Signal detection technique utilising ‘lock-in’ architecture using 2 ωc harmonic frequency for portable sensors

Signal detection technique utilising ‘lock-in’ architecture using 2 ωc harmonic frequency for portable sensors

For access to this article, please select a purchase option:

Buy article PDF
(plus tax if applicable)
Buy Knowledge Pack
10 articles for $120.00
(plus taxes if applicable)

IET members benefit from discounts to all IET publications and free access to E&T Magazine. If you are an IET member, log in to your account and the discounts will automatically be applied.

Learn more about IET membership 

Recommend Title Publication to library

You must fill out fields marked with: *

Librarian details
Your details
Why are you recommending this title?
Select reason:
Electronics Letters — Recommend this title to your library

Thank you

Your recommendation has been sent to your librarian.

A signal detection technique utilising a ‘lock-in’ architecture using the second-order harmonic frequency (2 ωc) applicable to portable optical-biosensor systems is presented. The properties of frequency synthesis and filtering techniques are used to detect a weak signal concealed in intense background noise, such as thermal noise, 1/f noise and shot noise. Using the 2 ωc lock-in, the main signal of interest keeps away from the influence of the 1/f noise, providing a much higher dynamic reserve. In this work, a portable biosensor system using the 2 ωc frequency detection technique is demonstrated. The technique further enhances the minimum detectable range of 20 dB compared to the conventional DC lock-in method under the same conditions.


    1. 1)
      • A.P.F. Turner . (1999) McGraw-Hill Yearbook of Science & Technology 2000.
    2. 2)
      • Stanford Research Systems: ‘About lock-in Amplifiers’ (Application Note #3).
    3. 3)
      • G. Ferri , P. De Laurentiis , A. D'Amico , C. Di Natale . A low-voltage integrated CMOS analog lock-in amplifier prototype for LAPS applications. Sens. Actuators A Phys. , 263 - 272
    4. 4)
      • F.N. Hooge , T.G.M. Kleinpenning , L.K.J. Vandamme . Experimental studies on 1/f noise. Rep. Prog. Phys. , 5 , 479 - 532
    5. 5)
      • H.-H. Son , I.-I. Jung , D.G. Kim , D.-G. Kim , Y.-W. Choi . Improved sensitivity of portable bio-sensor systems using lock-in detection method. Proc. SPIE
    6. 6)
      • Bentham Instruments Ltd: ‘Lock-in Amplifiers’ (Technical Guides, 255).

Related content

This is a required field
Please enter a valid email address