Phase shift deskew of oscilloscope current and voltage sensing probes by means of energy balance

To model losses of active devices in switching operation, such as for example in class E amplifiers, it is of interest to characterize equivalent switching losses in cut-off and conduction. These losses vary with frequency, drain (or collector) current and voltage, among others. Ideally, losses can be estimated by means of power balance. To be able to perform accurate power balance measurements, instant power has to be known and integrated. Recent advances in oscilloscope and current probes, allow time-domain measurements well in the RF and microwave frequency ranges. To obtain reliable results accurate phase shift between current and voltage sensing probes (skew) has to be known for the particular measurement frequency and test-set. This is particularly important when losses are small compared to overall power delivery which is the case of high efficiency power amplifiers and also because, in switching circuits, losses occur by simultaneous presence of voltage and current during conmutation in very short periods of time. This paper proposes a simple adjustment method, also based in power balance. Practical results obtained are consistent and included herein.