Amplifier bias adjustment circuit to maintain high-output third-order intermodulation distortion performance

• US 6,639,466 B2
• Filed: 06/11/2002
• Issued: 10/28/2003
• Est. Priority Date: 04/19/2001
• Status: Expired due to Term

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Anadigics Incorporated (Coherent Corp.)
• Inventors: Johnson, Douglas Matthew
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US10/167,604
• Publication Number:
  US 20030020540A1
• Time in Patent Office: 504 Days
• Field of Search: 330/129, 330/140, 330/149, 330/285
• US Class Current: 330/149
• CPC Class Codes: H03F 1/0272 by using a signal derived from the output signal
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• 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 circuit and method are provided for amplifying RF input signal to produce RF output signals with third-order intermodulation distortion products. The circuit and method use a feedback signal to control the bias voltage of the amplifier, such that the output third-order intermodulation distortion product increases monotonically with the RF input signal power. Specifically, the third-order intermodulation distortion product responds over a predetermined output power range by increasing three decibels in response to each one-decibel increase in input power.

Claims

1. A circuit for amplifying an input RF signal comprising:

(a) an RE amplifier having an input port that receives such input RF signal and an output port, wherein said RE amplifier produces at said output port an amplified RE signal comprising a third-order intermodulation distortion product signal;

(b) a power divider that is connected to said output port of said RE amplifier to divide said amplified RF signal into an output RE signal and a feedback signal; and

(c) a feedback circuit connected to said power divider to detect said feedback signal and to produce a DC voltage that is proportional to the power of said feedback signal and that is used to bias said RF amplifier circuit;

wherein said DC voltage causes said third-order intermodulation distortion product signal to increase in response to an increase in the level of said input RF signal over a predetermined range of power of said output RF signal.

2. The circuit of claim 1, wherein said DC voltage causes said third-order intermodulation distortion product signal to increase by a predictable amount in response to an increase in the level of said input RF signal over a predetermined range of power of said output RF signal.

3. The circuit of claim 2, wherein said DC voltage causes said third-order intermodulation distortion product signal to increase monotonically in response to an increase in the level of said input RF signal over a predetermined range of power of said output RE signal.

4. A method for amplifying an input RF signal comprising the steps of:

(a) amplifying said input RF signal in an amplifier to produce an amplified signal;

(b) dividing said amplified signal into an output RF signal and a feedback signal, said output RF signal comprising a third-order intermodulation distortion product signal;

(c) generating a DC signal with a DC voltage proportional to the power of said feedback signal; and

(d) biasing said amplifier based on said DC signal;

wherein the DC voltage causes said third-order intermodulation distortion product signal to increase in response to an increase in the level of said input RF signal over a predetermined range of power of said output RF signal.

5. The method of claim 4, wherein the DC voltage causes said third-order intermodulation distortion product signal to increase by a predictable amount in response to an increase in the level of said input RF signal over a predetermined range of power of said output RF signal.

6. The method of claim 5, wherein the DC voltage causes said third-order intermodulation distortion product signal to increase monotonically in response to an increase in the level of said input RF signal over a predetermined range of power of said output RF signal.