Capacitively coupled RF voltage probe having optimized flux linkage
AssigneeSematech, Inc.
InventorsJames A. Moore, Dennis O. Sparks
Life of this patent
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Abstract
An RF sensor having a novel current sensing probe and a voltage sensing probe to measure voltage and current. The current sensor is disposed in a transmission line to link all of the flux generated by the flowing current in order to obtain an accurate measurement. The voltage sensor is a flat plate which operates as a capacitive plate to sense voltage on a center conductor of the transmission line, in which the measured voltage is obtained across a resistance leg of a R-C differentiator circuit formed by the characteristic impedance of a connecting transmission line and a capacitance of the plate, which is positioned proximal to the center conductor.
Claims17
A voltage sensor for coupling to a power carrying transmission line to sense voltage on said transmission line, comprising:
- a center conductor coupled serially in-line to said transmission line;
- a housing surrounding said center conductor to shield said center conductor and to provide a return path for said transmission line;
- a plate disposed between said center conductor and said housing, having a first side of said plate proximal to and facing said center conductor, in which said center conductor and said plate function as capacitor plates to form a capacitor;
- a sensing line having a characteristic impedance of a resistive load coupled to terminate on an opposite side of said plate, wherein the resistive load of said sensing line and the capacitor forming a resistive-capacitive circuit,
- said plate being sufficiently short in length as compared to said center conductor, said center conductor being closer to said plate than said housing at a point on said center conductor where said plate is located and the opposite side of said plate being coupled to said resistive load, which places the opposite side of said plate at a potential near that of said housing, allowing for electric flux linkage from said center conductor to be coupled to both sides of said plate to reduce flux loss at the point where said center conductor is sensed;
- said sensing line providing a sensing voltage signal which is indicative of transmission line voltage.
A radio frequency (RF) voltage sensor for coupling to a power carrying transmission line to sense RF voltage on said transmission line, comprising:
- a center conductor for coupling serially in-line to an RF driven conductor of said transmission line, said center conductor coupled at each end to said transmission line;
- a sensor housing surrounding said center conductor to shield said center conductor and to provide a return path for said transmission line;
- a plate disposed within said housing and having a first side of said plate proximal to and facing said center conductor, in which said center conductor and said plate function as capacitor plates to form a capacitor;
- a sensing line having a characteristic impedance of a resistive load coupled to terminate on an opposite side of said plate, wherein the resistive load of said sensing line and the capacitor forming a resistive-capacitive circuit;
- said plate being sufficiently short in length as compared to said center conductor, said center conductor being closer to said plate than said housing at a point on said center conductor where said plate is located and the opposite side of said plate being coupled to said resistive load, which places the opposite side of said plate at a potential near that of said housing, allowing for electric flux linkage from said center conductor to be coupled to both sides of said plate to reduce flux loss at the point where said center conductor is sensed;
- said sensing line providing a sensing voltage signal which is indicative of transmission line voltage.
In a processing system in which radio frequency (RF) power is coupled from an RF source to a processing equipment by a transmission line, a method of monitoring RF voltage on said transmission line, comprising the steps of:
- providing a center conductor which is coupled serially in-line to said transmission line;
- providing a housing which surrounds said center conductor to shield said center conductor and function as a return path for said transmission line;
- providing a plate disposed between said center conductor and said housing, having a first side of said plate proximal to and facing said center conductor, in which said center conductor and said plate function as capacitor plates to form a capacitor;
- providing a sensing line having a characteristic impedance of a resistive load coupled to terminate on an opposite side of said plate, wherein the resistive load of said sensing line and the capacitor forming a resistive-capacitive circuit;
- said plate being sufficiently short in length as compared to said center conductor, said center conductor being closer to said plate than said housing at a point on said center conductor where said plate is located and the opposite side of said plate being coupled to said resistive load, which places the opposite side of said plate at a potential near that of said housing, allowing for electric flux linkage from said center conductor to be coupled to both sides of said plate to reduce flux loss at the point where said center conductor is sensed;
- measuring said sensing line which provides a sensing voltage signal indicative of transmission line voltage.
Dependencies are inferred from the claim text.