At NAB 2004, Rohde&Schwarz presented its Broadcast Test System R&S SFU as a 'test transmitter for innovative TV standards'.
However, the name 'test transmitter' would be an understatement. At IBC 2004, R&S then brought all facts to light: the R&S SFU displayed its true colours as a comprehensive system for all test applications related to TV. This article takes a look at this future-oriented platform.
One of the instrument's most important functions was presented at NAB 2004 - the R&S SFU as a TV test transmitter. In this application, it knows neither geographical borders nor limits defined by standards. It supports the latest standards: DVB-H is already fully integrated with DVB-T, offering 4 K mode, an in-depth interleaver and signalling of the DVB-H options via TPS carrier. With this, MPE-FEC (IP error protection ahead of the IP in MPEG-2 encapsulation) ensures a very high degree of safety with mobile reception. Time slicing saves power when handhelds are used, because data is transmitted in short bursts. DVB-H technology allows video streaming to be implemented efficiently for portable and mobile reception with small devices and mobile phones.
For satellite operation, the DVB-S2 standard is available with the broadcast services application in the R&S SFU. DVB-S2 provides network operators with considerably more transmission capacity. The method is extremely robust and ensures reliable reception even with C/N ratios of -2 dB.
With DMB-T (TDS-OFDM), the R&S SFU is a step ahead of the standard. China is awaiting the introduction of a DTV standard and is already performing field tests. DMB-T provides high-quality digital TV in the living room, but also exhibits superior characteristics for mobile and portable reception and its spread-spectrum function supports power-saving reception for handhelds.
Several international standards - DVB-C, DVB-S, DVB-DSNG, ITU-T/J.83/B, ATSC/8VSB and ISDB-T - will soon be available in the R&S SFU. The nice thing about this is that these codings (and future standards) can be easily loaded as software options.
Comprehensive diversity
Since the R&S SFU provides space for numerous enhancements, it can fully replace a test system consisting of diverse single units. An internal test signal generator provides transport streams in the baseband. The generator allows high-bit-rate MPEG-2 transport streams to be replayed without interruption. MPEG-2 transport streams with IP content (encapsulated MPEG-4, H264) for DVB-H applications are also available.
The familiar options from the R&S SFQ predecessor, are available on the RF end. A channel (fading) simulator provides sophisticated capabilities for simulating multipath and mobile reception. Up to 40 paths with all known profiles such as pure Doppler, Rice, Rayleigh and constant phase, are possible. The simulator uses dynamic fading and fine delay to meet even special requirements. All parameters - such as attenuation, phase, delay and Doppler speed, frequency and direction - can be varied until reception is no longer possible.
A digital AWGN generator allows measurements with a precise C/N ratio, regardless of whether it involves a one-path signal or a multipath signal from the fading simulator.
A new characteristic is the simulation of phase noise. This signal is used in the lab to simulate real oscillators and synthesisers with non-ideal phase noise.
RF signals can be generated and added to the useful signal with the integrated ARB generator, allowing effects from the adjacent channel and in the channel to be simulated. This makes an additional RF generator unnecessary in many cases.
The BER measurements option tests the effect of noise, single interference signals and poor channel conditions on the receiver. Two different measurements are available. A measurement with pure PRB sequences can check the demodulation component of the receiver; this involves feeding the data and the associated clock of the receiving component back to the R&S SFU. The error rate of the decoding path can be measured by feeding the MPEG-2 transport stream back from the DUT to the R&S SFU. In this case, the test signal comprises an MPEG-2 TS that contains a PRBS as payload. If path measurements on a live MPEG-2 signal are desired, this is easy to do if the null packets contain a PRBS as payload.
Open - especially for the future
The R&S SFU's tightly-sealed housing counters interfering effects that often occur when a number of devices are coupled with each other by cable. In contrast, the system is absolutely open for all applications. One may use the internal MPEG-2 generator, but do not have to, since all conventional input interfaces - including ASI/SPI with and without stuffing functionality, and SMPTE 310M - are available - some redundantly. Without stuffing, the R&S SFU passes the input signal through transparently; with stuffing, the data rate is adjusted to match the necessary symbol rate.
The digital internal I/O signal is processed by the I/Q modulator. Externally, the I/Q signal is available for applications in both digital and analog form. Externally-coded signals can be fed in or special interference signals added at an analog and a digital I/Q input. The internal I/Q modulator's high modulation bandwidth of 200 MHz is designed for future applications and can be used to maximum advantage with the aid of the external wideband analog I/Q input.
The R&S SFU is also open for applications of the future. With its numerous interfaces and ARB generator, from which samples or symbols can be replayed, it is a good choice of tool for evaluating new or modifying pending standards.
The output signal of the R&S SFU is not limited to the RF signal of the modulator; it also supplies internal signals such as the MPEG-2 transport stream, the noise signal and the ARB signal.
The R&S SFU is future-proofed: A base unit with a coder can be the start, then, with only a few exceptions, all enhancements can be quickly and easily activated later by the user by means of a firmware update/licence code.
Multitalented universal instrument
The R&S SFU covers virtually all areas of digital TV: research and development, production, quality assurance, service, propagation and reception tests performed by the network operator and EMC measurements. Together with the R&S CMU200, it can handle transmission simulations for mobile communications, coupled with DVB-H reception.
Its digital signal processing in the baseband provides excellent signal quality in the frequency range from 100 kHz to 3 GHz and ensures exact measurements. A new type of digital level control ensures high-level accuracy. The repeatability of the test system attains a superior level of 0,05 dB even with modulated signals. The overall level uncertainty is less than 0,5 dB.
The optional power sensor can be used not only for power measurements on equipment but also for making precise measurements of the output power of the system itself. The inherent noise of its synthesizer is typically less than -135 dBc (1 Hz) at 1 GHz and 20 kHz offset, and ensures the lowest modulation error in the near-carrier range.
Many other advantages make the system also ideal for use in development: wide variation range of all parameters; standard coder functions that can be switched off; signal impairment capabilities in the modulator; carrier manipulation in the RF range; noise generator; fading; interferer; external I/Q inputs and outputs.
A high output level is required in the development of TV equipment and in production; the R&S SFU supplies +13 dBm. The high power and overvoltage protection option permits +19 dBm for production lines or distribution networks, and up to +26 dBm in the over-range. The wear- and maintenance-free electronic attenuator, which ensures fast switching and a long life under all conditions, is specially designed for production. For chip tests, the level can be reduced to -120 dBm.
Responsive
The R&S SFU has an aesthetically-pleasing design and is user-friendly. Operation is based on Windows XP together with a finely-structured directory tree. The high-resolution colour display shows all information of the selected application, and applications still run in the background. If one of these applications has problems, this is indicated in the selected screen. Hardkeys provide direct access, soft-keys are used to operate the selected application, and the rotary knob allows all parameters to be quickly set. A keyboard and mouse can be used via the USB connectors. Settings that are frequently needed can be grouped together in the 'Favourites' menu, allowing quick access via the home key. If something is unclear, a help key opens a context-sensitive menu that contains the operating manual.
Settings do not have to be made directly on the R&S SFU as it can be fully-operated from any PC - either directly via an Ethernet connection or by remote control within a LAN via IP. This is easy to do using the pre-installed Remote Desktop software or the VNC software. The R&S SFU is also preconfigured with the DHCP; and is automatically assigned an IP address. The instrument can be integrated into existing test systems via an IEC/IEEE bus.
Conclusion
Have all the facts been put on the table? For now, yes. But as far as the future is concerned, no. This article shows in detail that even today, the R&S SFU is more than a mere successor to the proven R&S SFQ. For the future, Rohde&Schwarz is already working on a series of enhancements.
This modular platform is designed with sufficient capacity for challenges that are still unknown today, so stay tuned for further innovations to the Broadcast Test System R&S SFU.
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