Table 2.

Comparison table of proposed sensor and other RF sensors.

References	Sensing Material	Frequency [GHz]	Frequency Shift (Δf) † [MHz]	Electrical Size ††	Sensitivity † (MHz/εr)	Volume [μL]
[16]	Ethanol liquid	4.62–4.69	70	0.93λg × 0.81λg	12.73	1
[20]	Ethanol liquid	4.23–4.48	250	1.26λg × 0.63λg	45.45	5
[21]	Amonia gas	4.210–4.367	157	1.29λg × 1.29λg	N/A	N/A
[49]	Ethanol gas	14.85–15.07	220	2.71λg × 1.35λg	40	N/A
This Work	Ethanol liquid	3.89–4.16	270	0.63λg × 0.51λg	49.1	3

^† Frequency shift (Δf) and sensitivity (Δf/Δε_r) are estimated from air and ethanol; ε_r of ethanol is assumed to be 6.5; ^†† λ_g is guided wavelength.