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HHD-BNC for 12g SDI video router

Customer Challenge

A customer approached Winchester Interconnect during the design stages of its next generation video router. The  company wanted to reduce the size of its interconnects to have more real estate inside its router to fit more  connections into the same space. However, despite the smaller size, the customer also needed to meet the  industry’s specifications, which have evolved from High Definition (“HD”) to 12Gbit Serial Digital Interface (“SDI”),  and maintain the existing electrical performance in terms of upholding signal integrity. The customer had  evaluated alternative connector solutions but it failed to find a solution that could meet its size, frequency,  performance, and usability requirements.

Challenge Review

Winchester’s engineers reviewed the application with the  customer. Video production historically used 75 Ohm BNCs  as the coax connector of choice, but when density became an  issue a mini 75 Ohm BNC was introduced. However, since  the mini 75 Ohm BNC only offered limited benefit in terms of  a smaller form factor, the customer evaluated a 75 Ohm  1.0/2.3 “mini DIN.” This solution met the desired density but  the push/pull coupling method of the 1.0/2.3 proved  unreliable. Operators complained that there was little  assurance the connectors were mated properly and the  interface was difficult to un-mate when closely spaced. Also,  during trials the customer experienced intermittent signal  integrity failures related to the cable weight, creating a side  load on the mated interface which caused continuity issues.  RF performance was a critical factor for the customer. The broadcast industry’s interconnect needs have evolved  with higher resolution technologies (ex – 4k) pushing higher frequency interconnect solutions. Standard 75 Ohm  BNCs are only rated to 4 GHz, but to meet the evolving industry demands customers need BNCs that can  perform to 6 GHz (Nyquist frequency theory states 12 Gbit SDI transmits at approximately 6 GHz). Despite the  higher frequency demands, return loss could not exceed 5 dB.

Winchester Solution

Winchester Interconnect recommended that the customer evaluate its HHD-BNC High Density Bayonet style  printed circuit board and cable connectors. The HHD-BNC is rated to 12 GHz and performs at better than 5 dB of  return loss. In addition, Winchester Interconnect worked with the customer to design the printed circuit board  geometry to ensure that the signal transition generated minimum loss. Also, the HHD-BNC has a center line  density of 8 mm versus the 16 mm of standard 75 Ohm BNCs; this smaller form factor allows HHD-BNCs to have  twice the density as standard BNCs.  The HHD-BNC also met the customer’s usability preferences as this solution utilizes a bayonet style coupling  mechanism, which is how traditional BNCs stay mated. Bayonets proved more reliable than the push/pull coupling  method of the 1.0/2.3 mini DIN and the technicians were familiar with how this interface properly mated to the  PCB jacks. They would be certain the plug would be mated and stay mated. Testing showed signal integrity was  maintained when the weight generated by the cable, even bulky 1855 series cable, was applied.  Winchester’s HHD-BNCs are designed to be terminated in the same manner as widely adopted 75 Ohm  broadcast BNCs. This means cable strip and crimp tools, like those already used by the installation technicians,  work on Winchester’s HHD-BNCs. Installers would need no special tools, which greatly enhanced the usability of  the connector.

Customer Improvement

  • Winchester’s HHD-BNC provided the customer with:
  • A solution that exceeds the SMPTE 12Gbit SDI requirements with better than 5 dB return loss.
  • A solution that could meet higher performance expectations without increasing the size of the end product.
  • A mating style that operators were comfortable with and were confident would stay mated.
  • A robust design that would handle all the in-field requirements including performing when installed on 1855A cable.
  • A connector that utilizes standard installer tools.