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NIST offers a special-test service for measurement of repetitive pulse waveforms whose major frequency components are below 1 GHz. Waveform measurement data can be provided on diskette, along with a report of measurement uncertainties as a function of the duration from the mesial (50 %) point of the pulse transition. When required, certain derived waveform parameters can also be provided. For step-like waveforms, these include waveform settling errors, with respect to a defined reference level. For impulse-like waveforms, pulse energy into an ideal 50 Ω load can be provided. The waveforms are measured with the NIST Sampling Comparator System described above. Waveforms within ± 2 V into 50 Ω can be accommodated directly. Higher amplitudes require the use of external attenuators. Both 50 Ω and 2 kΩ attenuators are available for amplitudes up to 20 V peak; however, the 2 kΩ attenuator substantially reduces the bandwidth of the measurement system. Typical measurement epochs range from 10 ns to 1 µs, and record lengths range from 1000 to 4000 samples.Representative uncertainties for settling parameter measurements are listed in Table 9.22.
Representative uncertainties for settling parameter measurements are listed in Table 9.22.
Restrictions and Notes:
1. All measurements are performed with a 50Ω input impedance. The input connector is a female SMA type. The sampling probe is connected directly to the output connector of the waveform source; no intervening cables are used unless they are specifically provided for this purpose by the customer.
2. The settling error at time t (measured from the mesial point) is defined as the largest absolute difference between the waveform and the reference level occurring in the interval from time t to the end of the data record.
3. Unless otherwise requested, the reference level is the final dc or steady state value of the final level. This level is measured by inputting a steady state logic level to the generator under test corresponding to the final level.
4. Short term settling can also be measured with respect to the final level in a specified time epoch, if requested. In this case, long term settling error-the difference between the value at the end of the specified epoch and the dc value-also will be reported.
5. Pulse generators that are internally clocked must provide a separate trigger output pulse. For best results, this should lead the wave-form under test by at least 35 ns. If the trigger pulse leads by less than 35 ns, the waveform measurement will begin one cycle later, with a resulting increase in jitter and time-quantization errors. If the pulse generator can be clocked externally, NIST will provide the clock signal and the necessary trigger output signal, when required.
6. The clock pulse requirements should be specified including high level, low level, repetition rate, and duty cycle. Repetition rates between 10 kHz and 10 MHz are preferred. Measurements of other pulse parameters or parameter ranges may be provided by special arrangement. Consulting and advisory services also are available.
Measurements on peak-to-peak detectors are performed from 100 kHz to 500 MHz. The quantity measured by this service is the rf-ac difference defined as the percentage of difference between the rf and ac input voltages required to produce zero dc detector outputs. A 50 kHz ac reference signal is applied instead of dc. The services available are specified in Table 9.23.
References-Repetitive Pulse Waveform Measurements, Including Settling Parameters
A Custom Integrated Circuit Comparator for High-Performance Sampling Applications, O. B. Laug, T. M. Souders, and D. R. Flach, IEEE Trans. Instrum. Meas.41 (6), 850 (Dec. 1992).
Characterization of a Sampling Voltage Tracker for Measuring Fast, Repetitive Signals, T. M. Souders, H. K. Schoenwetter, P. S. Hetrick, IEEE Trans. Instrum. Meas. IM-36 (4), 956 (Dec. 1987).