Life of any automobile engine is largely dependent on the purity as well as the optimum ratios of their fuels, viz. petrol, diesel and ethanol. A device working on the electrical metamaterial concept, namely a complementary split ring resonator (CSRR), operating at 2.47 GHz (ISM band), is proposed to detect kerosene adulteration in petrol. Kerosene was varied upto 30 per cent with minimum detection limit as low as 10 per cent. Systematic shifts in the transmission resonance frequency were observed. The sensing was fast and the recovery was instantaneous. The underlying concept of interference of electromagnetic radiation through the CSRR circuit and its further manipulation with the changes in the dielectric ambience is elaborated.Keywords: Electrical metamaterials, complementary split ring resonator, adulteration, flex fuel sensors Defence Science Journal, Vol. 66, No. 4, July 2016, pp. 421-424, DOI : 10.14429/dsj.66.10217 2016
RESEARCH ARTIClEReceived : 04 May 2016, Revised : 24 May 2016 Accepted : 07 June 2016, Online published : 28 June 2016 DEF. SCI. J., VOL. 66, NO. 4, JULy 2016 422 perpendicular to the CSRR plane. This excitation can be accomplished by using a microstrip transmission line with the CSRR etched on the ground plane. The resonant frequency is given by the following standard expression 19 :ω o is the angular resonant frequency l C and C C are inductance and capacitance of the CSRR. Change in the permittivity of the sample material reflects the change in the capacitance of the CSRR (C C ) of the sensor 20 . The CSRR was designed with specific dimensions to yield the resonant frequency of 2.51 GHz. Figure 1(a) shows the copper structure which was fabricated on a commercially available FR4 epoxy (ε r = 4.4 thickness h = 1.6 mm) substrate. The structure was embedded in the PDMS mould, to make a cavity for liquid confinement which shifted the resonating frequency of the sensor to 2.47 GHz. A micro-pipette was used to drop-cast the liquids in the cavity, completely filling the cavity for pure as well as adulterated fuels. The color difference in the adulterated fuels, when compared to pure petrol, is hardly differentiable as shown in inset of Fig. 1(a). The measurements were carried out for 10 per cent, 20 per cent and 30 per cent adulterated fuels. The PDMS cavity was so designed that the walls of the cavity restricted the liquid sample strictly over the active area of the sensor. The CSRR unit cell structure and experimental set up has been mentioned in detailed by Rawat 10 , et al. The cell dimensions of the CSRR for the desired resonant frequency area = 6.82 mm, c =0.52 mm, d = 0.2 mm and g = 0.32 mm. The shape of the microstrip line was changed from rectangular to plus-sign as to further reduce the size while retaining the Q-factor of the device. Dimensions of the device was 26 mm x 20 mm.
results and dIscussIonThe simulation of CSRR design (with and without PDMS cavity) was carried out using CST Microwave Studio which matched well with experimental results (not shown). Fig 1(b) ...
