Most IoT products use wireless technologies to connect with the world. The type and number of wireless technologies used will impact the type and number of antennas needed. For example, 900MHz, 2.4GHz and 5GHz radios all may have different requirements for antenna design.
Module manufacturers often provide multiple options in this area, such as an on-board chip or ceramic antennas. They may also offer a wire (or “whip”) antenna, a “trace” antenna, or a “pin-out” so the manufacturer can add their own (either internal or external connector elsewhere on the circuit board).
In addition, manufacturers may offer U.FL (also called IPEX) connectors for external. In this case, the connection from the U.FL connector to the external antenna is accomplished with a short coaxial “pigtail” that has the mating U.FL connector on one end and the mating connector for the antenna on the other end. The costs of the pigtail and antenna are often overlooked but need to be included in a manufacturer’s BOM for their designs.
When selecting between internal and external antennas, designers must consider the material (metal, plastic, etc.) of the housing and the potential placement of the product within a home or business. If a product is placed behind a couch or under a desk, it may have difficulty getting a wireless signal from the nearest gateway, access point, or router. Metal housings almost always require an external antenna design because the metal in the housing greatly reduces the amount of radio frequencies getting in or out of the housing.
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