Tektronix, Inc.

Scott E Zink

Daniel G Baker

Evan Albright

Michael S Overton

Barry A McKibben

Michael D Nakamura

Robert W Parish

Gilbert A Hoffman

David C Woody, Jr

A flexible timebase for eye diagrams uses a stable free running oscillator as a sample clock for equivalent time sampling of an input serial digital signal and of a reference signal, derived from a subdivided recovered clock of the input serial digital signal. The reference signal samples are provided to a digital phase-locked loop that provides the flexible timebase to an eye pattern generator. The eye pattern generator accumulates the input serial digital signal samples at times corresponding to the reference signal samples to produce the eye diagram. A linear phase detector in the digital phase locked loop converts the reference signal samples to a complex signal using a Hilbert transform and then to a linear ramp of phase values using a CORDIC algorithm with arctangent lookup table. A subtractor then subtracts the digital phase-locked loop feedback from the linear ramp to provide the input to the loop filter.

Flexible timebase for eye diagram

A flexible timebase for eye diagrams uses a stable free running oscillator as a sample clock for equivalent time sampling of an input serial digital signal and of a reference signal derived from a subdivided recovered clock of the input serial digital signal. The reference signal samples are provided to a digital phase-locked loop that provides the flexible timebase to an eye pattern generator. The eye pattern generator accumulates the input serial digital signal samples at times corresponding to the reference signal samples to produce the eye diagram. A linear phase detector in the digital phase locked loop converts the reference signal samples to a complex signal using a Hilbert transform and then to a linear ramp of phase values using a CORDIC algorithm with arctangent lookup table. The digital phase-locked loop feedback is subtracted from the linear ramp to provide the input to the loop filter.

Flexible timebase for EYE diagram

Image alias rejection when converting a high resolution rasterized waveform to a lower resolution rasterized waveform for display uses a statistical filter. The statistical filter provides a shaped probability density function either by combining the outputs of multiple random number generators, such as linear feedback shift registers, or by using a corresponding look-up table to produce a dither signal. The statistical filter may be applied to one or both of the dimensional values for each data point of the high resolution rasterized waveform by combining the dimensional values with the dither signal. The resulting filtered dimensional values may then be subsampled, such as by truncation, to produce values for a lower resolution rasterized waveform display.

Image alias rejection using shaped statistical filtering

An instrument has a single video input port for receiving either analog or serial digital video signals coupled to both an analog and a serial digital video input path. The outputs of the analog and serial digital video input paths are provided as respective inputs to a video switch, the output of which is then provided to the instrument for further processing. Information from the serial digital video input path, which may include clock recovery lock, carrier detect and/or video standard, is provided to a decision module that generates a select signal for the video switch. As an example, if 'lock' is present, then the output from the serial digital video input path is selected automatically for output by the video switch, otherwise the output from the analog video input path is selected automatically. The automatic selection for the switch may be manually overridden. A text display is provided to indicate which video input path the instrument is processing according to the output from the video switch, as well as information about the video signal at the video input port.

Analog or serial digital video input with automatic video switch

A method and apparatus for transparently embedding data into a video signal modulates a particular carrier frequency with a randomized pattern representing the data. The randomized pattern may be a combination of the data with the output from a pseudo-random binary sequence generator, or the data may be converted first into a bi-orthogonal pattern selected from among a plurality of such patterns and then randomized. The resulting modulated carrier frequency is then amplitude modulated based upon a human visual model so that the modulated carrier frequency amplitude is greater in areas of high image complexity and lower in areas of low image complexity. The subliminal data represented by the modulated carrier frequency is added to the video signal. At a decoder the data is recovered using appropriate correlation techniques by first filtering the video signal to increase the subliminal data component relative to the image component, then demodulating the data component to produce the data pattern, and then correlating the data pattern with the possible data patterns to identify the particular pattern and associated data word.

Transparent embedment of data in a video signal

A system for phase-locking a clock to a digital audio signal embedded within a digital video signal uses an audio extractor, frequency dividers, and an adjusted bandwidth loop filter to prevent phase jitter associated with the digital audio signal preventing the functionality of the phase-lock loop or having unacceptable effects on the generated audio sample frequency signal. Extracted audio samples are divided down and input to a phase detector. The signal is then filtered using a series of loop filters, one of which has an adjusted bandwidth to reject phase jitter. A clock then outputs the generated synthesized audio sample frequency using the output from the series of loop filters, and the synthesized frequency signal is looped back through a second frequency divider to the phase detector.

System for phase-locking a clock to a digital audio signal embedded in a

A return-loss detector for a serial digital signal source uses a return-loss bridge circuit to exploit the broadband spectral characteristics of a serial digital signal from the signal source to monitor the termination conditions of a system being driven. A differential pair of serial digital signals from the source are input to the bridge circuit having a reference termination in one leg and the system termination in the other. A broadband detector is used at the output of the bridge circuit to generate an error signal, which is measured by a detector or metering circuit. The measured signal may be displayed as a value in dB or may be input to a comparator to provide an alarm or warning signal to an operator.

Return-loss detection for serial digital source

A stereo signal separation system for separating the L+R and L-R components of a BTSC stereo signal mixes the BTSC signal with a multiple of the pilot frequency. To recover the L+R component the mixer output is combined with the input BTSC signal, and to recover to L-R component the mixer output is combined with a second mixer output shifted ninety degrees. The combined output is low pass filtered to recover the desired component.

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Portland, OR, United States of America

Scott E Zink