Ground Loops result, when more than one wire is used for a ground connection. These wires span up an area which can really ruin your day. The design with a transformer is suiteable for RF-signals. For digital signals, optocouplers are more appropriate. This design is mainly intended to be used for the 10 MHz Reference which is distributed to many devices in our labs.

As the main application is the isolation of a 10 MHz Reference Signal, we used the SWB1010-PCL from Coilcraft. The datasheet says, that it works nicely from 5 kHz up to 100 MHz. However, the final device shows a slightly shifted upwards behaviour. We measured a lower cutoff frequency of approx. 30 kHz and an upper cutoff (both -3dB) of approx. 250 MHz.


Fig. 1 : The Frequency Response S21 at the lower end



Fig. 2 : The overall Frequency Response


The Insertion Loss in the frequency range of interest is approx. 0.5 dB.

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