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3D Modeling and the Zen of Antenna Design

Mon Apr 4, 2016

We have all heard about the digital revolution, and how analog technology is old school, something handled by old guys with gravy-stained ties and probably not much hair. But as so much of our digital devices have moved to wireless communication, analog design lives on in the form of antenna design. Some of the greatest challenges in designing digital products come in the form of designing the antenna.

How Hard Can it be?

Take a smartphone for example. It must be capable of transmitting voice and data over an analog (RF) signal to/from a base station over multiple frequencies. But we use our phones for more than just making phone calls. Now we want to also navigate using our phones, so add GPS signals to the mix. Oh, and we need WiFi, Bluetooth and NFC so we can pay for our latte with our phone.

So now the antenna or RF engineer has to design one or two antennas to handle all of these frequencies. However, he can’t just stick an antenna on the side of the phone like in the early days. It now has to all fit within the space available in the phone.

And with the coming 5G standard and beamforming, combined with the desire to pack more functionality into a smaller space, the job is going to only grow more complex.

A Day in the Life of an RF Engineer

Generally, the digital engineer doesn’t care how big the phone is, or rather, how big the phone is determines the limits of how much silicon can be packed inside. But once that determination has been made, the digital engineer goes about his business, more or less unaware of the package his solution is going into.

For the RF engineer, the size of the box, the space available, and what is in the box are all hugely important — all impact the performance of the antenna.

The RF engineer starts with an ideal antenna design for the desired radio bands, or maybe even a previous design from an earlier phone. Initial RF simulations are performed to ensure that initially, the antenna meets the new electrical design criteria. Using parametric modeling and an automated optimization strategy, the design can be refined to meet target performance criteria.

Once the initial package design is completed by the mechanical team, the RF engineer imports the 3D modeling files into the RF design tool. But the data needed by the RF engineer is incomplete. Not only is the RF engineer concerned about the space available for the one or more needed antennas, but also about all the other materials that can affect antenna performance — materials that can absorb and reflect RF signals: screws, device packaging, the circuit board, etc. Armed with this material data, the RF engineer needs to enter the electrical material parameters for each of these structures.

The next step in the process is to run a simulation for determining the RF performance of the antenna. But in order to reduce the simulation time, the engineer needs to eliminate inconsequential parts to reduce simulation time. By refining the meshing properties and priorities around important regions, the skilled RF engineer can ensure a higher level of accuracy in the analysis.

Often, just as the RF engineer is converging on a design that meets the design goals, the other product design teams will provide an updated CAD database. Because these teams are working simultaneously, the RF design tool needs to have the ability to merge changes from an updated model without losing any of the simulation setup work.

The Burden on the Tool

This design process imposes two major requirements on the RF design tool. The tool must be able to:

  • Read and display the design’s product structure to facilitate communication between teams.
  • Import additional product manufacturing information (PMI) such as the construction material, any finishing data, etc.
  • Support persistent IDs, which allows the antenna engineer to import a new package model while preserving all of the modifications made regarding the material and meshing priorities.
  • Write any modifications back to the native CAD format to keep teams in sync.

These capabilities can greatly reduce the burden on the engineer.

So the next time you are talking on your smart phone, via your Bluetooth headset, while navigating to the nearest coffee shop, spare a moment to think how hard the RF engineer worked to make that all happen.

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