Table 8.

Summary of various designs of microwave planar resonators in terms of physical and electric size including sensing and measurement types.

Ref.	Sensor	f (GHz)	Fabricated Material Substrate	${\mathit{ϵ}}_{\mathit{r}}$	Physical Size (mm/${\mathit{\lambda }}_{\mathit{o}}$)	Electrical Size (${\mathit{\lambda }}_{\mathit{g}}$)	Structure	Sensing	Measurement Type
[18]	Square SIW	2.1887	Rogers4003	3.55	55 × 50/0.4 × 0.36	0.76 × 0.69	Planar	Liquid	Non-invasive and contactless
[140]	SIW	13.48	Rogers RT5870	2.33	33 × 28/1.48 × 1.26	2.26 × 1.92	Planar	Liquid	Non-invasive and contactless
[141]	SIW circular	2.6	F4B	2.65	36 × 34/0.3 × 0.29	0.51 × 0.48	Planar	Liquid	Non-invasive and contactless
[118]	CSRR	2.4	FR4	4.1	35 × 25/0.28 × 0.2	0.57 × 0.4	Planar	Liquid	Non-invasive and contactless
[23]	MCSRR	1.618	Roger RO4350	3.66	78 × 50/0.4 × 0.27	0.8 × 0.52	Planar	Liquid	Non-invasive and contactless
[142]	CSRR	5.39	Thin substrate	2.9	30 × 30/0.54 × 0.54	0.92 × 0.92	Planar	Solid	destructive and contact
[76]	CSSSR	15.17	FR4	4.4 *	30 × 25/1.52 × 1.26	3.18 × 2.65	Planar	Solid	Destructive and contact
[143]	MIMring resonator	3.82	Rogers RO4003	3.38	34 × 34/0.38 × 0.38	0.7 × 0.7	Planar	Liquid	Non-invasive and contactless
[144]	CSRR	3.1	FR-4	4.4	64 × 48/0.66 × 0.5	1.39 × 1.04	Planar	Solid/soil water content	Destructive and contact
[101]	Circular SIW	4.4	Roger RT5880	2.2	79.92 × 79.92/1.2 × 1.2	1.7 × 1.7	Planar	Liquid	Non-invasive and contactless
[145]	SIW with negative order resonance	2.5	RO4003C	3.55	50 × 30/0.42 × 0.25	0.79 × 0.47	Planar	Liquid	Non-invasive and contactless
[146]	Electrically-coupled resonators	2.5	Roger 5880	2.2	45.44 × 45.44/0.38 × 038	0.56 × 0.56	Planar	Solid	Destructive and contact
[147]	CSRR	2.9	Neltec NY9217(IM)	2.17	40 × 26/0.39 × 0.25	0.57 × 0.37	Planar	Liquid	Non-invasive and contactless
[148]	Double microstrip microfluidic sensor	2.61	Rogers 5870	2.33	52 × 42/0.45 × 0.37	0.69 × 0.56	Planar	Liquid	Non-invasive and contactless
[149]	Circular SIW	5	Rogers RT5880	2.2	75 × 75/1.25 × 1.25	1.85 × 1.85	Planar	Liquid	Non-invasive and contactless

* Assumed value.