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Frequency-dependent phase center movement in near-field, unshielded, electromagnetic susceptibility testing using a log-periodic dipole can be significantly reduced by bending the rearmost dipole elements forward. Each bent dipole element has an inner portion and an outer portion connected to each o

Frequency-dependent phase center movement in near-field, unshielded, electromagnetic susceptibility testing using a log-periodic dipole can be significantly reduced by bending the rearmost dipole elements forward. Each bent dipole element has an inner portion and an outer portion connected to each other at a bend, the inner portion extending outward from a boom in substantially perpendicular relation to the boom, and the outer portion extending obliquely outward and forward from the bend. The frequency range of the antenna can be extended by forming each element of the longest dipole with an undulating shape when viewed in a direction along the boom.

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1. An electromagnetic susceptibility testing apparatus comprising:a broadband, unidirectional antenna comprising an array of dipoles in side-by-side relationship, the dipoles being of progressively increasing length and spacing from a forward end to a rearward end, and being fed by a common feeder w

1. An electromagnetic susceptibility testing apparatus comprising:a broadband, unidirectional antenna comprising an array of dipoles in side-by-side relationship, the dipoles being of progressively increasing length and spacing from a forward end to a rearward end, and being fed by a common feeder which extends in a direction from said forward end to said rearward end and alternates in phase between successive dipoles, and each dipole comprising two elements extending in opposite directions from said common feeder, wherein the elements of a plurality of adjacent ones of said dipoles, including the longest of said dipoles, are bent so that each element of said plurality of adjacent ones of said dipoles has an inner portion and an outer portion connected to each other at a bend, the inner portion extending outward from the common feeder, in substantially perpendicular relation to the common feeder, toward one of two spaces on opposite sides of said common feeder, and the outer portion extending obliquely outward and forward from the inner portion; and a device under test spaced forward of the forward end of the antenna; wherein each of said two spaces is substantially free of obstructions affecting the antenna radiation pattern, and wherein said spaces on opposite sides of said feeder are free of obstructions that are intersected by an arc centered on the bend of any of the dipoles of said plurality of adjacent ones of said dipoles and extending from a point on the obliquely extending outer Portion thereof to a point alianed with the inner portion thereof. 2. An electromagnetic susceptibility testing apparatus according to claim 1, in which said dipoles are substantially coplanar.3. An electromagnetic susceptibility testing apparatus according to claim 1, in which, on each side of the feeder, the oblique portions of the bent elements are in substantially parallel relationship to one another.4. An electromagnetic susceptibility testing apparatus according to claim 1, in which said dipoles are substantially coplanar, and in which, on each side of the feeder, the oblique portions of the bent elements are in substantially parallel relationship to one another.5. An electromagnetic susceptibility testing apparatus comprising:a broadband, undirectional antenna comprising an array of dipoles in side-by-side relationship, the dipoles being of progressively increasing length and spacing from a forward end to a rearward end, and being fed by a common feeder which extends in a direction from said forward end to said rearward end and alternates in phase between successive dipoles, and each dipole comprising two elements extending in opposite directions from said common feeder, wherein the elements of a plurality of adjacent ones of said dipoles, including the longest of said dipoles, are bent so that each element of said plurality of adjacent ones of said dipoles has an inner portion and an outer abortion connected to each other at a bend, the inner portion extending outward from the common feeder, in substantially perpendicular relation to the common feeder, toward one of two spaces on opposite sides of said common feeder, and the outer portion extending obliquely outward and forward from the inner portion; and a device under test spaced forward of the forward end of the antenna; wherein each of said two spaces is substantially free of obstructions affecting the antenna radiation pattern, and wherein each element of the longest dipole of said plurality of adjacent ones of said dipoles has an undulating shape when viewed in a direction along said feeder. 6. An electromagnetic susceptibility testing apparatus comprising:a boom composed of a pair of rigid conductors extending in spaced, side-by-side, relation to each other in a longitudinal direction from a forward end of the boom to a rearward end of the boom, and being insulated from each other; a two-conductor transmission line, the conductors of the transmission line being connected respectively to said rigid conductors of the boom at one of said forward and rearward ends of the boom; a series of dipoles composed of elements extending in transverse relation to the boom, the dipoles being disposed at stations spaced along the length of the boom, each dipole consisting of a first rigid element connected to one of the boom elements at one of said stations and a second rigid element connected to the other of the boom elements at said one of said stations, the elements of each dipole extending transverse to the length of the boom and on opposite sides of the boom, the dipoles being progressively longer, proceeding from the forward end of the boom to the rearward end of the boom, and successive dipoles being in alternating phase relationship to each other; wherein the elements of a plurality of adjacent ones of said dipoles, including the longest of said dipoles, are bent so that each element of said plurality of adjacent ones of said dipoles has an inner portion and an outer portion connected to each other at a bend, the inner portion extending outward from the boom in substantially perpendicular relation to the boom toward one of two spaces on opposite sides of said boom, and the outer portion extending obliquely outward and forward from the bend; and a device under test spaced forward of the forward end of the boom; wherein each of said two spaces is substantially free of obstructions affecting the radiation pattern of said apparatus, and wherein said spaces on opposite sides of said boom are free of obstructions that are intersected by an arc centered on the bend of any of the dipoles of said plurality of adjacent ones of said dipoles and extending from a point on the obliquely extending outer portion thereof to a point phoned with the inner portion thereof. 7. An electromagnetic susceptibility testing apparatus according to claim 6, in which said dipoles are substantially coplanar.8. An electromagnetic susceptibility testing apparatus according to claim 6, in which on each side of the boom, the oblique portions of the bent elements are in substantially parallel relationship to one another.9. An electromagnetic susceptibility testing apparatus according to claim 6, in which said dipoles are substantially coplanar, and in which, on each side of the boom, the oblique portions of the bent elements are in substantially parallel relationship to one another.10. An electromagnetic susceptibility testing apparatus comprising:a boom composed of a pair of rigid conductors extending in spaced, side-by-side, relation to each other in a longitudinal direction from a forward end of the boom to a rearward end of the boom, and being insulated from each other; a two-conductor transmission line, the conductors of the transmission line being connected respectively to said rigid conductors of the boom at one of said forward and rearward ends of the boom; a series of dipoles composed of elements extending in transverse relation to the boom, the dipoles being disposed at stations spaced along the length of the boom, each dipole consisting of a first rigid element connected to one of the boom elements at one of said stations and a second rigid element connected to the other of the boom elements at said one of said stations, the elements of each dipole extending transverse to the length of the boom and on opposite sides of the boom, the dipoles being progressively longer, proceeding from the forward end of the boom to the rearward end of the boom, and successive dipoles being in alternating phase relationship to each other; wherein the elements of a plurality of adjacent ones of said dipoles, including the longest of said dipoles, are bent so that each element of said plurality of adjacent ones of said dipoles has an inner portion and an outer portion connected to each other at a bend, the inner portion extending outward from the boom in substantially perpendicular relation to the boom toward one of two spaces on opposite sides of said boom, and the outer portion extending obliquely outward and forward from the bend; and a device under test spaced forward of the forward end of the boom; wherein each of said two spaces is substantially free of obstructions affecting the radiation pattern of said apparatus, and wherein each element of the longest dipole of said plurality of adjacent ones of said dipoles has an undulating shape when viewed in a direction along said boom.