A logarithmic reflection chart for presentation of antenna impedance

A logarithmic chart is proposed to offer some advantages over the familiar hemisphere chart of Carter and Smith. On log-log coordinates, the scales are the voltage standing-wave ratio (VSWR), respectively, of impedance variation with zero angle and of angle variation with constant impedance. A locus of constant reflection or VSWR then has two equal diameters but departs from a circle by equal flattening in all quadrants. A locus of impedance variation with frequency has the same shape for any reference value of impedance. The log chart is unbounded so it avoids the crowding near the rim which occurs with extreme values on the hemisphere chart. It is especially useful in presenting the impedance of a small antenna and an associated wide-band matching network.