Beam-forming Networks for Scannable Multi-beam Antenna Arrays using CORPS and Differential Evolution Marco A Panduro 1 and Carlos del Rio-Bocio 2 1. Unidad Académica Multidisciplinaria Reynosa-Rodhe, Universidad Autónoma de Tamaulipas (UAT) Carretera Reynosa-San Fernando, Reynosa, Tamaulipas, 88779 México Phone: (52) 899.921.3300, Fax: (52) 899.921.3301 mamendoza@uat.edu.mx ; pandurom@yahoo.com 2. Universidad Pública de Navarra, campus Arrosadia 31006, Pamplona, España carlos@unavarra.es Abstract— This paper deals with the design of beam-forming networks (BFN) for scannable multibeam antenna arrays using Coherently Radiating Periodic Structures (CORPS). This design of CORPS-BFN considers the optimization of the complex inputs of the feeding network by using the Differential Evolution (DE) algorithm. Simulation results for different configurations of CORPS-BFN for a scannable multibeam linear array are presented. The results shown in this paper present certain interesting characteristics in the array factor response for the scannable multibeam linear array and the feeding network simplification for the design of BFN based on CORPS. I. INTRODUCTION Modern antenna applications such as MIMO Systems, Smart Antennas, Phased Antenna Arrays, etc, require the capability to handle several beams independently. In this work, it is introduced the CORPS (Coherently Radiating Periodic Structures) concept to design BFN (Beamforming Networks) for multibeam antenna systems. The philosophy of CORPS [1]-[4] has been presented in several papers. In these papers, it has been illustrated the CORPS network as a key methodology to feed antenna arrays [3]. In [3], it has been considered the design of CORPS-BFN for antenna arrays of unique beam. In this paper, it is introduced an innovative way to analyze a CORPS-BFN for scannable multibeam antenna arrays. In this case, due to the predefined features of the CORPS-BFN introduced, the amplitude and phase excitations should be introduced to the network and not to the radiating elements, as usual. These amplitude and phase excitations are determined by using the method of Differential Evolution (DE). Due to the nonlinear and nonconvex dependence of the parameters involved, the determination of the amplitude and phase excitations becomes a highly complex problem. However, DE has proven to be a fast and efficient algorithm for complex real-valued problems [5]-[9]. The main objective of this paper is to combine this new technology based on CORPS to define the BFN and the DE to look for optimal excitations, in order to generate a scannable multibeam linear array. The contribution of this paper is to present a perspective of the design of CORPS-BFN considering scannable multibeam linear arrays. II. BEHAVIOR OF THE CORPS BEAMFORMING NETWORK The working principle of the CORPS concept to feed antenna arrays has been explained in [3]. In this section we will try to illustrate the behavior of the CORPS-BFN for scannable multibeam linear arrays based on the previous work presented in [3]. A schematic representation of a CORPS-BFN of n inputs, N outputs and 3 layers is presented in Figure 1. As shown in Fig. 1, a CORPS-BFN is conformed by a mesh interconnected by means of Split (S)-nodes and Recombination (R)-nodes. S R R S R S S S R R R R S S S S R R R R R S R S R S R 1 2 n Outputs Layers 1 2 3 Matched load Fig. 1 Schematic representation of a CORPS-BFN with S and R nodes. The CORPS-BFN works as follows. The signal entered by one input port is divided in two and added with the arriving signals of the neighboring input ports. Following the path of each signal, we will find something like an inverted triangle (see Figure 2) which has the lower vertex at the input port. The opposite side of this vertex will define the output ports receiving some information from this input port, or in other words, the effective radiating area from which every input signal (or orthogonal beam) will be radiated. Since the isolation between the input ports is ensured and the spreading of the signal inside the structure is controlled, the CORPS- BFN is able to handle simultaneously several orthogonal beams without any problem. In the outermost branches, the inputs that are not used are finished with a matched load in order to avoid reflections.