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Designing IoT Antennas that Make the Connection

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be handled with a single antenna or if it requires multiple antennas. In addition, the advanced antenna technologies used in some wireless standards, such as 4G's multiple- input, multiple-output (MIMO) technology, used to minimize the impact of interference from sur- rounding radio waves, can further complicate the design of IoT antennas. Typically, MIMO signals are typically handled by means of multiple antennas or a number of antenna resonant elements in an array pattern. Narrowband frequency cover- age for a single antenna may be sufficient for an IoT design meant to work within a single wireless band. For an IoT device designed to function across multiple wire- less standards, such factors as size and cost will help determine the optimum antenna solution. A single wideband or ultrawideband (UWB) antenna may provide the performance required for multiple wireless standards, including re- ception of GPS signals for precision location, while multiple more nar- rowband antennas may be needed to provide the performance needed for all bands. In some cases, even a single wireless standard may require multiple antennas. For example, an IoT device based on 3G can work with a single antenna while an IoT de- vice using 4G for internet access may need at least two antennas in support of that standard's MIMO technology. Antenna solutions for IoT devices must be small enough to be unobtru- sive. Many IoT devices are meant to be invisible, such as healthcare moni- toring units built into USB housings. Internal antennas for such devices must be small, typically with bandwidth optimized for 2.4-GHz WLAN/Wi-Fi use. Some IoT applica- tions are better served by an externally mounted antenna, such as an IoT device that must connect to an access point through a wall. An IoT device's housing can also influence an antenna's mount- ing point, with a plastic housing resulting in minimal loss for an internally mounted antenna while a metal housing and its shielding characteristics inviting the use of an external antenna. Sizing Up IoT Antennas No single antenna is a best fit for all wireless IoT devices. As noted, in some cases it makes more sense to locate an IoT antenna (or anten- nas) outside of a product's housing, and a simple monopole or dipole antenna may provide the frequen- cy and bandwidth needed to cover multiple wireless bands and stan- dards. But when an antenna must be mounted internally, and size is a concern, a number of miniature antenna types are candidates for single- or multiple-band frequency coverage. These include wire an- tennas, whip antennas, chip anten- nas, printed-circuit-board (PCB) antennas, and integrated-circuit (IC) antennas. Each approach has advantages, disadvantages, and cost differences that may guide the choice of antenna for a particular IoT product design. How do the different miniature antennas for IoT devices compare? • Wire antennas are relatively simple and straightforward to design, as the name suggests, and they are capable of wide bandwidths using a single device. However, the physical size of a wire antenna is wavelength- dependent, meaning that, as wavelengths increase with de- creasing frequencies, the size of the antenna must also increase. Wire antennas are well suited for external placement with an IoT module, although they can also be mounted internally given adequate package size. In manu- facturing, it can be challenging to achieve good performance repeatability with wire antennas, making them a better match for lower-volume applications. • Whip antennas tend to be the most expensive and largest of the IoT antenna types, although they are capable of excellent perfor - mance. As with wire antennas, they typically require a coaxial cable, coaxial connector, and a co- axial launch to connect with IoT PCB-based transceiver circuitry, although the external antenna provides mounting flexibility when installing an IoT module. 2. By exporting data from AntSyn to an EM simulator, detailed 3D field studies can be performed on an antenna design. A Supplement to Microwaves & RF Sponsored by Cadence

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