JET
PROPULSION
LABORATORY
PREFERRED PRACTICE NO. PD-ED-1225
RELIABILITY PAGE 1 OF 2
PRACTICES
CONDUCTED AND RADIATED
EMISSIONS DESIGN REQUIREMENTS
Practice:
Initially, the design requirements for each subsystem are established so that all non-functional
emissions will be at least 9 Db below the emission specification limit.
Benefits:
By initially selecting a 9 Db margin, the probability of complying with the electromagnetic
compatibility (EMC) specification during system test is high.
Programs That Certified Usage:
Voyager, Magellan, Galileo, and Ocean Topographic Experiment (TOPEX)
Center to Contact for Information:
Jet Propulsion Laboratory (JPL)
Implementation Method:
Radiated and conducted emission specifications established for the customer are based on overall
theoretical requirements which will meet the system specifications. The following design
practices for subsystems allow for measurement error, combined effects, and manufacturing
tolerance. This assures that an adequate margin will be realized when the final system
performance is evaluated.
In those cases where an outside agency imposes the allowable emissions levels, the included
margins must be taken into consideration so that excessive constraints are not applied. When a
specific requirement is identified as a major cost driver for design, margin allocations should be
reviewed for possible relief.
Conducted Emissions:
Out-of-specification conducted emission on power, control, and signal lines can usually be
controlled by a low-pass filter to reduce or eliminate unnecessary high-order harmonics. On
digital circuits, a compromise must be made between the need for square pulses and the
suppression of high-order harmonics.
Radiated Emissions:
Radiated emission can be reduced by cancellation, cross polarization, or by either
magnetic or electric field shielding.
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