Bandwidth limitations of impedance matched ideal dipoles

Minimum Q for Lossy and Lossless Electrically Small Dipole Antennas

“…Any tuning elements are included in V a . For the purpose of ‡ We restrict our attention to the quality factor of linear, passive antennas at isolated resonances (or antiresonances) and thus ignore increases in bandwidth that can be achieved, in principle, with overlapping multiresonances [19][20][21] or with nonlinear and/or active devices [22].…”

“…However, (57) holds for any ratio P e /P m and thus applies to a single electric or magnetic dipole. The factor of two reduction in the Chu lower bound for a single dipole brings to mind the approximate factor of two increase in half-power bandwidth for electrically small antennas using Bode-Fano matching networks [19,20] (π/ ln(s + 1/s − 1) = 1.95 ≈ 2 for half-power voltage standing wave ratio s = 5.828). In principle, the Bode-Fano networks create a lossless multi-resonance antenna rather than a single resonance antenna with highly dispersive lossy material required by the lower bound in (57).…”

On the Relation Between Optimal Wideband Matching and Scattering of Spherical Waves

“…By using Fano's approach, optimum broadband tuning limits of the higher-order spherical waves are considered in [29,30], giving important physical insight into the matching limitations for UWB antennas, see also [9,14,15,18,31,32,34]. Previously, the Fano broadband matching bounds have been applied mainly to the lowest order spherical waves, and there is hence a need to further develop analytical results as an aid in the related numerical analysis.…”

Understanding the bandwidth limitations of segmented capped monopole antennas using eigenmode analysis

“…These limits must be determined for the specific lumped element model used to represent the fundamental mode (Fig. 1a), see for example reference [9]. The formalism of reference [7] can be used to establish lower bounds on the modal Q-factor for structures of arbitrary shape.…”