Compact top-loaded, fractal monopole antenna system embodiments are
provided for multi-band airborne operation over ultrabroadband ranges
(e.g., 30 to 2000 MHz). These multi-band embodiments are self-contained,
aerodynamic and compact (e.g., blade height less than 9.5 inches) and are
power efficient with a low return loss (e.g., less than -7 dB). System
embodiments include a set of impedance-matching circuits configured to
substantially match an antenna impedance to a predetermined system
impedance over a set of predetermined frequency bands. In an embodiment,
at least one impedance-matching circuit includes a chain of selectable
air-core inductors which are novelly arranged to improve radiation
efficiency and prevent damage to support substrates. In an embodiment, a
lowest-frequency one of the impedance-matching circuits is configured to
process signals having a maximum wavelength .lamda..sub.max wherein a
fractal member is configured with a length that does not exceed
.lamda..sub.max/40. System embodiments are configured to respond to a
variety of existing radio systems that send commands via different
encoding formats.