Table 2.

Comparison of other recently published works and this work.

Ref.	Sensor Structure	Operating Frequency (GHz)	Relative Size †	Measured Loaded Q-Factor	RH Measurement Range (%)	Normalized Sensitivity (%/%RH)
[22]-1 [22]-2	SIW cavity	4.15 3.6	(0.43${\lambda }_0\times$0.43${\lambda }_0$) § 0.373${\lambda }_0\times$ 0.373${\lambda }_0$	263.25 308	0–80	2.43$\times {10}^{-3}$ 0.26$\times {10}^{-3}$
[23]	Air-filled SIW cavity	7.63	0.712${\lambda }_0\times$ 0.712${\lambda }_0$	273.2	20–85	15.8$\times {10}^{-3}$
[24]-1 [24]-2	QMSIW cavity❉	6 6.9	0.236${\lambda }_0\times$ 0.236${\lambda }_0$ 0.178${\lambda }_0\times$ 0.178${\lambda }_0$	35 86	0–80 0–70	0.608$\times {10}^{-3}$ 0.445$\times {10}^{-3}$
[25]	SIW interferometer	16.55	$5.4{\lambda }_0\times$ 2.54${\lambda }_0$	2400	20–70	0.858$\times {10}^{-3}$
This work	DFSIW re-entrant cavity	2.163	$0.161{\lambda }_0\times$ 0.161${\lambda }_0$	266	30–80	6.27$\times {10}^{-3}$

❉ QMSIW = quarter-mode SIW; † Only the sizes of cavity areas are calculated; § λ₀ represents the free space wavelength at operating frequency.