The authors paid particular attention to the problem of antenna impedance measurements in the RFID technique. These measurements have to be realized by using two ports of a vector network analyzer and dedicated passive differential probes. Since the measurement process and estimated parameters depend on the frequency band, operating conditions, type of the system component and antenna designs used, appropriate verification of the impedance parameters on the basis of properly conducted experiments is a crucial stage in the antenna synthesis of transponders and read/write devices. Accordingly, a systematized procedure of impedance measurements is proposed. It can be easily implemented by designers preparing antennas for different kinds of RFID applications. The essence of indirect measurements of the differential impedance parameters is discussed in details. The experimental verification has been made on the basis of a few representative examples.
This paper is devoted to measuring the continuous diagnosis capability of a system. A key metric and its calculation models are proposed enabling us to measure the continuous diagnosis capability of a system directly without establishing and searching the sequential fault tree (SFT) of the system. At first a description of a D matrix is given and its metric is defined to determine the weakness of a continuous diagnosis. Then based on the definition of a sequential fault combination, a sequential fault tree (SFT) is defined with its establishment process summarized. A key SFT metric is established to measure the continuous diagnosis capability of a system. Two basic types of dependency graphical models (DGMs) and one combination type of DGM are selected for characteristics analysis and establishment of metric calculation models. Finally, both the SFT searching method and direct calculation method are applied to two designs of one type of an auxiliary navigation equipment, which shows the high efficiency of the direct calculation method.