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The sources Vs1 and Vs2 are both measured by an ideal scope or ADC which has input impedance of 100Meg:

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The only difference between two sources are their output impedances 50 Ohm and 10k Ohm.

My aim is to simplify and demonstrate that high output impedance source picks up more noise than the lower. For simplicity, I first made the source outputs 0V.

Now where I am stuck at is:

How can I diagrammatically couple electric field or magnetic filed noise to both of these circuits above so that the simulation shows us the higher output impedance circuit results more interface pick up? I am stuck how to use a current or voltage source to mimic such interference in the circuits. A modified schematics of mine would be great help.

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There are two main near field coupling mechanisms for interference, inductive (magnetic field) or capacitative (electric field).

You can simulate the capacitative interaction by putting a mother ac source in your simulation coupled into the junction of the source and destination.

The actual value of the capacitance will depend upon the frequencies you wish to simulate. It should be low enough value that most of the source voltage is dropped across the capacitor. You will find that as the source impedance increases the amount of interference increases.

For magnetic field coupling you can use a transformer driven by your noise source and rather than in parallel, you put the secondary in series between the signal source and the load - you will find that the interference either is not affected by the source impedance or is worse at low impedances.

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