Input device employing backscatter transmission
First Claim
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1. A method for short range wireless transmission between a receiver and an input device, comprising:
- transmitting an interrogating field to the input device;
the input device having a tuned circuit comprised only of passive components that responds to the interrogation field by emitting a characteristic frequency;
employing a plurality of switches to each couple a passive circuit element with a unique value to the tuned circuit when the switch is actuated to change the characteristic frequency of the tuned circuit;
transmitting a backscatter return field to the receiver, employing a backscatter antenna coupled to the tuned circuit in the input device and coupled to the interrogating field; and
detecting the backscatter return field at the receiver to determine the switch actuated by the changed characteristic frequency from the tuned circuit.
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Abstract
A wireless keyboard and reader combination comprises a keyboard having a plurality of keys, an antenna, and a plurality of passive transponder circuits coupled to the antenna and associated with the keys. The passive transponder circuits are selectively coupled to receive power from the antenna and provide a coded response identifying a key in response to key activation. An associated reader includes a source of an interrogating field applied to the antenna of the keyboard and a decoder for determining the coded response from the passive transponder circuits.
9 Citations
8 Claims
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1. A method for short range wireless transmission between a receiver and an input device, comprising:
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transmitting an interrogating field to the input device; the input device having a tuned circuit comprised only of passive components that responds to the interrogation field by emitting a characteristic frequency; employing a plurality of switches to each couple a passive circuit element with a unique value to the tuned circuit when the switch is actuated to change the characteristic frequency of the tuned circuit; transmitting a backscatter return field to the receiver, employing a backscatter antenna coupled to the tuned circuit in the input device and coupled to the interrogating field; and detecting the backscatter return field at the receiver to determine the switch actuated by the changed characteristic frequency from the tuned circuit. - View Dependent Claims (2, 3, 4, 5)
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6. An input device for determining switch activations, comprising:
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an interrogator transmitting an interrogation field; a tuned circuit comprised only of passive components that responds to the interrogation field by emitting a characteristic frequency; a plurality of switches each coupling a passive circuit element with a unique value to the tuned circuit when the switch is actuated to change the characteristic frequency of the tuned circuit; a backscatter antenna coupled to the tuned circuit and the interrogation field to generate a return field; and a reader that detects the backscatter return field from the antenna to determine the switch actuated by the changed characteristic frequency from the tuned circuit. - View Dependent Claims (7, 8)
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Specification