Tuning an RFID reader with electronic switches
First Claim
1. A reader for an RFID system comprising:
- a signal driver for generating an excitation signal; and
a resonant circuit coupled with said signal driver having a capacitance tuning circuit and a transmitting antenna coupled with said capacitance tuning circuit for transmitting said excitation signal having a carrier frequency into a space surrounding said transmitting antenna,wherein said capacitance tuning circuit includes a fine-tuning capacitor having a fine-tuning capacitance and a fine-tuning capacitor switch having an open position and a closed position, further wherein said fine-tuning capacitor switch is a solid-state relay including a transistor.
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Accused Products
Abstract
A reader for an RFID system includes a signal driver for generating an excitation signal and a resonant circuit having an adjustable resonant circuit capacitance for retuning the resonant circuit in response to detuning. The resonant circuit has a capacitance tuning circuit which includes a fine-tuning capacitor having a fine-tuning capacitance and a fine-tuning capacitor switch having an open position and a closed position. The fine-tuning capacitance is added to the adjustable resonant circuit capacitance when the fine-tuning capacitor switch is in the closed position and is removed from the adjustable resonant circuit capacitance when the fine-tuning capacitor switch is in the open position.
28 Citations
19 Claims
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1. A reader for an RFID system comprising:
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a signal driver for generating an excitation signal; and a resonant circuit coupled with said signal driver having a capacitance tuning circuit and a transmitting antenna coupled with said capacitance tuning circuit for transmitting said excitation signal having a carrier frequency into a space surrounding said transmitting antenna, wherein said capacitance tuning circuit includes a fine-tuning capacitor having a fine-tuning capacitance and a fine-tuning capacitor switch having an open position and a closed position, further wherein said fine-tuning capacitor switch is a solid-state relay including a transistor. - View Dependent Claims (2)
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3. A reader for an RFID system comprising:
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a signal driver for generating an excitation signal; and a resonant circuit having an adjustable resonant circuit capacitance, said resonant circuit including a capacitance tuning circuit and a transmitting antenna coupled with said capacitance tuning circuit for transmitting said excitation signal having a carrier frequency into a space surrounding said transmitting antenna, wherein said capacitance tuning circuit includes a fine-tuning capacitor having a fine-tuning capacitance and a fine-tuning capacitor switch having an open position and a closed position, wherein said fine-tuning capacitance is added to said adjustable resonant circuit capacitance when said fine-tuning capacitor switch is in said closed position and said fine-tuning capacitance is removed from said adjustable resonant circuit capacitance when said fine-tuning capacitor switch is in said open position. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A reader for an RFID system comprising:
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a signal driver for generating an excitation signal; and a resonant circuit having a capacitance tuning circuit and a transmitting antenna coupled with said capacitance tuning circuit for transmitting said excitation signal having a carrier frequency into a space surrounding said transmitting antenna in the form of a magnetic field having a field strength, wherein said capacitance tuning circuit includes a capacitor having a capacitance and a capacitor switch having an open position and a closed position, further wherein said capacitor switch is a solid-state relay including a field effect transistor, a first switching diode positioned in series with said field effect transistor, a second switching diode positioned in parallel with said first switching diode and said field effect transistor, a first switch terminal coupled with said field effect transistor, a second switch terminal and a third switch terminal, said second and third switch terminals parallely coupled with one another by a first parallel path including said field effect transistor and said first switching diode in series and by a second parallel path including said second switching diode.
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14. A reader for an RFID system comprising:
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a signal driver for generating an excitation signal; and a resonant circuit having a capacitance tuning circuit and a transmitting antenna coupled with said capacitance tuning circuit for transmitting said excitation signal having a carrier frequency into a space surrounding said transmitting antenna in the form of a magnetic field having a field strength, wherein said capacitance tuning circuit includes a first series fine-tuning capacitor having a first series fine-tuning capacitance, a first series fine-tuning capacitor switch having an open position and a closed position, a second series fine-tuning capacitor having a second series fine-tuning capacitance, and a second series fine-tuning capacitor switch having an open position and a closed position, wherein said first series fine-tuning capacitor contributes said first series fine-tuning capacitance to said resonant circuit when said first series fine-tuning capacitor switch is in said closed position and said second series fine-tuning capacitor contributes said second series fine-tuning capacitance to said resonant circuit when said second series fine-tuning capacitor switch is in said closed position. - View Dependent Claims (15, 16, 17)
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18. A method for tuning a reader for an RFID system comprising:
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generating an excitation signal in a signal driver; conveying said excitation signal to a resonant circuit having a capacitance tuning circuit and a transmitting antenna coupled with said capacitance tuning circuit; transmitting said excitation signal having a carrier frequency into a space surrounding said transmitting antenna in the form of a magnetic field having a field strength; and retuning said resonant circuit to said carrier frequency in response to detuning by transitioning a capacitor switch from an open position to a closed position to add a fine-tuning capacitance of a fine-tuning capacitor coupled with said capacitor switch into said resonant circuit or by transitioning said capacitor switch from said closed position to said open position to remove said fine-tuning capacitance of said fine-tuning capacitor from said resonant circuit. - View Dependent Claims (19)
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Specification