Jitter Evaluation Using NCO and CORDIC for Digital Video
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Solution Overview
Problem
Existing jitter evaluation systems for high definition digital video signals require sophisticated and costly equipment to accurately measure timing and alignment jitter at high frequencies, and are complicated by calibration requirements.
Innovation Solution
A jitter evaluation apparatus that includes a numerically controlled oscillator for generating sine and cosine values, multipliers for producing products with sinusoid samples, and a CORDIC device for calculating phase, which uses low pass filters and high pass filters to derive peak-to-peak jitter values without the need for complex calibration, allowing for accurate measurement of timing and alignment jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sophisticated devices are used to evaluate jitter components at high frequencies, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex analog jitter measurement devices with a digital signal processing system. The system uses a numerically controlled oscillator to generate sine waves, an ADC to convert to digital domain, and digital signal processing algorithms to extract jitter components. This substitution of mechanical/analog systems with digital equivalents achieves high measurement precision while reducing device complexity and calibration requirements.
Solution Approach 2:
The patent transforms the jitter measurement problem by changing the frequency domain parameters. It separates timing jitter (low frequency components) from alignment jitter (high frequency components) through spectral analysis. By processing signals in the frequency domain rather than time domain, the system achieves precise measurement of different jitter types using standard digital signal processing techniques.
2Measurement precision
If sophisticated devices are used for high frequency jitter evaluation, then measurement precision is improved, but calibration requirements increase
Solution Approach 1:
The patent eliminates complex calibration procedures by replacing analog measurement paths with a fully digital signal processing chain. The numerically controlled oscillator generates precise sine waves with known characteristics, and the digital signal processing algorithms automatically extract jitter information without requiring manual calibration. This digital approach inherently provides the necessary precision without additional calibration steps.
3Measurement precision
If complex calibration procedures are implemented, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The patent implements a self-calibrating system where the digital signal processing automatically performs all necessary measurements and calculations. The numerically controlled oscillator and digital signal processing algorithms work together to extract jitter information directly from the input signal without requiring operator intervention for calibration. The system serves itself by automatically establishing the measurement baseline and processing signals consistently.
Data Source
AI summary
A jitter evaluation apparatus for receiving a digital test signal from which a clock signal is recovered, is shown. A clock recovery circuit (401) recovers a clock signal from the test signal and a synchronization circuit generates a synchronized system clock signal from said recovered clock signal. A sinusoid generator (403) generates a sinusoid signal from the synchronized system clock signal and a sampling analog to digital converter (404) samples the sinusoid signal by the recovered clock signal to provide sinusoid samples further comprising: A numerically controlled oscillator (401) is configured to produce sine values and cosine values in response to receiving an input from the system clock signal and a first multiplier (412) is configured to produce a first product of the sinusoid samples and the sine values. In addition, a second multiplier is configured to produce a second product of the sinusoid samples and the cosine values. Furthermore, a co-ordinate rotation device (416) is configured to receive said first product via a first low pass filter (414) and to receive said second product via a second low pass filter (415) to produce an output indicative of jitter phase.