System and method of measuring high-speed electrical waveforms using force microscopy and offset sampling frequencies

A method for measuring a periodic electrical waveform existing proximate the surface of a sample, said periodic waveform having a predefined repetition frequency, comprising the steps of:

• generating a sampling signal having a sample signal repetition frequency offset from said predefined repetition frequency by a difference frequency;
• transmitting said sampling signal along a signal path integrated with a cantilever to a position proximate the surface of said sample so as to generate an electrical force on said cantilever that is a nonlinear function of differences in amplitude between said sampling signal and said periodic electrical waveform, said electrical force displacing said cantilever such that said cantilever's displacement replicates said electrical waveform at a repetition rate equal to said difference frequency;
• wherein said cantilever has a mechanical resonance frequency that limits said cantilever's speed of movement, said mechanical resonance frequency is substantially less than said predefined repetition frequency, and said sample signal repetition frequency is set such that said difference frequency is less than said mechanical resonance frequency;
• whereby said cantilever low pass filters, with a cutoff frequency corresponding to said mechanical resonance frequency, said electrical force on said cantilever;
• and
• detecting said displacement of said cantilever.

An apparatus for measuring a periodic electrical waveform existing proximate the surface of a sample, said periodic waveform having a predefined repetition frequency, comprising:

• a sampling signal generator that generates a sampling signal having a sample signal repetition frequency that is offset from said predefined repetition frequency by a difference frequency;
• a mechanical sensor coupled to said sampling signal generator for carrying said sampling signal to a position proximate the surface of said sample so as to generate an electrical force on the mechanical sensor that is a nonlinear function of differences in amplitude between said sampling signal and said periodic electrical waveform, said electrical force displacing said mechanical sensor such that said sensor's displacement replicates said electrical waveform at a repetition rate equal to said difference frequency;
• wherein said mechanical sensor has a mechanical resonance frequency that limits said mechanical sensor's speed of movement, said mechanical resonance frequency is substantially less than said predefined repetition frequency, and said sample signal repetition frequency is set such that said difference frequency is less than said mechanical resonance frequency;
• whereby said mechanical sensor low pass filters, with a cutoff frequency corresponding to said mechanical resonance frequency, said electrical force on said mechanical sensor;
• and
• a displacement sensor for detecting said displacement of said mechanical sensor.

A method for measuring a periodic electrical waveform existing proximate the surface of a sample, said periodic waveform having a predefined repetition frequency, comprising the steps of:

• generating a sampling signal having a sample signal repetition frequency offset from said predefined repetition frequency by a difference frequency;
• transmitting said sampling signal along a signal path integrated with a mechanical sensor to a position proximate the surface of said sample so as to generate an electrical force on said mechanical sensor that is a nonlinear function of differences in amplitude between said sampling signal and said periodic electrical waveform, said electrical force displacing said mechanical sensor such that said mechanical sensor's displacement replicates said electrical waveform at a repetition rate equal to said difference frequency;
• wherein said mechanical sensor has a mechanical resonance frequency that limits said mechanical sensor's speed of movement, said mechanical resonance frequency is substantially less than said predefined repetition frequency, and said sample signal repetition frequency is set such that said difference frequency is less than said mechanical resonance frequency;
• whereby said mechanical sensor low pass filters, with a cutoff frequency corresponding to said mechanical resonance frequency, said electrical force on said mechanical sensor;
• and
• detecting said displacement of said mechanical sensor.