On Sun, Dec 15, 2024 at 01:45 PM, john23 wrote:
Hello, some videos were made from my lab to demostrated the situation.
The main issue is the controller .
There is a PI controller I have simulated.
When I simulation amplifier then I can see the gain on my scope in my lab.
But here its not a regulat gain , its understanding based on the ltspice simulation how it will affect the drift DC in a pll system.
There is nothing could be done in LTspice to see based on AC responve how it will affect the drift in my DC error signal?
I am only guessing here, because I do not understand the overall system.
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I'm guessing that the "drift" you are worried about, happens because of the transfer function of the YIG VCO.? In other words, the DC voltage needed to get the right VCO frequency, drifts over time and temperature.? Yes?
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And I'm guessing the amplifier using the LT1028 must be your error amplifier ("Servo amplifier").? It is approximately an integrator.? Therefore, it will attempt to drive its output voltage to whatever is needed to slew the VCO to the desired frequency.
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But it can drive only to +/- 7 volts, or so.? Is that sufficient to always drive the VCO to the correct frequency, even accounting for the drift?
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The .AC sweep in LTspice (if you extend the sweep down to 1 uHz or so) shows that the DC gain is nearly 150 dB.? It is not infinite, but it is quite large.? You could use a .DC sweep to actually simulate it at "DC".
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You can simulate the drift in LTspice, by adding a variable voltage source at the VCO's input, to inject a variable DC voltage there.
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Andy
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