RF Electronics Chapter 2: Computer Simulation Page 9
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Select the project window again and select Graph and right mouse click and select add
measurement. This opens the window shown in figure 2.4. RF devices are normally
specified by the Scattering (S) parameters. These are described in more detail in chapter
8 and equations 8.3 to 8.12. Pozar [7] in section 4.3 gives a detailed description of S
parameters. They give a simple performance measurement of the circuit. S
11
and S
22
are
the input and output return loss, indicating how well the device is matched. S
21
and S
12
are the forward and reverse gains. Select Linear Measurement type Port Parameter
and S parameter to obtain S parameter measurements of the filter, as shown in figure 2.4.
Save the project as "LowPassFilter" to keep these values. Since this circuit is to be
connected using TV Coaxial cable, ensure that the impedance of the ports is changed from
the default value of 50 to 75 .
Now set the operating frequency range using the Project options entry in the left bar. Set
the Global Units frequency to MHz and then set the operating frequency range in the
Frequencies window as shown in figure 2.5.
Figure 2.5. Project frequencies.
Figure 2.6. Frequency response of the low-pass filter.
RF Electronics: Design and Simulation
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