An Innovative Spline-Based Shaping Approach for Ultra-Wideband Antenna Synthesis

Antennas play a unique role in Ultra-wideband (UWB) systems because of their behaviour as a bandpass filter and the need of avoiding undesired distorsions in the spectra of the transmitted pulses. For this reason, traditional approaches for antenna characterization prove inadeguate, so innovative design procedures and measurement techniques are needed for antennas in UWB systems [1]. Up till now, the most common design approach (i.e., the Parametrical Approach) is based on the parametrization of some geometrical shapes and the optimization of their descriptors for fitting the requirements. The choice of the initial reference geometry is dictated by the a-priori knowledge on its range of application and achievable performance. In such a framework, examples of UWB antennas can be found in [2][3][4]. Another synthesis approach, called Non-Parametrical Approach, considers a description of the antenna structure in terms of a collection of elementary building blocks suitably-coded in an unknown array. In [5][6] some examples of antennas synthesized with such an approach and considering a binary encoding are presented. In this work, a novel UWB antenna design method is proposed in order to exploit the advantages of both the aformentioned approaches. In particular, some standard geometrical parameters (e.g., groundplane, feedline and substrate dimensions) are described according to a parametrical approach, while the design of the remaining features is obtained starting from a spline-based shape generator. This new design method exploits the simplicity of the classical parametric approach with the flexibility of the spline-based shape representation in order to obtain cheap and reliable antennas for UWB applications. In order to assess the effectiveness of the proposed approach, simulated and experimental results concerned with a representative UWB antenna design are presented and discussed. This is the author's version of the final version available at IEEE.