ABSTRACT This research designed a microwave sensor for measuring pesticide residue concentration in agricultural water, operating at a frequency range of 1-3 GHz. The sensor utilizes two types of substrates: Polyethylene Terephthalate (PET) with a thickness of 0.135 mm and FR-4 with a thickness of 1.6 mm. To achieve high sensitivity, the sensor employs a capacitive coupling technique to produc…