Permissive Changes against Full Retest after a Firmware Update
Firmware updates altering output power, channels, or DFS logic trigger mandatory permissive change filings or retests before distribution.
Occupied Bandwidth Mask
Meaning
Spectrum boundaries defined by regulatory agencies restrict the amount of power a wireless transmitter can radiate into adjacent frequency bands. The occupied bandwidth mask defines the permissible energy level as a function of the offset from the carrier frequency. This measurement is limited to active transmission states and does not apply when the radio is in standby mode.
Testing laboratories use spectrum analyzers to verify that the device complies with these limits.
Spectral Out-of-band
Transmitters often generate spurious energy outside their assigned channels because of non-linearities in the power amplifier. The occupied bandwidth mask specifies the attenuation required at various frequency offsets to prevent interference. This requirement protects adjacent communication services.
Measurement Settings
Laboratory technicians must configure the spectrum analyzer according to specific regulatory guidelines. To capture the occupied bandwidth mask, the resolution bandwidth and the detector type must be set precisely. These parameters ensure that the measurement is repeatable across different laboratories.
Filter Design
Digital and analog filters are integrated into the transmitter chain to shape the output signal. By aligning the signal with the occupied bandwidth mask, engineers ensure that the device does not cause radio interference. This step is a prerequisite for receiving market authorization.