Table 2.

Summary and comparison of measured results.

Ref.	${\mathit{f}}_{}$, ${\mathit{f}}_2$ (GHz)	R. BW † (%)	I. BW ‡ (%)	Directivity (dB)	${\mathit{k}}_{}$, ${\mathit{k}}_2$ (dB)	${\mathit{k}}_{}$/${\mathit{k}}_2$ (dB)	$\mathit{\angle }{\mathit{S}}_{}-\mathit{\angle }{\mathit{S}}_{31}$ (${}^{\circ }$)	Max. $|{\mathit{k}}_{}/{\mathit{k}}_2|$ * (dB)	Substrate ${\mathit{ϵ}}_{}$/h (mm)	Size (${\mathit{\lambda }}_0^2$)
[4]	1, 6	>84, >18 ${}^1$	>100, >100 ${}^3$	21.5, 14.5	0.4, 0.1	0.3	−90.9, −88.0	2.1	3.38/1.524	0.14 × 0.05
	2, 4	>23, >16.8 ${}^1$	>23, >11.5 ${}^3$	15.8, 13.1	0.5, 2.6	−2.1	−90.7, −93.0			0.64 × 0.11
[5]	1, 2.5	N.A	N.A	N.A	3.3, 2.9	0.4	87.6, −92.7	0.5	2.2/0.79	0.22 × 0.23
	1, 2.5	N.A	N.A	N.A	−2.5, −3.0	0.5	86.2, −98.4			0.23 × 0.21
[6]	2.45, 5.5	10.9, 9.4${}^{2,4}$		12.8, 15.8	−0.4, 2.7	−3.1,	88.0, −94.1	3.1	12.88/N.A	0.18 × 0.11
	2.45, 5.5	13.2, 9.2 ${}^{2,4}$		18.4, 16.5	2.8, 2.8	0	87.2, −95.0			0.14 × 0.01
[7]	2.45, 5.2	15.5, 23.5 ${}^{2,4}$	14.1, 15.5 ${}^{2,4}$	20.4, 19.5	3.2, 6.8	−3.6	87.8, 86.9	3.6	2.2/0.508	0.11 × 0.09
[8]	3, 5.5	N.A	N.A	N.A	−0.4, −9.7	9.3	−97.9, −92.4	10.2	2.33/1.57	0.14 × 0.19
	3, 4.5	N.A	N.A	N.A	10.3, 0.1	10.2	−97.3, −90.9			0.16 × 0.16
[9]	1.2, 2.52	24.8, 15.1	21.8, 11.9	>13.2	5.4, 4.8	0.4	88.9, −88.9	0.4	3.55/0.813	0.3 × 0.15
	1.0, 2.0	11.5, 9${}^{2,4}$	11, 8.3 ${}^{2,4}$	>15.5	1.5, 1.7	0.2	91.7, −92.8			0.37 × 0.18
[10]	2.4, 5.2	10.8, 28.6 ${}^{2,4}$	75.6, 13.4 ${}^{2,4}$	N.A	9.2, 5.7	3.5	61.9, 79.2	3.5	3.38/1.5	0.32 × 0.1
This work	1, 2.5	14.4, 6.3 ${}^{1,3}$	>65.1, 6.2 ${}^{1,3}$	24.0, 20.6	3.0, −3.5	6.5	90.2, −90.4	13.3	2.2/0.76	0.27 × 0.27
	1, 2.5	27.2, 8.4 ${}^{1,3}$	48.9, 31.1 ${}^{1,3}$	32.1, 17.4	−2.9, 2.8	−5.7	89.6, −91.3			0.28 × 0.3
	1, 2.5	23.5, 7.5 ${}^{1,3}$	26.7, >23.7 ${}^{1,3}$	23.4, 28.6	−0.2, 13.1	−13.3	89.5, −91.6			0.28 × 0.28

†: Reflection BW, ‡: Isolation BW. *: Achievable maximum power-split ratios difference between the two bands. ¹: (|S₁₁| < −10 dB), ²: (|S₁₁| < −15 dB), ³: (|S₄₁| < −10 dB), and ⁴: (|S₄₁| < −15 dB).