I have the following setup on a custom PCB. The WT32-ETH01 module can be normally booted into download/flash mode by holding the IO0 to the GND during the start. The IO0 is also used as a clock between the ESP32 and the LAN8720A ethernet PHY chip on the same module.
I had the IO0 trace leading from the WT32-ETH01 across the entire board to the boot button. Everything worked except it made a huge antenna for the 50MHz frequency, which was a problem during EMC testing.
I hoped to overcome this issue by "isolating" the frequency physically near the WT32-ETH01 module with this simple circuit. However, the 50MHz signal leading from LAN8720A ended up partially sinking into the Q1 MOSFET even in its fully closed state. I suppose that as a result of this, the communication between ESP32 and LAN8720A is not working. Though I am not entirely sure as the signal should be ok for clock purposes even with the Q1 connected (see measurements).
I never dealt with such a high frequency, maybe someone can give me a lead here?
Below are also the results of measurements on IO0.
IO0 not connected to the isolation circuit:
IO0 connected to the isolation circuit:
IO0 connected to the isolation circuit and boot button pressed: