I have a question about how to interpret the power gain circles plotted using Spectre's SP analysis
For plotting the power gain circles on the Z-smith chart , there are 2 options: Frequency and Gain Level
Suppose I select sweep "Gain level" Start = 5dB , Stop = 20dB , step = 5
In my circuit, input port = 50-ohms , output port = 500-ohms.
Will this sweep the value of the output port impedance and create circle with all the points where the power gain is the same?Are the values that we read off the smith chart are output reflection coefficients? Are they normalised to the input port or output port resistance?
Is there any technote/tutorial that explains how to use the different 'Main-Form" options in the SP analysis?
Please check out the appendix D of the SpectreRF User guide. The appendix is called: Plotting Spectre S-parameter Simulation Data
You may also want to check out the example: LNA Design Using SpectreRF AppNote
Sr. Staff Support AE, Global Customer Support
Cadence Design Systems, Inc.
In reply to Tawna:
Thanks a ton! Great pointers.
At the University we have a complete Cadence Installation, could you tell me where I can find the schematic for the differential amplifier described that LNA design spectre RF note (LNA_62_appnote). In case it comes with the installation, there must be some standard path I can search
It is not present in the rfExample directory @ $CDS/tools/dfII/samples/artist/rfExamples
rfExamples only has a single ended BJT based LNA circuit.
In reply to bVenu:
I recommend looking in the hierarchy at:
In the directory, there are appNotes there, as well as workshops - one in particular on LNAs.
For more information, please see my blog post from February 2009: "Shhhh....SpectreRF Tutorials and Appnotes - One of our best kept secrets!"
Good luck and have fun!