Spectrum Inversion Detection Using Frequency Offset Estimation
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Solution Overview
Problem
In Second Generation Satellite Digital Video Broadcasting (DVB-S2) receivers, existing methods for detecting spectrum inversion are inefficient, leading to prolonged time for digital receivers to reach a locked working state, as they rely on Bit Error Rate (BER) calculations by the Forward Error Correction (FEC) module.
Innovation Solution
A method and apparatus that utilize a frequency offset estimator and a spectrum inversion detector to determine and correct spectrum inversion by swapping in-phase and quadrature-phase components based on estimated frequency offsets, allowing for early detection and correction before the FEC module reaches a locked state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spectrum inversion detection is performed using BER calculation by FEC module, then detection accuracy is improved, but locking time is prolonged
Solution Approach 1:
The patent performs spectrum inversion detection using frequency offset estimation during the carrier frequency estimation phase, which occurs before the FEC module completes its BER calculation. This preliminary detection action allows the system to identify and correct spectrum inversion early in the signal processing chain, avoiding the prolonged locking time that would occur if detection were delayed until BER calculation completed.
Solution Approach 2:
The patent introduces frequency offset estimation as an intermediary method for spectrum inversion detection. Instead of directly using BER calculation results, the system uses frequency offset as an intermediate parameter that can be estimated earlier in the processing chain. This intermediary approach enables earlier detection while maintaining reasonable detection accuracy through the mathematical relationship between frequency offset and spectrum inversion.
2Loss of time
If spectrum inversion detection is performed early during carrier frequency estimation, then locking time is reduced, but detection reliability may be compromised
Solution Approach 1:
The patent replaces the traditional mechanical approach of using BER calculation (which requires complete frame processing and error correction) with a signal processing-based frequency offset estimation method. This substitution allows detection to occur at the carrier frequency estimation stage using mathematical transformations of the received signal, achieving both early detection and maintained reliability through the robustness of frequency offset estimation algorithms.
Data Source
AI summary
Methods and apparatuses to detect spectrum inversion based on estimated frequency offset in carrier signal. In one embodiment, a receiver includes an I/Q swap module to output an in-phase component and a quadrature-phase component; a frequency offset estimator to determine an offset in carry frequency of the in-phase and quadrature-phase components; and a spectrum inversion detector coupled to the frequency offset estimator and the I/Q swap module. The spectrum inversion detector is configured to signal the I/Q swap module to swap the in-phase component and the quadrature-phase component when an absolute value of the offset in carry frequency is above a predetermined threshold.