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To get 5V output, you'll supply about 5.5 - 6V to SG3525 Vc pin. Apparently actual Vc voltage is too low.
We don't know which modules you are using and how they connect Vc.
We don't know enough about the application to determine if hardware sensor calibration is feasible. It's however obvious that resolution at 25 S/s will be noise limited. A detailed calculation is necessary as design starting point.
You are right, I overlooked the divider. I appreciate your approach to break down the problem into detail measurements. However post #3 sample variance already shows a serious problem of the test setup.
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Comparing the variance of low R_t and high R_t measurements suggests that we see...
I think it's not the appropriate ADC for your application. (25 S/s, nV resolution). If these are strain gauge bridges, we would use modulated bridge supply if ever possible, eliminating the need for offset compensation. If not possible some kind of auto-zero would be applied. It's your job to...
Nominal U1A output of the shown circuit for R_t range of 10k to 1M is 3.75 to 5 V, all outside STM32 ADC voltage range with forward biased schottky diode. I suppose the schematic doesn't show the real circuit.
Whatever the actual circuit is, the table shows that present measurement value...
It's completely unrealistic to implement the mentioned parameters (tpw 500 ns, trf 10 ns, td 1 ms) with a LC delay line. Digital pulse generation is most likely the best way.
The Kemet equivalent circuit is unusual, I didn't yet see it in other literature. But it's still a simplified circuit and you shouldn't read too much into it. Better measure the real complex impedance curve. And if it's important for you to have an exact model, see which model can be fitted best...
Intended switching speed gives an upper limit for control signal bypass capacitors.
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Right, and I gave an explanation why they are probably not necessary. But explicitly mentioned in datasheet or not, there's nothing against thinking on your own.
Does the evaluation board use bypass capacitors at control inputs? Image in datasheet suggests it doesn't. GaAs RF switches are typically involving inbuilt series resistance at control inputs acting as low pass. Small capacitors (100 pF range) can help to completely block RF entering or leaving...
A battery usually doesn't generate noise. Loaded voltage and possibly impedance of the rechargeable battery may be different and affect transmitter operation. I'd measure battery voltage in operation as first step.
You are apparently assuming that the battery incorporates an electronic circuit...
Yes I know, but this makes the concept almost unrealizable. Limitations are inductor voltage, resonator Q, inductor size (~ I^2 L). I'd consider high frequent inductive transmission in the first place.
I'd like to refer to my statement in a previous post
https://www.edaboard.com/threads/about-separating-supplies-on-pcb.385857/#post-1657995
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Another related previous discussion
https://www.edaboard.com/threads/ferrite-bead-usage-in-adcs.388093
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