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Problem with ez430-TMS37157 evaluation kit

Dear friend:

I have problem with direction of the antenna and how to miniaturization it.

Then I made a new antenna(2.66 mH   20Ω) and I have tuned the capacitance , It’s work ,  next step I want to miniaturization it.

So I made another antenna(2.59mH  100Ω,  smaller coil diameter ), I tune the best  capacitance  value with my antenna.

And  I got  this waveform. I don’t know  why TMS37157 ,it’s doesn’t send all of the FSK signal  back to the Reader.

At the first , I guess TMS37157 run out of power because of  antenna resistance is bigger than original one , so I connect the battery, but it

still doesn’t work. or because of the antenna resistance change too much (20Ω->100Ω) ?

Could anyone give me any suggest to solve this issue?  Thank you.