Phase Error Correction Circuit for VSB Signals
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Solution Overview
Problem
Existing phase error correction circuits for VSB modulated signals face challenges in achieving precise correction while minimizing circuit size, as they either require large waveform equalizers for complex signals or suffer from frequency component degradation when correcting complex signals generated from real signals.
Innovation Solution
A phase error correction circuit that includes a complex phase rotator, a specific frequency component elimination filter, a waveform equalizer outputting a real signal, and a phase correction signal generator using a Hilbert transformer to detect and smooth phase errors, allowing for precise phase correction without increasing circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the waveform equalizer outputs a complex signal to enable phase error correction, then phase correction capability is improved, but circuit size increases due to requiring more filters
Solution Approach 1:
Instead of the conventional approach where the waveform equalizer outputs a complex signal for phase correction, this patent inverts the sequence by having the waveform equalizer output a real signal first, then generating the complex signal afterward. This inversion resolves the contradiction by avoiding the need for the waveform equalizer to handle complex signals, thus reducing circuit size while maintaining phase correction capability through the subsequent complex signal generation using Hilbert transform.
2Reliability
If a complex signal is generated from a real signal using Hilbert transformer for phase correction, then phase correction is enabled, but frequency component degradation occurs around DC
Solution Approach 1:
The patent applies preliminary phase correction to the real signal before generating the complex signal via Hilbert transform. By performing phase correction in advance on the real signal, the subsequent complex signal generation does not suffer from frequency component degradation around DC, thus maintaining both phase correction capability and frequency accuracy.
3Manufacturing precision
If the waveform equalizer uses a large number of taps to correct waveform distortion, then waveform distortion correction is improved, but circuit complexity increases
Solution Approach 1:
The patent inverts the signal processing sequence so that the waveform equalizer operates on real signals with fewer taps, reducing circuit complexity. The phase correction function, which would otherwise require the waveform equalizer to handle complex signals with many taps, is separated and performed afterward using Hilbert transform and phase error detection, thus achieving waveform distortion correction with reduced complexity.
Data Source
AI summary
A phase error correction circuit includes a complex phase rotator for multiplying an input VSB (vestigial-sideband) signal by a phase correction signal and outputting a resultant signal, a specific frequency component elimination filter for eliminating a specific frequency component from the signal output from the complex phase rotator and outputting a resultant signal, a waveform equalizer for performing waveform distortion correction to the signal output from the specific frequency component elimination filter and outputting a resultant signal and a phase correction signal generator for detecting a phase error based on the signal output from the waveform equalizer and outputting a complex signal corresponding to the detected phase error as the phase correction signal.