Medical Design Briefs - February 2021 - 27

tivity for a variety of IoT applications,
including next-generation " smart " medical devices.
To accomplish this PCB effective-area
reduction task, chipset manufacturers
like Semtech create reference designs -
technical blueprints of a system - that
third parties can adapt and modify as
required for their products' applications.
The reference design serves as proof
of the platform concept and is usually
targeted for specific uses. The goal is to
fast-track products to market by using
Johanson's front-end solutions, thereby
reducing risk in the OEM's integration
project.
" The starting point is the chipset, but
the chipset requires specific RF circuitry
to connect to the antenna, " explains
Manuel Carmona of Johanson Technology, a developer of high-frequency
ceramic components, including chip
antennas, integrated filters/baluns,
High Q capacitors, and EMI chip filters.
For the LoRa® platform, specifically,
the ability to integrate all of the RF components into a much smaller, low-profile
package would only increase the attractiveness of the chipset for miniaturized,
battery-powered IoMT products. Without
this option, medical OEM's would have to
design the entire capacitor/inductor
scheme and mount many separate components onto the printed circuit board.
" Medical OEMs now have the option
to utilize the integrated solution as
opposed to the inductor and capacitor
discrete solution. Using a Johanson integrated passive device (IPD) makes the
final PCB size smaller and simpler, "
explains Carmona. " Also, any changes in
the geometry of the layout can affect the
output performance, battery life and signal range. "
In this case, the RF circuitry required is
used to convert the signal from differential to single-ended in a specific impedance ratio using an impedance matching
network and a balun. Most chipsets
require this type of conversion due to the
differential, two pin input/output configuration to connect with the single-ended
antenna.
" For many chipsets, the output straight
out of the chipset is usually not matched
to 50 , which requires one to have an
impedance matching network that must
be designed in order to avoid loss of
power signal, reduced battery life, and
decreased signal range, " says Carmona.
To meet the requirements, Johanson
Technology collaborated with Semtech

to develop an IPD that serves as an
impedance-matched-balun-filter.
Manufactured using low-temperature
cofired ceramic (LTCC) technology that
allows the passive components to be layered three-dimensionally, IPDs deliver
the same functionality as 10-40 individual RF components. With this approach,
the entire front end between the chipset
and the antenna is manufactured in a
single, ultra-low-profile package that is
less than 40 percent the total size of the

same circuit comprised of discrete components.
With this device, which combines an
impedance matching network, balun,
and a filter, the entire front-end RF circuitry is reduced to a single EIA 0805
(2.0 × 1.25 mm) SMT component. The
impedance-matched balun-filter is designed to operate within the license-free
868 MHz RF band used in Europe and
the 915 MHz band in Australia and the
Americas. The product pairs seamlessly

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Medical Design Briefs, February 2021

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Medical Design Briefs - February 2021

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