Power sensor for RF power amplifier

• US 6,307,364 B1
• Filed: 08/27/1999
• Issued: 10/23/2001
• Est. Priority Date: 08/27/1999
• Status: Expired due to Term

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Augustine, Paul J.
• Primary Examiner(s): Nguyen, Vinh P.
• Application Number:
  US09/384,679
• Time in Patent Office: 788 Days
• Field of Search: 324/95, 324/158.1, 324/119, 343/703, 330/130, 330/138, 330/279, 330/280, 455/126, 455/127, 455/91
• US Class Current: 324/95
• CPC Class Codes: G01R 21/00 Arrangements for measuring electric power or power factor G01R7/12 takes precedence
• 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

Abstract

A system for sensing RF amplifier output power includes an amplifier transistor and a sampling transistor that is physically smaller than the amplifier transistor. The sampling transistor is configured to sample the same RF input signal that is amplified by the amplifier transistor. A bias circuit associated with the transistors includes a selection of components based upon operating parameters as well as actual physical sizes of the transistors. The selection of component values in association with transistor sizes is used to enable generation of a current sensing signal that is proportional to the power level of the RF output signal generated by the amplifier transistor.

Claims

1. A system for sensing RF amplifier output power comprising:

a RF amplifier transistor configured to receive and amplify a RF signal;

a sampling transistor configured to receive and amplify a RF signal, wherein the sampling transistor is physically smaller than the RF amplifier transistor such that the sampling transistor is capable of producing a proportionally smaller amplified RF signal than that capable of being produced by the RF amplifier transistor for a RF input signal common to both the RF amplifier transistor and the sampling transistor; and

a current sensing circuit configured to receive a RF signal amplified by the sampling transistor and generate a current proportional to a RF signal amplified by the RF amplifier transistor.

2. The system according to claim 1 further including a bias network configured to establish a quiescent operating point for the RF amplifier transistor.

3. The system according to claim 2, wherein the bias network is further configured to establish a quiescent operating point for the sampling transistor, by associating a first bias resistor with the sampling transistor.

4. The system according to claim 3, wherein the bias network comprises a second bias resistor associated with the RF amplifier transistor.

5. The system according to claim 4, wherein a ratio of resistor values between the second bias resistor and the first bias resistor is substantially equal to a ratio of physical sizes between the sampling transistor and the RF amplifier transistor.

6. The system according to claim 5 further comprising a first RF signal coupling capacitor configured to pass a RF signal to the RF amplifier transistor.

7. The system according to claim 6 further comprising a second RF signal coupling capacitor configured to pass a RF signal to the sampling transistor.

8. The system according to claim 7, wherein a ratio of capacitor values between the first RF signal coupling capacitor and the second RF signal coupling capacitor is substantially equal to a ratio of physical sizes between the RF amplifier transistor and the sampling transistor.

9. A system for sensing RF amplifier output power comprising:

means for amplifying a RF input signal and generating a RF output signal therefrom;

means for sampling a RF input signal that is associated with both the amplifying means and the sampling means and generating a sampled signal therefrom; and

means for sensing the sampled signal and generating a current sensing signal therefrom proportional to a power amplitude associated with the RF output signal.

10. The system according to claim 9 further comprising biasing means for biasing the sampling means and further for biasing the amplifying means such that a bias current associated with the sampling means is proportional to a bias current associated with the amplifying means.

11. The system according to claim 10 wherein the amplifying means comprises a first transistor.

12. The system according to claim 11 wherein the sampling means comprises a second transistor, wherein the second transistor is configured to be physically smaller than the first transistor such that a ratio of bias currents associated with the sampling means and the amplifying means is equal to a ratio of physical sizes associated with the first and second transistors.

13. A method for sensing RF signal power amplitude, the method comprising the steps of:

(a) providing a RF signal amplifier comprising a first transistor having a first predetermined size;

(b) providing a sampling amplifier comprising a second transistor having a second predetermined size that is smaller than the first predetermined size;

(c) amplifying a RF input signal to produce a first RF output signal; and

(d) sampling the RF input signal to produce a second RF output signal proportional to the first RF output signal, wherein the proportion is associated with a ratio determined by the first and second predetermined sizes.

14. The method of step 13 further comprising the step of:

(e) converting the second RF output signal to a current sensing signal such that the current sensing signal is proportional to a power amplitude associated with the first RF output signal.

15. A system for sensing RF amplifier output power comprising:

a RF amplifier transistor configured to receive and amplify a RF signal;

a sampling transistor configured to receive and amplify a RF signal, wherein the sampling transistor is physically smaller than the RF amplifier transistor such that the sampling transistor is capable of producing a proportionally smaller amplified RF signal than that capable of being produced by the RF amplifier transistor for a RF input signal common to both the RF amplifier transistor and the sampling transistor;

a current sensing circuit configured to receive a RF signal amplified by the sampling transistor and generate a current proportional to a power amplitude associated with the RF signal amplified by the RF amplifier transistor; and

a bias circuit configured to establish quiescent operating characteristics associated with the RF amplifier transistor and the sampling transistor, the bias circuit comprising a first bias resistor associated with the RF amplifier transistor and further comprising a second bias resistor associated with the sampling transistor, wherein a ratio of resistor values between the first bias resistor and the second bias resistor is substantially equal to a ratio of physical sizes between the sampling transistor and the RF amplifier transistor.