Quality Factor of an Antenna With Closely Spaced Resonances

The exact and corrected approximate QZE(ω) quality factors of an electrically small antenna were derived by using an equivalent circuit of the antenna. The quality factors complying with the lower bound on the quality factor Q_lb(ω) were defined by means of magnitudes of frequency derivatives of reactance of resonant and antiresonant subcircuits to provide their additivity in the vicinity of an antiresonant frequency ω_a. The quality factor QZE(ω) was used to approximate the conductance bandwidth of an antenna with overlapped resonances. The quality factors at the maximums of the bands of conductance and return loss Q_ZE(ω_1,2) were utilized to calculate the composite quality factor of the antenna Q_ZEc(ω_a) >; Q_lb(ω).