Evaluating Permissive Change Compliance Paths for Potted RF Transmitter Modules
Adding potting compound to an unpotted RF module demands Class II permissive change re-testing if dielectric loading increases radiated spurious emissions.
Spurious Emissions Scan
Meaning
Spectrum analysis sweeps are performed across a broad frequency range to detect unwanted radio-frequency signals generated by a device outside its allocated band. A spurious emissions scan is used during pre-compliance and formal certification testing to ensure that the device does not cause interference to other wireless systems. It stops applying once the measurement frequency extends beyond the range defined by regulatory bodies for the specific class of device.
Spectral Analysis
Receiver sweeps must cover several gigahertz of spectrum to identify any harmonic or intermodulation products. When executing a spurious emissions scan, the device under test is rotated through three hundred and sixty degrees on a turntable to find the angle of maximum radiation. This scan is repeated with both horizontal and vertical antenna polarizations to capture all possible radiated emissions.
The results are compared directly against regulatory limit lines to identify any non-compliant spikes.
Precompliance Filter
Noise floors are minimized by using pre-amplifiers and band-reject filters to isolate the signals of interest. These tools allow engineers to distinguish between ambient noise and the device’s emissions.
Compliance Report
Data points that exceed the margin of safety are recorded in the final test log for review by the certification authority. This documentation is required to proceed with product launch plans.