Envelope modulated amplifier bias control and method

• US 6,025,754 A
• Filed: 07/02/1998
• Issued: 02/15/2000
• Est. Priority Date: 11/03/1997
• Status: Expired due to Term

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Czora, William J.
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Nguyen, Patricia T.
• Application Number:
  US09/109,269
• Time in Patent Office: 593 Days
• Field of Search: 330/296, 330/285, 330/136, 330/298, 330/207 P
• US Class Current: 330/296
• CPC Class Codes: H03F 1/0222 by using a signal derived from the input signal
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/462 the current being sensed
• CPC Class Codes: H03F 2200/504 the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier
• CPC Class Codes: H03G 3/004 Control by varying the supply voltage
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

A RF amplifier and method wherein the bias current is varied dynamically as a function of the envelope of the RF modulation to increase the efficiency and improve the linearity of the amplifier. Alternatively, the supply voltage may be dynamically varied as a function of modulation envelope.

Claims

1. A method of reducing the power requirements for Class A operation of a RF amplifier comprising the steps of:

(a) sensing the envelope of the RF signal being amplified; and

(b) modifying the power consumed by the amplifier by modifying the amplifier bias current in response to the sensed envelope.

2. The method of claim 1 wherein the current through the amplifier is sensed by a resistor between the voltage supply and the active element in the amplifier.

3. The method of claim 1 wherein the current through the amplifier is sensed by a resistor between the active element in the amplifier and ground.

4. The method of claim 1 wherein the power consumed by the amplifier is also modified by the steps of:

sensing the energy in the RF envelope; and

modifying the voltage of the power supply in response to the sensed energy.

5. A method of improving the linearity for Class C operation of a RF amplifier comprising the steps of:

(a) sensing the envelope of the RF signal being amplified; and

(b) modifying the power consumed by the amplifier by modifying the amplifier bias current in response to the sensed envelope.

6. A method of dynamically biasing a RF amplifier comprising the steps of:

(a) sensing the envelope of the RF signal being amplified; and

(b) modifying the power consumed by the amplifier by modifying the amplifier bias current in response to the sensed envelope.

7. A method of reducing power consumption in an RF amplifier comprising the steps of:

(a) sensing the envelope of the RF signal being amplified; and

(b) modifying the power applied to the amplifier by modifying the amplifier a bias current in response to the sensed envelope.

8. In an RF amplifier having an input terminal, an output terminal, bias and a source of power:

means for sensing the envelope of the RF signal applied to the input terminal;

means for modifying the power applied to the amplifier responsive to said sensing means, said means for modifying including a means for varying the bias current of the amplifier.

9. The amplifier of claim 8 wherein said energy sensing means includes:

an envelope detector;

a power supply current sensor;

an error amplifier for comparing the sensed current with the detected envelope;

a pulse width modulator responsive to said error amplifier for applying a signal to control the voltage of said source of power.

10. The amplifier of claim 9 wherein said power consumption varying means includes:

means for varying the bias of the amplifier in response to said envelope detector; and

means for sensing the energy in the envelope of the RF signal and for varying the potential of said source of power in response to said envelope detector.