In this paper we present a novel architecture for phase-locked loop (PLL) based high-speed demodulation of frequency-modulated (FM) atomic force microscopy (AFM) signals. In our approach, we use single-sideband (SSB) frequency upconversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency (IF) of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. In addition, the upconversion to a fixed IF renders the PLL demodulator independent of the cantilever's resonance frequency, allowing the system to work with a large range of cantilever frequencies. To investigate if the additional noise introduced by the SSB upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in PLLs incorporating a phase-frequency detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by both electrical and AFM measurements obtained with a PCB-based prototype implementing the proposed demodulator architecture.
%0 Journal Article
%1 6800103
%A Schlecker, B.
%A Dukic, M.
%A Erickson, B.
%A Ortmanns, M.
%A Fantner, G.
%A Anders, J.
%D 2014
%J IEEE Transactions on Biomedical Circuits and Systems
%K AFM single-cycle
%N 2
%P 206-215
%R 10.1109/TBCAS.2014.2307696
%T Single-Cycle-PLL Detection for Real-Time FM-AFM Applications
%U https://ieeexplore.ieee.org/document/6800103/
%V 8
%X In this paper we present a novel architecture for phase-locked loop (PLL) based high-speed demodulation of frequency-modulated (FM) atomic force microscopy (AFM) signals. In our approach, we use single-sideband (SSB) frequency upconversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency (IF) of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. In addition, the upconversion to a fixed IF renders the PLL demodulator independent of the cantilever's resonance frequency, allowing the system to work with a large range of cantilever frequencies. To investigate if the additional noise introduced by the SSB upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in PLLs incorporating a phase-frequency detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by both electrical and AFM measurements obtained with a PCB-based prototype implementing the proposed demodulator architecture.
@article{6800103,
abstract = {In this paper we present a novel architecture for phase-locked loop (PLL) based high-speed demodulation of frequency-modulated (FM) atomic force microscopy (AFM) signals. In our approach, we use single-sideband (SSB) frequency upconversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency (IF) of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. In addition, the upconversion to a fixed IF renders the PLL demodulator independent of the cantilever's resonance frequency, allowing the system to work with a large range of cantilever frequencies. To investigate if the additional noise introduced by the SSB upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in PLLs incorporating a phase-frequency detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by both electrical and AFM measurements obtained with a PCB-based prototype implementing the proposed demodulator architecture.},
added-at = {2020-10-11T10:13:58.000+0200},
author = {{Schlecker}, B. and {Dukic}, M. and {Erickson}, B. and {Ortmanns}, M. and {Fantner}, G. and {Anders}, J.},
biburl = {https://puma.ub.uni-stuttgart.de/bibtex/230d900b3a61e60fe4a1f1696889d0183/jens.anders},
doi = {10.1109/TBCAS.2014.2307696},
interhash = {7a3523ab873c99603a222a94846a95f5},
intrahash = {30d900b3a61e60fe4a1f1696889d0183},
issn = {1940-9990},
journal = {IEEE Transactions on Biomedical Circuits and Systems},
keywords = {AFM single-cycle},
month = {April},
number = 2,
pages = {206-215},
timestamp = {2020-10-12T13:46:57.000+0200},
title = {Single-Cycle-PLL Detection for Real-Time FM-AFM Applications},
url = {https://ieeexplore.ieee.org/document/6800103/},
volume = 8,
year = 2014
}
