Design and implementation of a wideband 8×8 Butler Matrix for AWS and PCS 1900 MHz beamforming networks

Abstract

This paper describes the design and implementation process of a wideband 8×8 Butler Matrix for beamforming networks in the AWS and PCS 1900 MHZ bands. In order to obtain a system able to operate in the frequency range of 1710 MHz to 2155 MHz, compact wideband branch-line hybrids, Schiffman phase shifters, parallel Schiffman phase shifters and no crossovers were used to implement the wideband 8×8 Butler Matrix. The final operation range for the 8×8 Butler Matrix is 1.65 GHz to 2.3 GHz and 2.4 GHz to 2.6 GHz. Finally, an 8-element linear array of printed Quasi-Yagi antennas was introduced in the system to verify the beamforming functionality of the 8×8 Butler Matrix. Measured radiation patterns show that the 8×8 Butler Matrix is able to provide adequate phase difference and uniform amplitude to the antenna array in order to function as a beamforming network in the frequency range of interest.