A typical wheastone bridge consists of 4 resistor is amplified by a instrumentation amplifier and an ADC reads the output value. It is required to work under the exposure of UHF signal (900MHz band), the Tx power of the UHF signal is 1W. If the UHF signal is not presented, the ADC value is stable. However, if the UHF signal is presented, the ADC value will fluctuate. For example, under a fixed gain, the ADC value is stable at 20 but it will ripple between 20-400.
The reason is that the wires(traces) on the PCB act as antenna which rectify the RF interference. As a result, a rectified voltage will be added onto the input of INA (Instrumentation amplifier).
To eliminate the rectified voltage, a low pass filter (LFP) [1] as shown in the figure is added at the two input port (V+, V-) of the INA. The LFP indeed works and it reduce large amount of the rectified voltage. However, it is not enough. The ADC value will still ripple between 20-100. Also trying to change the capacitance of the filter capacitor but it does not help.
Any solution to tackle this remain voltage ripple?
[1] https://www.analog.com/media/en/training-seminars/design-handbooks/designers-guide-instrument-amps-complete.pdf
You could try using series notch filters to cut out the 900 MHz band.
for example
https://www.wainwright-filters.com/application/mobile-communication/lte/wrct8-670-1000-5-25-40-28-x-fo-quote/22
You may be able to build your own.
Analog Devices has some updated recommendations, e.g. use of feed-through capacitors
https://www.analog.com/media/en/training-seminars/tutorials/MT-070.pdf
Application note of the ADC usually presents solutions for such problems.
It seems that the solution must be focused mainly on the PCB design (the power layer, the ground layer, vias to ground layers, filtering capacitors....).
However, using BALUNSs (balance to unbalance transformers) at the input of ADC is very effective.
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