Directive metamaterial antenna using high impedance surface

/spl lambda//2 is the minimum length along the propagating direction to support a cavity mode. Here we show experimentally that metamaterial cavity formed by a high impedance surface (HIS) and an electrically responded surface can make a dipole highly directive. 3dB angular width is less than 30/spl deg/. Thickness of the cavity is much less than /spl lambda//4 at working wavelength with return loss up to -40dB. This study is of great potential in realizing subwavelength antenna with high directivity in the future.