A planar rectangular array of C-shaped wire elements is placed over a Dallenbach absorbing layer to further reduce the reflection from a metallic plane. An analytical formula for the reflection coefficient for such a structure is given, and numerical results are presented to illustrate the antireflection effect of the C-particle array. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 302–307, 2000.