Hewlett-Packard Company

Keith M Ferguson

Scott R Patterson

Douglas E Hoover

David W Clark

David C Chu

Jeff Benjamin

Alan Davis

Ryan Porter

A method for examining an input signal and setting a modulation domain measuring instrument to a state which will produce a measurement and a stable, centered, properly scaled display of the signal, automatically. After finding the 50 percent voltage threshold of the input signal, an iterative process determines the minimum and maximum input frequency, then checks the ratio of these two frequencies against instruments limits, and adjusts the display values, if necessary to show only the higher frequencies. The method then varies the measurement parameters to seek the best frequency resolution while maintaining the measurement and display of frequency modulation. The display frequency scale is set to display the signal in the center half of the display, using values with no more than two significant digits for the center and span. The time scale is set to display a selected number of modulation cycles.

Automatic scaling for display of modulation domain measurements

A method and apparatus makes rapid frequency measurements by measuring time intervals for a series of blocks of event counts with the number of events in each block held constant. This makes the numerator of the events/time relationship constant so it does not have to be measured, processed or stored. The frequency of the signal is determined by measuring the time interval, then taking the inverse of the measured value and multiplying by the appropriate constant. A fast inverse circuit uses a Taylor series expansion technique implemented in digital circuit, with the slope resolution adjusted for regions of small slope to improve accuracy.

Constant events frequency measurement and fast inverse circuit

The relative occurrence of first and second input signals is determined by sampling the output signal of a comparator which compares a predetermined voltage source output signal with the output signal from a ramp generator which is triggered by the first input signal. The sampling signal is provided in response to the second input signal after a preselected time delay. A balancing calibration is used to insure that if the signals are coincident, the ramp generator signal is equal to the voltage reference signal at the moment of sampling. Therefore, the precedence of the first and second input signals is determined by sampling the comparator output signal in response to the sampling signal and determining the relative values of the ramp voltage signal and the voltage reference signal at the time of sampling.

Apparatus for detecting signal precedence

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Saratoga, CA, United States of America

Keith M Ferguson