The Intermodulation Lockin Analyzer

TL;DR

This paper introduces a digital lock-in analyzer implemented on FPGA for nonlinear system analysis using intermodulation products, demonstrated with atomic force microscopy and generalized to arbitrary waveforms.

Contribution

It presents a real-time, FPGA-based lock-in analyzer specifically designed for intermodulation spectral analysis of nonlinear systems, with a generalization to arbitrary drive signals.

Findings

Real-time analysis capability demonstrated

Applicable to atomic force microscopy

Generalization to arbitrary waveforms discussed

Abstract

Nonlinear systems can be probed by driving them with two or more pure tones while measuring the intermodulation products of the drive tones in the response. We describe a digital lock-in analyzer which is designed explicitly for this purpose. The analyzer is implemented on a field-programmable gate array, providing speed in analysis, real-time feedback and stability in operation. The use of the analyzer is demonstrated for Intermodulation Atomic Force Microscopy. A generalization of the intermodulation spectral technique to arbitrary drive waveforms is discussed.