Salt and sugar detection system using a compact microstrip patch antenna

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Return loss of the antenna in different concentrations of sugar in water_

S. No.	Frequency	Return loss (concentration: 20%)	Return loss (concentration: 50%)	Return loss (concentration: 80%)
1	2.38 GHz	23.558 dB	19.123 dB	13.022 dB
2	2.56 GHz	24.251 dB	22.012 dB	13.223 dB
3	2.72 GHz	24.097 dB	21.293 dB	13.144 dB
4	2.86 GHz	22.044 dB	17.272 dB	11.962 dB

Comparison of proposed antenna with existing antennas for salt and sugar detection_

Reference	Antenna type	Center frequency	Dimensions of the antenna	Substrate parameters
Cheng et al. (2014a)	Rectangular microstrip antenna	2.45 GHz	0.47λ0 × 0.388λ0	εr = 2.2, h = 1.575 mm
Cheng et al. (2014a)	Circular microstrip antenna	2.45 GHz	0.465λ0 × 0.465λ0	εr = 2.2, h = 1.575 mm
Cheng et al. (2014a)	Square microstrip antenna	2.45 GHz	0.529λ0 × 0.529λ0	εr = 2.2, h = 1.575 mm
Rahman et al. (2018b)	Circulated psi-shaped patch	16 GHz	1.28λ0 × 0.96λ0	εr = 2.2, h = 1.57 mm
Islam et al. (2018)	Crescent-shaped microstrip antenna	10.6 GHz	1.13λ0 × 0.777λ0	εr = 4.6, h = 1.6 mm
Rahman et al. (2018a)	Fork-shaped patch	9.5 GHz	0.76λ0 × 0.57λ0	εr = 2.2, h = 1.57 mm
Proposed method	Rectangular microstrip antenna	2.4 GHz	0.41λ0 × 0.41λ0	εr = 4.3, h = 1.5 mm

Optimized dimensions of the compact antenna_

S. No.	Dimensional parameter	Values
1	L	25.65 mm
2	W	25.65 mm
3	Lg	51.3 mm
4	Wg	51.3 mm
5	Lg1	25.65 mm
6	Wg1	25.65 mm
7	Lg2	24.41 mm
8	Wg2	5.1525 mm
9	g	2.5875 mm
10	h	1.5 mm
11	t	0.035 mm
12	εr	4.3

Dimensions of the antenna with and without DGS_

S. No.	Antenna type	Area of patch	Area of ground plane
1	Antenna without DGS	838.1 mm2	3,352.4 mm2
2	Antenna with DGS	657.9 mm2	2,631.7 mm2

Gain, directivity, and efficiencies of the antenna at 2_4 GHz 2_4 GHz _

Radiation efficiency	Total efficiency	Max. gain	Max. directivity
−1.84 dB	−1.97 dB	2.12 dB	3.95 dBi

Effect of slot length on various parameters_

S. No.	Slot length	Resonant frequency	VSWR (at 2.4 GHz)	|S11| (at 2.4 GHz)
1	24.95 mm	2.466 GHz	1.514	−13.433 dB
2	25.65 mm	2.402 GHz	1.389	−15.768 dB
3	26.45 mm	2.336 GHz	1.68	−11.913 dB
4	28.95 mm	2.082 GHz	4.624	−3.817 dB

Return loss of the antenna in different concentrations of salt in water_

S. No.	Frequency	Return loss (concentration: 20%)	Return loss (concentration: 50%)	Return loss (concentration: 80%)
1	2.38 GHz	23.271 dB	21.017 dB	13.334 dB
2	2.56 GHz	23.757 dB	20.54 dB	13.281 dB
3	2.72 GHz GHz	24.582 dB	19.84 dB	13.046 dB
4	2.86 GHz	23.253 dB	17.095 dB	11.691 dB