Bandwidth and quality factor of a small antenna with coupled impedance resonances

Interrelation of the quality factor, the lower bound on the quality factor (Q_lb(ω)), and bandwidth was examined for an electrically small antenna with coupled impedance resonances around its antiresonance. Bands corresponding to the resonances and the total bandwidth of the antenna are limited by values of Q_lb^-1(ω) calculated at frequencies of their centers. The approximate quality factor determined from the frequency derivative of impedance of the antenna at the antiresonant frequency (Q_z(ω_α)) is less than Q_lb(ω_α). The approximate quality factors at the maximums of the bands are utilized to define the composite quality factor of the antenna with coupled resonances- Q_zc(ω_α), which complies with the lower bound on the quality factor.