RF current sensor

Claim 2

A current sensor for coupling to a power carrying transmission line to sense current on said transmission line, comprising: a center conductor for coupling serially in-line to said transmission line, said center conductor is hollow along a portion of its length and has an opening which extends to its hollow center, said center conductor is encased within a return path of said transmission line and separated from said return path by a dielectric gap; a looped pickup coil disposed within said dielectric gap, wherein an apex of a loop formed by said pickup coil and located at its mid-way point along a length of said loop resides within said opening of said center conductor; said pickup coil, which includes an inner conductor and an outer conductor, for providing a voltage signal which is representative of actual current on said transmission line; said inner conductor of said pickup coil is terminated at one end by a termination impedance and the other end for providing said voltage signal; said outer conductor of said pickup coil is coupled to said return path at both ends, but is cut at its mid-way point from its ends to break electrical continuity, said cut being at an apex of said loop and extends into said opening of said center conductor; said loop of said pickup coil fully extending across said dielectric gap to link magnetic flux generated by current flowing in said transmission line along a length of said center conductor coupled by said pickup coil.

Claim 3

The current sensor of claim 1 wherein said center conductor is axisymmetric.

Claim 4

The current sensor of claim 2 wherein said center conductor is cylindrically shaped.

Claim 5

The current sensor of claim 3 wherein said return path has a cylindrically shaped inner surface which is concentric to said cylindrically-shaped center conductor.

Claim 6

The current sensor of claim 4 wherein said outer conductor of said pickup coil, including said cut, functions as a Faraday shield.

Claim 7

The current sensor of claim 5 wherein said actual current (I) is determined by an equation ##EQU31## where Vt is a value of said voltage signal, a is a radius from a concentric center of said center conductor to said outer surface of said center conductor, b is a radius from said concentric center to said inner surface of said return path encasing said center conductor, L is said length of said center conductor coupled by said pickup coil, f is a frequency of operation and μ o is a permeability factor.

Claim 8

The current sensor of claim 6 wherein a dielectric for said dielectric gap is air.

Claim 9

A radio frequency (RF) current sensor for coupling to a power carrying transmission line to sense RF current on said transmission line, comprising: a sensor housing coupled to said transmission line; a center conductor for coupling serially in-line to an RF driven conductor of said transmission line, said center conductor is disposed within said housing, is hollow along a portion of its length and has an opening which extends to its hollow center; said center conductor is encased within said housing, which also is a return path of said transmission line, and separated from said housing by a dielectric gap; a looped pickup coil disposed within said dielectric gap, wherein an apex of a loop formed by said pickup coil and located at its mid-way point along a length of said loop resides within said opening of said center conductor; said pickup coil, which includes an inner conductor and an outer conductor, for providing a voltage signal which is representative of actual RF current on said transmission line; said inner conductor of said pickup coil is terminated at one end by termination impedance and the other end for providing said voltage signal; said outer conductor of said pickup coil is coupled to said housing at both ends, but is cut at its mid-way point from its ends to break electrical continuity, said cut is at an apex of said loop and extends into said opening of said center conductor; said loop of said pickup coil fully extends across said dielectric gap, located between said center conductor and said housing, to link magnetic flux generated by current flowing in said transmission line along a length of said center conductor coupled by said pickup coil.

Claim 10

A radio frequency (RF) current sensor for coupling to a power carrying transmission line to sense RF current on said transmission line, comprising: a sensor housing coupled to said transmission line; a center conductor for coupling serially in-line to an RF driven conductor of said transmission line, said center conductor is disposed within said housing, is hollow along a portion of its length and has an opening which extends to its hollow center; said center conductor is encased within said housing, which also is a return path of said transmission line, and separated from said housing by a dielectric gap; a looped pickup coil disposed within said dielectric gap, wherein an apex of a loop formed by said pickup coil and located at its mid-way point along a length of said loop resides within said opening of said center conductor; said pickup coil, which includes an inner conductor and an outer conductor, for providing a voltage signal which is representative of actual RF current on said transmission line; said inner conductor of said pickup coil is terminated at one end by termination impedance and the other end for providing said voltage signal; said outer conductor of said pickup coil is coupled to said housing at both ends, but is cut at its mid-way point from its ends to break electrical continuity, said cut is at an apex of said loop and extends into said opening of said center conductor; said loop of said pickup coil fully extends across said dielectric gap, located between said center conductor and said housing, to link magnetic flux generated by current flowing in said transmission line along a length of said center conductor coupled by said pickup coil.

Claim 11

The RF current sensor of claim 8 wherein said center conductor is axisymmetric.

Claim 12

The RF current sensor of claim 9 wherein said center conductor is cylindrically shaped.

Claim 13

The RF current sensor of claim 10 wherein said housing has a cylindrically shaped inner surface which is concentric to said outer cylindrical surface of said center conductor.

Claim 14

The RF current sensor of claim 11 wherein said outer conductor of said pickup coil, including said cut, functions as a Faraday shield.

Claim 15

The RF current sensor of claim 12 wherein said actual current (I) is determined by an equation ##EQU32## where Vt is a value of said voltage signal, a is a radius from a concentric center of said center conductor to said outer surface of said center conductor, b is a radius from said concentric center to said inner surface of said housing, L is said length of said center conductor coupled by said pickup coil, f is a frequency of operation and μ o is a permeability factor.

Claim 16

The RF current sensor of claim 13 wherein a dielectric for said dielectric gap is air.

Claim 17

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 current on said transmission line; comprising the steps of: providing a sensor housing which is coupled to said transmission line; providing a center conductor which is coupled serially in-line to an RF driven conductor of said transmission line, said center conductor being disposed within said housing, being hollow along a portion of its length and having an opening which extends to its hollow center; said center conductor being encased within said housing, which also is a return path of said transmission line, and separated from said housing by a dielectric gap; providing a looped pickup coil which is disposed within said dielectric gap, wherein an apex of a loop formed by said pickup coil and located at its mid-way point along a length of said loop resides within said opening of said center conductor; said pickup coil, which includes an inner conductor and an outer conductors providing a voltage signal which is representative of actual RF current on said transmission line; said inner conductor of said pickup coil being terminated at one end by a termination impedance and the other end for providing said voltage signal; said outer conductor of said pickup coil being coupled to said housing at both ends, but being cut at its mid-way point from its ends to break electrical continuity, said cut being at an apex of said loop and extending into said opening of said center conductor; said loop of said pickup coil fully extending across said dielectric gap, located between said center conductor and said housing, to link magnetic flux generated by current flowing in said transmission line along a length of said center conductor coupled by said pickup coil.

Claim 18

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 current on said transmission line; comprising the steps of: providing a sensor housing which is coupled to said transmission line; providing a center conductor which is coupled serially in-line to an RF driven conductor of said transmission line, said center conductor being disposed within said housing, being hollow along a portion of its length and having an opening which extends to its hollow center; said center conductor being encased within said housing, which also is a return path of said transmission line, and separated from said housing by a dielectric gap; providing a looped pickup coil which is disposed within said dielectric gap, wherein an apex of a loop formed by said pickup coil and located at its mid-way point along a length of said loop resides within said opening of said center conductor; said pickup coil, which includes an inner conductor and an outer conductors providing a voltage signal which is representative of actual RF current on said transmission line; said inner conductor of said pickup coil being terminated at one end by a termination impedance and the other end for providing said voltage signal; said outer conductor of said pickup coil being coupled to said housing at both ends, but being cut at its mid-way point from its ends to break electrical continuity, said cut being at an apex of said loop and extending into said opening of said center conductor; said loop of said pickup coil fully extending across said dielectric gap, located between said center conductor and said housing, to link magnetic flux generated by current flowing in said transmission line along a length of said center conductor coupled by said pickup coil.

Claim 19

The method of claim 15 wherein said center conductor is axisymmetric.

Claim 20

The method of claim 16 wherein said center conductor is cylindrically shaped.

Claim 21

The method of claim 17 wherein said housing has a cylindrically shaped inner surface which is concentric to said outer-cylindrical surface of said center conductor.

Claim 22

The method of claim 18 wherein said outer conductor of said pickup coil, including said cut, functions as a Faraday shield.

Claim 23

The method of claim 19 wherein said actual current (I) is determined by an equation ##EQU33## where Vt is a value of said voltage signal, a is a radius from a concentric center of said center conductor to said outer surface of said center conductor, b is a radius from said concentric center to said inner surface of said housing, L is said length of said center conductor coupled by said pickup coil, f is a frequency of operation and μ o is a permeability factor.

Claim 24

The method of claim 20 wherein a dielectric for said dielectric gap is air.