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Subharmonic Tags for Localization, Ranging and Navigation in GPS-denied Environments

Northeastern researchers have invented a new type of Subharmonic Tag for ranging, localization and navigation in GPS-denied environments

Published: 28th July 2022
Subharmonic Tags for Localization, Ranging and Navigation in GPS-denied Environments


Researchers at Northeastern have invented a new type of Subharmonic Tag which uses new dynamics never explored before that allow for activation of an output signal showing a frequency comb in its spectrum. Such a spectral characteristic is the key for the actual implementation of the localization and ranging applications. The presented device consists in a passive, chip-less and battery-less component leveraging exotic dynamics to trigger a never reported frequency read-out mechanism that makes it suitable to operate as a beacon for ranging, localization and navigation. This kind of operation has never been reported and permits to overcome the intrinsic limitations affecting the performance of any previously reported passive tags due to multi-path, readers’ self-interference and clutter.

Technology Overview

Northeastern researchers have invented a device which consists of a subharmonic tag where one or more resonators are used in its output network. This enables the dynamics that ensure the activation of the localization functionality. When this tag is interrogated by a signal coming from a reader that has a frequency that is twice any one of the parallel resonance frequencies of the adopted acoustic devices, it stops generating a frequency divided by two output signals. Instead, it triggers the activation of a frequency comb with comb line separation that correlates directly to the actual received input power level. Readers can then extrapolate their exact distance from the tag by assessing the comb-line separation characterizing the received portion of the tag’s output signal. Since such a comb line separation (e.g. modulation frequency) is not affected by multipath, self-interference and clutter, it can be used to provide an accurate localization even in indoor and noisy electromagnetic mediums. Through its use, it is therefore possible to navigate in GPS-denied environments without requiring any periodic maintenance, which in many cases is very hard to make.


  • It achieves localization and ranging with high resolution without requiring any batteries or any integrated circuits.
  • The achieved sensing performance is not affected by multi-path, self-interference and clutter
  • All the components in the subharmonic tag for localization can be fabricated on-chip and if needed, while requiring a very reduced fabrication complexity.
  • The device can also rely on cheap printed substrates commonly used in the assemble of any printed circuit board today.


  • Indoor Localization
  • Indoor Navigation
  • Wireless Sensing
  • Radio-frequency identification
  • Internet-of-things devices


Seeking licensee and/or industry partner.

IP Status
  • Provisional patent
  • Development partner
  • Commercial partner
  • Licensing