Dual-Band Orthogonally Polarized Single-Layer Reflectarray Antenna

Design and implementation of a dual-band and orthogonally polarized single-layer microstrip reflectarray are presented in this communication. The proposed reflectarray operates in two separated broad frequency bands within
$X$
- and
$K$
-bands. The reflectarray element consists of a circular patch surrounded by a microstrip ring. Two curved phase delay lines are attached to the patch and two curved phase delay lines are attached to the ring. The ring and patch are designed for the operation at
$X$
- and
$K$
-bands, respectively. Phase delay lines attached to the ring are spatially rotated by 90° with respect to the delay lines attached to the patch. This produces a linear polarization at
$X$
-band, which is perpendicular to the linear polarization produced at
$K$
-band. This also provides a high polarization isolation, which enables by adjusting the phase of the elements at each band independent of the phase at the other bands. At both operation bands, the required phase shifts are obtained by varying the lengths of the phase delay lines. The proposed element provides more than 450° linear phase range over the bands 8.7–10.7 GHz (
$X$
-band) and 18–20.4 GHz (
$K$
-band). Measurement results show the maximum gain of 27.7 dB at 9.7 GHz with 25% 1 dB gain bandwidth and the maximum gain of 31.8 dB at 19.2 GHz with 18% 1 dB gain bandwidth. By proper arrangement of the elements in the array, the cross polarization is reduced. The measured efficiency is 63% at 9.7 GHz and 42% at 19.2 GHz with a center-fed design for the reflectarray.