SDR solves the Digital Radio Conundrum

With the advent of portable music players LTE connectivity and Internet radio, one may wonder “what is the point of the ubiquitous car radio?”  Due to our mobile, on-the-go culture, 41 percent of adult music listening is done in a moving vehicle, and more than half of that time is spent listening to broadcast radio.  As new cars replace existing vehicles, drivers and passengers are being introduced to a host of potential entertainment sources including radio services broadcasting digital music, talk, news and entertainment content (and often delivered in a cohesive user interface, as my colleague Brad Ballard wrote a few weeks back). What you may not be aware of is the fact that none of the broadcast radio standards are consistent around the globe.  Even AM and FM broadcasts are not consistent in the transmission frequencies or bandwidths used in different countries.  This presents a conundrum for vehicle manufactures wishing to sell vehicles across the globe.

The digital radio landscape further complicates the situation. In the US, parts of South America and South East Asia HD RadioTM   is available, which utilizes the AM and FM band infrastructure by overlaying digital content with the existing analog broadcast, further augmenting entertainment and data capabilities. Digital Audio Broadcast (DAB) radio, which started in Europe and has spread to other regions, utilizes the analog TV band and L-band frequency bands to provide multiple data and audio services from each locally transmitted signal. DAB operates in many modes with choices of audio decoders, and requires a very flexible receiver to decode the various services.  Finally, Digital Radio Mondiale (DRM) is emerging in countries with large geographic area and little infrastructure such as India, Russia and now Brazil. Since DRM utilizes lower frequency transmitters in the medium wave (AM) band and shortwave bands, each transmitter can cover large areas enabling a less expensive infrastructure. Like DAB, DRM operates in various modes requiring a flexible tuner and baseband decoder.

All of this global diversity poses a challenge to vehicle manufactures wanting to produce vehicles in one location then sell them in other countries.  The traditional approach was to ship manufactured vehicles to a country and swap out the radio head unit with a unique radio capable of operating in that specific country at port of entry. This approach results in logistics issues, impacts quality and includes increased obsolescence.

The preferred method is to design the receiver using a flexible RF tuner capable of receiving all of the necessary broadcast frequencies in conjunction with a software defined receiver (SDR) baseband processor. The SDR processor can be altered to receive any broadcast stream, in any mode simply by reprogramming the system memory for the specific broadcast type. It is even possible to design the radio to receive multiple broadcast modes depending on user selection.  The SDR approach also allows manufacturers to enable new radio features and new radio standards after the vehicle is in the customer’s hands by way of a software upgrade. 

The TI “Jacinto” family of automotive processors is the perfect device to use for SDR baseband processing. The powerful DSP processor on “Jacinto” is capable of decoding multiple digital radio streams and presenting the decoded audio and data to the infotainment application. Since the DSP is integrated on the application processor System-On-Chip (SoC), “Jacinto” provides a low cost mechanism for receiving any global radio standard, and a path to upgradeability as standards evolve.

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