Ultra-Wideband and Miniaturized Back-Cavity Spiral Antenna with Ferrite Loading

A ferrite-loaded ultra-wideband miniaturized back-cavity Archimedean spiral antenna is proposed in this paper. The antenna is supported by a reflector cavity and exhibits unidirectional radiation patterns across its entire operating frequency range. To minimize the impact of the metal cavity on antenna performance, a ferrite material is situated beneath the substrate. Based on this structure, a compact spiral antenna with a profile of only 0.05λ
0
is obtained. (The wavelength which related to the minimum operating frequency that corresponds to the value of λ
0
where the antenna is capable of functioning). In addition, the antenna is combined with the method of bending the spiral arm to further achieve miniaturization. By this design, the equivalent electrical length of the presented spiral antenna could increase while maintaining its same size. The dimension of the proposed spiral antenna is only 0.17λ
0
× 0.17λ
0
× 0.05λ
0
, and has the bandwidth (|S
11
|<-10 dB) of 180% (0.5-10 GHz).