Backscatter Wireless Keyboard Using Passive Key Transponders
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Solution Overview
Problem
Wireless keyboards face limitations due to battery replacement needs and inconsistent transmission reliability, particularly with infrared systems requiring line of sight and RF systems being more expensive and power-intensive.
Innovation Solution
A wireless keyboard and reader combination using passive transponder circuits coupled with an antenna, where the transponder circuits receive power and provide coded responses upon key activation, and an interrogating field from the reader determines these responses, minimizing interference and optimizing power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If passive transponder circuits are used instead of battery-powered circuits, then power consumption is reduced and battery life is extended, but the system requires an interrogating field from the reader to activate the transponders
Solution Approach 1:
The patent introduces an intermediary interrogating field from the reader as a mediator between the power source and the keyboard transponders. The reader's electromagnetic field serves as the energy transfer medium, eliminating the need for batteries while enabling passive transponder operation. This resolves the contradiction by providing power through an external intermediary rather than internal battery power sources.
2Reliability
If continuous key scanning is performed to detect key depression, then key response accuracy is maintained, but battery power is consumed even when there is no data entry
Solution Approach 1:
The patent implements periodic action by having the reader transmit interrogating fields at specific intervals rather than continuously scanning keys. The passive transponders are activated only when the reader's field is present, creating a periodic detection rhythm that maintains key response reliability while eliminating continuous power consumption during idle periods.
Solution Approach 2:
The passive transponder circuits serve themselves by harvesting energy from the reader's interrogating field rather than relying on internal battery power. This self-service mechanism allows the transponders to operate without continuous external power connections, activating only when needed and eliminating the need for continuous battery power during idle scanning periods.
3Ease of manufacture
If infrared transmission is used for wireless communication, then system cost is reduced, but transmission reliability deteriorates when line of sight is blocked or keyboard is moved
Solution Approach 1:
The patent uses the reader's electromagnetic field as an intermediary that eliminates line-of-sight requirements. Instead of direct infrared transmission between keyboard and reader, the passive transponders are activated by the reader's field and respond through backscatter modulation, allowing communication through non-line-of-sight paths and improving reliability while maintaining cost-effectiveness.
Solution Approach 2:
The patent replaces the mechanical line-of-sight infrared transmission system with an electromagnetic field-based activation system. The reader's electromagnetic field penetrates obstacles and doesn't require direct alignment, substituting the fragile infrared mechanical system with a more robust electromagnetic field approach that maintains cost advantages while improving reliability.
4Reliability
If RF transmission is used instead of infrared, then transmission reliability is improved, but system cost and power consumption increase
Solution Approach 1:
The passive transponder circuits harvest energy from the reader's electromagnetic field to power their own operation, eliminating the need for separate battery power sources and high-power RF transmitters in the keyboard. This self-service approach achieves reliable RF-like communication without the high cost and power consumption of traditional active RF systems.
Solution Approach 2:
The patent changes the operational parameters by using passive transponders that respond to electromagnetic fields rather than active RF transmission. This parameter change allows the system to achieve reliable transmission at lower frequencies and power levels, reducing both system cost and power consumption while maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances transmission reliability and battery life by allowing power-efficient operation and reducing the need for frequent battery replacements, while maintaining a cleaner and more flexible user experience.
Implementation Method 1
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
Implementation Method 2
provide a coded response identifying a key in response to key activation. A reader includes a source of an interrogating field applied to the antenna of the keyboard and a decoder for determining the coded response
Data Source
AI summary
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.