Table 7.

Comparison of the recent designs of microwave resonators in terms of the electric field profile.

Ref.	Sensor	${\mathit{f}}_{\mathit{o}}$ (GHz)	Applications	Electric Field (v/m)
[117]	Closed-loop enclosed SRR	6.1	For aqueous and blood-glucose measurements	1.225 × ${10}^4$
[118]	Circular CSRR	2.4	For water-ethanol mixtures	5.000 × ${10}^3$
[23]	Differential MCSRR	1.618	Liquid/PDMS	1.066 × ${10}^3$
[78]	Asymmetric CPW SRR	1.57	Solid and liquid sensing	5.000 × ${10}^3$
[119]	Metamaterial-based sensor	12-Aug	Branded and unbranded diesel	1.512 × ${10}^4$
[120]	Microwave planar resonator	4.5∼4.6	For monitoring organic contaminants in water	1.000 × ${10}^4$
[79]	CPW open stub resonator	1.8	Liquid permittivity sensing	1.130 × ${10}^4$
[82]	Dual-band using CSRR	2.45 & 5.8	For investigation of liquid impurity concentration	2.000 × ${10}^4$
[121]	Two CSRRs	2.36	For full characterization of magneto-dielectric materials	1.574 × ${10}^3$
[122]	SIW	2.2	Fully characterizing magneto-dielectric (MD) materials	1.905 × ${10}^3$
[123]	Symmetric CPW with IDC	4.5	For permittivity characterization	1.250 × ${10}^4$
[10]	Metamaterial-based microwave sensor	3.43	Liquid sensor	4.000 × ${10}^4$
[96]	Open CSRR	0.330–0.204	Dropping-based liquid dielectric characterization	1.800 × ${10}^4$
[124]	A sensor based on SSPPs	≈8.7	To detect defects in film-coated metals and non-metallic materials	1.000 × ${10}^3$
[101]	Circular SIW sensor	4.4	For aqueous dielectric detection	1.535 × ${10}^4$
[84]	Planar cylindrical resonant RF sensor	1.5	For the characterization of dielectric samples	4.524 × ${10}^3$
[125]	Microwave sensor based on an interdigital capacitor-shaped defect ground structure	1.5	For permittivity characterization	8.000 × ${10}^3$
[126]	Planar microwave probe	11.56	For adulteration detection in edible oils	8.295 × ${10}^3$
[127]	Radio frequency (RF) resonator-based noncontact sensor	1.37	Accurate quantification of uric acid in temperature-variant aqueous solutions	3.008 × ${10}^3$
[128]	SIW resonator	2.39	A binary water alcohol mixture	2.000 × ${10}^4$
[129]	Radio-frequency dielectric measurement	0.15	Determination of meat moisture content	1.312 × ${10}^4$
[130]	A resonator-based metamaterial	7.6	Solid materials	1.086 × ${10}^4$
[131]	Dual band planar microwave sensor	2.5 & 3.8	For dielectric characterization using solid and liquid samples	9.750 × ${10}^3$
[132]	Transmission line integrated metamaterial-based liquid sensor	8 to 12	Liquid materials	2.500 × ${10}^3$