Backscatter Tag Frequency Modulation for Millimeter Wave Clutter Rejection
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Solution Overview
Problem
Backscatter communication in millimeter wave spectra faces challenges such as low power signals being vulnerable to errors due to ambient reflection and limited scalability due to inability to access wide bandwidths, especially in environments with frequent signal reflections.
Innovation Solution
A communication method using an interrogator that outputs interrogation signals with consecutive unit chirp signals changing from a first frequency to a second frequency, and a backscatter tag that frequency-modulates these signals, allowing for demodulation and separation of data signals from clutter noise, enabling efficient channel allocation and simultaneous communication across a wide bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If backscatter communication is used in millimeter wave spectra, then low-power operation and long-term sustainability are achieved, but the backscattered signal power becomes lower than clutter noise power making the system vulnerable to errors
Solution Approach 1:
The patent employs periodic chirp signals as interrogation waves, where each chirp signal sweeps through a frequency band in a periodic manner. This periodic action allows the backscatter tag to modulate the reflected signal at specific frequency positions, enabling the interrogator to distinguish the tag signal from clutter noise through frequency-domain analysis. The periodic structure creates predictable spectral patterns that facilitate signal separation and improve reliability without increasing power consumption.
Solution Approach 2:
The patent changes the frequency parameter of the interrogation signal by using chirp signals that sweep through different frequency bands. The backscatter tag modulates the reflected signal by changing its impedance state, which alters the frequency characteristics of the backscattered signal. This parameter change in the frequency domain enables the system to separate the weak backscatter signal from clutter noise, improving signal reliability while maintaining low power operation.
2Use of energy by moving object
If backscatter devices use low-cost circuits for ultra-low-power operation, then power consumption is reduced, but the devices are unable to access wide bandwidth of millimeter waves limiting scalability
Solution Approach 1:
The patent makes the simple backscatter tag circuit universally applicable across wide millimeter wave bandwidths by using a frequency-agile interrogator that sweeps through different frequency bands. The backscatter tag maintains its simple ultra-low-power design while the interrogator handles the complexity of wideband operation through periodic chirp signals and frequency-domain processing. This multi-functionality allows the same simple tag circuit to operate across different frequency bands and bandwidths, achieving scalability without compromising power efficiency.
Solution Approach 2:
The patent introduces the periodic chirp interrogation signal as an intermediary that bridges the gap between the simple backscatter tag and the wide bandwidth requirement. The chirp signal acts as a mediator that spreads the interrogation across a wide frequency band, allowing the simple tag to access wide bandwidth capabilities through the interrogator's frequency sweeping action without requiring complex circuits in the tag itself.
3Device complexity
If backscatter devices operate with limited bandwidth, then circuit complexity is reduced, but channel sharing for simultaneous communication becomes impossible reducing scalability
Solution Approach 1:
The patent transitions from time-domain or single-frequency operation to frequency-domain operation by using periodic chirp signals that sweep through wide bandwidths. This dimensional change in the frequency domain allows multiple tags to be addressed simultaneously at different frequency positions within the chirp cycle. The interrogator can distinguish between multiple tags by their frequency-modulated responses, enabling channel sharing and simultaneous communication while keeping individual tag circuits simple.
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 signal-to-noise ratio, improves communication performance, and allows for large-scale networking by separating data signals from clutter noise and enabling frequency-division multiple access without additional overhead, thus overcoming limitations in existing backscatter technologies.
Implementation Method 1
a backscatter tag configured to receive the interrogation signals and frequency-modulate the interrogation signals to generate and provide tag signals
Data Source
AI summary
A communication device includes an interrogator configured to output interrogation signals including consecutive unit chirp signals that change from a first frequency to a second frequency, and a backscatter tag configured to receive the interrogation signals and frequency-modulate the interrogation signals to generate and provide tag signals, wherein the interrogator is further configured to receive the tag signals and demodulate the tag signals.