De-embedding microwave fixtures with the genetic algorithm

Direct measurement of frequency characteristics of a device under test (DUT) at microwave frequencies is often difficult due to some intervening fixture used for feeding the DUT. In contrast to a great number of self-calibration techniques, the method proposed in the paper does not require any calibration standard and allows us to de-embed an effect of the fixture from experimental data obtained at the network analyzer reference plane being based only on characteristics of the "Thru" experiment. It is shown that the traditional de-embedding problem being posed in a finite frequency range may be reduced to a problem of fitting the characteristics of the "Thru" experiment. The latter is proposed to be solved by using the genetic algorithm. A special trick is suggested to take fixture power loss into consideration, which sometimes is necessary to increase the goodness of fitting the characteristics. The results of the experiments performed have validated a high efficiency of the method proposed.