Frequency measuring and control apparatus with integrated parallel synchronized oscillators

Abstract

A frequency measuring and control apparatus includes a plurality of synchronized oscillators integrated in parallel into one programmable logic device.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This present application claims priority from U.S. patent application Ser. No. 13 / 583,952 filed on Sep. 11, 2012, PCT Patent Application PCT / US2011 / 28859 filed on Mar. 17, 2011, and U.S. Provisional Patent Application No. 61 / 315,823 filed Mar. 19, 2010, all of which are incorporated herein by reference in their entireties.TECHNICAL FIELD[0002]This disclosure relates generally to frequency measuring and control and, more particularly, to frequency control with phase locking.BACKGROUND[0003]Many technologies employ phase locked loops (PLLs). For example, in scanning probe microscopy, scientists use scanning probe microscopes (SPMs) to reveal data about various properties of materials, like gold or silicon, at very fine resolution down to molecules and atoms of the materials. SPMs are a family of ultra-high magnification instruments that include Scanning Tunneling Microscopes (STMs), Atomic Force Microscopes (AFMs), Near Field Scanning Optica...

AI Technical Summary

Benefits of technology

The patent describes a device that has multiple oscillators that work together to measure and control frequency. This device is designed to be programmable, meaning it can be customized easily to perform different tasks.

Problems solved by technology

But the disadvantage of this configuration is that it is not possible to run cantilever excitation and PLL detection at harmonic frequencies of each other.

But such a configuration is considerably costly for each additional lock-in, and runs on an external reference.

Modern digital lock-ins generate the reference using a PLL with very low time constant and, thus, cannot handle constant changes in frequency very well.

In any event, it is not possible with such a configuration to provide a fixed offset from the fluctuating PLL reference frequency or a harmonic thereof.

But this design does not permit setting up the two DDS chips with different frequencies as is required for detecting or exciting relatively high harmonics.

Finally, with analog PLL circuits, although it is possible to create integer and fractional multiples of a base frequency with frequency dividers between a VCO and a mixer, it is complicated to build a variable frequency ratio frequency multiplier this way and it is impossible to have the circuit output pure sine waves this way.

Images