Broadband center-fed spiral antenna
First Claim
1. A spiral antenna comprising at least one electrically conductive antenna arm, each said antenna arm extending outwardly about an axis of rotation, each said antenna arm including at least one choke element serially disposed between adjoining innermost and outermost regions of said antenna arm, each said choke element corresponding to a section of transmission line and including a central conductive region extending between said adjoining innermost and outermost regions of said antenna arm, each said choke element including at least one outer conductive region that is electrically interconnected with said central conductive region and extends in spaced-apart relationship therewith, each said choke element being dimensioned for resonance at a predetermined signal frequency and positioned along the associated antenna arm to reflect signal currents having a predetermined phase relationship relative to signal currents flowing within adjacent antenna arms.
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Abstract
Spiral antennas are disclosed wherein each antenna arm includes one or more choke elements that resonate at predetermined operating frequencies to eliminate or minimize undesired radiation and reception characteristics. Multi-arm arrangements for broadband applications requiring sum and difference mode operation with both right-hand and left-hand circularly polarized radiation characteristics are attained by including a plurality of selectively positioned and dimensioned choke elements in each antenna arm. A variety of transmission line sections, suitable for use as choke elements in several types of spiral antennas, is described.
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Citations
28 Claims
- 1. A spiral antenna comprising at least one electrically conductive antenna arm, each said antenna arm extending outwardly about an axis of rotation, each said antenna arm including at least one choke element serially disposed between adjoining innermost and outermost regions of said antenna arm, each said choke element corresponding to a section of transmission line and including a central conductive region extending between said adjoining innermost and outermost regions of said antenna arm, each said choke element including at least one outer conductive region that is electrically interconnected with said central conductive region and extends in spaced-apart relationship therewith, each said choke element being dimensioned for resonance at a predetermined signal frequency and positioned along the associated antenna arm to reflect signal currents having a predetermined phase relationship relative to signal currents flowing within adjacent antenna arms.
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20. An improved N-arm spiral antenna of the type configured for operation with both right-hand and left-hand circularly polarized radiation patterns wherein a first set of operating modes Mn =1,2, . . . , p of a first polarization sense is associated with supplying feed currents to the inner ends of the antenna arms with the phase difference between the signals induced in adjacent antenna arms being 2π
- Mn /N and wherein a second set of operating modes Mc =1,2, . . . , q having a polarization sense opposite to that of said first set of operating modes is associated with supplying feed currents to said inner ends of said antenna arms with the phase difference between the signals supplied to adjacent antenna arms being 2π
(N-Mc)/N and reflecting the signal currents induced in said antenna arms at a point along said antenna that lies radially outward of the radiation region associated with said radiation mode Mn =p and radially inward of the radiation region which would normally emit a radiation mode N-q having said first sense of circular polarization, p and q being preselected non-zero integers with p+q≦
(N-1), wherein the improvement comprises choke elements for reflecting a substantial portion of said currents associated with feed currents having said phase difference of 2π
(N-Mc)/N, at least one of said choke elements being serially interposed between circumferentially spaced-apart inner and outer portions of each of N antenna arms, each of said choke elements comprising a first conductive strip physically and electrically interconnecting said spaced-apart inner and outer portions of an associated antenna arm, each of said choke elements further comprising at least one second conductive strip spaced apart from and extending circumferentially along at least a portion of said first conductive strip, each of said second conductive strips being physically and electrically interconnected to a single one of said inner portion of said associated antenna arm, said outer portion of said associated antenna arm and said first conductive strip. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
- Mn /N and wherein a second set of operating modes Mc =1,2, . . . , q having a polarization sense opposite to that of said first set of operating modes is associated with supplying feed currents to said inner ends of said antenna arms with the phase difference between the signals supplied to adjacent antenna arms being 2π
Specification