Component placement

It is recommended to categorize and prioritize connections between nRF9160 and application components according to how critical they are.

For nRF9160's performance, RF routings are the most critical due to the mandatory impedance control and noticeable impact that they have on the user experience. Power supply routings are also important, because insufficient power supply design causes nRF9160 to work improperly. In addition, the Subscriber Identity Module (SIM) and MIPI RF Front-End Control Interface (RFFE) interfaces are sensitive and should be prioritized in the layout work.

It is also recommended to categorize application components according to which ones can be adjacent to one another on the Printed Circuit Board (PCB). For example, sensitive antennas and noisy DC converters or LEDs should never be adjacent to each other on a PCB. Two antennas, such as Global Positioning System (GPS) and LTE, should never be adjacent to each other on a PCB because of the risk of mutual load effect between two nearby radiators. The load effect can noticeably deteriorate antenna efficiency and radiation pattern and have a major impact on the overall performance of the end product.

Some components, such as the LTE antenna and SIM holder, should be close to nRF9160 to minimize the negative impact of a long PCB routing, but not near each other. These components should not be too far from nRF9160, but their mutual distance should be maximized. It is recommended to place these components on the opposite sides of the PCB if possible.

Based on connections and component categorization, layout and component placement mockup can be started. Start the layout work from the most critical routings. Aim to have at least one dedicated PCB metal layer as a common ground plane for the entire PCB, keeping it as intact as possible. This metal layer also acts as the main thermal dissipation power relief path for nRF9160 and other active components on the application board.

A small form factor PCB sets constraints for component placement, especially for the antenna and its ground layer. Optimal placement for antennas is important and helps guarantee radiated performance and a good user experience for the end product. Therefore, it is recommended to estimate with 3D simulation tools the impact of different antenna locations and grounding on the PCB. Antenna design and simulation services are provided by various design houses globally.

Antenna vendors often provide design and measurement services, but typically they are meant only for their own products. If the end product includes antennas from more than one vendor, it is important to make sure that all antennas are verified to perform as expected simultaneously on a small form factor PCB or in the end product.