FROM EDN EUROPE: Multi-standard software-defined-radio adds DRM format

DRM (Digital Radio Mondiale, www.drm.org) is a proposed standard for digital radio that enables broadcasters to reuse frequencies below 30 MHz as the conventional services there (AM, LW, and "Short Wave") are listened to by progressively smaller audiences. DRM uses compressed audio and QAM digital modulation to achieve robust transmission and reception with added service features. Broadcasters can achieve extended coverage—in some cases continent-wide—with the same power that previously covered a more limited area, or can cover the same geography with reduced power. They can also package multiple channels in the same spectrum allocation. A further attraction for operators is that broadcasters often only need a modest upgrade to their transmitters installations. Depending on the data rate and codec used, quality of "near-FM" standard is achieved. Many broadcasters are already experimenting with transmissions.

Now, RadioScape—which has for some time produced modules to receive DAB digital radio—has introduced the RS500 module that adds DRM to DAB (and FM/RDS, LW, MW and SW). It includes the same features as the earlier RS300 module, forming the core of a complete digital radio with pause, rewind and record to MMC memory card, plus full access to electronic programme guide data. DRM permits features such as frequency shifts, where the broadcaster moves the transmission between his allocated frequencies in the course of a day to cope with the variable nature of propagation below 30 MHz, with receivers enabled to track the channel shifts. RadioScape recently changed its profile to be a manufacturer of complete modules rather than a supplier of silicon and provider of licensed module designs.

RadioScape builds the module around the same Texas Instruments TMS320 DSP chip used in the earlier design, now coded TMS320DRM350 (which will also be available direct from TI).

RadioScape suggests a full-featured digital radio with DRM can now be marketed for around €250. Such a set will manage all of the sources of a particular station, offering the listener a selection of all possible sources of the programme material. Digital radio, according to RadioScape, will come to mean (in the territories where they are in use) the sum of DAB and DRM services. DRM is a permitted format in many regions of the world including the US, but so far is little used in the US, the main momentum in that market for digital radio having gone into satellite-based subscription services. RadioScape suggests that one area where it may gain a foothold is in the provision of local—city-wide, or even more local—services to special-interest or specific-language audiences. With DRM, these can be served with very low radiated power, and a high level of frequency reuse in geographical terms.

RadioScape, +44 20 7317 1969, www.radioscape.com.

Texas Instruments, www.ti.com.