Non-contact measurement of electrical waveforms on the surface of a

Abstract

A method and an apparatus for providing non-contact measurement of waveforms proximate to a surface of a sample. In one version, the describe apparatus includes a probe waveform generator that generates probe waveforms with the same repetition rate as a sample waveform to the measured from the sample. The apparatus includes a cantilever with a signal path to carry the probe waveform to a position above the sample surface where the sample waveform is to be measured. The apparatus of the present invention also includes a gate to periodically route the probe waveforms to the cantilever tip. The gate is controlled by a periodic gating signal with a period substantially longer than the signal period of the sample waveform. In one version, the gate is switched at a repetition rate substantially equal to a mechanical resonant repetition rate of the cantilever. Capacitive coupling between the cantilever and the signal line of the sample results in a periodic motion of the cantilever at the gating repetition rate. The periodic mechanical motion may be measured and the electrical waveform flowing in the signal line in the sample is determined. By adjusting the time delay of the pulse waveform impressed upon the tip of the cantilever, the amplitude of the sample waveform can be measured with the present invention during various portion of each cycle of the sample waveform.