Speeding up N-port VNA calibration eliminating one-port calibrations

With the advent of new RF devices which have an increasing number of ports and to provide the opportunity to simultaneously test several devices in production, there is a growing need for Vector Network Analyzers (VNA) with an equally increased number of ports. At RF frequencies, Short-Open-Load-Thru (SOLT) is one of the favorite calibration methods, where the thru is either considered to be known or assumed to be an unknown reciprocal device. This article describes a variant of such a calibration method, where it is only necessary to connect a Short, Open and Load to either one or two ports instead of all ports, as such simplifying and speeding up the calibration. This alternative method requires however that the VNA has a second source which can be routed to the ports where no Short, Open and Load are connected.