947867.fig.003a
(a) Wireless sensor proposed by Lynch et al. in 2003 [29]
947867.fig.003b
(b) The two-layer circuit board [34]
947867.fig.003c
(c) The enclosed two-layer circuit board with batteries [34]
947867.fig.003d
(d) Narada wireless sensing prototype [37]
Figure 3: Prototypes of wireless sensor.