Guard band
Guard band turns up in 2 fields: metrology, telecom & it. Here is what it means to the people in each one.
Guard band in metrology
A margin that pulls acceptance limits inside the tolerance limits to cut the risk of passing nonconforming items.
A margin, usually based on the expanded uncertainty, that moves the acceptance limit inward from the tolerance limit, so a reading must fall comfortably inside spec to count as a pass. With a guard band equal to U at k = 2, a reading sitting exactly on the acceptance limit carries only about a 2 % chance of actually being out of tolerance. Guard banding buys lower false-accept risk at the price of more false rejects, rework and adjustment.
"With the guard band applied the acceptance limit is plus or minus 0.85, so that 0.9 is a fail even though it's inside tolerance."
Guard band in telecom & it
An intentionally unused portion of the radio spectrum placed between active channels.
A narrow frequency range left empty between adjacent radio channels or frequency bands. This dead space prevents signal bleed and adjacent-channel interference, ensuring that transmissions do not overlap or degrade one another. Engineers size these bands based on the roll-off characteristics of the filters used in the transmitters and receivers.
"Check the spectrum analyzer to make sure our carrier isn't spilling over into the guard band."