Retrodirective Backscatter Tags for Low-Power IoT Localization
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Solution Overview
Problem
Current IoT devices face high power consumption and bulkiness due to active transceivers, limiting their battery life and requiring aggressive duty-cycling, while existing RFID and FMCW-based solutions struggle with multiplexing and power efficiency.
Innovation Solution
A system utilizing ultra-thin, flexible semi-passive tags with a frequency modulated continuous wave (FMCW) radar module and retrodirective antenna arrays for backscatter communications, enabling low-power, energy-autonomous operation and spatial multiplexing for IoT applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If active transceivers are used for wireless communications, then communication range and data rate are improved, but power consumption increases significantly
Solution Approach 1:
Instead of using active transceivers that generate their own transmission signals, the patent employs passive backscatter tags that reflect and modulate incident electromagnetic waves from external readers. This inverts the traditional communication paradigm by eliminating the need for high-power onboard transmitters, achieving long-range communication with ultra-low power consumption (microwatt level) while maintaining functional capability
2Use of energy by moving object
If RFID backscatter communications are used to reduce power consumption, then power efficiency is improved, but communication range is limited and multiplexing becomes difficult
Solution Approach 1:
The patent transitions from traditional RFID operating in the 900 MHz and 2.4 GHz bands to mm-wave frequencies (e.g., 24 GHz, 60 GHz, 73-76 GHz, 81-86 GHz). This parameter change in operating frequency enables longer communication ranges and improved spatial resolution for multiplexing, while the passive backscatter mechanism maintains ultra-low power consumption. The higher frequencies provide better directionality and penetration characteristics
3Measurement precision
If FMCW radar with active backscatter tags is used for localization, then localization precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts the active radar transmission function from the tag device and relocates it to the reader system. The tags become purely passive backscatter elements that modulate the incident FMCW signals received from the reader. This extraction eliminates the need for complex active transmitters, power amplifiers, and signal generation circuits in the tags, reducing device complexity while preserving FMCW-based localization precision through the reader's processing capability
4Adaptability or versatility
If substrate thickness is increased to support active transceivers, then device functionality is improved, but device thickness and flexibility are worsened
Solution Approach 1:
The patent removes the active transceiver components (transmitters, power amplifiers, signal generators) from the tag device, leaving only passive backscatter elements, sensors, and minimal circuitry. This extraction enables the use of extremely thin substrates (millimeter or sub-millimeter scale) that maintain flexibility and conformability while supporting essential sensing and communication functions through the passive backscatter mechanism
Solution Approach 2:
The patent employs flexible substrate materials and thin-film fabrication techniques to create ultra-thin, conformable tag devices. The passive backscatter architecture is inherently compatible with thin-film implementations since it requires no bulky active components, enabling the tags to be integrated into flexible wearables, skin-mounted sensors, and conformable IoT devices
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
The solution achieves real-time localization and data communication with ultra-low power consumption, enabling compact, flexible, and energy-autonomous IoT devices for ubiquitous sensing applications, such as the 'Internet of Skins' concept.
Implementation Method 1
The array of antennas reflects an incident wave transmission from the reader back to the receiver as the backscatter wave emissions in a cross-polarized state
Implementation Method 2
The array of antennas reflects an incident wave transmission from the reader back to the receiver as the backscatter wave emissions in a cross-polarized state
Implementation Method 3
An array of antennas is connected to the output of the timer circuit such that the output of the timer circuit modulates backscatter wave emissions from the array
Data Source
AI summary
A system for using thin and energy-autonomous backscatter tags and corresponding sensing nodes may operate with 24 GHz backscatter reflectarray tags having low power consumption. A digital beam steering, frequency-modulated continuous wave (FMCW) radar may be used for detection, localization, identification and communications. The tags may include environmental sensors that are used to modulate backscatter waves for data communications directed to a reader or may digitally modulate the backscatter transmissions without sensor data for independent localization of each tag in a network.