Multi-Carrier Reflectometry Signal Shaping for Lower PAPR
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Solution Overview
Problem
Existing multi-carrier reflectometry signals, particularly OFDM-based signals, suffer from high peak-to-average power ratios (PAPR) leading to non-linear amplifier saturation and degraded signal-to-noise ratios, making it difficult to accurately detect and localize electrical faults in cables due to signal attenuation and distortion.
Innovation Solution
A method involving carrier reservation and normalization to generate a multi-carrier reflectometry signal with reduced PAPR by applying an inverse Fourier transform, clipping, masking, and adding a compensation signal, followed by a direct Fourier transform and normalization to ensure uniform power spectral density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional multi-carrier OFDM signal is used for reflectometry, then the signal can be injected into the cable for fault detection, but the high peak-to-average power ratio causes amplifier saturation and signal distortion
Solution Approach 1:
The patent applies parameter changes by modifying the signal characteristics through clipping operations on the time-domain signal and subsequent normalization in the frequency domain. This transforms the original high PAPR OFDM signal into a modified signal with reduced peak power, preventing amplifier saturation while maintaining fault detection capability
Solution Approach 2:
The patent introduces an intermediary compensation signal generated from the clipped time-domain signal. This compensation signal is added to the original frequency-domain signal to cancel out peak excursions, thereby reducing PAPR without completely altering the signal structure
2Power
If signal amplification is applied to compensate for attenuation during propagation, then the signal strength is increased, but non-linear behavior leads to saturation and degraded signal-to-noise ratio
Solution Approach 1:
The patent applies preliminary action by reducing the peak power of the signal before injection into the cable. By pre-processing the signal to lower PAPR, the signal can be amplified without reaching saturation levels, thereby maintaining linearity and preserving signal-to-noise ratio throughout propagation
3Object-generated harmful factors
If the peak power of the multi-carrier signal is reduced, then amplifier saturation is avoided, but the autocorrelation properties may be degraded affecting fault localization accuracy
Solution Approach 1:
The patent employs feedback by using the clipped time-domain signal to generate a compensation signal that is fed back to the frequency-domain signal. This iterative process adjusts the signal to reduce PAPR while monitoring and preserving the autocorrelation properties necessary for accurate fault localization
Data Source
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AI summary
Method for generating a reflectometry signal intended to be injected into a transmission line to identify the presence of at least one possible fault on the line, the method comprising the steps of: generating (601) a first digital multi-carrier signal in a first set of frequency carriers, generating (602) a second digital multi-carrier correction signal in a second set of frequency carriers separate from the first set, summing (603) the first digital correction signal and the second digital correction signal to generate a reflectometry signal, normalising (604) the frequency carriers of the reflectometry signal, the second digital correction signal being determined so as to reduce the ratio between the peak power and the average power of the reflectometry signal relative to the first digital signal.