Philippa Young

Designing an Analogue Low Pass Filter System for a Quantum Ion Trap.

Testing

These filters can be tested in the exact same way as the first six.

To test the filters an oscilloscope and a frequency generator are needed. The oscilloscope is used to first measure the voltage out from the frequency generator each time. This should remain constant.

The filter is then connected into the loop so that the V_in comes from the frequency generator, and V_out goes to the scope.

The voltage out is measured on the scope as the frequency is increased in order to obtain enough data to plot a graph, or until the V_out is minimal and is no longer falling.

If the filter gives satisfactory results then the process can be repeated for each of the 100 filters.

Results

Unfortunately there was a problem with this prototype filter which I spent my last week trying to rectify. The response of the filter was very different from expected and was most likely caused by such small value inductors which were behaving as capacitors above a certain frequency.

In order to fix this the specification sheets for the components will need to be looked at to ensure the inductors are inductors at our frequency and the capacitors are capacitors.

Once this problem is fixed the circuit can be re tested and if successful a whole batch can be made.

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