Abstract: A primary slotted array antenna operates at 10 GHz. In front of the primary antenna there is disposed a secondary antenna which operates at 1 GHz and is substantially transparent at 10 GHz. The secondary antenna is formed by an array of patch radiators and a transmission line feed network. The radiators and feed network are all formed by a conductive grid sandwiched between dielectric layers and designed to achieve the transparency at 10 GHz. At 1 GHz the grid appears as a continuous conductor forming one conductor of a microstrip transmission line. The other conductor (ground plane) is formed by the conductive front surface of the primary antenna. The grid/dielectric sandwich is suitably spaced from the ground plane by low dielectric pads. Other embodiments use slotline or coplanar stripline techniques. The ground plane may be an integral part of the secondary antenna, also constructed to be transparent at primary frequency.