Antenna Placement Decisions Made Too Late in Enclosure Design
Early co-simulation of enclosure dielectric loading and counterpoise geometry prevents costly mold tooling revisions and regulatory recertification delays.
Harmonic Emission
Meaning
Unwanted electromagnetic radiation generated at integer multiples of a transmitter’s fundamental operating frequency can cause interference in adjacent wireless systems. High-frequency circuit boards often produce a harmonic emission due to non-linearities in power amplifiers or switching regulators. These spurious signals must be suppressed to ensure electromagnetic compatibility and regulatory approval.
Frequency Disturbance
Spurious signals propagate through both radiation and conduction to disrupt nearby sensitive receiver circuits. For example, a second harmonic emission from a cellular modem operating at nine hundred megahertz can severely degrade the performance of a co-located global positioning system receiver. Sourcing and engineering teams must identify these unwanted signals during early design stages to avoid costly reworks.
Mitigation Technique
Suppressing these unwanted signals involves integrating low-pass filters or band-stop filters directly into the radio frequency path. Shielding enclosures and optimized board grounding also prevent a harmonic emission from radiating directly from the printed circuit traces. Engineers must select components with high linearity and low parasitic capacitance to minimize the generation of these signals in the active stages of the design.
Regulatory Limit
Compliance standards define strict maximum power levels for out-of-band spurious signals to protect the radio spectrum. If the harmonic emission exceeds these thresholds, the product will fail laboratory certification and cannot be sold.