Individual characterization of broadband sampling oscilloscopes with a 'nose-to-nose' calibration procedure

A method is proposed to find the individual impulse response of broadband sampling oscilloscopes. The method is based on the fact that, when the oscilloscope is sampling a DC voltage, pulses are launched from the sampler toward the input connector. These pulses contain information on the scope characteristics. They can be measured by a second oscilloscope. This type of measurement is called a nose-to-nose calibration. By applying deconvolution techniques to the results of this measurement, the characteristics of the two scopes can be found, supposing that the two scopes are identical. To avoid this assumption, three oscilloscopes can be used. The nose-to-nose is then applied three times. Each time a different pair of scopes is connected together. The individual characteristics of the three sampling oscilloscopes are then calculated. Both SPICE simulations and close correspondence between swept sine measurements and this method indicate that it is probably the most accurate method available at this moment to calibrate broadband sampling oscilloscopes. Several measurement uncertainties and practical problems are identified.<
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