## Antenna systems::Bandwidth (signal processing)

### ::concepts

Filter::maximum    Signal::range    Which::passband    Example::channel    Spectral::width    Where::value

Antenna systems

In the field of antennas, two different methods of expressing relative bandwidth are used for narrowband and wideband antennas.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> For either, a set of criteria is established to define the extents of the bandwidth, such as input impedance, pattern, or polarization.

Percent bandwidth, usually used for narrowband antennas, is used defined as $\%B=100 \times \frac{f_H-f_L}{f_c}=200 \times \frac{f_H-f_L}{f_H+f_L}$. The theoretical limit to percent bandwidth is 200%, which occurs for $f_L = 0$.

Fractional bandwidth or Ratio bandwidth, usually used for wideband antennas, is defined as $B = f_H/f_L,$ and is typically presented in the form of $B:1$. Fractional bandwidth is used for wideband antennas because of the compression of the percent bandwidth that occurs mathematically with percent bandwidths above 100%, which corresponds to a fractional bandwidth of 3:1.

If $\%B =200 \times \frac{f_H-f_L}{f_H+f_L} = p$

then $B = \frac{200+p}{200-p}$.

Bandwidth (signal processing) sections