Nolen matrix with tapered amplitude law for linear arrays with reduced side lobe level

This paper introduces a design method for Nolen matrices with tapered amplitude law adapted from a design method used for modified Butler matrices. Tapered amplitude law is particularly attractive to reduce side lobe level in linear array antennas. Using the proposed beam forming network enables to produce a multiple beam antenna with reduce side lobes while maintaining low insertion losses. The method is illustrated with the specific design of a 4×8 Nolen matrix in microstrip technology. The performances of this matrix associated with a theoretical 8-element linear array are investigated to confirm the side lobe level improvement. The proposed Nolen matrix is compared with its Butler matrix counterpart in terms of complexity and appears to be very comparable while leading to potentially more compact design.