Miniaturization of Spiral Antenna Based on Fibonacci Sequence Using Modified Koch Curve

A new fractal curve along with its iterative function system based on Koch curve is proposed and used for the miniaturization of Fibonacci spiral antenna (FSA). This curve possesses semicircular sections so as to maintain the symmetry with quarter circular sections of FSA. The modified Koch curve owing to its curvatures facilitates a smoother flow of surface current along the spiral arms fractalized with it, unlike uneven current distribution when fractalized with conventional sharp-cornered Koch curve. The second iterate of this curve has resulted in nearly 50% of size reduction by maintaining an equivalent arm length needed for the operation at lowest frequency. The numerical analysis and measurements confirm the retention of inherent broadband characteristics of the FSA and its miniaturized prototypes in the absence of ground plane with excellent radiation properties.