3. Experimental Procedure
In this work, an antenna in the form of traditional interdigitated electrodes (IDE) was used to provide
maximum interaction with the tested oil samples. Fig. 1 details the layout used along with IDE
dimensions, which are in mm. Standard 1.57 mm thick FR4 substrate (supplied by Mega-UK) covered
with 35 μm Cu layers from both sides was used, on one side of which IDE antenna was patterned with
Bungarde CNC router. Standard MOLEX 5-pin SMA connector was soldered to both antennas to feed the
microwave signal, as shown in Fig. 2. Various vegetable oil samples were bought from local
supermarkets (see Fig. 3) and tested (20 ml volume) to verify the applicability of the proposed novel
microwave sensor. The experimental setup used to test the IDE antenna response is shown in Fig. 4. It
comprises a Hewlett Packard Vector Network Analyser (VNA), microwave sensor and N-type cable to
connect the VNA and sensor. The connection arrangement allowed reflected power S11 analysis.