Where To Find This Example
Select Help > Open Examples... from the menus and type either the example name listed above or one of the keywords below.
Or in Version 14 or higher you can open the project directly from this page using this button. Make sure to select the Enable Guided Help before clicking this button.
10 GHZ LOW NOISE AMPLIFIER:
This project demonstrates the following Microwave Office features used in designing a 10GHz Low Noise amplifier:
Icells for layout
Freq. subset Smith Chart plots
X-Models for Discontinuities Accuracy
This project shows the design of a 10 GHz LNA built on 10 mil alumina using a NEC 76038 GaAs MESFET. The LNA has 7.7dB gain and 2.15dB NF at 10 GHz.
Label Project Name, Date, and Time
For any schematic or graph if you add text ( Draw > Add Text) with the exact names, Project:, Time:, or Date: (notice the semicolons). You can run a script to fill in that information. Select Scripts > Global Scripts > Project > Label_Time_Date_Project_Name .
In this project, these text strings are on the Stable_Amplfiier schematic in the lower right corner, run this script to see these values appear. You may have to zoom to see the text after the script runs.
Activate the Final Amplifier schematic by clicking on the title bar of the "Final Amplifier" schematic. Notice the context sensitive tool bars along the top of AWR change to present the available commands when a schematic window is active. Press the Tune icon to active the real-time tuner. The second variable tunes the length of the shunt stub in the "Output Match" schematic. Hold the Ctrl key down while moving the slider and you can see the layout change while the Gain and Output Match change in the "Gain and Match" graph.
By looking at the layout one can see that the shunt stub will extend beyond the substrate if the length is tuned too long. This is the advantage of seeing the layout in addition to the electrical response when tuning variables.
Open the "Output Match" schematic, press the New Schematic Layout View icon along to top of the AWR Design Environment. Double-click on the shunt stub in the layout, black drag handles will appear. Click and drag the drag handles to adjust the length and width of the stub. Notice how the dimensions in the schematic update as the drag handles in layout are moved. This demonstrates the tight dependency of layout on schematic and ensures that layout matches simulation.
Icells($) for Layout
Staying with the "Output Match" schematic and layout, notice that when the width of the shunt stub is changed, the MTEE junction adjusts itself to match the new width of the stub. The MTEEX$ element is an Icell, it checks the width of the MLIN elements connected to it and adjusts itself to match the MLIN width. This further insures that the simulation is accurate with the layout and eliminates the need to write a bunch of equations to try to make sure the MTEE junction widths are correct.
Frequency Subset Plots on Smith Chart
When designing an LNA it is necessary to look at the noise circles in order to design the input match to the device. However, plotting noise circles at every project frequency can make it difficult to see which noise circle corresponds to a particular frequency. In order to solve this problem, Microwave Office allows the user plot individual the frequency range of the schematic instead of the project or plot subsets of the selected frequency range associated with the measurement. In the project browser window, double click on the "Stable Amplifier:NFCIR(1,1)" measurement under "Noise Circles". A measurement dialog box appears. Find the Sweep Freq(FDOC) box and press the up arrow to change the Sweep Freq to (FPRJ). Notice how all of the noise circles for all of the project frequencies are displayed. The FDOC frequency range is set from the "Stable Amplifier" schematic. Right click on "Stable Amplifier" in the project browser, select Options. Under the Frequencies tab you will see 9, 10, 11 GHz for the frequency range.
If you want to use a subset of the measurement frequency range, right click in the "Noise Circles" graph and select properties. From the Grid tab, you can change the Sweep Value Limits. By default it is set to use whatever is set in the measurement dialog box.
The finished design can be exported from MWOffice in various formats, including Gerber, GDSII, DXF, or PADS files.
Modeling and Simulation
The X-Models rely on pre-generated equations based on a given substrate definition. Many of these have been simulated by AWR and can be found under the <Root AWR installation>\EM_Models folder. To generate new X-Models for your specific substrate definition if they do not already exist is simple. Please see the examples under the X-Models folder in the examples directory.