In a PM*, Jainu11 wrote:
Hey Jim,
I am Jainu, student at Wayne State University, designing an under-graduate class project which picks up signals from different pace - maker circuits and identify the frequency. I have found a similar paper:
https://www.secure-medicine.org/icd-study/icd-study.pdf and using it as a reference. However, since I do not know much about the internal circuitry of the pace - maker, I am having tough time displaying the signal on the oscilloscope. If you could help me with a circuit that can be used to display 175Khz frequency picked up from that device at a distance of 15cm, using a pcb circuit.. it would be great.
Thanks for your help
-- Jainu
In the paper in the link, they state that they used a ferrite rod antenna from an AM radio, this can be clearly seen in the photo.
My initial thoughts were that a coil of wire would be a good solution.
Make the coil 3 inches diameter with 50 turns of 28 gauge wire.
I also thought that it would be a good idea to add a parallel capacitor to resonate the coil at 175khz, and thus increase to output voltage.
However, reading the paper, it appears that the signal from the pacemaker is two frequency FSK, centred on 175khz.
The two frequencies being 150 and 200khz.
To get a reasonable response from a single tuned coil under such conditions would result in such a low Q that the improvement would not be worthwhile.
Also, the paper tells us that it is necessary to trigger the pacemaker using a magnet before it will transmit data, otherwise, nothing.
JimB
*It is a good idea to keep information and correspondance within the forum, it increases your chances of a meaningfull reply.
Note that this is the second attempt at typing this, on the first attempt ETO threw a fit and declared a database error, losing my words in the process!