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For the next generation of low-cost, battery operated, wireless IoT products, the design goal is to provide exceptional RF signal range and stability, while also reducing power consumption, in a miniaturized package. As a result, leading RF chipset and component manufacturers are increasingly fine-tuning and improving their products to do just that.
According to Semtech’s web site, LoRa® and LoRaWAN® are already the “de facto technology for Internet of Things (IoT) networks worldwide” and will provide long-range connectivity for a variety of IoT applications including next generation “smart” everything – cities, homes, buildings, agriculture, metering, supply chain and logistics, and others.
To accomplish this PCB effective-area reduction task, leading 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 leader in 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 the RF components into a much smaller, low profile package would only increase the attractiveness of the chipset for miniaturized, battery powered IoT products. Without this option, OEM’s would have to design the entire capacitor/inductor scheme and mount many separate components onto the printed circuit board.
“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 or “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 ohms, 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 “3-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% 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 (2.0mm x 1.25mm) SMT component.