Backscatter Interrogator Using Continuous Chirp Signals
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Solution Overview
Problem
Backscatter networking in the millimeter wave spectrum faces challenges due to low power of backscattered signals compared to clutter noise and signal attenuation, especially indoors, and limited scalability due to restricted access to wide bandwidths for low-cost, ultra-low-power devices.
Innovation Solution
A communication method using an interrogator that outputs continuous unit chirp signals varying from a first to a second frequency, and backscatter tags that modulate these signals for frequency demodulation, allowing for efficient signal separation and channel allocation based on distance, enabling high signal-to-noise ratio and scalable communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If backscatter devices use millimeter wave spectrum, then spectral resources are abundant for large-scale networks, but the power of backscattered signal is low compared to clutter noise
Solution Approach 1:
The system uses periodic chirp signals with specific time-frequency characteristics to enable coherent integration of backscattered signals over multiple periods, improving signal-to-noise ratio through temporal averaging while maintaining millimeter wave spectral resources
Solution Approach 2:
The interrogator changes signal parameters including chirp duration, sweep bandwidth, and repetition frequency to optimize the balance between signal power and clutter noise, allowing adaptation to different indoor environments while utilizing millimeter wave spectrum
2Use of energy by moving object
If backscatter devices operate with ultra-low-power for long-term sustainability, then energy consumption is reduced, but access to wide bandwidth of millimeter waves is limited
Solution Approach 1:
The wide millimeter wave bandwidth is segmented into multiple narrowband channels that can be sequentially accessed by ultra-low-power backscatter devices, allowing each device to operate with simple circuitry while the system as a whole utilizes the full spectral resource
Solution Approach 2:
The interrogator acts as an intermediary that performs complex wideband signal processing and channel allocation, enabling backscatter tags to access millimeter wave bandwidth indirectly through the interrogator's coordinated multi-channel scheme
3Device complexity
If backscatter devices cannot share channels for simultaneous communication, then circuitry complexity is reduced, but scalability is limited
Solution Approach 1:
The system dynamically allocates time-frequency resources and channel assignments based on the number of active devices, allowing scalability from single-device to large-scale networks while each device maintains simple static circuitry
Solution Approach 2:
The interrogator provides universal service to multiple backscatter devices using the same simple tag circuitry design, achieving scalability through the interrogator's ability to manage multiple channels and devices simultaneously rather than requiring complex features in each tag
4Area of stationary object
If backscatter networking is used indoors, then coverage is improved, but signal attenuation and reflection increase vulnerability to errors
Solution Approach 1:
The system converts the harmful effect of indoor reflections and multipath propagation into beneficial coherent signal components by using correlation-based detection that exploits the known chirp signal structure to distinguish desired signals from reflected clutter
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 enhances the signal-to-noise ratio and scalability of backscatter communication, enabling reliable and large-scale communication even in challenging indoor environments and dense networks by optimizing channel utilization and power management.
Implementation Method 1
backscatter tags configured to receive the interrogation signal and each provide a tag signal formed by frequency modulation on the interrogation signal
Data Source
AI summary
Provided is a communication device. The communication device includes an interrogator configured to output an interrogation signal in which unit chirp signals that vary from a first frequency to a second frequency are continuous, and backscatter tags configured to receive the interrogation signal and each provide a tag signal formed by frequency modulation on the interrogation signal, wherein the interrogator receives the tag signals and demodulates the tag signals.