Products

13. August 2015

Coax

4k - New resolution for the digital video world

What the new format brings and what challenges face coaxial cables and connectors as a result

For some years, the media landscape has been discussing the new digital video format 4k or UHD (Ultra HD) which is to replace the Full HD format widely used today. With the four times higher resolution and higher image frequency, the new format should offer a brilliant picture sharpness and greater colour depth. The definition for UHD was passed in 2014 by the Digital Video Broadcasting Consortium.

The designation 4k is based on the number of pixels: about 4,000 pixels in width. A distinction is made between 2 versions today:  QFHD (Quad Full HD) with 3840x2160 pixels and UHD-1, also known as 4k, with 4096x2160 pixels. The second version is usually used as cinema format.

Format Resolution Number of pixels Lines Clock Frequency Bandwidth
HD 1080 x 720 about 0,78 million Single-Link 1,5 GHz 1,5 Gb/s
Full HD 1920 x 1080 about 2,07 million Single-Link 3 GHz 3 Gb/s
QFHD 3840 x 2160 about 8,30 million Dual-Link 10,6 GHz 2 x 3 Gb/s
UHD-1 oder 4k 4096 x 2160 about 8,85 million Quad-Link 12 GHz 4 x 3 Gb/s

 

Transmission technology

Adapting infrastructure to the transmission of high data volumes is a great challenge for the technology. The transmission length of a cable depends on the bandwidth. The distance decreases with increasing bandwidth. Four lines, the so called Quad-Link, are required to transport the 4k bandwidth of 12 Gb/s over the same distance with the same cables as for HD with only 3 Gb/s. Chip manufacturers are also looking for solutions. After all, progress depends on the performance of the electronics – the chips cannot transmit the bandwidths of 12 Gb/s yet.

In order to be able to transmit this bandwidth nevertheless, the signal is split up by the appropriate electronics into 4 separate signals which are later reunited by one receiver. The aim is to be able to transmit the necessary data volumes over the single cable (Single-Link). The signal propagation speed can be increased among other things by reducing the permeability of the dielectric.

 

Plug connectors for HDTV and 4k

Telegärtner offers several alternatives for transferring large data volumes in the video range:

BNC HDTV

BNC HDTV

BNC HDTV plugs were specially adapted to the wave resistance of 75 Ohms and have excellent return loss values – up to 6 GHz typ. -30 dB. For the special requirements for the transmission of HDTV signals in professional applications such as studios, outside broadcasting vans or major events, the high quality "BNC EasyGrip HD³" series was developed.

Mini HD-BNC

Mini HD-BNC

The plug connections of the new "Mini HD-BNC" series are also much lighter than common standard BNCs in addition to the 4 times greater packing density.

The signal quality plays a decisive role for the choice of a plug connection. The new "Mini HD-BNC" exhibits good return loss values and therefore meets the requirements for common Serial Digital Interfaces (SDI).  By minimising the tolerance with regard to the impedance to 75 Ω, very good return loss values of up to 6 GHz could be achieved.

Mini HD-BNC: Return loss up to 6 GHz

Frequency Attenuation
1,000 GHz - 27,13 dB
2,000 GHz - 25,69 dB
3,000 GHz - 26,55 dB
4,000 GHz - 27,81 dB
5,000 GHz - 27,81 dB
6,000 GHz - 30,92 dB
   (typ.)

 

Thanks to these excellent transmission properties, the connector series can be used for the formats HD, Full HD, QFHD (as Dual-Link) and 4k (as Quad-Link).

And where do we go from there

Although the new format promises a considerable improvement in detail, colour saturation and sharpness, the advantages of 4k are noticed most of all on large TV screens. The best effect is therefore achieved by using beamers. Videos in the new format are offered on various streaming portals. Videos in 4k are possible in YouTube already since 2010.

With the introduction of 4k the limits of coaxial technology have not yet been reached. First of all, the coaxial connectors and cables support the high frequencies. Secondly, the coaxial technology is fairly simple, robust and inexpensive in comparison with fibre optic technology.

4k is the next step after Full HD and the new format sets new challenges for the infrastructure manufacturers. The manufacturers are planning the next step up to 8k by 2020. But there is a lot of development to be done until then.