General measurement-based circuit model for symmetrical four-port RF transformers

An equivalent circuit has been developed for a four-port RF transformer by exploiting the symmetry of the device. The circuit consists of four driving-point admittance RLC networks mutually connected via a transforming circuitry, ensuring the symmetry. The measured 4-port frequency responses are converted to respective driving-point admittances, which are approximated by fitting the values of the lumped equivalent circuit 1-ports. Here, a commercial RF transformer has been modelled.