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RF Electronics Chapter 2: Computer Simulation Page 37 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. Figure 2.46. Frequency response of the calculated Bandpass T matching network. S Parameter Measurements The network of figure 2.45 is used to generate an S parameter file. Such a data file is similar to S parameter data obtained from a network analyser. This file is obtained by exporting the trace data of a table-graph containing the complex S parameters of the circuit in figure 2.45. This can be saved as a text file. Change the .txt extension to .S2p to denote a 2-port S parameter file. This file can then be imported as a Touchstone file, by right clicking on Data Files and selecting Import Data File or by using the Project Add Data File Import Data File dropdown menu. This data file can be named "Measurements". The Touchstone heading "#MHz S RI" needs to be added, to denote that the frequency is in MHz , it is an S parameter file and the data are Real and Imaginary values. "R 50" denotes that a 50 Ω source and load impedance is used. That is the default. The Touchstone file format for a 2-port S parameter network typically is as follows: # GHZ S RI R 50 f1 ReS11 ImS11 ReS21 ImS21 ReS12 ImS12 ReS22 ImS22 f2 ReS11 ImS11 ReS21 ImS21 ReS12 ImS12 ReS22 ImS22 f3 ReS11 ImS11 ReS21 ImS21 ReS12 ImS12 ReS22 ImS22 In addition the heading lines of text need to be denoted as comments by inserting a "!" at the beginning of the line. The resulting Touchstone file is as shown in table 2.2. To keep the number of lines in this table small a 10 MHz frequency increment is chosen in the project options, resulting in 21 frequencies being used. In practice, many more frequencies would be used. This table is produced by calculating the S parameters for the network of figure 2.45 when the port impedances are 50 Ω. Figure 2.47. Circuit containing the Measurements Touchstone file. RF Electronics: Design and Simulation 37 www.cadence.com/go/awr

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