Hewlett-packard Company

Robert A Witte

Matthew S Holcomb

A new sampling technique for waveform measuring instruments (including methods and circuits for implementing same) comprises the step of processing a series of digital signal samples through a decimator to extract a decimated sample value from each decimated sample interval in a series of decimated sample intervals. The series of digital signal samples is simultaneously processed through a digital peak detector to extract maximum and minimum values (peak detect sample values) from each decimated sample interval. For a given decimated sample interval, a difference between the maximum and minimum sample values for the interval is calculated. If the difference exceeds a glitch detect threshold value, the maximum and minimum sample values for the given decimated sample interval are transferred to a video sample memory. If not, the decimated sample value for the given decimated sample interval is transferred to the video sample memory.

Sampling technique for waveform measuring instruments

A filtering apparatus permits alias-free frequency domain measurement in any of a plurality of measurement bandwidths. The input signal is first passed through one of a plurality of low-pass filters. The appropriate filter is selected by a controller to provide a cut-off frequency at least as great as the selected measurement bandwidth. An analog-to-digital convertor ('ADC') samples the filtered input signal at a sample rate (f.sub.s) set by the controller to be at least twice the measurement bandwidth. The digitized samples are then processed by a digital low-pass filter (i.e. a finite impulse response filter) to further reduce the bandwidth of the input signal to the measurement bandwidth. Operation of the digital filter is controlled by a number of filter coefficients provided by the controller as a function of the desired measurement bandwidth. A memory is provided between the ADC and the digital filter. The samples output by the ADC can be processed in real time by the digital filter if the sample rate is sufficiently low, or the samples can be stored in the memory for subsequent processing by the digital filter if a higher sample rate is required. The number of samples can be reduced by adding a decimator which outputs only one sample from each series of K samples received from the digital filter, provided f.sub.s /K is at least twice the measurement bandwidth.

Growing community of inventors

Monument, CO, United States of America

Robert A Witte