EMC integration notes

What these notes are for#

An FPGA Mezzanine Card has no electromagnetic behaviour of its own: its emissions and its immunity are set by the carrier board it is mounted on, the FPGA design driving it, the power supply, the cables attached to its connectors and the enclosure around the whole. Opsero assesses each card under a stated reference configuration and publishes the result so that an integrator can see what the card contributes and design the apparatus accordingly. These notes say what that configuration was and what the integrator controls.

What the integrator controls#

• Carrier and grounding. Mount the card on all of its FMC standoffs and bond the standoffs to the carrier’s ground. The connector shells and shields on the card return through the carrier; an unbonded card floats them.
• Enclosure. The reference measurements were made on an open development board with no enclosure. An enclosure with the card’s connectors presented through a bonded panel normally reduces radiated emissions and improves immunity; large apertures near the card’s connectors can do the opposite.
• Cables. Emissions from an external port are carried by its cable. Use shielded cables where Class A margin matters and wherever the reference measurement used them (see the table below). Keep unused ports unconnected or terminated. Cable length changes coupling; the reference measurements state the lengths used.
• Power. The card is powered from the carrier’s FMC rails within the VITA 57.1 limits given in the specifications. Supply noise on those rails appears on the card; the carrier’s regulators and decoupling are part of the apparatus’s EMC.
• Firmware. Worst-case emissions occur with every interface active at full rate. Idle links, unused lanes and disabled clocks lower emissions; a design that keeps unused interfaces powered down helps.
• Environment and class. The card is assessed against Class A limits (commercial and industrial environments). An apparatus intended for a residential environment must meet Class B and must be verified at apparatus level; the card’s Class A assessment does not cap the apparatus, and Opsero’s published measurements show the margin available.
• Indoor use of network ports. Where the card has Ethernet or other network ports, the assessment covers indoor connections. Surge protection for cables leaving a building is the apparatus designer’s responsibility.

What Opsero publishes#

For each card: the reference configuration, the laboratory report reference, the emission class and, as they become available, the measured emission levels against the Class A and Class B limit lines. The laboratory reports are available on request through the Product compliance page.

Reference configuration for this product#

Emissions characterisation planned. Design guidance above applies; emission class A; assessed for indoor network connections.