T-Junction Loaded With Interdigital Capacitor for Differential Measurement of Permittivity

The microwave sensors have been successfully used for permittivity measurement. These suffer from limited sensitivity and environmental effects. This paper presents a novel T-junction highly sensitive sensor measurement of low loss solid materials. proposed operation principle is based on downshifting the transmission zero outputs with coupling material under test (MUT). sensing section consist an interdigital capacitor (IDC) located in between lines T-junction. IDC directly connected to output arms so that it could disturb strongly. Any change electric field concentration transmitted translated as TZ change. Design steps including effects are presented details. described through equivalent circuit model which validated by simulation experimental results. Two show same electrical performances allow differential mode. Hence, cross due factors can be tolerated sensor. Measurement results fabricated prototype shows 112 MHz frequency shift per unit change, normalized 3.9 %, larger than available similar sensors. implemented 22.22 × 18.76 1.6 mm3 printed board.