Hewlett-Packard Company

John A Wendler

Michael S Marzalek

Stephen R Peterson

Ronald J Hogan, Jr

Richard C Keiter

A sampling signal analyzer in which the frequency of an input signal to be measured is initially ascertained, an appropriate sampling frequency is then determined, data needed to reconstruct the wave form of the input signal is acquired, and the input signal wave shape is reconstructed with a calibrated time axis and preferably displayed. The sampling signal analyzer synthesizes a sampler drive signal to enable continuous sampling of the input signal and therefore has the advantage over known data sampling signal measurement instruments that it is not triggered directly in response to the level of the input signal to be measured. Instead, sample timing is based on numerical analysis of the intermediate frequency (IF) signal produced by the sampler. The IF frequency can be an arbitrarily low frequency, which allows digitizing and digital signal processing for aligning measurement data from sweep to sweep with precision. The sampling signal analyzer operates so that all frequency components of the input signal will lie within plus or minus an IF bandwidth away from a comb tooth of a sampling frequency and will translate (i.e., mix) and compress into the IF. The sampling signal analyzer determines where to mix the input signal in the IF based on the frequency of the input signal and a display time range selected by the operator. The number of cycles of the wave form being displayed can be selected by the operator, and the time axis is automatically rescaled to display the selected number of cycles, notwithstanding a change in the input signal frequency. A pulse profiling method enables the recoverable modulation bandwith of the sampling signal analyzer to be as wide as a high-frequency input bandwidth so that the response of high-frequency devices stimulated by pulsed or otherwise modulated signals can be measured.

Sampling signal analyzer

Representations of signal edges of a repetitive signal are sampled without triggering, then sorted out based on frequency and sequence and then superimposed along a common time base of one period in order to reconstruct a signal. In a specific embodiment of a method according to the invention, a string of samples of a repetitive, input signal with high frequency components is captured without triggering with relatively low time resolution to determine an approximate waveform from the low resolution samples, then digital signal processing techniques in the form of a fast Fourier transform are applied to a reconstructed time record of the input signal to obtain an accurate frequency for each signal component, and finally the sampled waveform is reconstructed by overlaying sampled components with reference to a common time or phase reference. The FFT is employed to determine the frequency of each signal component very accurately. Further processing, such as bin interpolation based on a window function, may be employed to improve resolution still further.

Growing community of inventors

Urbana, IL, United States of America

John A Wendler