Because there is no power signal P which is proportional to output power P in the simplified control scheme, power transducer gain Kp must be determined indirectly. The product (Kp•P) may be considered as apparent power signal P = (Kp•P)
In order to calculate SSE, closed-loop gain of power control loop P/P* and power sensor’s gain Kp must be known. As P/P* is known as in (11), only Kp will be determined.