The Flow of Information #10
davejames
Posts: 4,047
Hi All,
Here's an interesting article concerning data compaction transmission.
I'm not affiliated with National Semi,
DJ
To Shield or Not to Shield: Industrial Video Ser/Des and EMI Considerations
Industrial serializers and deserializers, also known as Ser/Des devices, offer a means of reducing the bus width of a high-bandwidth data interface. The data is converted from a wide parallel data stream to a reduced number of bits or even a single LVDS lane with a serializer, enabling low-cost and flexible cabling options. The data is then expanded at the destination with a deserializer back into a parallel data stream.
This technology enables many new products and solutions, but it also raises some very important questions regarding Electromagnetic Interference (EMI) including: How does the choice between a twisted pair cable like Unshielded Twisted Pair (UTP) or Shielded Twisted Pair (STP) differ from each other and how does it compare to a coaxial cable with regards to EMI?
http://www.national.com/vcm/national3/en_US/resources/signal_path_designer/national_sp_designer123.pdf
Here's an interesting article concerning data compaction transmission.
I'm not affiliated with National Semi,
DJ
To Shield or Not to Shield: Industrial Video Ser/Des and EMI Considerations
Industrial serializers and deserializers, also known as Ser/Des devices, offer a means of reducing the bus width of a high-bandwidth data interface. The data is converted from a wide parallel data stream to a reduced number of bits or even a single LVDS lane with a serializer, enabling low-cost and flexible cabling options. The data is then expanded at the destination with a deserializer back into a parallel data stream.
This technology enables many new products and solutions, but it also raises some very important questions regarding Electromagnetic Interference (EMI) including: How does the choice between a twisted pair cable like Unshielded Twisted Pair (UTP) or Shielded Twisted Pair (STP) differ from each other and how does it compare to a coaxial cable with regards to EMI?
http://www.national.com/vcm/national3/en_US/resources/signal_path_designer/national_sp_designer123.pdf
Comments
1) This isn't really data compaction. The same amount of data is going from point A to point B at the same overall rate. You're just using fewer wires carrying the same bits at a higher bit rate.
2) Ideally, with proper driving, neither twisted pair cables nor coaxial cables should radiate any signal. In practice, given real-world cable construction and termination, both can radiate. How much depends on the frequency, power levels, cable construction and termination, cable routing, etc. So, the choice of cable depends on the details of the situation, but generally, it's easier to get quiet coax than quiet unshielded twisted pair and shielded twisted pair is similar to coax depending on the construction of the cable.
Bean