Wide band balun

Claim 2

A wide band balun comprising: an unbalanced coaxial input transmission line, said input line having a first and a second portion, said first portion being separated from said second portion by a gap in the outer conductor of said input line, said second portion being terminated in an open circuit for providing a series stub with respect to said gap; a first coaxial output line, the outer conductor of said first output line being electrically connected to the outer conductor of said first portion of sAid input line; a second coaxial output line, the outer conductor of said second output line being electrically connected to the outer conductor of said second portion of said input line; means located only in the region of said gap for electrically connecting the inner conductor of said first output line to the outer conductor of said second output line; means located only in the region of said gap for electrically connecting the outer conductor of said first portion of said input line to the inner conductor of said second output line; and means for providing a short circuit between a first region on the outer conductor of said first portion of said input line and a second region on the outer conductor of said second portion of said input line, said first and second regions each being substantially a quarter wavelength from said gap at a predetermined frequency.

Claim 3

The balun according to claim 1, further comprising: impedance transformation means interposed between an unbalanced coaxial line and said first portion of said input line for transforming the impedance of said first portion of said input line to a desired impedance.

Claim 4

The balun according to claim 1, wherein the outer conductor of said first output line is electrically connected to and coextensive with said first portion of said input line for a length of at least a quarter wavelength from said gap at said predetermined frequency and wherein the outer conductor of said second output line is electrically connected to and coextensive with said second portion of said input line for a length of at least a quarter wavelength from said gap at said predetermined frequency.

Claim 5

The balun according to claim 1 wherein the impedance of said series stub is substantially lower than the impedance of said first portion of said input line.

Claim 6

The balun according to claim 1 wherein the means for providing a short circuit comprises a conductive cylindrical-like member, the base at one end of said member being connected to the outer conductor of said first portion of input line in said first region, the base at the other end of said member being connected to the outer conductor of said second portion of input line in said second region.

Claim 7

A wideband balun, comprising: an unbalanced coaxial input line, said input line having a first portion exhibiting a first characteristic impedance and a second portion exhibiting a second characteristic impedance, said second characteristic impedance being lower than said first characteristic impedance, said input line further having a gap in the outer conductor thereof separating said first and second portions of said input line, said second portion of said input line being terminated in an open circuit: a first coaxial output line, said first coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of the first portion of said input line for a predetermined length along said first portion of said input line; a second coaxial output line, said second coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of said second portion of said input line for a predetermined length along said second portion of said input line; means for connecting the inner conductor of said first coaxial output line to the outer conductor of said second coaxial output line only in the region of said gap; means for connecting the outer conductor of said first portion of said input line to the inner conductor of said second coaxial output line only in the region of said gap; and means for providing a short circuit between a first region on the outer conductor of said first portion of said input line and a second region on the outer conductor of said second portion of said input line, said first and second regions each being substantially a quarter wavelength from said gap at a predetermined frequency of operation.

Claim 8

A wideband balun, comprising: an unbalanced coaxial input line, said input line having a first portion exhibiting a first characteristic impedance and a second portion exhibiting a second characteristic impedance, said second characteristic impedance being lower than said first characteristic impedance, said input line further having a gap in the outer conductor thereof separating said first and second portions of said input line, said second portion of said input line being terminated in an open circuit: a first coaxial output line, said first coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of the first portion of said input line for a predetermined length along said first portion of said input line; a second coaxial output line, said second coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of said second portion of said input line for a predetermined length along said second portion of said input line; means for connecting the inner conductor of said first coaxial output line to the outer conductor of said second coaxial output line only in the region of said gap; means for connecting the outer conductor of said first portion of said input line to the inner conductor of said second coaxial output line only in the region of said gap; and means for providing a short circuit between a first region on the outer conductor of said first portion of said input line and a second region on the outer conductor of said second portion of said input line, said first and second regions each being substantially a quarter wavelength from said gap at a predetermined frequency of operation.

Claim 9

The balun according to claim 6, including impedance transformation means coupled to said first portion of said input line for transforming said first characteristic impedance to a desired impedance.

Claim 10

A wide band balun for connecting an unbalanced coaxial line to a balanced line, comprising: an unbalanced coaxial input transmission line, said input line having a first portion at a first characteristic impedance and a second portion at a second characteristic impedance, said second characteristic impedance being lower than said first characteristic impedance, said input line further having a gap in the outer conductor thereof separating said first and said second portions of said input line, said second portion of said input line having an open circuit termination, said second portion of said input line providing a low impedance series stub with respect to said gap; impedance transformation means coupled to said first portion of said input line for matching said first characteristic impedance to a desired impedance; a first coaxial output transmission line, said first coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of the first portion of said input line for a predetermined length along said first portion of said input line; a second coaxial output transmission line, said second coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of said second portion of said input line for a predetermined length along said second portion of said input line line; means for connecting the inner conductor of said first output line to the outer conductor of said second output line only in the vicinity of said gap; means for connecting the outer conductor of said first portion of said input line to the inner conductor of said second output line only in the vicinity of said gap; and a conductive cylinder surrounding said coextensive length of said first portion of input line and said first output line and said coextensive length of said second portion of input line and said second output line, said cylinder being electrically connected at one end thereof to the outer conductor of said first portion of input line at a quarter wavelength from said gap at a predetermined frequency and electrically connected at the other end thereof to the outer conductor of said second portion of input line at a quarter wavelength from said gap at said predetermined frequency, said cylinder providing two shunt stubs with respect to said gap; said first output line inner conductor and said second output line inner conductor comprising said balanced line.

Claim 11

A wide band balun for connecting an unbalanced coaxial line to a balanced line, comprising: an unbalanced coaxial input transmission line, said input line having a first portion at a first characteristic impedance and a second portion at a second characteristic impedance, said second characteristic impedance being lower than said first characteristic impedance, said input line further having a gap in the outer conductor thereof separating said first and said second portions of said input line, said second portion of said input line having an open circuit termination, said second portion of said input line providing a low impedance series stub with respect to said gap; impedance transformation means coupled to said first portion of said input line for matching said first characteristic impedance to a desired impedance; a first coaxial output transmission line, said first coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of the first portion of said input line for a predetermined length along said first portion of said input line; a second coaxial output transmission line, said second coaxial output line having an outer conductor which is coextensive with and electrically connected to the outer conductor of said second portion of said input line for a predetermined length along said second portion of said input line line; means for connecting the inner conductor of said first output line to the outer conductor of said second output line only in the vicinity of said gap; means for connecting the outer conductor of said first portion of said input line to the inner conductor of said second output line only in the vicinity of said gap; and a conductive cylinder surrounding said coextensive length of said first portion of input line and said first output line and said coextensive length of said second portion of input line and said second output line, said cylinder being electrically connected at one end thereof to the outer conductor of said first portion of input line at a quarter wavelength from said gap at a predetermined frequency and electrically connected at the other end thereof to the outer conductor of said second portion of input line at a quarter wavelength from said gap at said predetermined frequency, said cylinder providing two shunt stubs with respect to said gap; said first output line inner conductor and said second output line inner conductor comprising said balanced line.