  In this paper, a liquid reconfigurable stealth window constructed by
metamaterial absorber at microwave band is proposed. The stealth window
consists of an anti-reflection glass with indium tin oxide (ITO) as resistive
film and a liquid container made of polymethyl methacrylate (PMMA). Since the
materials constituting the window are all transparent, the metamaterials that
can be switched through the liquid control system can always maintain high
light transmission. The proposal can obtain a transmission passband from 2.3
GHz to 5 GHz with low insertion loss, especially at 2.45 GHz and 5 GHz with the
insertion loss of the passband reach 0.51 and 0.99 , by alcohol drainage. It
can also reflect electromagnetic waves at 2.45 GHz and absorb them from 4.5 GHz
to 10.5 GHz with a strong absorptivity over 90% by alcohol injection,
exhibiting the reconfigurable electromagnetic characteristic of switching
between transmission state and absorption state. Furthermore, the proposed
absorber shows its good transmission/absorption performance under different
polarizations and obtains absorptivity over 90% when alcohol injection in an
oblique incidence of 50{\deg}. Finally, the prototype window has been
fabricated to demonstrate the validity of the proposed structure, which
indicates that the proposal presents significant implications for smart stealth
systems and WLAN communication that require switching of working states in a
complex electromagnetic environment.
