Compact multiband antennas of self-similar analytic geometry inspired by the chirp waveform

Analytic geometry antennas, including Sinusoidal and Chebyshev antennas, have shown a good potential for integration into miniature devices like wireless sensors. This paper augments the field of analytic geometry antennas by introducing a genre of antennas inspired by the chirp waveform; attention shifts to multifrequency antennas. Pre-fractal antennas are well-known multiband radiators, owing to their fractal self-similarity. Chirp antennas introduce the concept of analytic self-similarity, which enables smooth Euclidean antennas to produce functional operating bands apart from their natural resonances; these generalized sinusoidal structures manage to transform the non-uniform spatial sweeping of Chebyshev antennas into a multifrequency response. The designed Chirp variant produced eight non-harmonically-related resonances inside a 2.6 octave bandwidth (1-6 GHz). Numerical results indicate an aggregate bandwidth (BW) equal to 0.53 GHz and fractional BWs in the range 1-6%. The Chirp antenna is also highly efficient, scoring a 90% average efficiency. Measured data corroborate the multifrequency response of Chirp antennas. Proper adjustment of the dimensions of the chirp-like element and the ground plane leads quickly to an efficient radiator that displays a radiation resistance close to 50 Ω and a reactance that is adjustable between inductive and capacitive response.