Signal Sampling Phase Adjustment for Digital TV Decryption Timing
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Solution Overview
Problem
Existing digital TV systems face challenges in accurately detecting voltage level transition intervals, leading to timing drift issues during signal decryption, which affects the precision of sampling points and overall protection of encrypted data streams.
Innovation Solution
A signal sampling method that calculates the maximum and minimum transition timings of an input signal relative to a reference clock signal, defining a voltage level transition interval, and adjusts the sampling clock signal or input signal phase to align with these intervals for precise sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the encrypted TV data stream is stored without being decrypted and sent to CAM for decryption, then the protective strength is stronger, but timing drift occurs during decryption affecting sampling precision
Solution Approach 1:
The patent replaces traditional timing calibration methods with a voltage level transition detection mechanism. Instead of relying on fixed timing relationships that drift during decryption, the system dynamically detects actual voltage transitions in the decrypted signal and uses these detections to establish accurate sampling points, thereby maintaining sampling precision despite timing drift
Solution Approach 2:
The patent implements a feedback mechanism where the detection results of voltage level transitions are used to adjust and determine the phase of the sampling clock signal. This closed-loop approach ensures that sampling points are continuously aligned with actual signal transitions, compensating for timing drift introduced during decryption while preserving security
2Adaptability or versatility
If different CAM manufacturers use different internal signal paths and loads, then device compatibility increases, but timing shift error calibration becomes difficult
Solution Approach 1:
The patent enables each CAM device to automatically calibrate its own timing characteristics through voltage level transition detection. The system uses the actual decrypted signal from each specific device to detect transition points and determine sampling clock phase, eliminating the need for external calibration procedures and making the solution universally applicable across different manufacturers' devices
Solution Approach 2:
The patent changes the approach from fixed timing parameters to dynamically detected voltage level transitions. By monitoring actual voltage transitions in the decrypted signal rather than relying on predetermined timing values, the system adapts to the specific electrical characteristics of each CAM device's internal signal paths and loads
Data Source
AI summary
In one embodiment of the present invention, a signal sampling method is provided. It comprises: (a) sampling an input signal with respect to a sampling clock signal; (b) calculating a maximum transition timing and a minimum transition timing of the input signal according to a relation between the sampling in step (a) and a reference timing clock; (c) defining a voltage level transition interval according to the maximum transition timing and the minimum transition timing; and (d) determining phase of the sampling clock signal or phase of the input signal according to the voltage level transition interval.