Tech Briefs
RF testing facility

Ford Taurus on the turntable inside Johnson Control's new RF testing facility.

Automotive interiors supplier Johnson Controls has opened a state-of-the-art radio frequency (RF) testing facility. The new facility — located at the company's interiors technical center in Holland, MI — represents a million dollar investment toward advancing the testing of RF signals emitted from electronic products in automobiles.

The 297-m² (3200-ft²) facility allows Johnson Controls to maximize the performance of its current electronic RF products such as the HomeLink Universal Transceiver and PSI (Pressure Safety Information), which uses RF technology to transmit real-time tire pressure data, while designing new and improved electronic products for future automobile interiors. Construction on the facility was completed last August. The facility was certified by the Federal Communications Commission (FCC) in December.

"This facility was a year in the making," said Jim Geschke, Vice President of Electronics Integration for Johnson Controls. "We spent 6 months benchmarking the best RF test facilities in North America and then worked to develop a facility that would provide us, and our customers, with the best value and performance."

The traditional arena of RF testing sends engineers out into a field to test a product. Variation in ground-moisture saturation can skew results, making repeatable measurements difficult. Adverse weather conditions can postpone or hamper testing.

"Previously, weather and technician stamina had to be taken into account when scheduling tests," Geschke said. "With a dedicated, secure, all-weather RF test site we now have the ability to conduct accurate, repeatable testing year-round regardless of the environmental conditions."

Every motor vehicle utilizing RF products must meet FCC requirements and be certified to part 15 of FCC regulations covering RF devices by measuring the RF power received at a distance of 10 m (32.9 ft) from a vehicle. The new RF test facility accommodates "range" testing to a distance of 100 m (328 ft). Engineers can conduct FCC required testing at 3, 10, and 30 m (9.8, 32.9, and 98.4 ft).

In the past, FCC certification was performed at the module level prior to installation inside of the vehicle. Engineers can now place an entire vehicle upon a rotating 360° turntable and measure the RF signal at 36 points around the vehicle. The control center allows engineers to control turntable position, antenna polarization, and height from 1 to 4 m (3.3 to 13.1 ft), for compilation, documentation, and reporting of test data. The measurements are taken every 6 m (20 ft) starting at 60 m (200 ft).

"Being able to test how the product performs once integrated into the interior of the automobile is a critical factor," Geschke said. "We can now take into account the vehicle's characteristics and interfering factors such as vehicle metal and wire harnesses in order to optimize the performance of our RF products while meeting FCC certification."

Developed in-house, the RF test site contains no metal, which could interfere with testing. From the ground-plane up, fasteners consist of composite materials, fiberglass bolts, and plastic rivets. The rounded roof is made of rubber and attached without screws. All door handles in the building are non-metallic and custom made. A wire mesh ground surface acts as a mirror to the RF signals and includes a snow-melt system for testing year round. With a reflecting ground, and no other reflections, the combination of incident and reflected signals remains consistent.

Geschke added that the advanced RF test site and enclosed building provides for a safer and secure environment for testing. "We can pull future model year vehicles into the facility and ensure that we are getting the maximum electronics performance out of our product as it interacts with that vehicle."

Jean L. Broge