Self-tuning radio frequency identification antenna system
First Claim
1. A self tuning antenna comprising:
- a main antenna;
an impedance compensation circuit coupled to the main antenna to vary the input impedance of the main antenna; and
a controller coupled to the main antenna and impedance compensation circuit to automatically determine when an impedance mismatch occurs on the main antenna and automatically adjust the impedance compensation circuit to minimize the impedance mismatch, wherein the impedance compensation circuit includes a digital variable capacitor that is adjusted by the controller to minimize impedance mismatch, the digital variable capacitor includes a plurality of individually controllable parallel plate capacitors that are added or removed from the impedance compensation circuit by the controller.
3 Assignments
0 Petitions
Accused Products
Abstract
A self-tuning antenna that automatically adjusts its input impedance to compensate for externally induced impedance variations is provided. A variable impedance is adjusted by a control circuit to reconfigure the input impedance of than antenna to compensate for different environmental situations and different transponder mismatch situations. A negative-feedback signal is employed to determine or infer impedance mismatches and reconfigure the antenna input impedance (e.g., capacitance and/or resistance) until a desired equilibrium of the antenna input impedance is reached. A reference measurement (e.g., VSWR measurement) is automatically performed by an antenna tuning circuit that adjusts the antenna'"'"'s impedance matching circuit to compensate for object interference. The antenna'"'"'s impedance matching circuit includes a variable capacitor circuit having a plurality of individually controlled parallel plate capacitors that can be added or removed from the variable capacitor circuit, as necessary.
26 Citations
12 Claims
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1. A self tuning antenna comprising:
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a main antenna; an impedance compensation circuit coupled to the main antenna to vary the input impedance of the main antenna; and a controller coupled to the main antenna and impedance compensation circuit to automatically determine when an impedance mismatch occurs on the main antenna and automatically adjust the impedance compensation circuit to minimize the impedance mismatch, wherein the impedance compensation circuit includes a digital variable capacitor that is adjusted by the controller to minimize impedance mismatch, the digital variable capacitor includes a plurality of individually controllable parallel plate capacitors that are added or removed from the impedance compensation circuit by the controller. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An antenna tuning device comprising:
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an impedance compensation circuit to vary the input impedance of a self-tuning antenna; and a controller coupled to the impedance compensation circuit to automatically adjust the impedance compensation circuit based on a feedback signal, wherein the impedance compensation circuit includes a digital variable capacitor that is adjusted by the controller to minimize impedance mismatch, the digital variable capacitor includes a plurality of individually controllable parallel plate capacitors that are added or removed from the impedance compensation circuit by the controller. - View Dependent Claims (9, 10)
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11. A self tuning antenna apparatus, comprising:
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a first antenna; a second antenna in proximity to the first antenna to capture radio frequency radiations from the first antenna; a controller coupled to the second antenna to receive a feedback signal from the second antenna and adjust the input impedance of the first antenna to minimize impedance mismatch for the first antenna; and an impedance compensation circuit coupled to the first antenna and the controller, the controller configured adjust the impedance compensation circuit to vary the input impedance of the first antenna, the impedance compensation circuit including a digital variable capacitor including a plurality of individually controllable parallel plate capacitors that are added or removed from the impedance compensation circuit by the controller.
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12. An antenna tuning device, comprising:
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means for automatically determining whether the antenna has an impedance mismatch; and means for automatically adjusting the input impedance for the antenna and compensate for the impedance mismatch by adjusting a plurality of individually controllable parallel plate capacitors that are added or removed to compensate for the impedance mismatch.
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Specification