MEASURING HUM IN A DIGITAL TV SIGNAL
First Claim
Patent Images
1. A method for measuring Hum in a digital TV signal comprising QAM signals using a testing device for testing QAM signals on a cable TV network, the method comprising:
- a) receiving the digital TV signal with the testing device, which comprises a tuner, a QAM demodulator coupled to receive a digital channel signal from the tuner, and a controller having memory, the QAM demodulator including an automatic gain control (AGC) circuit, the AGC circuit including an AGC register for storing a current AGC value,b) sampling values stored in the AGC register at a pre-defined sampling rate R that exceeds a characteristic Hum frequency to obtain a plurality of AGC register values;
c) providing the plurality of AGC register values to the controller for analysis to obtain one or more Hum characteristics; and
,d) reporting to a user or storing in memory the one or more of Hum characteristics.
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Abstract
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.
30 Citations
20 Claims
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1. A method for measuring Hum in a digital TV signal comprising QAM signals using a testing device for testing QAM signals on a cable TV network, the method comprising:
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a) receiving the digital TV signal with the testing device, which comprises a tuner, a QAM demodulator coupled to receive a digital channel signal from the tuner, and a controller having memory, the QAM demodulator including an automatic gain control (AGC) circuit, the AGC circuit including an AGC register for storing a current AGC value, b) sampling values stored in the AGC register at a pre-defined sampling rate R that exceeds a characteristic Hum frequency to obtain a plurality of AGC register values; c) providing the plurality of AGC register values to the controller for analysis to obtain one or more Hum characteristics; and
,d) reporting to a user or storing in memory the one or more of Hum characteristics. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A battery powered testing device for testing a digital TV signal on a cable TV network, comprising:
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an input port for receiving the digital TV signal; a tuner coupled to the input port for selecting a digital QAM channel signal from the digital TV signal; a QAM demodulator coupled to the tuner to receive the digital QAM channel signal from the tuner and including an automatic gain control circuit (AGC) for generating AGC values, the AGC circuit including an AGC register for storing said AGC values, and an AGC register communication port for accessing the content of the AGC register; a controller coupled to the tuner for controlling operation thereof and to the AGC register port of the QAM demodulator for sampling the content of the AGC register; and
,an output device coupled to the controller; wherein the controller is programmed to perform operations comprising; a) sampling values stored in the AGC register at a pre-defined sampling rate R that exceeds a characteristic Hum frequency to obtain a plurality of AGC register values; b) analyzing the plurality of AGC register values to obtain one or more Hum characteristics; and
,c) providing the one or more of Hum characteristics to the output device for storing therein or reporting to a user. - View Dependent Claims (17, 18, 19, 20)
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Specification