Apparatus, system, and method for measuring power delivered to a load

• US 7,392,021 B2
• Filed: 08/03/2005
• Issued: 06/24/2008
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: Eagle Technology, LLC (L3Harris Technologies, Inc.)
• Original Assignee: M/A Com
• Inventors: Rajanish, Jain, Nitin, Alexanian, Angelos
• Primary Examiner(s): Nguyen; Duc M.
• Application Number:
  US11/196,371
• Publication Number:
  US 20070032209A1
• Time in Patent Office: 1,056 Days
• Field of Search: 455/115.1, 455/126, 455/127.1, 330/2, 330/127, 330/129, 330/290
• US Class Current: 455/115.1
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control

Abstract

Apparatus, system, and method including a circuit including an element having an electrical impedance, an input node to receive a signal, and an output node to couple to a load; a sensing circuit coupled to the input node and the output node to sense a differential voltage between the input and output nodes and to sense a detected voltage at the input node; and a multiplier circuit to receive the differential voltage and to receive the detected voltage. The multiplier circuit provides an output voltage proportional to the instantaneous power delivered to the load based on the differential voltage, the detected voltage, and the impedance of the element. A system may further include a radio frequency (RF) power amplifier (PA). A method may further include controlling a gain of the RF PA to maintain the power delivered to the load at a predetermined level based on the output voltage of the multiplier circuit.

Claims

1. An apparatus, comprising:

a first circuit comprising a first element having an electrical impedance and having an input node to receive a signal and an output node to couple to a load;

a sensing circuit coupled to said input node and said output node to sense a differential voltage between said input and output nodes and to sense a detected voltage at said input node; and

a multiplier circuit to receive said differential voltage and to receive said detected voltage, said multiplier circuit to provide an output voltage proportional to an instantaneous power delivered to said load based on said differential voltage, said detected voltage, and said impedance of said first element of said first circuit.

2. The apparatus of claim 1, wherein said first element of said first circuit is selected from the group consisting of a resistor, capacitor, inductor, semiconductor, transistor, diode, and transmission line.

3. The apparatus of claim 1, wherein said sensing circuit comprises:

a first element coupled to said input node;

a second element coupled to said output node;

a third element coupled to said input node;

wherein said first, second, and third elements of said sensing circuit have an impedance selected to prevent said sensing circuit from loading said signal.

4. The apparatus of claim 3, wherein the impedance of said first element of said first circuit and the impedance of said first element of said sensing circuit is selected to prevent said sensing circuit from loading said signal.

5. The apparatus of claim 3, wherein said first element of said first circuit and said first, second, and third elements of said sensing circuit are selected to provide a phase matched relationship between said differential voltage and said detected voltage for a given frequency of said signal.

6. The apparatus of claim 5, wherein:

said first element of said first circuit comprises a capacitor (C_m);

said first element of said sensing circuit comprises an inductor (L₂), a first resistor (R_2a), and a second resistor (R_2b) connected in series therewith; and

said second and third elements of said sensing circuit each comprise a resistor (R₁) and a capacitor (C₁) connected in series therewith.

7. The apparatus of claim 6, wherein said differential voltage and said detected voltage are determined from the relationships, which are represented in a Laplace transformed format:

8. The apparatus of claim 6, wherein said first, second, and third elements of said sensing circuit are determined by the relationship:

9. The apparatus of claim 6, wherein instantaneous power delivered to said load (P_del) is determined by the relationship:

P_del=V_a(t)·

I_c(t)=A·

(V₁(t)−

V₂(t))·

V₃(t)·

(1+ω

²·

R₁²·

C₁²)

wherein V_a(t) is the instantaneous signal voltage at said input node;

wherein I_c(t) is the instantaneous current through said capacitor C_m;

wherein V₁(t)−

V₂(t) is the instantaneous differential voltage sensed by said sensing circuit;

wherein V₃(t) is the instantaneous detected voltage sensed by said sensing circuit;

wherein ω

is the radian frequency of said signal; and

wherein A is determined by the relationship;

10. The apparatus of claim 1, comprising:

a control circuit coupled to said multiplier circuit and to a radio frequency (RF) power amplifier (PA), said control circuit to receive said output voltage from said multiplier circuit and to adjust the gain of said RF PA to maintain said power delivered to said load to a predetermined value.

11. A system, comprising:

a radio frequency (RF) power amplifier (PA); and

a circuit, wherein said circuit comprises;

a first circuit comprising a first element having an electrical impedance and having an input node to receive a signal and an output node to couple to a load;

a sensing circuit coupled to said input node and said output node to sense a differential voltage between said input and output nodes and to sense a detected voltage at said input node; and

a multiplier circuit to receive said differential voltage and to receive said detected voltage, said multiplier circuit to provide an output voltage proportional to an instantaneous power delivered to said load based on said differential voltage, said detected voltage, and said impedance of said first element of said first circuit.

12. The system of claim 11, wherein said first element of said first circuit is selected from the group consisting of a resistor, capacitor, inductor, semiconductor, transistor, diode, and transmission line.

13. The system of claim 11, wherein said sensing circuit comprises:

a first element coupled to said input node;

a second element coupled to said output node;

a third element coupled to said input node;

wherein said first, second, and third elements of said sensing circuit have an impedance selected to prevent said sensing circuit from loading said signal.

14. The system of claim 13, wherein the impedance of said first element of said first circuit and the impedance of said first element of said sensing circuit is selected to prevent said sensing circuit from loading said RF PA.

15. The system of claim 13, wherein said first element of said first circuit and said first, second, and third elements of said sensing circuits are selected to provide a phase matched relationship between said differential voltage and said detected voltage for a given frequency of said signal.

16. The system of claim 15, wherein:

said first element of said first circuit comprises a capacitor (C_m);

said first element of said sensing circuit comprises an inductor (L₂), a first resistor (R_2a), and a second resistor (R_2b) connected in series therewith; and

said second and third elements of said sensing circuit each comprise a resistor (R₁) and a capacitor (C₁) connected in series therewith.

17. The system of claim 16, wherein said differential voltage and said detected voltage are determined from the relationships, which are represented in a Laplace transformed format:

18. The system of claim 16, wherein said first, second, and third elements of said sensing circuit are determined by the relationship:

19. The system of claim 16, wherein instantaneous power delivered to said load (P_del) is determined by the relationship:

P_del=V_a(t)·

I_c(t)=A·

(V₁(t)−

V₂(t))·

V₃(t)·

(1+ω

²·

R₁²·

C₁²)

wherein V_a(t) is the instantaneous signal voltage at said input node;

wherein I_c(t) is the instantaneous current through said capacitor C_m;

wherein V₁(t)−

V₂(t) is the instantaneous differential voltage sensed by said sensing circuit;

wherein V₃(t) is the instantaneous detected voltage sensed by said sensing circuit;

wherein ω

is the radian frequency of said signal; and

wherein A is determined by the relationship;

20. The system of claim 11, comprising:

a control circuit coupled to said multiplier circuit and to a radio frequency (RF) power amplifier (PA), said control circuit to receive said output voltage from said multiplier circuit and to adjust the gain of said RF PA to maintain said power delivered to said load to a predetermined value.

21. A method, comprising:

sensing a differential voltage across an element between an input node and a load;

sensing a detected voltage at said input node;

multiplying said differential voltage and said detected voltage;

determining power delivered to said load based on said multiplied differential and detected voltages and an impedance of said element; and

providing an output voltage that is proportional to said power.

22. The method of claim 21, comprising controlling power delivered to said load based on said output voltage.

23. The method of claim 22, wherein controlling said power comprises controlling a gain of a radio frequency (RF) power amplifier (PA) based on said output voltage.

24. The method of claim 22, comprising maintaining said power delivered to said load at a predetermined level based on said output voltage.