predetermined power level.

Claims

1. An amplifier circuit for use in a wireless transmission system capable of operating in one of at least two different modulation modes, each of the modulation modes having a corresponding desired data rate associated therewith, the amplifier circuit comprising:

an attenuator configurable for receiving an input signal associated with one of the at least two modulation modes of the transmission system, the attenuator being operative to control an attenuation of the input signal;

an amplifier coupled to the attenuator, the amplifier receiving the attenuated input signal and generating an amplified output signal;

at least one power detector configurable to independently detect at least a portion of an incidental wave and a reflected wave corresponding to the amplified output signal and to generate first and second signals representative of the detected incidental and reflected waves, respectively; and

a controller operatively coupled between the at least one power detector and the attenuator in a feedback configuration, the controller controlling at least one of the attenuation of the input signal and an amplification of the input signal as a function of the first and second signals from the power detector and being operative to control a linearity of the amplifier such that the desired data rate of the received input signal is substantially maintained for the corresponding modulation mode of the transmission system;

whereby the output signal of the amplifier circuit is maintained at a substantially constant power level.

2. The amplifier circuit of claim 1, wherein the at least one power detector is selectively operable in at least one of a first mode and a second mode, the at least one power detector in the first mode receiving at least a portion of the incidental wave corresponding to the amplified output signal and generating the first signal comprising a direct current (DC) value representative of a power level of the incidental wave, and the at least one power detector in the second mode receiving at least a portion of a reflected wave corresponding to the amplified output signal and generating the second signal comprising a DC value representative of a power level of the reflected wave.

4. The amplifier circuit of claim 1, further comprising a directional coupler including an incidental port and a reflected port operatively coupled to the at least one power detector, the incidental port being configurable for sampling at least a portion of the incidental wave, and the reflected port being configurable for sampling at least a portion of the reflected wave.

5. The amplifier circuit of claim 1, wherein the at least one power detector comprises:

a first power detector circuit for detecting the at least a portion of the incidental wave and generating the first signal representative of the detected incidental wave; and

a second power detector circuit for detecting the at least a portion of the reflected wave and generating the second signal representative of the detected reflected wave;

wherein the first and second power detector circuits are configurable to substantially simultaneously detect the incidental and reflected waves, respectively.

6. The amplifier circuit of claim 1, wherein the controller further comprises:

an analog-to-digital converter configurable for receiving the first and second signals from the power detector and generating first and second digital codes, respectively, in response thereto;

wherein the controller is operative;

(i) to compare the first digital code with a first predetermined value representing a desired incidental power level of the amplifier circuit;

(ii) to compare the second digital code with a second predetermined value representing a desired reflected power level of the amplifier circuit; and

(iii) to generate the control signal in response to the comparison of the first and second digital codes with the first and second predetermines values, respectively, for controlling the attenuator for maintaining the output signal of the amplifier at a substantially constant power level.

7. The amplifier circuit of claim 6, wherein at least one of the first and second predetermined values are stored in memory.

8. The amplifier circuit of claim 1, wherein the at least one power detector comprises a logarithmic amplifier.

9. The amplifier circuit of claim 1, wherein the amplifier is configurable for selectively generating a plurality of output power levels.

10. The amplifier circuit of claim 1, wherein the amplifier comprises a bias circuit configurable for selectively generating a plurality of bias current levels.

11. The amplifier circuit of claim 10, wherein a bias current level of the amplifier is selectively adjusted in response to at least a power level of the reflected wave detected by the at least one power detector, whereby a linearity of the amplifier is substantially maintained.

12. The amplifier circuit of claim 1, wherein at least a portion of the attenuator, the amplifier, the at least one power detector, and the controller associated with the amplifier circuit are implemented in accordance with one or more semiconductor devices.

3. An amplifier circuit having a controllable output power level, comprising:

an attenuator configurable for receiving an input signal and being operative to control an attenuation thereof;

an amplifier coupled to the attenuator, the amplifier receiving the attenuated input signal and generating an amplified output signal;

at least one power detector configurable to independently detect at least a portion of an incidental wave and a reflected wave corresponding to the amplified output signal and to generate first and second signals representative of the detected incidental and reflected waves, respectively, the at least one power detector being selectively operable in at least one of a first mode and a second mode, the at least one power detector in the first mode receiving at least a portion of the incidental wave corresponding to the amplified output signal and generating the first signal comprising a direct current (DC) value representative of a power level of the incidental wave, and the at least one power detector in the second mode receiving at least a portion of a reflected wave corresponding to the amplified output signal and generating the second signal comprising a DC value representative of a power level of the reflected wave;

a switching circuit operatively coupled to the at least one power detector, the switching circuit generating a control signal for selectively controlling a mode of operation of the at least one power detector; and

a controller operatively coupled between the at least one power detector and the attenuator in a feedback configuration, the controller controlling at least one of the attenuation of the input signal and an amplification of the input signal as a function of the first and second signals from the power detector;

whereby the output signal of the amplifier circuit is maintained at a substantially constant power level.

13. In a wireless transmission system capable of operating in one of at least two different modulation modes, each of the modulation modes having a corresponding desired data rate associated therewith, a method for controlling a linearity of an amplifier such that a desired data rate of an input signal received by the amplifier is maintained for a given one of the modulation modes of the transmission system, the method comprising the steps of:

generating a first signal representative of at least a portion of an incidental wave corresponding to an output signal generated by the amplifier;

generating a second signal representative of at least a portion of a reflected wave corresponding to the output signal from the amplifier;

comparing the first and second signals with desired incidental and reflected power levels of the amplifier corresponding to a given one of the at least two different modulation modes; and

controlling at least one of an attenuation and an amplification of an input signal to the amplifier as a function of the first and second signals, so as to control a linearity of the amplifier such that the desired data rate of the input signal is substantially maintained for the corresponding modulation mode of the transmission system.

14. The method of claim 13, wherein the steps of generating the first and second signals are performed substantially simultaneously.

15. The method of claim 13, further comprising the step of adjusting a bias current level of the amplifier in response to at least the second signal so as to maintain a linearity of the output signal from the amplifier.

16. The method of claim 13, further comprising the step of adjusting an input power level of the amplifier so as to maintain a linearity of the output signal from the amplifier.

17. The method of claim 13, wherein the step of generating the first signal comprises converting at least a portion of the incidental wave to a first digital code representative thereof, and the step of generating the second signal comprises converting at least a portion of the reflected wave to a second digital code representative thereof.

18. The method of claim 17, wherein the step of comparing the first and second signals with desired incidental and reflected power levels of the amplifier circuit comprises comparing the first digital code with a first digital representation of the desired incidental power level and comparing the second digital code with a second digital representation of the desired reflected power level.

19. Apparatus comprising one or more semiconductor devices, the one or more semiconductor devices comprising at least one amplifier circuit for use in a wireless transmission system capable of operating in one of at least two different modulation modes, each of the modulation modes having a corresponding desired data rate associated therewith, the at least one amplifier circuit comprising:

an attenuator configurable for receiving an input signal associated with one of the at least two modulation modes of the transmission system, the attenuator being operative to control an attenuation of the input signal;

an amplifier coupled to the attenuator, the amplifier receiving the attenuated input signal and generating an amplified output signal;

at least one power detector configurable to detect at least a portion of an incidental wave and a reflected wave corresponding to the amplified output signal and to generate first and second signals representative of the detected incidental and reflected waves, respectively; and

a controller operatively coupled between the at least one power detector and the attenuator in a feedback configuration, the controller controlling at least one of the attenuation of the input signal and an amplification of the input signal as a function of the first and second signals from the power detector and being operative to control a linearity of the amplifier such that the desired data rate of the received input signal is substantially maintained for the corresponding modulation mode of the transmission system;

whereby the output signal of the at least one amplifier circuit is maintained at a substantially constant power level.

20. The apparatus of claim 19, wherein the at least one power detector is selectively operable in at least one of a first mode and a second mode, the at least one power detector in the first mode receiving at least a portion of the incidental wave corresponding to the amplified output signal and generating the first signal comprising a direct current (DC) value representative of a power level of the incidental wave, and the at least one power detector in the second mode receiving at least a portion of a reflected wave corresponding to the amplified output signal and generating the second signal comprising a DC value representative of a power level of the reflected wave.

21. Apparatus comprising one or more semiconductor devices, the one or more semiconductor devices comprising at least one amplifier circuit having a controllable output power level, the at least one amplifier circuit comprising:

an attenuator configurable for receiving an input signal and being operative to control an attenuation thereof;

an amplifier coupled to the attenuator, the amplifier receiving the attenuated input signal and generating an amplified output signal;

at least one power detector configurable to independently detect at least a portion of an incidental wave and a reflected wave corresponding to the amplified output signal and to generate first and second signals representative of the detected incidental and reflected waves, respectively, the at least one power detector being selectively operable in at least one of a first mode and a second mode, the at least one power detector in the first mode receiving at least a portion of the incidental wave corresponding to the amplified output signal and generating the first signal comprising a direct current (DC) value representative of a power level of the incidental wave, and the at least one power detector in the second mode receiving at least a portion of a reflected wave corresponding to the amplified output signal and generating the second signal comprising a DC value representative of a power level of the reflected wave;

a switching circuit operatively coupled to the at least one power detector, the switching circuit generating a control signal for selectively controlling a mode of operation of the at least one power detector; and

a controller operatively coupled between the at least one power detector and the attenuator in a feedback configuration, the controller controlling at least one of the attenuation of the input signal and an amplification of the input signal as a function of the first and second signals from the power detector;

whereby the output signal of the amplifier circuit is maintained at a substantially constant power level.