Part Number: TRF7970A
In an effort to increase ISO15693 read range with the TRF7970A I added an output amplifier, which works fine. On the receive side, I am experimenting ways to improve the receive path without much success, so far. Perhaps you can enlighten me regarding of one of my concepts:
Feedback to RX_IN1 is through a capacitive divider & small resistor, keeping the input to ~3V p-p. Thinking I could improve SNR by reducing the 13.56 MHz content, I added a trap to the signal. Modifying the capacitive divider to bring the input back to 3V p-p, this should return more of the modulated 423.75 kHz carrier to the detector.
Well, that didn't work. As the input circuit is pretty much a black box (envelope detector, two stage filter & AGC -- that's the limit of my knowledge of the internals), there may be a fundamental fallacy in my thinking. Before continuing down this path, I'd like some opinions.
Thank you.
-Mark