Offset Quadrature Phase-Modulated Signal Carrier Frequency Synchronization
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Solution Overview
Problem
Existing methods for carrier-frequency synchronization fail to effectively estimate frequency and phase offsets in offset quadrature-phase-modulated signals due to inter-symbol interference and phase displacements, which disrupt the phases of complex rotary phasors in the received signal.
Innovation Solution
A method and device that utilize pre-filtering and signal processing to convert offset quadrature-phase-modulated signals into modified signals with phases dependent only on the frequency and phase offsets, allowing for maximum-likelihood estimation by stabilizing the phase characteristic and removing additional phases through complex multiplication and modulus-scaled squaring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If maximum-likelihood estimation is applied to offset quadrature-phase-modulated signals, then frequency and phase offset estimation is attempted, but inter-symbol interference and phase displacements disrupt the phases of complex rotary phasors, causing estimation failure
Solution Approach 1:
The patent applies preliminary action by implementing a pre-filtering step before the maximum-likelihood estimation. The pre-filter processes the received offset quadrature-phase-modulated signal to eliminate inter-symbol interference and phase displacements that would otherwise disrupt the complex rotary phasors. This preliminary processing ensures that the subsequent maximum-likelihood estimation operates on clean signal data, enabling accurate frequency and phase offset estimation.
2Measurement precision
If pre-filtering and signal processing are applied to convert offset quadrature-phase-modulated signals, then phases become dependent only on frequency and phase offsets, but device complexity increases
Solution Approach 1:
The patent applies the extraction principle by isolating and removing the harmful components (inter-symbol interference and phase displacements) from the signal through pre-filtering. The pre-filter is designed to extract only the essential information needed for maximum-likelihood estimation, separating the useful signal components from the interfering elements. This selective extraction achieves phase dependency purity while keeping the processing structure relatively simple.
Data Source
AI summary
A method and a device for synchronizing the carrier frequency of a carrier signal comprising a frequency offset and/or a phase offset. According to the invention, the method estimates the frequency offset and/or phase offset of the carrier signal by means of a maximum likelihood estimation from a received signal, which comprises temporally discrete, complex rotary indices, for which only the temporally discrete phases are dependent on the frequency offset and/or phase offset. An offset quadrature-modulated received signal is thus converted into a modified received signal comprising temporally discrete, complex rotary indices, for which only the temporally discrete phases are dependent on the frequency offset and/or the phase offset.