Power amplifier saturation prevention method, apparatus, and communication system incorporating the same

• US 6,430,402 B1
• Filed: 09/14/1998
• Issued: 08/06/2002
• Est. Priority Date: 09/14/1998
• Status: Expired due to Term

• Current Assignee: Alpha Industries Incorporated (Skyworks Solutions Incorporated)
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Agahi-Kesheh, Darioush
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): PEREZ GUTIERREZ, RAFAEL
• Application Number:
  US09/152,439
• Time in Patent Office: 1,422 Days
• Field of Search: 455/126, 455/522, 455/115, 455/117, 455/127, 455/234.2, 455/239.1, 455/240.1, 455/234.1, 455/232.1, 455/116, 330/129, 330/285, 330/278
• US Class Current: 455/115.3
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 1/345 using hybrid or directional couplers
• CPC Class Codes: H03G 3/3047 for intermittent signals, e.g. burst signals

Abstract

An apparatus for controlling the power level of an output signal from the output of an electronic amplifier. The electronic amplifier has a control signal input for receiving an amplifier control signal and has a power input for receiving current from a power supply. The apparatus comprises an amplifier output power detector, coupled to the output of the amplifier, used for generating a power measurement signal representing the output power of the amplifier. The apparatus contains a current detector arranged to detect the current received by the amplifier from the power supply and to provide a current measurement signal dependent on the amount of current received from the power supply. The apparatus contains a digital signal processor which receives the current measurement signal and provides a reference signal dependant on the current measurement signal. The apparatus also contains a comparator coupled to receive the reference signal and the power measurement signal which is used for generating the control signal to prevent saturation of the amplifier.

Claims

1. An apparatus for transmitting signals over a communications channel, the apparatus comprising:

an input signal source;

a power amplifier having a data signal input coupled to the input signal source, a control signal input for receiving a control signal for controlling the power output of the power amplifier, and a power input for receiving a current from a power supply;

an output power detector, coupled to the output of the amplifier, for generating a power measurement signal representing the power output of the amplifier;

a current detector arranged to detect the current received by the power amplifier from the power supply and providing a current measurement signal representative of the current received from the power supply;

a digital signal processor coupled to receive the current measurement signal and provide a reference signal dependant on the current measurement signal;

a comparator, coupled to receive the reference signal and the power measurement signal, for generating an amplifier control signal;

means for coupling the power amplifier output to the communications channel;

a controller for increasing a power output of the amplifier in order to determine a current threshold value that limits the reference signal provided by the digital signal processor; and

a storage device for storing the current threshold value.

2. An apparatus as in claim 1 wherein:

the digital signal processor comprises means to prevent saturation of the power amplifier by tracking the changes in the reference signal from the digital signal processor, and comparing the changes in the reference signal from the digital signal processor with the changes in the current measured by the power amplifier current detector, in order to limit the value of the reference signal.

3. An apparatus as in claim 1 wherein:

the digital signal processor comprises means for comparing the value of the current drawn by the power amplifier to a predetermined current value and for controlling the reference signal to a maximum level which produces said predetermined current value.

4. An apparatus as in claim 1 wherein said power amplifier is an RF amplifier contained within a radiotelephone unit.

5. An apparatus for controlling the power level of an output signal from the output of an electronic amplifier, the electronic amplifier having a control signal input for receiving an amplifier control signal and having a power input for receiving current from a power supply, the apparatus comprising:

an amplifier output power detector, coupled to the output of the amplifier, for generating a power measurement signal representing the output power of the amplifier;

a current detector arranged to detect the current received by the amplifier from the power supply and to provide a current measurement signal dependent on the amount of current received from the power supply;

a digital signal processor coupled to receive the current measurement signal and provide a reference signal dependant on the current measurement signal;

a comparator, coupled to receive the reference signal and the power measurement signal, for generating an amplifier control signal;

a controller for increasing a power output of the amplifier in order to determine a current threshold value that limits the reference signal provided by the digital signal processor; and

a storage device for storing the current threshold value.

6. An apparatus as in claim 5 wherein:

said digital signal processor comprises means to prevent saturation of the power amplifier by tracking the changes in the reference signal generated by the digital signal processor, and comparing the changes in the reference signal generated by the digital signal processor with the changes in the current drawn by said power amplifier from the power supply, in order to detect and prevent the on set of saturation of the power amplifier.

7. An apparatus as in claim 5 wherein:

the digital signal processor comprises means for comparing the value of the current drawn by the power amplifier from the power supply to a predetermined current value and for controlling the reference signal to a maximum level which produces the predetermined current value.

8. An apparatus as in claim 5 wherein said power amplifier is an RF amplifier contained within a radiotelephone unit.

9. A method for controlling a reference signal for an electronic amplifier, the method comprising:

measuring a current drawn by a power amplifier;

comparing the current measurement to a predetermined current value minus a desired derating factor; and

limiting the reference signal depending on the difference between the current measurement signal and the predetermined current value, wherein the predetermined current value is determined by;

providing a power supply to power the power amplifier, the power supply having its voltage output set at a minimum voltage level determined for the operation of the power amplifier;

connecting the power supply to power the power amplifier;

increasing the power output of the power amplifier to a predetermined power level;

measuring an amount of current flowing into the power amplifier; and

setting the predetermined current value equal to the amount of current flowing into the power amplifier minus a desired derating factor.

10. A method for controlling a reference signal for an electronic amplifier, the method comprising:

measuring a current drawn by a power amplifier;

comparing the current measurement to a predetermined current value minus a desired derating factor; and

limiting the reference signal depending on the difference between the current measurement signal and the predetermined current value, wherein the predetermined current value is determined by;

establishing the power amplifier'"'"'s maximum power output prior to saturation;

increasing the power amplifier'"'"'s output to the maximum power output prior to saturation;

measuring a current flowing into the power amplifier at the maximum power output point prior to saturation; and

setting the predetermined current value equal to the measured current being drawn by the power amplifier at the maximum power output point prior to saturation minus a desired derating factor.

11. A method for controlling a reference signal for an electronic amplifier, the method comprising:

measuring a current drawn by a power amplifier;

comparing the current measurement to a predetermined current value minus a desired derating factor; and

limiting the reference signal depending on the difference between the current measurement signal and the predetermined current value, wherein the predetermined current value is determined by;

establishing the power amplifier'"'"'s maximum allowable power dissipation;

increasing the power amplifier'"'"'s output to a point where the maximum allowable power dissipation occurs;

measuring a current at the point where the maximum allowable power dissipation occurs; and

setting the predetermined current value equal to the measured current at the point where the maximum allowable power dissipation occurs minus a desired derating factor.

12. A method for controlling a reference signal for an electronic amplifier, the method comprising:

measuring a current drawn by a power amplifier;

comparing the current measurement to a predetermined current value minus a desired derating factor; and

limiting the reference signal depending on the difference between the current measurement signal and the predetermined current value, wherein the predetermined current value is determined by;

establishing the power amplifier'"'"'s minimum allowable linearity;

increasing the power amplifier'"'"'s output to a point where the minimum allowable linearity is detected;

measuring a current flowing into the power amplifier at the point where the minimum allowable linearity is detected; and

setting the predetermined current value equal to the measured current at the point where minimum allowable linearity is detected minus a desired derating factor.

13. A method for controlling a reference signal for an electronic amplifier, the method comprising:

measuring a current drawn by a power amplifier;

comparing the current measurement to a predetermined current value minus a desired derating factor; and

limiting the reference signal depending on the difference between the current measurement signal and the predetermined current value, wherein the predetermined current value is determined by;

establishing the power amplifier'"'"'s maximum allowable distortion;

increasing the power amplifier'"'"'s output to a point where the maximum allowable distortion occurs;

measuring a current flowing into the power amplifier at the point where the maximum allowable distortion occurs; and

setting the predetermined current value equal to the measured current at the point where the maximum allowable distortion occurs minus a desired derating factor.

14. A method for controlling a reference signal for an electronic amplifier, the method comprising:

measuring a current drawn by a power amplifier;

comparing the current measurement to a predetermined current value minus a desired derating factor; and

limiting the reference signal depending on the difference between the current measurement signal and the predetermined current value, wherein the predetermined current value is determined by;

establishing the power amplifier'"'"'s maximum power output;

increasing the power amplifier'"'"'s output to the maximum power output;

measuring a current flowing into the power amplifier at the maximum power output; and

setting the predetermined current value equal to the amount of current flowing into the power amplifier minus a desired derating factor.

15. A method for controlling a reterence signal for an electronic amplifier, the method comprising:

determining the difference in reference signals;

determining the difference in current measurement signals at the corresponding reference signals;

making a comparison of the change in the reference signals to the change in the current measurement signals;

setting an allowed range for the comparison of the reference signals to the change in the corresponding current measurement and signals;

limiting the maximum reference signal based on the allowed range and the results of the comparison.