  A dc voltage induced by an external ac current is observed in system of
asymmetric mesoscopic superconducting loops. The value and sign of this dc
voltage, like the one of the persistent current, depend in a periodical way on
a magnetic field with period corresponded to the flux quantum within the loop.
The amplitude of the oscillations does not depend on the frequency of the
external ac current (in the investigated region 100 Hz - 1 MHz) and depends on
its amplitude. The latter dependence is not monotonous. The observed phenomenon
of rectification is interpreted as a consequence of a dynamic resistive state
induced by superposition of the external current and the persistent current. It
is shown that the dc voltage can be added in system of loops connected in
series: the dc voltage oscillations with amplitude up to 0.00001 V were
observed in single loop, up to 0.00004 V in a system of 3 loops and up to
0.0003 V in a system of 20 loops.
