FMeXtra™ Technical Information
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FM broadcasts are made up of several signals that are added together as shown below. Even though you can't hear most of them directly, some of these signals may already be familiar, such as the stereo pilot which, when present, often shows up as "ST" on the radio display. FMeXtra uses additional inaudible signals known as subcarriers, or more precisely, SCA signals. The amount of bandwidth available for FMeXtra's SCA signal depends upon the individual station's configuration - whether it is broadcasting mono audio or stereo audio, and whether or not there are already existing SCA signals. FMeXtra is designed to be flexible and to accommodate many possible configurations. In a typical stereo FM signal, FMeXtra can utilize the spectrum between 53kHz and 99kHz. This is enough bandwidth for over 4 AM signals! Unlike FMeXtra's signal, the hybrid mode IBOC signal is not part of the FM signal. IBOC signals are generated completely independently. FMeXtra is compatible with hybrid mode IBOC.

The FM spectrum has been underutilized for many years because digital communication technology was not advanced enough to embed a useful number of bits into the available space. The older RDS SCA signal contains only about 700 bits/second, which is a very low data rate, much slower than even early phone modems. By comparison, DRE's FMeXtra technology embeds up to 64,000 bits/second in stereo configurations. FMeXtra technology makes use of the most advanced communication theory principles known at the present time. The most powerful realization of FMeXtra occurs when the analog broadcast is mono audio as shown below.

In this configuration, FMeXtra can use all the bandwidth between 20kHz and 99kHz and can deliver over 128,000 bits/sec, more bits than a dedicated ISDN data line!
The bottom line is that FMeXtra turns underutilized spectrum into bits. How the bits are used is completely flexible and up to the broadcaster. By combining FMeXtra with advanced audio compression technology, such as aacPlus™ from Coding Technologies, Inc., it is possible to deliver multiple channels of high quality audio or lifelike surround sound. FMeXtra can also be used to deliver real-time video clips, telematics data, and many other services, limited only by the imagination of the broadcasters and the receiver's individual capabilities.

DRE believes the future of FM digital radio is the complete digitization of the stereo and SCA subcarrier signals, as shown above, with or without additional hybrid IBOC signals, while maintaining analog mono audio service indefinitely for compatibility with the hundreds of millions of existing FM radios worldwide.