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Abstract

A method of characterizing a modulated carrier signal by generating electrical signals which represent arithmetic ratios and which can be used to construct a histogram indicative of the quality of the modulated carrier signal. For a digitally modulated carrier signal, time spaced samples of in band amplitude dispersion of the signal are generated and first counts are made of the number of occurrences of particular values of in band dispersion, over a range of such values. The error ratio of the decoded modulated carrier signal is also monitored and seconds counts are accummulated, of the numbers of occurrences of respective values of in band amplitude dispersions which at least substantially coincide with the value of said error ratio crossing a predetermined level. The ratio of each second count to each corresponding first count is then taken and these ratios are then representative of the probability that, at the respective in band amplitude dispersion value, the value of the error ratio will cross the predetermined level. When practicing the method with analogue modulated carrier signals, values of the signal to noise ratio are employed instead of the values of error ratio. A method of the invention permits construction of a histogram which pictorially represents the quality of the modulated carrier signal.

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First Claim