Table 1. Characteristics of electrically small tag antennas proposed for metallic applications.

Freq.[MHz]	Size(L×W×H)[mm3]	εr (tan δ)	BW[MHz]	FBWG[%]	Greal[dBi]	S11[dB]	Gtag[dBi]	GT[dBi]	η[%]	Author [Year]	D[m]	Chip[Ref.]
915	31×19.5×3.065	2.55(0.001)	14.5	1.58	0.01	−15.9	0.12	4.8	24	Proposed Coplanar	4.2L	Mu
915	77.68×35.5×1.6N	4.6(0.02)	21c	2.2	−2.99	−12.5	−2.86	4.8	17.1	Md.2 [2016]	8.3	G2iL [65]
915	80×44×1.6N	4.6(0.02)	290c	30.1	−0.09	−24	−0.09	4.8	32	Md.2 [2015]	11.9	G2iL [66]
923	26×14×2.4	2.65(0.0016)	8	0.87	−1.4	−5.5	0.08	4.8	23	Zhang2 [2014]	5.5	NXP [60]
915	36.7×18.1×3.165	4.4(0.02)	38	4.15	−13.9	−23	−13.9	4.8	1.3	Ali [2013]	0.82L	Mu [46]
930	28×14×3.2	4.4(0.01)	40	4.3	−11.1	−10	−10.6	4.8	2.8	Zhang1 [2013]	1.8+	NXP [67]
915	36×36×0.8	4.4(0.02)	91c	10.0	−12.8	−19	−12.7	4.8	1.8	Chen2 [2010]	1.2	TI [68]
926	32×18×4.2G	4.2(0.02)	55	5.9	−11.7	−8.5	−11.0	4.8	2.6	Chen1 [2009]	1.5	H2 [69]
911	33.5×20×2	3.0(0.1)	40c	4.4	−11.3	−20	−11.3	4.8	2.5	Park [2008]	1.6	H2 [70]
910	42×22×2.2	4.3(0.017)	30	3.3	−4.0	−17	−3.9	4.8	13.5	Son [2008]	NA	H2 [71]
910	34×34×5*	22(0.002)	33	3.6	−4.4	−16	−4.3	4.8	12.4	Kim2 [2008]	5.0L	H2 [10]
915	25×25×3	48(0.002)	21	2.3	−4.4	−25	−4.4	4.8	12.1	Kim1 [2008]	5.0L	H2 [21]
911	25×25×3	37(0.002)	13c	1.4	−2.8	−17	−2.7	4.8	17.8	Choi2 [2008]	6.0L	H2 [22]
911	19×19×3	22(0.002)	27c	3.0	−7.5	−20	−7.5	4.8	6.0	Choi1 [2008]	3.5L	H2 [47]

^G Represents that this antenna size has included the gap from antenna ground plane to the metallic surface;

* represents that this antenna size is given out in form of diameter × diameter × height;

^c represents that this 3-dB bandwidth is calculated from the corresponding 10-dB one;

^{Mu, H₂} and^T_I represents that these tag chips are Murata, Higgs-2 and Taxes Instruments respectively;

^L represents that this read range was measured with a LR reader antenna;

⁺ represents that this read range was measured in frequency band 920–925 MHz (Limitation by firmware).

^N represents that this antenna is not electrically small antennas (ESA).