The Ultrasphere in-building wireless antenna

The Ultrasphere in-building wireless antenna

A 2006 Product of the Year Award winner, the Ultrasphere in-building wireless antenna from Laird Technologies (St. Louis, MO) owes its success to its small size—it can be hidden almost anywhere to providing a virtually invisible solution for many applications. But, it took several years and several iterations before the Ultrasphere of today was designed, and we asked the company to take us beyond the specs and give us an idea of how this unique device came to be.

Beginnings

The Ultrasphere was born out of an original concept called the Microsphere, a single-band antenna originally developed at 800 MHz. Market demands and customer requests prompted Randy Bancroft, an antenna engineer and technology fellow, to develop a dual-band antenna using Microsphere technology. Bancroft proposed the idea of an integrated diplexer circuit.

“I had read this incidental paper about this low-pass filter that was really simple; it was made of copper traces,” he said. “Then I thought, you know a diplexer is essentially a pair of back-to-back filters, but not low-pass filters.”

To protect the antenna without using a costly plastic or rubber molding, an engineering team worked with a coating supplier to develop a new spray process that improved quality and throughput in the manufacturing process. This process is still used today, over eight years since the first products were supplied.

Pushing ahead

In the last few years, the demand has grown for a product that could include Wi-Fi frequencies up to 2.5 GHz with all the other bands. To meet these needs, Bancroft invented some new techniques and pushed the technology even further, achieving the Ultrasphere.

Using advanced simulation and optimization techniques allowed Bancroft to increase the bandwidth of both the upper and lower frequency bands of the diplexer. The result was an antenna system that operates efficiently from below 800 to 2,500 MHz.

One area that was unusual was the soldering process used to attach the connector directly to the circuit board. Although all antennas are 100% RF tested before shipment, engineers needed to find a way to mechanically test the connector assembly without damaging the antenna.

“Edward Ward developed a unique torque test which ensures the mechanical reliability of the connector solder joint,” said Blaine Bateman, strategic business development director. “Using statistical analysis, test limits were established that ensure every part that ships will work in the field.”

Ralph Raiola