COBHAM SOL4MTX Especificaciones descargar pdf (Pagina 4)

SOLO Central Receiver – COFDM Digital Video Products

For further information please contact +44 (0)1489 566 750

How does SOLO technology work?

The basic video source used in Cobham Surveillance products is your

current stock of cameras and lenses with a PAL or NTSC output. The

SOLO product range has been designed to make use of many common

connectors, user interfaces and mounting patterns found on your

analogue products, helping to minimise your investment in transitioning

to Cobham digital.

It’s helpful to think of the transmitter and receiver in three distinct

steps:

The ﬁrst step is the conversion of your analogue camera’s output •

to a digital, compressed signal consisting of “1s” and “0s”, your

digital data stream. Cobham has chosen to use the MPEG2 and

MPEG4 standard, which is mature and well deﬁned

The next step is to optionally encrypt the data using AES, and •

then modulate the data and prepare it for RF transmission.

COFDM utilises signiﬁcant redundancy, producing excellent results

in high-multipath environments

The data is duplicated many times during interleaving process. •

Because of the interleaving and redundancy the information is

presented in different carriers or even within different frames.

If one carrier is corrupted, it has little impact on video quality,

as the data is repeated on another carrier. This provides the

robustness in the system. Digital Signal Processing on the receive

side is able to recombine all this data into a single video stream.

In the SOLO product range, you have the option of narrowband

transmission at 1.25MHz or 2.5MHz channelisation, or wideband

transmission, at 6, 7, or 8MHz per channel.

In the narrowband configuration, approximately 400 carriers are used,

versus about 2000 in the wideband configuration. A major benefit of

using the 400 carriers, is that fewer carriers give you more power per

carrier, which extends the coverage area. 1.25MHz and 2.5MHz are

inherently lower noise due to a narrower bandwidth. Although fewer

carriers are more susceptible to multipath, this is negated by the full

time spatial maximum ratio combining technology that is used. The

second benefit simplifies the RF front end design where phase noise is

easier to manage.

In testing, the narrower channelisation is often found to be the best

mode of operation, in particular when transmitters are within close

proximity to each other.

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