In this work, a planar dual beam Sinusoidally Modulated Reactance Surface (SMRS) antenna is presented. Our method is based on the implementation of a surface impedance modulated by the superposition of two sinusoidal functions. In particular, the full process of designing a dual beam antenna that radiates at -14 and 28 off broadside at 10 GHz is described. In a second proposed structure, manipulation of the side lobe level (SLL) is achieved by varying the leakage constant along the antenna with negligible changes in the pointing directions. SLL reductions of 3.4 dB and 1.8 dB for each of the synthesised beams are obtained through full wave simulations, as well as gains 13.4 dBi and 13.6 dBi respectively. An excellent agreement between theoretical and simulated results is observed.This project has received funding from the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU), the Agencia Estatal de Investigación (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER) (Programa Estatal de I+D+i Orientada a los Retos de la Sociedad) under grant RTI2018-097098-JI00. It has also been undertaken within the context of a Research Collaboration Grant of the I Plan Propio de Investigación y Transferencia of the University of Málaga
