Frequency measuring and control apparatus with integrated parallel synchronized oscillators

A computer-controlled SPM system, comprising:

• equipment to carry out scanning probe microscopy, and including:
• a probe;
• an actuator in communication with the probe to oscillate the probe;
• and
• an oscillation sensor to sense oscillation of the oscillating probe and generate an analog oscillation signal corresponding to the sensed oscillation of the oscillating probe;
• instrumentation in communication with the equipment to transmit excitations to the equipment and receive responses produced by the equipment, and including:
• a digital-to-analog converter in communication with the actuator;
• an analog-to-digital converter in communication with the oscillation sensor to convert the analog oscillation signal to a digital oscillation signal;
• and
• a phase locked loop to compare the digital oscillation signal from the analog-to-digital converter with a digital reference oscillation signal and generate a digital phase difference signal;
• and
• a plurality of oscillators in parallel downstream communication with the phase locked loop to receive the digital phase difference signal, wherein the oscillators include a plurality of phase accumulators to generate a plurality of digital phase signals for a corresponding plurality of channels and a plurality of phase-to-amplitude converters downstream of the phase accumulators to convert the plurality of digital phase signals into a plurality of digital amplitude signals for the corresponding plurality of channels;
• wherein the phase locked loop and the plurality of oscillators are defined by a single programmable logic device in communication with the analog-to-digital converter and configured to apply a plurality of channel-specific synchronization factors to the digital phase difference signal upstream of the phase accumulators;
• and
• a computer in communication with the instrumentation and including at least one input device to receive from a user the plurality of channel-specific synchronization factors.

An electronic frequency measuring and control apparatus, comprising:

• an analog-to-digital converter to convert an analog oscillation signal to a digital oscillation signal;
• and
• a phase locked loop to compare the digital oscillation signal from the analog-to-digital converter with a digital reference oscillation signal and generate a digital phase difference signal;
• and
• a plurality of oscillators in parallel downstream communication with the phase locked loop to receive the digital phase difference signal, wherein the oscillators include a plurality of phase accumulators to generate a plurality of digital phase signals for a corresponding plurality of channels and a plurality of phase-to-amplitude converters downstream of the phase accumulators to convert the plurality of digital phase signals into a plurality of digital amplitude signals for the corresponding plurality of channels;
• wherein the phase locked loop and the plurality of oscillators are defined by a single programmable logic device in communication with the analog-to-digital converter and configured to apply a plurality of channel-specific synchronization factors to the digital phase difference signal upstream of the phase accumulators.