Broadband Measurements of S-Parameters Utilizing 4x4 Butler Matrices

A novel application of 4 × 4 Butler matrices in a multiport measurement technique has been investigated. The proposed measuring system consists of two standard Butler matrices. By application of numerical procedure in measurement system calibration, an enhanced accuracy has been achieved. An influence of power detectors' uncertainty and imperfect Butler matrix parameters on calibration procedure and measurement results has been investigated. The proposed measuring system has been verified by measurements of scattering parameters of two attenuators and a narrowband bandpass filter in frequency range of 2-3 GHz. It has been shown that the proposed system allows for achieving results corresponding closely to the measurements obtained with the commercial vector network analyzer.