. 2022 Dec 6;22(23):9549. doi: 10.3390/s22239549

Table 3.

Comparison of UWB antennas based on various parameters.

Ref. No.	Size (mm²)	Operating Frequency Range (GHz)	Substrate	Gain (dB)	SAR (W/Kg) (Frequency GHz)	Efficiency (%)	Methodology	Merits/Demerits	Demerits
[34] 2018	$80 \times 67$	7.2–9.2	Kapton ( $ε_{r}$ = 3.48, tanδ = 0.002)	3.1	-	-	Ellipse patch with CPW feed.	Simple structure and highly flexible.	Large physical dimensions. Higher cross-polarization components wen antenna is crumpled.
[59] 2020	$32 \times 52$	4.1–8.0	Graphene film ( $ε_{r}$ = 3.2)	4.1	-	-	Rectangular patch with two “H” shaped slots.	Super flexible having bending insensitive bandwidth.	The antenna has a lesser impedance bandwidth and resonant frequencies shift at different bending scenarios.
[60] 2019	$33 \times 50$	1.35–16.4	Polyimide ( $ε_{r}$ = 3.5, tanδ = 0.001)	2.8	-	86%	Elliptical-shaped radiating element, fed by a linearly coplanar waveguide with ladder-shaped ground planes.	Wider impedance bandwidth, contains the entire 3.1–10.6 GHz UWB band and relatively compact.	Low gain and bending effect the far-field radiation patterns of the antenna.
[61] 2020	$30.4 \times 48$	3.06–13.5 15.9–20.5 20.9–22	Kapton Polyimide ( $ε_{r}$ = 3.5)	1.69	-	59%	Circle- rectangular hybrid shaped antenna.	Wider bandwidth and compact design. The proposed antenna maintains wide bandwidth when ε_r changes from 1 to 4.	Low gain and efficiency
[26] 2020	$75 \times 75$	2.85–8.6	PDMS ( $ε_{r}$ = 2.77, tanδ = 0.02–0.076)	6.2	-	45%	Angular ring circular patch loaded with two rectangular slots.	Stable radiation pattern across the frequency band.	Complex design, very low efficiency and large dimension.
[62] 2021	$106 \times 300$	0.34–1.4	Polyimide ( $ε_{r}$ = 3.5, tanδ = 0.0027)	>4	-	60%	Flaring ground with arrow section slots on radiating patch.	The antenna is intended for UHF application and highly flexible due to low thickness of the substrate.	Lower bandwidth and large dimension
[43] 2018	$33.1 \times 32.7$	3.2–30.0	Photo paper ( $ε_{r}$ = 2.85, tanδ = 0.05)	4.87	-	86.60%	Circular patch with double stepped symmetric ground.	Super wideband and high efficiency.	SAR analysis is not studied.
[24] 2022	$67 \times 44$	1.5–15	PDMS ( $ε_{r}$ = 2.7, tanδ = 0.0134)	6.76	1.1979 (1.8 GHz) 1.376 (2.4 GHz) 1.0696 (0.6 GHz) 0.6966 (4.2 GHz) 0.4046 (4.8 GHz) 0.5206 (5.2 GHz) 0.3293 (5.8 GHz)	-	A fork-shaped antenna with a circular patch at the center and a crescent-shaped slot below the circle relative to the ground plane.	Better radiation characteristics, gain and bandwidth.	Large physical dimensions.
[28] 2020	$40 \times 45$	1.198–4.055	Polyester fabric ( $ε_{r}$ = 1.7, tanδ = 0.004)	2.9	0.0014 (10 g) (2 GHz)	56.4% to 70.96%	Interdigit-based radiating patch with triangle slot.	Structure of the design is relatively unique. The antenna retains its performance when it is being bent or working in the proximity of tissue-mimicking phantoms.	An interdigit based radiator contribute to the coupling. Gain and bandwidth are small. The radiation patterns of the bent on-phantom antenna are slightly altered.
[63] 2021	$29 \times 37.5$	4–8	Soda-lime glass ( $ε_{r}$ = 7.3, tanδ = 0.04)	1.2	-	>63%	Circular monopole antenna with dual substrates and proximity coupling fed.	Compact and transparent antenna.	Complex design and low gain
[64] 2020	$55 \times 30$	1.77–6.95	Kapton ( $ε_{r}$ = 3.5, tanδ = 0.007)	5.9	-	60%	Two inverted L shaped elements with a matching stub and defected ground structure.	Simple to fabricate and highly flexible.	Large dimension with low efficiency. The radiation patterns are slightly affected on bending.
[65] 2018	$33 \times 10$	2.632–14.57	Felt ( $ε_{r}$ = 1.44, tanδ = 0.044)	4.84	-	68%	Combination of half elliptical shaped patch with metamaterial unit cell array and Partial ground with slot.	Modified conventional rectangular compact radiator covering the UWB spectrum.	Relatively low gain and efficiency.
[66] 2018	$32 \times 52$	3.68–10.3	PDMS (εr = 2.7, tanδ = 0.02–0.07)	4.53	0.147 (5 GHz) 0.174 (7 GHz) 0.09 (9 GHz)	27%	Two arc-shaped patch with full ground plane	Simple structure with full ground to suppress antenna loading and back radiation.	Large size and very low efficiency.
[6] 2021	$33 \times 50$	7–28	Denim ( $ε_{r}$ = 1.7)	10.5	0.25 (3.8 GHz) 0.7 (5.8 GHz) 1.29 (7 GHz) 2.04 (28 GHz)	96%	Photonic band gap structures and substrate integrated waveguide.	Full ground, large gain and efficiency.	Complex structure.
[29] 2019	$30.4 \times 48$	8.2–13	Felt (nylon-based substrate) ( $ε_{r}$ = 1.22, tanδ = 0.016)	7	0.0996 (8 GHz) 0.704 (10 GHz) 0.102 (12 GHz)	-	AMC antenna with square conductive elements and annularly shaped slots.	Stable radiation properties and large gain.	High SAR and on bending resonance frequency shift.