Instrumentation & Measurement Magazine 26-3 - 24

project-training of doctoral students " of the Croatian Science
Foundation funded by the European Union from the European
Social Fund.
Fig. 7. Schematic of the wake-up detectors presented in [13] and [14].
The onset of an acoustic wave or acceleration of interest opens and closes
the MEMS switches, thus defining the state of the output wake-up signal.
The number of utilized switches varies with the application and detection
complexity.
Conclusion and Future Challenges
This paper presents a review of energy autonomous wake-up
detectors that achieve their autonomy by utilizing a combination
of energy harvesting and ultra-low-power detection.
Energy autonomous detectors have been achieved with multiple
sensor modalities, from acoustic, vibration, optical,
magnetic to chemical and temperature sensors. The mechanical
power-gating wake-up detectors were shown to be the
simplest detectors, characterized by relatively complex transducer
design coupled with an electromechanical switch. The
electronic power-gating detectors utilized a simple signal conditioning
chain and electronic switch driven by an energy
harvester. The thresholded harvester detector subgroup was
characterized by their somewhat complex harvester design,
featuring a threshold which determined its mode of operation.
Additionally, the electronic design complexity of this group
of detectors was comparable or higher than that of the powergating
groups. The electromechanical signal processing
detector had the most complex electronic design and implemented
a somewhat more sophisticated (and potentially more
accurate) method of detection.
Regardless of their subgroup, these autonomous wake-up
detectors present a fundamental achievement in continuous
event detection and allow the design of autonomous sensor
nodes that will be able to operate with no need for interventions
or maintenance, allowing non-invasive long-term study
and preservation of our surroundings. However, despite the
promises the autonomous detector concept shows, as seen
from the state-of-the-art, this concept is still relatively novel,
which means it has numerous challenges ahead. The microand
nano-electromechanical parts used in these detectors
must be characterized in detail, with special emphasis on their
robustness. The production costs of these detectors must be
lowered to allow their practical use. Seamless integration of
this concept with other dominant technologies must also be
achieved. Seeing the amount of recently published research
on this concept, satisfactory solutions are quickly expected to
overcome all these challenges and allow autonomous wake-up
detectors to achieve a wider application field and an even more
prominent position in the basis of event detection.
Acknowledgment
The work of the doctoral student Marko Gazivoda has been
supported by the " Young researchers' career development
24
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Marko Gazivoda (S'17) (marko.gazivoda@fer.hr) works as a
Senior Hardware Architect at a global IoT company called Intis
in Zagreb, Croatia. His research interests include energy
efficient sensors, detectors, interfaces and electronic systems.
IEEE Instrumentation & Measurement Magazine
May 2023
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