Antenna simulation boosts Bluetooth performance

Simulation saves two to three months of development time compared with the time that would have been required to build and test physical prototypes.

Johnson Controls has improved the range of a version of its BlueConnect hands-free system by simulating the antenna with Flomerics' 3D electromagnetic simulation software.

Based on the simulation results, Johnson Controls engineers modified the initial design.

"We estimate that simulation saved us about two to three months of development time compared with the time that would have been required to build and test physical prototypes", says Scott Mee, EMC Engineering Manager for Johnson Controls, Holland, Michigan.

BlueConnect by Johnson Controls is the leading Bluetooth hands-free system and is available as a factory installed standard or optional feature in many vehicles.

BlueConnect uses a planar inverted-F antenna which is fixed on a printed circuit board (PCB) and has rectangular shaped radiation and grounding elements.

JCI engineers recently designed custom versions of BlueConnect to be installed by a major automobile manufacturer.

The traditional approach to designing the antenna would have used a trial-and-error process consisting of building a series of prototypes and testing their performance while iterating to an optimised design.

"With proper correlation between simulation and physical test results, computer simulation can evaluate new design concepts in much less time and can provide very detailed diagnostic information that can be used to improve the performance", Mee says.

Johnson Controls uses Flomerics' Flo/EMC 3D electromagnetic simulation software, which shares the same technology engine as Flomerics' MicroStripes software.

MicroStripes and Flo/EMC provide an advanced analysis environment for simulating electromagnetic interactions in and around electronic equipment for the purpose of generating quick solutions to tough design problems.

The initial results from Flomerics' Flo/EMC 3D electromagnetic simulation software showed that the initial inverted-F antenna performance was influenced by several design parameters including area fills, vias and the antenna structure itself.

After simulating about a dozen design options, JCI engineers found one that matched the performance expectations of the increased range.

Mee and the design team adjusted the dimensions of the antenna as well as many of the connections to vias and area fills until the phase of the voltage and current were both centred on the Bluetooth frequency band.

Then he ran a cylinder scan to evaluate the radiation pattern and range of the updated design.

These results showed improvements in both gain and directivity.

When the simulation results indicated that he and the team had achieved an optimised design, they order the second prototype.

As Mee had expected, the physical testing results of the antenna performance metrics was closely correlated to the simulation results.

"This Bluetooth antenna example is typical of the time savings that we achieve on a periodic basis by simulating designs prior to building prototypes", Mee says.

"Using traditional methods we would have probably built and tested between six and 10 prototypes, which may have taken four months to complete".

"Instead we quickly identified the area fills, vias, and antenna structures that could have been optimised in the design through the use of the 3D electromagnetic engineering solution".

"Instead of four months, the project was completed with the final design updated in less than two months".

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