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Sampling signal analyzer
| Details |
Inventors: Marzalek, Michael S.; Keiter, Richard C.; Wendler, John A.; Peterson, Stephen R.; Hogan, Ronald J.;
Assignee: Hewlett-Packard Company (Palo Alto, CA)
Primary Examiner: Wieder; Kenneth A.
Assistant Examiner: Solis; Jose M.
Attorney, Agent or Firm: Milks, III; William C.
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. |
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DETAILED DESCRIPTION One embodiment of the present invention provides 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 for display.
The sampling signal analyzer comprises means for synthesizing 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.
In the case that the frequency of the input signal to be measured is unknown, the sampling signal analyzer first must ascertain the frequency of the input signal by determining the frequency components (fundamental and any harmonics) of the input signal using frequency translation and frequency compression, as well as using digital signal processing resident in firmware, to perform input signal frequency identification.
This is preferably accomplished by initially setting the IF bandwidth as wide as allowable, then setting the frequency of a sampling signal oscillator, preferably a low-phase-noise fractional-N synthesized source, to a frequency less than twice the IF bandwidth.
This assures that all frequency components of the input signal will lie within plus or minus an IF bandwidth away from a comb tooth of the sampling signal oscillator frequency and will translate (i.
e.
, mix) into the IF.
Next, the sampling signal analyzer acquires a first set of measurement data using the sampler and digitizes the sampled data by means of an analog-to-digital converter
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Processing Data 
