Battery-Powered QAM Hum Measurement via Internal Clock Triggering
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Solution Overview
Problem
Current methods for measuring Hum in digital QAM signals, particularly in battery-operated testers, are inadequate as they require a power line for triggering and fail to evaluate unsynchronized Hum components, such as those from switching-type power supply faults, and are not applicable in battery back-up power scenarios.
Innovation Solution
A battery-powered testing device with a tuner, QAM demodulator, and automatic gain control (AGC) circuit that samples AGC register values at a pre-defined rate exceeding the characteristic Hum frequency to analyze and report Hum characteristics, eliminating the need for a power line connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power line triggering is used to measure Hum in digital QAM signals, then measurement precision is improved, but device portability and ease of operation deteriorate due to requiring power line connection
Solution Approach 1:
The device uses its own internal clock to generate the trigger signal for Hum measurement, eliminating the need for external power line triggering. The microcontroller's internal clock provides the timing reference needed to sample AGC values at the correct intervals to detect Hum components at 60Hz and 120Hz, making the device fully portable and battery-operated while maintaining measurement capability
Solution Approach 2:
Instead of using an external power line signal to trigger measurements, the invention inverts the approach by using an internal clock to generate the trigger signal. This reversal allows the device to operate independently of power line infrastructure while still achieving synchronized sampling for accurate Hum detection
2Measurement precision
If power line synchronization is used for Hum measurement, then measurement precision is improved, but adaptability to battery back-up power scenarios deteriorates
Solution Approach 1:
The device becomes self-sufficient by using its internal clock as the timing reference for Hum measurement, rather than relying on external power line synchronization. This allows the device to operate accurately in battery back-up power scenarios and other environments where power line triggering is unavailable or unreliable
3Device complexity
If fixed sampling rate is used in AGC circuit, then device complexity is reduced, but measurement precision of Hum characteristics deteriorates
Solution Approach 1:
The AGC sampling rate is made dynamic and adjustable rather than fixed. The microcontroller can configure the AGC circuit to sample at different rates depending on the specific measurement requirements, allowing optimization of Hum detection precision while maintaining reasonable device complexity through software control
Data Source
AI summary
The invention relates to a method for measuring Hum on a digital QAM carrier using a testing device for testing digital TV signals including a QAM demodulator therein, and to a testing device implementing the method. A micro-controller is used to sample a register associated with an AGC circuit in the QAM demodulator, and to process the collected register values to obtain one or more Hum characteristics.