BROADCASTING Sound transmitters Exciter R&S ® SU800 Digital FM exciter – compact and versatile The new Exciter R&S ® SU800* State-of-the-art technology The exciter provides a built-in AES/EBU in only one height unit interface for direct input of digital audio combines the excellent specifica- data and thus makes full use of the The Exciter R&S ® SU800 (FIG ) is a com- advantages offered by digital signal pro- tions of the best analog exciters with ponent of the new VHF FM Transmitter cessing. This feature eliminates all ana- Family R&S ® NR800 [1]. All signal pro- log interferences from the studio up to the reliability of modern digital signal cessing including frequency modulation the output of the frequency modulator. is performed digitally. By using power- processing. Thus, it is very compact ful digital technology and state-of-the- You can switch the signal feed from ana- art D/A converters, this exciter meets log to digital at any time. Analog audio and occupies only one height unit in a the high requirements for spurious and signals can be applied in parallel, either spectrum masks. as AF (left / right) or as multiplex (MPX) rack. It provides an integrated digital signals. You can connect two of the The R&S ® SU800 is very compact – input three possible signal feeds simultane- AES/EBU interface as standard. interface, digital signal processing, RF ously; this allows you to easily switch to section, control and power supply are all standby feed from a remote location. integrated on one board. Input interface Analog (left / right) and digital audio sig- nals (AES/EBU) are applied separately (FIG 1). Additionally, you can supply an MPX signal which has been generated in an external stereo coder. FIG 1 Block diagram of the Exciter R&S ® SU800. The input interface provides three ana- log inputs for RDS, SCA and DARC sig- Ethernet CCU nals. The R&S ® SU800 digitizes these Data Control Ethernet local signals and adds them to the inter- TX RDS nal MPX signal. It decodes the AES sig- nal and converts it into a constant sam- pling rate. This allows you to process SCA Digital signal processing RF section input data at different sampling rates up Frequency ¤ Upconverter to 19 kHz and to eliminate jitter effects DARC modulator simultaneously. Audio RF RF monitor To suppress interference, all incoming MPX analog data input signals are first routed Digital Stereo coder via analog lowpass filters, their level audio Synthesizer External Analog Reference adjusted, and then separately digitized Pilot AES Input Power supply 12 V * The development of this innovative product interface was co-financed by the European Union. 54 News from Rohde & Schwarz Number 187 (005/III) 44315/1 FIG 2 The new Exciter R&S ® SU800 occupies only one height unit: input interface, digital signal processing, RF section, control and power supply are all integrated on one board. and fed to the digital signal processing RF section and operation significantly. During oper- system. Digitization is handled by high- ation, for example, the exciter is config- quality A/D converters – with 4-bit res- The RF section converts the digital sig- ured and monitored by the Control Unit olution for analog audio signals and with nal into an analog signal by means of a R&S NetCCU ® 800 via the Ethernet inter- 16-bit resolution for MPX and additional fast 16-bit D/A converter. The signal is face on the rear panel. data. You can define a specific level for then filtered – to meet the requirements nominal deviation for each input. for spurious and spectrum masks – and If the control unit is not available, you converted to the output frequency. The can also operate the exciter from a local selected switching concept allows fre- PC via the Ethernet interface on the Digital signal processing quency switching without adjustments. front panel. To do this, you simply need to open the web browser and estab- The fully digital signal processing func- The synthesizer provides all necessary lish a connection to the exciter. No spe- tion, which is handled by a powerful clock and mixer frequencies. If you need cial operation software is needed since a field programmable gate array (FPGA), exceptionally good frequency stability, web server providing all necessary func- ensures a consistently high level of sig- the exciter allows you to synchronize the tions runs on the exciter. nal quality, free from random sources of internal clock to an external reference Jan Gulde error such as temperature fluctuations or (10 MHz or 1 pps). quality variations of the component. Due to the consistent use of digital technol- ogy, the entire module needs virtually no Control adjustment. A powerful microcontroller configures The digitized audio signals are routed via and monitors the R&S ® SU800. It ini- a lowpass, and a bandpass suppresses tializes the hardware from a compact More information and data sheet interfering signal components outside flash memory that contains the com- at www.rohde-schwarz.com the data signal spectrum. The internal plete software and firmware as well as (search term: SU800) stereo coder processes the filtered audio all settings. signals to yield a standard-conforming REFERENCES MPX signal. For stereo signals, you can The R&S ® SU800 concept is based on the [1] Family of VHF FM Transmitters set the level of the pilot tone. The digital R&S ® Nx8000 transmitter platform and is R&S ® NR800: Compact, air-cooled transmitters for .5 kW to 30 kW. News MPX signal is used for frequency mod- also used in the TV Exciter R&S ® Sx800 from Rohde & Schwarz (005) No. 186, ulation of a high-precision direct digital []. Important control features are thus pp 44–45 synthesizer (DDS). uniform, which simplifies maintenance [] Exciter R&S ® Sx800: Multistandard exciter for ATV and DTV. News from Rohde & Schwarz (005) No. 186, pp 41–43 55 News from Rohde & Schwarz Number 187 (005/III).