Eigenmode analysis of small multi-resonant antennas

There are many examples of antennas with exemplary bandwidth performance for their size that are characterized as having multiple impedance resonances within their operating bandwidth are presented in this paper. While the relationship between bandwidth and Q-factor is well defined for single resonance antennas, the relationship is more complex for multi-resonant antennas, and the degree of optimality with respect to size and the lower bound on Q (Chu limit) is difficult to quantify in these cases.To better understand the behavior and performance limitations of multi-resonant small antennas, we introduce a method of analysis that elucidates the physical mechanisms underlying multi-resonant behavior. The impedance response of the driven antenna is then described as a multi-pole RLC network, where the component values of the network are determined by the parameters of the various eigenmodes of the antenna.