Low profile, antenna array for an RFID reader and method of making same
First Claim
1. An apparatus, comprising:
- a ground support;
an electrically conductive, first endless element mounted on, and at an elevation away from, the ground support, the first endless element extending about a central axis at a first distance transversely of the central axis along a first perimeter; and
first ports successively arranged apart along the first perimeter of the first endless element about the central axis for conveying radio frequency signals in a first operating band of frequencies, a first one of the first ports including;
a series capacitor formed by a first plate spaced apart from the first endless element at a first location between the first endless element and the ground support; and
a shunt capacitor formed by a second plate spaced apart from the ground support at a second location between the first endless element and the ground support;
wherein;
the first perimeter is substantially equal to an odd multiple of one-half of a guided wavelength at a center frequency of the first operating band,each adjacent pair of the first ports is successively spaced apart by a first spacing constituting a whole multiple of one-half of the guided wavelength at the center frequency of the first operating band, andthe first location is proximate to the first endless element and the second location is proximate to the ground support.
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Accused Products
Abstract
An antenna array, especially for use with a radio frequency identification reader, includes a ground plane and a pair of concentric, first and second, circular elements mounted at an elevation relative to the ground plane. First ports are arranged along the perimeter of the first element, and second ports are arranged along the perimeter of the second element. Each port conveys radio frequency signals in an operating band of frequencies. Each perimeter is substantially equal to an odd multiple of one-half of a guided wavelength at a center frequency of the respective operating band. Each adjacent pair of first ports, or adjacent pair of second ports, is successively spaced apart by a spacing constituting a whole multiple of one-half of the guided wavelength at the center frequency of the respective operating band. A polarized patch antenna may be positioned within the circular elements.
79 Citations
19 Claims
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1. An apparatus, comprising:
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a ground support; an electrically conductive, first endless element mounted on, and at an elevation away from, the ground support, the first endless element extending about a central axis at a first distance transversely of the central axis along a first perimeter; and first ports successively arranged apart along the first perimeter of the first endless element about the central axis for conveying radio frequency signals in a first operating band of frequencies, a first one of the first ports including; a series capacitor formed by a first plate spaced apart from the first endless element at a first location between the first endless element and the ground support; and a shunt capacitor formed by a second plate spaced apart from the ground support at a second location between the first endless element and the ground support; wherein; the first perimeter is substantially equal to an odd multiple of one-half of a guided wavelength at a center frequency of the first operating band, each adjacent pair of the first ports is successively spaced apart by a first spacing constituting a whole multiple of one-half of the guided wavelength at the center frequency of the first operating band, and the first location is proximate to the first endless element and the second location is proximate to the ground support. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 18)
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10. A method of making an antenna array, comprising:
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mounting an electrically conductive, first endless element on, and at an elevation away from, a ground support, and extending the first endless element about a central axis at a first distance transversely of the central axis along a first perimeter; successively arranging first ports apart along the first perimeter of the first endless element about the central axis for conveying radio frequency signals in a first operating band of frequencies; forming a series capacitor by mounting a first plate spaced apart from the first endless element at a first location between the first endless element and the ground support; forming a shunt capacitor by mounting a second plate spaced apart from the ground support at a second location between the first endless element and the ground support, wherein the first location is proximate to the first endless element and the second location is proximate to the ground support; configuring the first perimeter to be substantially equal to an odd multiple of one-half of a guided wavelength at a center frequency of the first operating band; and successively spacing each adjacent pair of the first ports apart by a first spacing constituting a whole multiple of one-half of the guided wavelength at the center frequency of the first operating band. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 19)
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Specification