what is bandwidth of antenna

The bandwidth of an antenna is broadly defined as the range of frequencies within
which the performance of the antenna, with respect to some characteristic, conforms
to a specified standard. In general, bandwidth is specified as the ratio of the upper
frequency to the lower frequency or as a percentage of the center frequency. Since
antenna characteristics are affected in different ways as frequency changes, there is
no unique definition of bandwidth. The two most commonly used definitions are
pattern bandwidth and impedance bandwidth.