ESP32 Based RF Monitor and Ambient Noise Sensor

Overview

This system monitors high frequency RF power in environments. The core of the system is the AD8318 logarithmic detector which is used to measure RF signals between 1 MHz and 8 GHz. This system converts the surrounding RF energy into a DC voltage that is sampled and processed by the ESP32 for real time analysis or data logging.

Key features

• ESP32 WROOM 32U with antenna attachment for logic and Wi-Fi data logging.
• AD8318 demodulating logarithmic amplifier converts antenna RF into a decibel-scaled output voltage.
• LM358 dual op amp scales the detector output into ~1.5–5 V for reliable ESP32 ADC reads.
• AMS1117-3.3 regulates USB-C 5 V down to 3.3 V for the ESP32.
• USB-C input for efficient 5 V supply.
• Board-edge SMA (BWSMA) input for ambient RF pickup from the antenna.

PCB layout

The SMA connector and the AD8318 were placed on the corner of the PCB to minimize interference from the ESP32. The trace between the SMA and AD8318 is kept short to reduce resistance and stray inductance. The LM358 sits between the AD8318 and the ESP32 as buffer/gain, and the 1.5–5 V analog traces are routed away from high-speed digital lines to limit crosstalk. The bottom layer is a solid ground pour for a low-impedance RF return path.