Tektronix, Inc.

Edward D Wardzala

Michael S Overton

Douglas C Stevens

John C Reynolds

Laurent A Melling, Jr

Alan E Mathieu

A test signal generator applies a test pattern to a device under test. The output of the device under test is displayed on a video picture monitor. The test signal generator inserts a cursor into the test pattern, the position of the cursor within the test pattern being variable. From the cursor the test signal generator also generates a trigger signal. The trigger signal may be used to trigger the horizontal sweep of a waveform display device to which the output of the device under device is input. By observing the picture monitor an operator may adjust the cursor to a position just prior to an anomaly in the displayed test pattern so that only that portion of the output waveform of the device under test in the vicinity of the cursor is displayed on the waveform display device.

Test signal generator position cursors

An edge integrating phase detector for a phase locked loop passes a portion of a sync edge of an input video signal as a sampled signal to an integrator in response to a gate pulse nominally centered on a timing reference point of the sync edge. The sampled signal has a positive and negative portion. The integrator produces from the sampled signal a control signal for a VCO that is proportional to the unbalance between the positive and negative portions. The gate pulse is generated from the output of the VCO as a function of the nominal period of the input video signal.

Edge integrating phase detector

A method of measuring timebase jitter for component video compares a test signal from a reference signal generator, such as a bowtie signal or a fixed carrier frequency signal, with the same test signal from a local phase locked signal generator for which timing jitter is to be determined. The test signals are timed to be coincident by adjusting appropriate delay lines and timing controls. For a bowtie signal the width of an indeterminate region for the intersection of the bowtie signal is a measure of the timebase jitter, the value of which is determined using the cursors provided by the bowtie signal. For a fixed carrier frequency signal the respective test signals are equalized in amplitude and timed for coincidence, and then modulated together. The modulated signal is lowpass filtered and processed by a fast Fourier transform to provide a display of the timebase jitter.

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Portland, OR, United States of America

Edward D Wardzala