XM Satellite Radio

XM2Go XM Portable Satellite Radios

Sarantel's SkyTune antenna allowed us to improve the performance of XM2Go products while drastically shrinking their size.

Craig Wadin, VP - RF Systems
XM Satellite Radio

The Company

XM is America's number one satellite radio service with more than 6 million subscribers. Broadcasting live daily from studios in Washington, DC, New York City, the Country Music Hall of Fame in Nashville, Toronto, and Montreal, XM's lineup includes 160 digital channels of choice from coast to coast: the most commercial-free music channels, plus premier sports, talk, comedy, children's and entertainment programming; and 21 channels of the most advanced traffic and weather information.

XM was the first satellite radio company to offer portable satellite radio receivers with the introduction of the Delphi MyFi portable XM2Go radio in 2005.

The Products

Samsung's "Helix" and Pioneer's "Inno" are the 2nd generation of XM2Go portable radios, introduced at the International Consumer Electronics Show in Las Vegas, Nevada in January 2006. 60% smaller than previous generation portables, the Helix and Inno are the first products to bring together a complete satellite radio receiver and an MP3 player in one, small, portable product. Innovative features include the ability to "bookmark" songs heard on the radio, then purchase the songs from an XM + Napster account when connected to an on-line computer.

The Challenge

In order to improve upon the award-winning first generation of XM2Go portables, XM wanted to shrink the size of the radio while adding features and not compromising on performance. One of the more difficult challenges in doing this was maintaining antenna efficiency in a smaller device.

Conventional patch antennas resonate against a ground plane, which increases the apparent size of the antenna relative to the size of the device to which it is attached. As radio performance and size of antenna are linked, shrinking the size of the radio diminishes the performance of the antenna. Further, when the user grasps a portable radio, the user's hand absorbs near-field energy from the antenna, further decreasing its efficiency. This leads directly to impairments like audio dropout.

Sarantel's PowerHelix® antenna technology provided a possible solution for XM. PowerHelix antennas are balanced, and therefore do not require a ground plane. This means they are also isolated from the device, and maintain their efficiency regardless of the size of the device. They are also dielectrically loaded, which means that they give up very little efficiency to the user's hand when the radio is held.

The Solution

XM turned to Sarantel to develop an antenna for their next generation XM2Go devices based on the PowerHelix technology. The result was the SkyTune®-P 2.3GHz satellite radio antenna. Working with different dielectric materials, Sarantel was able to achieve near or better than isotropic gain over a broad bandwidth covering the XM spectrum, 2332.5 to 2345MHz. The SkyTune antenna is left-hand circularly polarized, but provides excellent performance in the terrestrial, vertically polarized portion of the XM band.

One of the chief benefits of the SkyTune antenna for the XM2Go application in addition to higher gain in the absence of a ground plane is the noise rejection characteristic of the antenna. Portable receivers packing a lot of functionality into a small physical space tend to generate a lot of common-mode noise. Conventional antennas channel that noise directly into the receiver chain. The SkyTune antenna however is isolated from that noise, and incapable of contributing to noise impairments in the receiver. That fact results in increased signal-to-noise in the radio, which could mean the difference between hearing a symphony or silence.

Their Comment

Sarantel and XM worked closely together to deliver a world-beating product. Craig Wadin, Vice President, RF Systems and Quality Assurance at XM said, "We are excited to add yet two more great products to our industry-leading portfolio. Sarantel enabled us to create the portable radio our customers wanted - small enough to go anywhere without compromising reception or sound quality. The SkyTune antenna even allowed us to improve the performance of XM2Go products while drastically shrinking their size, two things that don't usually go hand-in-hand. The SkyTune antenna is a major contributor to the success of the Inno and Helix."

Markets

US, Canada

Where To Buy

Available Spring 2006 from http://www.xmradio.com and leading electronics retailers who carry XM Satellite Radio Products.