Dual 4-port bidirectional network analyser with vector-null detection for the frequency range 1-800 MHz

The network analyser described in the paper is an extension of a technique published in a previous paper by the authors. A number of limitations of the original system described are overcome by the use of a bidirectional four-channel superheterodyne detection system with vector-null detection. Advantages of the bidirectional analyser over the unidirectional analyser are discussed, and a comparison of accuracy assessment is made.