Itelco offers DAB exciter for Band III and L-Band including single board COFDM encoder and digital precorrector.
Our DAB exciter fully complies with ETSI "ETS 300 401" DAB specifications and supports all modes of DAB operation. The exciter has a very innovative and flexible design integrating all functions from channel coding to RF output. Particularly innovative is its single board COFDM encoder which represents the heart of the system. The DAB exciter has been entirely developed by Itelco.
The exciter receives an ETI (NI/NA) 2048 Kbps DAB ensemble from the multiplexer. The ensemble becomes demultiplexed by extracting all services which are then individually scrambled, error protected, and time interleaved. The protection level can be individually set in the multiplexer in order to define an appropriate protection for each service (sharing quality with bit rate). Afterwards the OFDM modulator generates the DAB signal which is then transposed to the desired radio frequency (up converter) and amplified to a 1 Wattrms RF signal in Band III or L-Band. The exciter can lock the local oscillator to an external reference or to a very stable internal reference (optionally a GPS).
The main features of the Itelco DAB exciter are:
Itelco design philosophy aims to reach a high level of modularity. All functions of the equipment are designed as plug-in cards such as our innovative single board COFDM encoder and internal GPS receiver. The user-friendly modular design allows easy access or replacement of any plug-in card and easy integration of future improvements.
Due to the innovative and simplified design the equipment offers:
A wise use of the latest technologies and the innovative and downsizing design of the plug-in cards, in particular the innovative single board COFDM encoder, have enabled us to reduce significantly the overall dimensions of the exciter. All functions from ETI (NI/NA) input to RF output are housed in just a single 19 inch 4HE frame.
The integration of the digital and RF stages in a single rack simplifies and improves the equipment. Signals and synchronisms are internally connected avoiding the use of external cables that can cause signal losses, emissions, and susceptivity to external electromagnetic fields.
Furthermore, setting and supervision are simplified by the possibility of using a single controller and a single RS232C.
Due to the single frame exciter transmitter configurations require smaller racks, reducing weight, saving space and consequently costs. For transmitters with passive exciter standby, the single rack exciter simplifies the system due to the straightforward interface between the supervisory system and the active and passive exciter.
Finally, equipment with a lower number of cards and components offers higher reliability - higher MTBF, reduced costs for spare parts, and lower power consumption.
Itelco DAB exciter achieves highest performance through sophisticated digital signal processing. The primary design features are:
- perfect I and Q mixers matching,
- no needfor D/A converters matching,
- perfect 90� rotation of the frequency reference for I and Q mixers,
- no thermal sensitivity of I and Q channels (filters, mixers, 90� phase rotation,...),
- perfect phase linearity of the whole conversion stage.
Itelco DAB exciter is designed to permit the integration of a digital precorrector which allows to compensate for non-linearity distortion effects of high power amplifiers and to obtain the maximum amplifier efficiency. A preplanned improvement is an adaptive system which allows to automatically modify the system characteristics according to the room temperature variations, power supply variations, power amplifiers aging, etc.
Our DAB exciter has been designed with extensive use of reprogrammable devices making the equipment easy to be reconfigured.
This allows adjusting the equipment according to:
Possible adjustments are used to: modify the peak level over the mean-power level ratio; use the exciter for digital television transmission; optimize the power amplifier module output power and the intermodulation; modify the inband-ripple and the out-of-band-rejection of the final spectrum to equalize the mask of the RF filter and combiner; and modify parameters like the guard interval or the null symbol for experimental purposes.
Thanks to the use of reprogrammable devices, modifications can be done without replacing any part. This avoids additional costs for different cards and service interruption.
It must be emphasized that no ASICs (Application Specific Integrated Circuits) are used but only off-the-shelf components from leading companies in the market. This results in reduced costs and easy availability of spare components.
Itelco design ensures effective self-diagnostic capability that means that each card is able to indicate its own fault status.
All plug-in cards are able to perform a test on-line (during the equipment operation) or a test on-request (off-line) for improved self-diagnostic.
The high modularity and effective self diagnostic capability result in shorter MTTR (Mean Time To Repair) in the event of a failure. Furthermore these minimize the requirement for staff training and reduce repair costs.
Itelco DAB exciter complies with the European Directive 891 336/EEC known as EMC compatibility.
This means that our exciter:
The microprocessor-based control unit makes supervision and monitoring clearer and more effective, makes operation easier, and improves remote control. A front-panel LED display provides the most important DAB and RF parameters, such as transmission mode, TII, delay, forwarded and reflected power, etc. Unattended operation is achieved through a standard remote control and monitoring interface (parallel and RS232).
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