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.
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.
174 Citations
20 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An antenna tuning device comprising:
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an impedance compensation circuit to vary the input impedance of an antenna; and
a controller coupled to the impedance compensation circuit to automatically adjust the impedance compensation circuit based on a feedback signal. - View Dependent Claims (11, 12, 13)
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14. A digital variable capacitor for a self-tuning antenna, comprising:
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a plurality of parallel plate capacitors formed on opposite surfaces of a circuit board, the plurality of parallel plate capacitors coupled to each other in parallel; and
a plurality of switches, each switch coupled in series to a corresponding parallel plate capacitor and individually adjustable to activate or deactivate its corresponding parallel plate capacitor. - View Dependent Claims (15)
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16. An antenna tuning system 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; and
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. - View Dependent Claims (17)
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18. A method for automatically tuning an antenna, comprising:
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automatically determining whether the antenna has an impedance mismatch;
automatically adjusting a variable capacitor to change the input impedance for the antenna and compensate for the impedance mismatch. - View Dependent Claims (19)
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20. 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.
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Specification