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Designing IoT Antennas that Make the Connection

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• Chip antennas are formed by means of metallization on a ce- ramic substrate, such as low-tem- perature-cofired-ceramic (LTCC) substrate. These antennas can be made extremely small, and treated in IoT circuit assembly much like any surface-mount- technology (SMT) component. On the downside, they are lim- ited in bandwidth and efficiency, and sensitive to ground-plane variations. • PCB-based antennas, such as the patch antennas commonly used in mobile telephones, are capable of wideband frequency coverage and relatively low in cost, since they are formed by etching pat- terns on the same PCB that holds the IoT transceiver. However, a planar antenna can occupy a large area on a PCB and increase the size of an IoT module. • IC antennas are perhaps the smallest but most complex of the IoT antenna options, although such active antenna designs are capable of wide bandwidths and multiple wireless bands. They can be integrated with additional functionality, such as voltage regulation and temperature sens- ing for stable performance over wide temperature ranges. Like passive chip antennas, they can be mounted like SMT compo- nents on a PCB, although they require a power supply and the associated bias circuitry. IC an- tennas are ideal for high-volume applications, but fabricating such antennas, which requires time at a commercial semiconductor foundry, can be expensive. Antennas mounted internally in an IoT device, particularly PCB- type antennas, will contribute to that electromagnetic (EM) environ- ment and will impact the overall circuitry. While the performance of a PCB antenna alone can be known, that performance is never totally independent of an IoT's associated wireless transceiver circuitry, and the combined perfor- mance can vary from the measured performance levels of the separate circuit portions. For this reason, it is useful to take advantage of design help from proven antenna models and computer-aided-engineering (CAE) simulation software before committing to a prototype IoT circuit and antenna design. Such simulation software makes it pos - sible to change input parameters for different design scenarios to better understand the results of the parameters on antenna and IoT system performance. As an example, the software could be used to weigh the performance tradeoffs between a patch an - tenna fabricated on low-cost FR-4 circuit-board material versus a more expensive PCB mate- rial with more tightly controlled dielectric properties. AntSyn, a new synthesis software product offering from AWR provides design sup-port beyond standard simulation software. This cloud-based (avail- able online through any standard browser) software-as-a-service (SaaS) provides antenna design, synthesis, and an optimization tool that allows users to see the effects of their requirements on output antenna performance, for many different types of RF/microwave antennas. The flexible and easy-to- use software can design single- and multiple-band, broadband, patch, wire, horn, phased-array, even multi-function and dual-polariza- tion antennas. AntSyn uses powerful EM op- timization based on proprietary genetic algorithms to explore more design space and accelerate the early phases of the antenna design process (Fig. 1). The software fea- tures a browser-based interface with intuitive operation. It includes a diverse database of proven antenna design "seeds" with geometries that are effectively modified to meet the desired performance and size requirements entered by the user. If the user does not select an antenna template as a starting point for optimization, AntSyn will select antenna templates automatically based on the specifications entered. Performance requirements include frequency, bandwidth, impedance, antenna gain pattern, polarization, and return loss or voltage standing wave ratio (VSWR), in the form of a blank data sheet for each antenna design. Maximum antenna size can also be specified, along with some basic geometric layout parameters, which is very important for IoT devices. Once AntSyn is run, it provides completed designs, CAD files (e.g., STEP) that can be down - loaded, and simulated results in familiar formats, such as gain versus frequency and return loss versus frequency, for ease of comparison with measured results (when build - ing that prototype). For those who need further analysis, AntSyn can export design data to commercially available EM simulation software (Fig. 2). For higher-level simulations, AntSyn can export data to full-featured circuit/system simulation software tools such as Cadence® AWR® Design Environment, where EM simulations of an antenna design such as a PCB antenna can be combined with simulations of the active circuitry of an IoT module to gain insights into the interactions between the antenna and the IoT transceiver circuitry. Antennas are often one of the last components considered in the design of an IoT product, although the choice of antenna can have an impact on the size and perfor- mance of the IoT device. Fortu- nately, software design tools such as the AntSyn antenna synthesis and optimization tool provide designers with an efficient tool to quickly explore different antenna types, different layout/geometry choices, and design parameters prior to committing to a physical prototype. The software makes it possible to try different antenna types when searching for the best match for the target IoT system performance parameters and wire- less bandwidths. n A Supplement to Microwaves & RF Sponsored by Cadence

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