Feature: Communications design
The impedance-matched balun filter is designed to
For the next generation of low-cost, battery-operated, wireless IoT products, the goal is to offer exceptional RF signal range and stability, with reduced power consumption in a miniaturised package
For the LoRa platform specifically, the ability to integrate
all the RF components into a much smaller, low-profile package would also increase the chipset’s attractiveness for IoT products. Without this option, OEMs would have to design the entire capacitor/inductor scheme and mount many separate components on the PCB. “OEMs now have the option to use the integrated
solution as opposed to inductor and capacitor discrete solutions. Using a Johanson integrated passive device, or IPD, makes the final PCB size smaller and simpler,” said Carmona. “Also, any changes in the geometry of the layout can affect 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 their differential, two-pin input/output configuration to connect with the single-ended antenna. “For many chipsets the output is usually not matched to
50 ohms, which requires an impedance-matching network that must be designed to avoid loss of power signal, reduced battery life and decreased signal range,” said Carmona.
IPDs 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 co-fired ceramic (LTCC) technology that allows the passive components to be layered, IPDs deliver the same functionality as 10-40 individual RF components. With this approach, the entire front-end between chipset and antenna is manufactured in a single, ultra-low-profile package that is 40% smaller than the same circuit made of discrete components. With this device, which combines an impedance-matching network, a balun and a filter, the entire front-end RF circuitry is reduced to a single EIA 0805 (2.0mm x 1.25mm) SMT component.
operate within the license-free 868MHz RF band used in Europe and the 915MHz band for Australia and the Americas. The product pairs seamlessly with Semtech’s LoRa and LoRa Smart Home RF transceivers SX1261, SX1262 and LLCC68. “The IPD is a plug-and-play solution for OEMs using
the Semtech LoRa chipsets,” said Carmona. “By working with leading manufacturers, we complete all the R&D, and ensure it is optimised for a specific chip. It will also comply with any FCC and ETSI regulatory emissions requirements.” IPDs are also very reliable. By creating a circuit
within a small LTCC package, variability and potential points of failure are all but eliminated when compared to mounting many discrete components. “We have to guarantee that the performance of this
much smaller solution is equal to or better than its discrete components equivalent. So, each integrated package is 100% RF tested,” says Carmona. According to Carmona, Johanson Technology’s
background in material development is key to its ability to create the entire circuit in such a small package. The product uses a novel, proprietary ceramic material in an LTCC manufacturing process, designed to improve performance up to high-Q levels.
A specific process Manufacturing IPDs is similar to the technology used to create multi-layer SMD component parts, such as capacitors and inductors. However, LTCC manufacturing allows the circuits to be embedded in as many as 40 separate layers in a three-dimensional package, which is still very low-profile. “We are a materials company first and foremost,
constantly developing new materials that will better integrate circuits, reduce power consumption and eliminate power loss,” said Carmona. Because IPDs require much less board space, IoT
devices with RF circuitry can be designed in much smaller formats. “With PCB real estate at a prime, the size and
placement of the passive components are critical, because, as everything gets smaller, it becomes increasingly difficult to place more components on the board. Therefore, design engineers are looking to components manufacturers to deliver miniaturised solutions that occupy less and less board space,” adds Carmona. Beyond size, a smaller PCB also impacts the
aesthetics of a product, allowing for slim, low profiles. The elimination of components by a factor of ten or more also reduces the overall weight of devices, even if the saving is measured in tenths of grams.
www.electronicsworld.co.uk November 2021 29
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