AWR eBooks

RF Electronics Chapter 2: Computer Simulation Page 21 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. use by Universities for this library can be obtained from their web site [22]. The linear models for resistors, capacitors and inductors include the effects of surface mount pads, leads and substrates, to permit accurate modelling of the components at microwave frequencies. Non-linear models for active devices are also included. The technique for importing SPICE files into AWR DE, is shown in appendix 1. Alternately, one can simply change the format by entering the BFP720 parameter values shown above into the secondary parameters window shown in figure 2.20 for the Gummel-Poon transistor and then renaming and saving the device. If needed circuit symbols can also be changed, by right clicking on the device and then selecting Symbol to select the desired symbol to be linked. Figure 2.21 shows the circuit diagrams for the amplifiers shown in figure 2.17, but using nonlinear models instead. The first and very critical step of any transistor design is the biasing. By right clicking on the circuit-schematic and selecting "Add Annotation" and then selecting "DCVA_N" will provide voltages at all the nodes in the circuit, to enable the biasing voltages to be checked and compared with the design values. The node voltage annotation is shown in figure 2.21. To save simulation time, Data Sets, results from simulation are stored. If after simulation, the annotation is not shown in the schematic, delete any Data Sets from the project and re-simulate the project to refresh the annotation. Similarly, currents in and out of all the nodes can also be shown. The biasing resistors for the 3 circuits are adjusted to give 7 V at the collectors. Those resistor values were then used in figure 2.17 to provide an accurate comparison between the linear and nonlinear model. Figure 2.21. Nonlinear simulation of amplifiers of figure 2.17. The left 2 circuits in Figure 2.21 shows the circuit configuration for the time response shown in figures 2.22 and 2.23. The right circuit in figure 2.21, shows how these circuits can be changed to obtain the frequency responses shown in figure 2.24. For figures 2.22 and 2.23 an input voltage of 0.6Vp and APLAC Trans simulators are used. The APLAC Trans simulator provides a more accurate waveform simulation than can be obtained using harmonic balance simulators. To plot the time waveforms, Right click on Graphs, and create a new graph. Add a new measurement and select Nonlinear Voltage Vtime and then select the desired Data Source Name, Measurement Component and Sweep Frequency to be shown. For a frequency plot of the voltage gain select Linear Voltage VGT and then select the desired Data Source Name, ports and dB Magnitude. RF Electronics: Design and Simulation 21 www.cadence.com/go/awr

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