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180-degree phase shifter shows -90 degree in the graph measurement

FormerMember
FormerMember

Hello,

I am testing a simple high-pass/low-pass phase shifter using lumped elements in AWRDE/Microwave Office. 

The 90-degree shifter looks about right, but the 180-degree shifter shows -90 degrees instead of +/- 180 degrees of shift at 146MHz.

(The L and C values are calculated using the equations here, they are right based on the spreadsheet at 146MHz: https://www.microwaves101.com/encyclopedias/high-pass-low-pass-phase-shifters )

Here is a screenshot of my schematics and graph.  What can I do to read the correct shift for the 180-degree shifter?

Thank you for your help!

-Eric

  • Dear Eric,

    Unknown said:
    The 90-degree shifter looks about right, but the 180-degree shifter shows -90 degrees instead of +/- 180 degrees of shift at 146MHz.

    That is totally consistent with the result I am observing in a different simulator using a high Q inductor. However, the phase shifter will be highly dependent on th Q you have chosen for your inductors and capacitors. I will provide a plot of the variation in phase with respect to inductor real impedance when it completes. This is expected for phase shifters. Recall that the phase of a signal is far more sensitive than the magnitude. Hence, a change in inductor real part may not impact the magnitude of your transfer function significantly but can have a very significant impact on phase - which I believe may be the reason your simulation result differs from your expected value.

    What Q have you chosen for your components? 

    Shawn

  • FormerMember
    FormerMember in reply to ShawnLogan

    Hi Shawn, thanks for the reply.  These are just closed form ideal inductor/capacitors ("IND"/"CAP") in AWR, this model doesn't define a Q value I don't think, so please correct me if I'm wrong and need to change something.  Since they are ideal, shouldn't it behave the way as the HP/LP shifter equations? 

    Here's the description for the "HP-LP phase shifter" spreadsheet: www.microwaves101.com/download-area

    Here is the Excell spreadsheet directly:

    www.microwaves101.com/.../HPLP-Phase-Shifter101-Rev2.xlsx

    All you have to do is enter 0.146 GHz on the 2nd sheet named "Single bit with plots" and set the phase shift to 180 if you want to see the details.

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