High quality audio for low-power in-car portable applications

June 30, 2011 // By Henry Muyshondt , SMSC
Today’s sophisticated infotainment systems have the ability to deliver many different types of content to occupants of the car. The system itself can provide AM/FM radio, CD, DVD, MP3 and many other kinds of audio sources and the consumer can also bring his or her own content stored on a memory card or MP3 player.

All this content is networked together and different people in the car can choose to listen to different audio sources, whether through the car's speakers or through headphones that enable individualized enjoyment of the various programs available.

Wireless audio has been around for some time. You can put on a headset without having to be physically tethered to the audio source. However, for portable applications, there has always been a challenge to find a solution that is both low power and can also transmit full CD-quality audio.

There are two options to transmit audio wirelessly: infrared and radio frequencies (RF). Infrared has heretofore been the most widely used due to low cost and high fidelity. However, is severely limited by line of sight issues since there can be no obstruction between the sender and the receiver. It is also susceptible to the heat of the sun on the dashboard. Any heat source can be a source of infrared interference. RF is more versatile. Some solutions operate on the FM band, but that limits their audio quality. Most higher quality solutions operate in what is called the Industrial, Scientific and Medical band (ISM band), because it is largely unregulated and doesn't require specific licensing. There are rules for how much power can be radiated, and the like, so there are some compliance requirements, but a provider does not need to apply for licenses to get spectrum allocated.

Technologies such as WiFi and Bluetooth operate in this band. They can also be used to transmit wireless audio, but there are some issues in terms of battery life and coexistence when there are several devices operating in close proximity.

Kleer technology, from SMSC, was developed with a goal to consume only small amounts of power to optimize portable, battery-powered operation, and to use a very narrow band in order not to interfere with or be affected by other devices in the ISM band.

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