Design of Ultra-Wideband and Miniaturized Spiral Antenna

A miniaturized ultra-wideband (UWB) conical spiral antenna (CSA) with the bandwidth of 15 octaves has been proposed. Firstly, based on the CSA, the radial dimension of the CSA was miniaturized by combining the loading of cylindrical spiral, meander lines, and lumped resistors. Then, the variant conical technique was used to achieve miniaturization of the axial dimension of the CSA. The measured results show that the VSWR <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq 2.5$</tex> of the antenna can cover the entire frequency band; Except for differences in the high-frequency band, the measured and simulated results of the realized-gain pattern of the antenna have a high degree of agreement; In addition, except for a slightly worse axial ratio in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\theta=0^{\circ}$</tex> at the 0.26<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f$</tex>0, the axial ratio in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\theta=0^{\circ}$</tex> in the remaining frequency bands of the antenna is less than 3.9dB.