A Look at New Coaxial Cable Design for “True” 4K

Multi-cable formats (dual and quad links) can be used today because the bandwidth on each cable is the same as HD or 3G bandwidths currently used.  This is possible because recent video cards contain chips that will separate the video data misc. sign 9_Original_22638into two or four signals. The signals then run over separate coax cables at a maximum speed of 3GHz (3GHz for 3G and 1.5 GHz for HD) and at the receiver, they will be transformed back to 6GHz or 12 GHz. Belden believes that its current line of cables will work to 6 GHz, but 12 GHz will require re-design and new cables.

New Cable Design

There are a number of things that can be done to improve performance of the 4K versions listed above. First is to increase Velocity of Propagation (Vp) by means of nitrogen gas injection. The limits of this technique are closely guarded secrets for most manufacturers. So can we get much higher? The problem is, as more nitrogen gas is added, dimensional stability suffers. This leads to impedance variations or “return loss”, which negatively affects performance. The solution is to reduce the size of the bubbles in the foam. Belden already offers better Vp in its well-known RF cable line with a Velocity of Propagation of 86% – 1694A has currently 82%. Unfortunately these RF cables are 50 ohm and not 75 ohm as needed in the broadcast world. So, there is still some work to be done. Thankfully Belden has both the technology and the experience, so we will be able to develop the correct cable for this new 12 GHz requirement. Improvements in shield design, such as multi-layer shielding, are also possible, although these improvements are not tied to the raw performance, such as attenuation. But shielding is certainly tied to noise immunity, which speaks to signal integrity in longer runs or noisy environments.

What About Connectors?

We see a trend towards DIN 1.0/2.3 connectors instead of BNC connectors at those high frequencies needed for “true” 4K. The outer diameter of a DIN 1.0/2.3 connector is much smaller compared to traditional BNC types. The smaller DIN 1.0/2.3 connectors (secure locking with push/pull) are less stressed than traditional BNCs, and they do not require a tight bending radius. This contributes to a better RF launch profile, and a better return loss. The smaller dimension of a DIN connector is an advantage: because of their specific design, DIN connectors for such high frequencies (up to 12 GHz) are easier to manufacture than traditional BNC connectors. Which design will ultimately take the lead? The future will tell.

Conclusion

If the revised distance formula, -40 dB at ½ the clock, is adopted, and if performance improvements are made, such as higher Velocity of Propagation, single-link coaxial cable for 4K formats will be able to provide the right performance for future video transmission.

If you need more details about our solutions let me know and Email me at werner.eich@belden.com

See Belden at IBC 2013 – and be amazed by our scope

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Preparations are well underway for our booth at IBC 2013.  I have always enjoyed being at the show, focusing on Belden’s cable and connectivity products (“the most trusted brand for Broadcast cables”).

This year, however, we have so much more to offer. Since Belden’s acquisition of Miranda Technologies, we are now also able to provide hardware and software solutions for television broadcast, cable, satellite and IPTV.

Our booth will reflect our expanded capability to deliver world-class solutions for immediate and uninterrupted transmission, flawless HD, 3G and 4K audio and video streams. We will also be introducing some new products.

To highlight just two of them, our new Duobond® Plus HD Digital Video Cables with bonded foil over the dielectric will make the termination of Belden’s 1-Piece HD BNC very easy and much faster than traditional methods with 3-Piece BNCs. It is the absolute reliable combination to deliver the needed performance!

Moreover we will be launching our extremely rugged and flexible Belden CatSnake® Tactical Heavy Duty Category 6A shielded data cables, which are designed for use in high traffic areas in a broadcast studio or for use out of doors, in broadcast truck applications, and for portable, professional audio/video use.

And if that is not enough, visitors to our booth have the opportunity to meet Steve Lampen, Belden’s Manager for Multimedia Technology and Product Line – Entertainment Products. Steve is a prolific blogger, public speaker and writer, and was named “Educator of the Year” by the Society of Broadcast Engineers in 2011.

So if you are looking for maximum reliability and performance in your broadcasts, be sure to visit our booth and see for yourself what Belden has to offer.  My team and I will be delighted to see you at the show.

Tales of the Cliff – Part 4

This is a 4 part series blog post:

We’ve spent a whole month taking about the “digital cliff”, about measuring bandwidth, wavelength and critical distance. And we’ve talked about our “safe distance” table based on the B54_CliffAheadformulas in the HD standard (SMPTE 292M). Use those safe numbers and you don’t have to think about anything, you don’t have to measure anything. Just put on some connectors and plug it in. If you get failures at these short distance, you have something very wrong, a lot more wrong than a cable a bit too long. Is everything intended for HD? Tested by each manufacturer to AT LEAST 2.25 GHz?  (Last time I mentioned how one project was stymied by using analog 75 ohm terminators!)

Read more »

Impedance and Return Loss

When you deal with high frequencies, above around 100 MHz, you have entered the zone of the “transmission line.” It has to do with the wavelength of the signal, and that is a discussion we’ll have in future blogs. But what it means is that the impedance of the cable is now important and you have to match the impedance of the source and destination devices.

This also means that everything in-between must match the impedance chosen and, by “everything,” I mean cable, connectors, patch panels, patch cords, adaptors, bulkheads, feedthroughs – erything! It also means that any variation in impedance can affect the signal on the line. This is true for every transmission line, whether we’re talking about a 50kW RF signal going up to an antenna or an HD video signal going between boxes. Of course, in these two examples the impedance is different (50 ohms for that high-power line and 75 ohms for that video cable). Read more »

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