MEMS varactor for measuring RF power

• US 6,803,774 B2
• Filed: 09/23/2002
• Issued: 10/12/2004
• Est. Priority Date: 09/23/2002
• Status: Expired due to Fees

• Current Assignee: Avago Technologies Wireless IP Singapore Pte Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Park, Chul Hong
• Primary Examiner(s): Lo, N.
• Assistant Examiner(s): Lair, Donald M.
• Application Number:
  US10/253,383
• Publication Number:
  US 20040056668A1
• Time in Patent Office: 750 Days
• Field of Search: 324/658, 324/684, 324/660, 324/661, 324/662, 324/680, 738/00, 455/73, 455/425
• US Class Current: 324/661
• CPC Class Codes: G01R 21/10 by using square-law characteristics of circuit elements, e.g. diodes, to measure power absorbed by loads of known impedance G01R21/02 takes precedence

Abstract

A meter for measuring the root-mean-squared potential of an AC signal characterized by a frequency f is disclosed. The meter includes first and second capacitors. The AC signal is applied to the first capacitor, which includes first and second plates separated by a distance that depends on the root-mean-squared potential of the AC signal, but not on changes in the AC signal that occur over a time of 1/f. The second capacitor has first and second plates separated by a distance that depends on the separation of the first and second plates in the first capacitor. A detection circuit measures the capacitance of the second capacitor. The first plate of the first capacitor is preferably connected to the first plate of the second capacitor by a non-conducting mechanical link.

Claims

1. A meter for measuring an AC signal characterized by a frequency f, said meter comprising:

a first capacitor for receiving said AC signal, said first capacitor having first and second plates separated by a distance that depends on the root-mean-squared potential of said AC signal, but not on changes in said AC signal that occur over a time of 1/f;

a second capacitor having first and second plates separated by a distance that depends on the separation of said first and second plates in said first capacitor; and

a circuit for measuring the capacitance of said second capacitor.

2. The meter of claim 1 wherein said second electrode of said first capacitor comprises a conducting layer on a substrate and wherein said first plate of said first capacitor comprises a conducting plate suspended over said first plate by a spring supported on said substrate.

3. A meter for measuring an AC signal characterized by a frequency f, said meter comprising:

a first capacitor for receiving said AC signal, said first capacitor having first and second plates separated by a distance that depends on the root-mean-squared potential of said AC signal, but not on changes in said AC signal that occur over a time of 1/f;

a second capacitor having first and second plates separated by a distance that depends on the separation of said first and second plates in said first capacitor; and

a circuit for measuring the capacitance of said second capacitor,

wherein said first plate of said first capacitor is connected to said first plate of said second capacitor by a non-conducting mechanical link.

4. A method for measuring the root-mean-squared potential of an AC signal characterized by a frequency f, said method comprising:

applying said AC signal across the plates of a first capacitor, said first capacitor having first and second plates separated by a distance that depends on the root-mean-squared potential of said AC signal, but not on changes in said AC signal that occur over a time of 1/f;

providing a second capacitor having first and second plates separated by a distance that depends on the separation of said first and second plates in said first capacitor; and

measuring the capacitance of said second capacitor.

5. A method for measuring the root-mean-squared potential of an AC signal characterized by a frequency f, said method applying said AC signal across the plates of a first capacitor, said first capacitor having first and second plates separated by a distance that depends on the root-mean-squared potential of said-AC signal, but not on changes in said AC signal that occur over a time of 1/f;

providing a second capacitor having first and second plates separated by a distance that depends on the separation of said first and second plates in said first capacitor; and

measuring the capacitance of said second capacitor,

wherein said first plate of said first capacitor is connected to said first plate of said second capacitor by a non-conducting mechanical link.