Method of forming a helical antenna

Claim 1

A method of forming a high-gain helical antenna for irradiating an earth formation penetrated by a borehole to approximate the distance to an electromagnetic discontinuity in said formation from said borehole, comprising the steps of: a. forming a two-wire electromagnetic coupling means having a single input terminal connectable to a source of electromagnetic energy, and a plurality of radially directed output terminals terminating exterior of and axially spaced along the midportion of an axially elongated central cylindrical conducting element of an electrically conductive material, by the substeps of: forming a plurality of axially elongated plates of an electrically conductive material having broad surfaces; grooving adjacent broad surfaces thereof to form a distribution pattern including a single input groove and a plurality of output grooves; locating a single-wire conductor within the grooves having a single input end and a plurality of remote output ends; stacking the plates into a unitary assembly; attaching a two-wire transmission line to said assembled plates, one wire of said transmission line connected to said wire conductor within said grooves, the other wire of said transmission line being connected to said plates; inserting the assembled plates within and in contact with the central cylindrical element whereby said plurality of remote near ends of said single-wire conductor within said grooves are alignable with openings in said central element so as to terminably contact said plurality of output terminals exterior of said control element; b. forming first and second pairs of helical conducting elements of an electrically conductive material about said central conducting element, each of said pairs of helical conducting elements adapted to helically wind about said central conducting element in the same circumferential direction having near ends at said midportion of said cylindrical conducting element and remote ends terminating at a remote end of said cylindrical conducting element; c. spacing each helical conducting element in an axial direction along said central cylindrical element, so that each turn is adapted to have a common circumferential length equal to an integral operating wavelength of the electromagnetic energy in said formation; and d. connecting the plurality of output terminals of said near ends of the first and second pairS of helical conducting elements so as to shorten one of said helical conductors of each pair of helical conducting elements a circumferential distance relative to said other helical conductor of each pair of helical conductors, said distance being about a half of one integral turn of said helical conductors, and thereby enable the production of first and second pairs of electromagnetic waves propagating in opposed axial directions from said coupling means.

Claim 2

A method of forming a high-gain helical antenna for irradiating an earth formation penetrated by a borehole to approximate the distance to an electromagnetic discontinuity in said formation from said borehole, comprising the steps of: a. forming a two-wire electromagnetic coupling means having a single input terminal connectable to a source of electromagnetic energy, and a plurality of radially directed output terminals terminating exterior of and axially spaced along the midportion of an axially elongated central cylindrical conducting element of an electrically conductive material, by the substeps of: forming a plurality of axially elongated plates of an electrically conductive material having broad surfaces; grooving adjacent broad surfaces thereof to form a distribution pattern including a single input groove and a plurality of output grooves; locating a single-wire conductor within the grooves having a single input end and a plurality of remote output ends; stacking the plates into a unitary assembly; attaching a two-wire transmission line to said assembled plates, one wire of said transmission line connected to said wire conductor within said grooves, the other wire of said transmission line being connected to said plates; inserting the assembled plates within and in contact with the central cylindrical element whereby said plurality of remote near ends of said single-wire conductor within said grooves are alignable with openings in said central element so as to terminably contact said plurality of output terminals exterior of said control element; b. forming first and second pairs of helical conducting elements of an electrically conductive material about said central conducting element, each of said pairs of helical conducting elements adapted to helically wind about said central conducting element in the same circumferential direction having near ends at said midportion of said cylindrical conducting element and remote ends terminating at a remote end of said cylindrical conducting element; c. spacing each helical conducting element in an axial direction along said central cylindrical element, so that each turn is adapted to have a common circumferential length equal to an integral operating wavelength of the electromagnetic energy in said formation; and d. connecting the plurality of output terminals of said near ends of the first and second pairS of helical conducting elements so as to shorten one of said helical conductors of each pair of helical conducting elements a circumferential distance relative to said other helical conductor of each pair of helical conductors, said distance being about a half of one integral turn of said helical conductors, and thereby enable the production of first and second pairs of electromagnetic waves propagating in opposed axial directions from said coupling means.