The fractional bandwidth of an antenna is a proportion of how wideband the antenna is.
Assuming the antenna works at centre frequency fc between lower cutoff frequency fL and upper cutoff frequency fh (where fc=(fL+fH)/2), then, at that point, the fractional bandwidth FBW is given by:
fractional bandwidth is an element of the range and the centre frequency.
The fractional bandwidth differs somewhere in the range of 0 and 2, and is frequently cited as a rate (somewhere in the range of 0% and 200%).
The higher the rate, the more extensive the bandwidth.
Wideband antennas normally have a Fractional Bandwidth of 20% or more.
Antennas with a FBW of more noteworthy than half are alluded to as super wideband antennas.