Coherent Multichip RFID Tag Signal Addition
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Solution Overview
Problem
Multiple microradio RFID chips in a single tag often experience destructive interference due to non-coherent transmission, leading to garbled signals and reduced signal strength, especially when using protocols like slotted ALOHA that aim to prevent collisions by staggering transmission times.
Innovation Solution
All microradio chips in the tag are programmed with the same seed for their pseudo-random number generators, ensuring they transmit identical data in the same time slot, mimicking a single chip tag and avoiding collisions by initially programming each tag with a unique seed that can be changed if collisions occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple microradio RFID chips are used in a single tag to increase signal strength, then the aggregate signal strength is improved, but destructive interference occurs when chips transmit at different times causing garbled signals
Solution Approach 1:
The patent applies preliminary action by programming all microradio chips with the same seed value before the tag is deployed. This pre-configuration ensures that when the tag is interrogated, all chips will generate identical time slots and transmit simultaneously, avoiding destructive interference while maintaining coherent signal addition.
Solution Approach 2:
The patent changes the parameter of the pseudo-random number generator seed to be identical across all microradio chips in a tag. This parameter uniformization ensures synchronized transmission timing, transforming the signal addition from destructive to cooperative, thereby improving both signal coherence and reliability.
2Reliability
If the slotted ALOHA protocol is used to prevent collisions between tags, then transmission conflicts are reduced, but the chips transmit at different times causing destructive interference and signal degradation
Solution Approach 1:
The patent applies preliminary action by pre-programming all microradio chips with the same seed value. This ensures that despite using slotted ALOHA protocol for collision avoidance, all chips in a tag will simultaneously select the same time slot, enabling coherent transmission while maintaining collision avoidance capabilities at the tag level.
Solution Approach 2:
The patent changes the seed parameter of the pseudo-random number generator to be uniform across all chips in a tag. This parameter standardization allows the system to maintain slotted ALOHA for inter-tag collision avoidance while ensuring intra-tag coherent transmission, as all chips will synchronize their transmission timing.
3Ease of manufacture
If microradios are made microscopic in size to reduce cost and increase manufacturing efficiency, then manufacturing cost is reduced, but the output signal from each chip is minuscule requiring cooperative addition
Solution Approach 1:
The patent applies merging by combining multiple microradio chips with identical seed values into a single tag assembly. This merging ensures that all chips transmit coherently, and their minuscule individual outputs add constructively to produce a robust aggregate signal that is indistinguishable from a conventional single chip tag, thereby maintaining manufacturing efficiency while achieving sufficient signal output.
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
This approach achieves coherent transmission among multiple microradio chips, enhancing signal strength and maintaining compliance with standard protocols, ensuring robust and readable signals without destructive interference.
Implementation Method 1
the microradios will be in a proper orientation and polarity to receive interrogating signals and to transmit the requisite information out through the antenna to which they are coupled
Implementation Method 2
the pseudo-random generators generate different numbers to set different time slots for transmission so that the tags would have a staggered output that would be readable by the reader
Implementation Method 3
the reader sends out a burst of RF energy and any tag that can receive this energy uses this RF energy to charge up some kind of energy storage like a capacitor that is inside the tag
Data Source
AI summary
An RFID tag (10), containing at least two independent microscopic RFID chips (16) or microradios is programmed with the same unique identifier for each chip. The unique identifier is used in the RFID chips (16) to key the RFID chip (16) transmitting to produce outputs in the same time slot so that the outputs add coherently, thus to create an output that is identical to that of a conventional tag containing only one such chip.