IEEE Solid-States Circuits Magazine - Fall 2023 - 37

Some wirelessly powered cage designs
have been specifically developed
to accommodate the standard rodent
cage, ensuring compatibility with the
standard rodent cage racks found in
animal facilities. One noteworthy example
is the EnerCage-HC system families,
which incorporate a resonance-based
multicoil inductive link [Figure 8(a)
and (b)] [15], [70]. These systems are
conveniently mountable on racks, enabling
researchers to operate multiple
EnerCage-HC systems simultaneously
within a single rack [71]. This not only
enhances the amount of data that can
be gathered from a particular experimental
section but also streamlines the
overall experimental procedure. In each
EnerCage-HC, a single Tx coil located at
the central bottom of the cage, in combination
with multiple Tx resonators
wrapping around the cage, enables reliable
WPT across the entire cage. The
Tx resonators are strategically angled,
providing increased resilience against
angular misalignments between the Tx
and Rx coils. For the design of the Tx
resonator geometries, it is essential to
consider their compatibility with the dimensions
of the standard-sized rodent
cage while maximizing their overlap
with the Tx coil.
However, this particular configuration
of the Tx coils exhibits a relatively
lower EM flux density and mutual
coupling, leading to a reduced PTE
in the central region of the cage, as
shown in the measured PTE distribution
within the cage [Figure 8(c)].
Moreover, as the size of the cage inPower
Supply
(5 V, 12 V)
Driver, BLE2
Headstage, BLE1
Headstage
Driver
PA
PCB I
+
PCB II
PC-GUI BLE Dongle (Master)
(a)
20
16
12
8
4
-12
-6
Avg PTE: 8.3%
11.3%
18.1%
26.6%
26.9%
Electrode
L31-L34
(b)
PTE: 6.7% - 10.1% PTE (%)
35
Z
6.1% - 14.9%
14.2% - 20.1%
23.6% - 33.3%
15.6% - 31.1%
X
6 12
22
11
(c)
FIGURE 8: The configuration of the resonance-based multicoil inductive link implemented in (a) the EnerCage-HC system and (b) the EnerCageHC2
system; adapted from [70] and [15], respectively. (c) Measured PTE distribution within the cage arena when the Rx is swept at heights of
4 cm, 8 cm, 12 cm, 16 cm, and 20 cm (adapted from [15]). BLE: Bluetooth Low Energy; Avg: average.
IEEE SOLID-STATE CIRCUITS MAGAZINE
FALL 2023
37
Y
-11
-22
30
25
20
15
10
5
L4
=
L1
Variable Cap.
creases, the uneven distribution of
the PTE becomes more prominent.
Consequently, the scalability of the
EnerCage-HC system is limited compared
to the modular designs that can
adapt to various cage sizes.
Considering that the inductive link is
already built for WPT, it is desired to reuse
the same inductive link for wireless
data transmission. This eliminates the
need for a separate data coil or antenna,
facilitating IMD device miniaturization.
The IMD typically monitors a variety
of biomedical signals obtained from
sensors or electrodes. To collect data
and control the device, it is necessary to
establish a wireless data transmission
between the IMD and the end user, such
as a phone, laptop, or desktop. When
implementing data communication
L21-L25
Z Axis
Y Axis
X Axis
20 mm
22 mm
11 mm

IEEE Solid-States Circuits Magazine - Fall 2023

Table of Contents for the Digital Edition of IEEE Solid-States Circuits Magazine - Fall 2023