ME1010 RF Circuit Design (Agilent Genesys)
Lab 3
RF Low-Pass and Band-Pass Filters Design
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Objectives
i)To design low-pass and band-pass filters in Genesys
ii)To implement a band-pass filter using available commercial part library
1Background
For this lab, you will create a schematic-based Butterworth low-pass filter with cut-off at 900 MHz. Then, you will proceed to design a band-pass filter operating from 820 MHz to 1400 MHz, with the specification summarized in Figure 1.
Figure 1 – Band-Pass Filter Specifications
2Low-Pass Filter and Band-Pass Filters
2.1Creating a New Low-Pass Filter from Pre-configured Synthesized Template
1.Run Genesys from Windows desktop.
2.Click File > New and the Getting Started with Genesys page will appear. Under the Synthesize a new design template, select the Passive Filter and click OK(See Figure 2). This will create a new workspace which consists of filter schematic, analysis, and graph files.
Figure 2 – Creating a New Workspace in Genesys
3.When the dialog box appears, select Factory Default Values, type in a name such as LC_lowpass and click OK as seen in Figure 3.
Figure 3 – Naming a New Schematic
4.A default synthesized filter template is displayed with a 7th order Chebyshev low-pass filter and now Workspace Tree has Analysis, Dataset, Schematic, and graph files, as shownin Figure 4.
Figure 4 – Default Filter Template
5.In order to organize the workspace, use the mouse to drag and drop both the LC_lowpass properties and LC_lowpass Response files into the LC_lowpass_Dir, as shownin Figure 5.
Figure 5–Arranging the Files into a Folder
6.Finally, save the workspace file as Lab3_filtersas shown in Figure 6.
Figure 6 – Saving the Workspace Files
2.2Entering the Low-Pass Filter Specifications
- In the Filter Properties dialog box, under the Topology tab, select the Butterworth filter shape and leave the rest as default (Type : Lowpass and Subtype : Minimum Capacitor).Refer to Figure 7. Note that if the Filter Properties dialog is not displayed, double-click the file in Workspace Tree to open it.Refer to Figure 6.
Figure 7 – Changing the Filter Type and Shape
- In the Settings tab, set the Cutoff Frequency (MHz) to 900 and the Order of the filter to 3 as shownin Figure 8. The circuit in the schematic window will appear with 3 sets of LC components.Also,the filter response is updated in the LC_lowpass_Response window.
Figure 8 – Changing the Filter Order
- Save the workspace.
2.3Creating a New Folder for Band-Pass Filter Design in the Workspace Tree
1.In the Workspace Tree window, right-click the Lab3_filters folder and click Add > Syntheses > Add Passive Filter to open the Create a new Passive Filter dialog box. When the dialog box appears, select the Factory Default Values, type in a name such as LC-bandpass and click OK.Refer to Figure 9.
Figure 9 – Creating a New Passive Filter Folder in Workspace
2.Same as before, all initial analysis, dataset, schematic, and graph files are automatically created.
3.Move both the LC_bandpass and LC_bandpass_ Response files into the LC_bandpass_Dir, as shown in Figure 10.
Figure 10 – Reorganizing Files into Folder in theWorkspace Tree
4.Save the workspace.
2.4Entering theBand-Pass Filter Specifications
1. In the Filter Properties dialog box, under the Topology tab, select the Chebyshev filter shape,Bandpass filter type with Minimum Inductor subtype as shownin Figure 11. Note that there could be a warning shown in the Issues window.
Figure 11 – Setting the Band-pass Filter Topology
2. In the Settings tab, set the following: Low Cutoff (MHz) to 851.5, High Cutoff (MHz) to 1349, Order to 3, Passband Ripple (dB) to 0.5, and Attenuation at Cutoff (dB) to 0.5. Note that the
3dB cutoff frequencies are displayed at the bottom of the dialog box, corresponding to the specification listed in Figure 1. The circuit schematic and graph are also automatically updated as shown in Figure 12.
Figure 12 – Setting the Band-Pass Filter Parameters
3. Save the workspace again.
2.5ImplementingBand-Pass Filter with Commercial LC Components
1.Unzip ZIP package named Johanson Tech.exe located in folder C:\Program Files\ Genesys2010.05\SData\Johanson Tech\ into C:\Program Files\Genesys2010.05\SData\ Johanson Tech\ folder.
2.Go to the LC_bandpass_Design schematic window. From the menu, click View > Part Selector A to open the part selector window. In the Current Library and Category areas, select Johanson Tech and Capacitor. Next, scroll down to search for the R14C1R2 capacitor corresponding to a value of 1.2 pF and the R14C100 capacitor corresponding to a value of
10 pF. Next, insert one RC14C1R2 and two RC14C100 capacitors into the schematic.Refer to Figure 13.
Figure 13 – Searching and Inserting Commercial Capacitors into Schematic
3.Repeat the same procedure to search and insert three commercial Johanson Tech inductors into the schematic, namely L-14C15N_SNT corresponding to 15 nH and L-14C2N2_SERcorresponding to 2.2 nH.Refer to Figure 14.
Figure 14 – Searching and Inserting Commercial Inductors into Schematic
4.Now, connect all the components (capacitors and inductors) together to form the band-pass filter designed previously. Also, insert all the other components such input port (as Port_3), output port (as Port_ 4) and grounds into the schematic. The final circuits should be in the same schematic as the previous design using ideal components.Refer to Figure 15.
Figure 15– Band-Pass Filter Design with Ideal and Commercial Components
5.Right-click on the LC_bandpass_Response graph and select GraphProperties. In the properties dialog box, click the Add button to insert two additional plots namely S33 and S43 corresponding to the LC_bandpass_Analysis_Data into the graph response.Refer to Figure 16.
Figure 16– Plotting the Results of the Filter Design Using Commercial Parts
6.The graph response corresponding to the ideal and commercial components is plotted in the same graph as seen in Figure 17.
Figure 17 – Results of Using Ideal and Commercial Componentsin Band-Pass Filter Design
7.Save the workspace.
3Review Questions
- Construct and simulate the following LC circuit schematic in GENESYS:
- What type of filter is it?
- Determine the 3dB cutoff frequency for this filter.
- Repeat question 1 with the component interchanged as shown below: