**3.3.1 The pros and cons for simple direct comparison transfer**

The above analyses based on the method illustrated in Fig. 2 are the simple direct comparison transfer calibration method. It is the most basic microwave power transfer technique. The system setup is fast, easy and simple.

But it is only for relatively rough measurement, since the reflection coefficient of a generator *ΓG*, is more difficult to measure than that of a passive load. *ΓG* varies with time and frequency. Many signal generators and amplifiers have non-linear output impedance. There are several developments on the measurement methods for *ΓG* (Shimaoka et al., 2006; Torok et al., 2001) which is beyond the discussion of this chapter.
