The navtec GmbH has developed a full
equalisation with automatic delay normalisation for a manufacturer of
broadcasting systems as a replacement for a conventional analog
The system was realised using a 80-MHz DSP. The technical
specifications can be found at the end of this page.
||As it is customary in digital
systems, the analog part and the digital part are strictly separated
each other. One can clearly make out the division between the analog
the digital part in the picture.
The analog part (above) consists of:
|The 100x160mm sized board with a DSP module for the digital equalisation system.||
(The board's layout was not realised by navtec GmbH.)
The problem with simultaneous broadcasting systems is to measure and compensate two or more unknown routes in their electrical characteristics (frequency, phase response and time delay behaviour). It is aimed to transmit a signal that is sent from a joint LF-source in such a way, that it will appear at the end of all routes with a marginal group delay difference error, in order to transmit it contemporaneously.
The presented system performs the measurement and compensation tasks automatically. To achieve this, suitable test signals are generated, transmitted and evaluated. After that suitable compensation filters and delay elements are calculated and applied on the signals.
The system can be scaled. This means, that up to 15 (full duplex) routes can be compensated against each other. The DSP on the respective modules are cross-linked for data exchange.
|DSP-clock and instruction rate||78,75 MHz / 39,37 MIPS|
|sample rates||8,5 kHz und 25,6 kHz (Mixed-Rate)|
|Memory||32 k - Worte|
|Memory for data retention||8 kByte|
|Number of channels||2 - 15|
|Maximum group delay between channels||20 ms|
|Maximum group delay error after equalisation||< 39 * 10 -6 s|
|Amount of frequency response equalisation||> 24 dB|
|Amount frequency response error (ripple)||< 1 dB|
|group delay distortion (300 Hz ... 3 kHz)||< 50 * 10 -6 s|
|Time reference for measurement||