Reconstruction of the S-matrix of N-port waveguide reciprocal devices from 2-port VNA measurements

Two approaches to reconstruct the S-matrix of N-port waveguide reciprocal devices from 2-port S-matrix measurements are proposed and discussed. The main advantage of the proposed approaches is that measurements are done always at the same two ports, without moving the device. The remaining N-2 ports are loaded with different loads, either matched or short. The first approach, based on a manipulation of the 2-port S-matrices, requires N-2 matched and two other loads, while the second approach, based on the evaluation of an equivalent circuit, requires N-2 short and two other loads. The measurement technique is based on standard loads (short, shift and matched) in the waveguide calibration kit of the 2-port VNA.