A four port microstrip testset for network analyzers

This paper describes the design of a microstrip four port testset for use in narrow band network analyzers. The testset configuration comprises of four section branch line couplers and power combiners, which are integrated to realize the testset. It has one port for an RF input, one for an arbitrary DUT, and remaining two ports for incident (reference) and reflected power detectors. The couplers are designed to provide uniform magnitude and phase characteristics that help obtaining isolation above 30 dB between the RF input port and reflected power detector. The power combiners are designed to provide good matching between the couplers and the DUT/reference detector ports, and also to distinguish matched and mismatched loads on Port 2. The designed testset achieves raw uncalibrated load dynamic range of 20 to 59 dB between 1.68 and 2.54 GHz. The high dynamic range makes the designed testset suitable for use in a narrow band network analyzer.