V23849-R3x-C55

Application Notes

Preliminary Product Information

20

2004-06-28

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.