Antenna array in an RFID system
First Claim
1. A radio frequency identification system, comprising:
- an interrogator having a transmit antenna and a receive antenna, an antenna gain of said transmit antenna being less than an antenna gain of said receive antenna, and a vertical beamwidth of said receive antenna being greater than a horizontal beamwidth of said receive antenna.
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Accused Products
Abstract
In accordance with the present invention, a general antenna system is disclosed suitable for applications in which an RFID Tag passes by an Interrogator. We then disclose a specific antenna design that uses a single planar antenna for transmit and a multi-element planar antenna array for receive. The multi-element planar antenna array is spaced such that each of the planar elements is four inches apart, center-to-center, thus defining a narrow 30° receive beamwidth in the horizontal plane. The vertical receive bandwidth is much greater than 30°, facilitating the Interrogator receiving signals at a variety of elevations. Furthermore, a multi-way microstrip combiner is used to sum the signals received from each of the planar antennas. To block interference from the transmit antenna and to improve receive sensitivity, this multi-way microstrip combiner is shielded using, in one embodiment, copper tape along its edges. In a specific embodiment, a four element receive antenna design is disclosed.
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Citations
10 Claims
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1. A radio frequency identification system, comprising:
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an interrogator having a transmit antenna and a receive antenna, an antenna gain of said transmit antenna being less than an antenna gain of said receive antenna, and a vertical beamwidth of said receive antenna being greater than a horizontal beamwidth of said receive antenna. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
said in-phase power combiner comprises three binary combiners in cascade. -
10. The radio frequency identification system of claim 9, wherein said four planar antenna elements are mounted back-to-back with said in-phase power combiner.
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Specification