Aerospace and Electronic Systems Magazine October 2017 - 15

A single SansEC sensor is an open-circuit self-resonating coil
having a unique electromagnetic signature comprising of a response frequency, amplitude, bandwidth, and phase. The sensor
is wirelessly powered and interrogated by an oscillating magnetic
field. It is important to note that while the electromagnetic resonance theory is well established for traditional electromagnetic
resonators such as resonant cavity and inductance-capacitanceresistance resonant circuits [13]-[16], the SansEC open-circuit
resonator represents an emerging technology with several unique
features and applications.
In this article, a pair of SansEC sensors are mounted on the
highly flexible wings of a model aircraft. The model is tested on a
static bench and in a wind tunnel, and the relationship between the
wing deflection and the sensor's frequency response is investigated.

PRINCIPLES OF OPERATION OF THE SANSEC SENSOR
In this section, the basic operating principles of the SansEC sensor are first discussed. This is followed by a discussion of how a
"floating electrode" system was incorporated into the basic SansEC sensor as a means towards measuring bending displacements.

the electrons are uniformly distributed along the conductive trace.
When an electromotive force is induced in this conductive trace, it
exhibits a resonating behavior, resulting in a nonuniform electron
density distribution along the trace. The current distribution along
the trace is sinusoidal with zero value at the two ends of the trace
[12].
At resonance, the electric and magnetic fields produced by the
sensor occupy the gaps in the conductive trace, as well as penetrate
into the space beyond the planar surface of the sensor. This electric and magnetic field response depends on the material's relative
permeability μr, relative permittivity εr, and electrical conductivity.
The SansEC sensing is manifested by a shift in the sensor's free
space resonant frequency, and this shift is associated with localized changes in its electric and magnetic fields as a consequence of
the sensor's deformation and/or changes in its environment. This
frequency shift can be correlated with the magnitude of change in
the physical property being sensed.
A laboratory-level system design for SansEC sensing is illustrated in Figure 2. This figure shows a radio-frequency network
analyzer interrogating the sensor with a near-field loop antenna.
This network analyzer generates electromagnetic waves across a
broadband frequency range. These waves reach the sensor via a

BASIC OPERATING PRINCIPLES
The SansEC sensor is made of copper
and comprises of a pattern of electrically conductive material, as shown
in Figures 1 and 2. When the material is exposed to an externally generated magnetic field, an electromotive
force is induced within the pattern.
This makes the sensor electrically active, and it then responds with its own
electric and magnetic fields. The information contained within these reciprocated electric/magnetic fields can then
be used to make inferences about the
phenomena that the SansEC is being
used to measure.
The electro-dynamic process within the SansEC is governed by Maxwell's equations. Prior to excitation,
OCTOBER 2017

Figure 2.

Laboratory-scale SansEC sensor interrogation.

IEEE A&E SYSTEMS MAGAZINE

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine October 2017