V23849-R35-C55 Datasheet, PDF (20/34 Pages) Infineon Technologies AG – iSFP-Intelligent Small Form-factor Pluggable 1.25 Gigabit Ethernet 4.25/2.125/1.0625 Gbit/s Fibre Channel

V23849-R3x-C55
Application Notes
In many situations the question on which ground concept to implement in the design
cannot be easily decided prior to the receipt of first EMI measurement results. Infineon
thus offers both module versions; V23849-Xx5-Xxx for common ground and
V23849-Xx6-Xxx for separate ground concept.
The return path of RF current must also be considered. Thus a split ground plane
between Tx and Rx paths may result in severe EMI problems irrespective of which
module ground concept has been applied.
The bezel opening for a transceiver should be sized so that all contact springs of the
transceiver cage make good electrical contact with the face plate. Please consider that
the PCB may behave like a dielectric waveguide. With a dielectric constant of 4, the
wavelength of the harmonics inside the PCB will be half of that in free space. Thus even
the smallest PCBs may have unexpected resonances.
Large systems can have many openings in the front panel for SFP transceivers. In
typical applications, not all of these ports will hold transceivers; some may be
intentionally left empty. These empty slots may emit significant amounts of radiation.
Thus it is recommended that empty ports be plugged with an EMI plug as shown in
Figure 6. Infineon offers an EMI/dust plug, P/N V23818-S5-B1.
Preliminary Product Information
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2004-06-28