What is FBW (fractional bandwidth)?

The fractional bandwidth of an antenna is an examination of how wideband the antenna is. The fractional bandwidth fluctuates somewhere in the range of 0 and 2. This is simply the absolute bandwidth isolated by the center frequency of the antenna.
FBW = BW / fc
The FBW is a more significant expression of the valuable recurrence range of an array and an essential indicator of expected imaging execution.