AbstractA solution is presented to the problem, which arises in two‐port modelling, of determining a second driving‐point function from a given driving‐point function and a transfer function. the given functions must have a common denominator and satisfy the necessary positive real (PR) matrix conditions: the driving‐point function must be PR and on the imaginary axis the real part of the transfer function must be zero whenever the real part of the driving‐point function is zero. By using a partial fraction expansion and determining a required first‐order polynomial, a unique second (minimum) driving‐point function is obtained. Examples to illustrate the method a