Fob with increased power level from hand-antenna coupling
First Claim
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1. A fob, comprising:
- a power amplifier including an output having an output impedance;
a radio frequency antenna connected to the power amplifier output representing a first load impedance to the power amplifier output in a space free of interference for radio frequency transmissions resulting in a first level of output power, and a second load impedance to the power amplifier output when a hand of a user is capacitively coupled to the antenna, the second load impedance determined at least in part by a combination of the first load impedance and a capacitive coupling of the hand to the antenna;
wherein a difference between the second load impedance and the output impedance of the power amplifier is less than a difference between the first load impedance and the output impedance, resulting in a second level of output power, the second level of output power greater than the first level of output power, without adjusting the second load impedance subsequent to the capacitive coupling of the hand to the antenna.
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Abstract
A key fob includes a power amplifier including an output having an output impedance. A radio frequency antenna connected to the power amplifier output represents a first load impedance to the power amplifier output in a space substantially free of interference for radio frequency transmissions, and a second load impedance to the power amplifier output when a hand of a user is capacitively coupled to the antenna. The difference between the second load impedance and the output impedance of the power amplifier is less than the difference between the first load impedance and the output impedance.
33 Citations
20 Claims
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1. A fob, comprising:
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a power amplifier including an output having an output impedance; a radio frequency antenna connected to the power amplifier output representing a first load impedance to the power amplifier output in a space free of interference for radio frequency transmissions resulting in a first level of output power, and a second load impedance to the power amplifier output when a hand of a user is capacitively coupled to the antenna, the second load impedance determined at least in part by a combination of the first load impedance and a capacitive coupling of the hand to the antenna;
wherein a difference between the second load impedance and the output impedance of the power amplifier is less than a difference between the first load impedance and the output impedance, resulting in a second level of output power, the second level of output power greater than the first level of output power, without adjusting the second load impedance subsequent to the capacitive coupling of the hand to the antenna. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A fob, comprising:
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a power amplifier including an output having an output impedance; a radio frequency antenna connected to the power amplifier output representing a first load impedance to the power amplifier output in a space free of interference for radio frequency transmissions resulting in a first level of output power, and a second load impedance to the power amplifier output when a hand of a user is capacitively coupled to the antenna, the second load impedance determined at least in part by a combination of the first load impedance and a capacitive coupling of the hand to the antenna;
wherein a matching of the second load impedance to the output impedance is improved relative to a matching of the first load impedance to the output impedance, resulting in a second level of output power, the second level of output power greater than the first level of output power, without adjusting the second load impedance subsequent to the capacitive coupling of the hand to the antenna. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification