Folded Sierpinski monopole antenna with self-similar radiation properties

The Sierpinski gasket is a well-known multi-band antenna structure popular for its self-similar radiation properties at designed harmonic frequencies, pertaining to its symmetric structure on different length scales. One of the main limitations of this structure is its large size. In this paper, we present a planar Sierpinski antenna whose size is reduced by folding the upper portion of the largest gasket (responsible mainly for the lowest resonance) on the back of the substrate. In addition, the lateral size is also reduced by cutting those parts of the metallisation which contribute little to the radiation. The antenna is fed with a microstrip line to improve the input matching. It is shown by simulation and measurement that the self-similarity of the structure is preserved after folding and lateral size reduction.