A phased array antenna adapted to be mounted in a helmet. In the illustrative embodiment, the antenna comprises a substrate and an array of radiating elements disposed on said substrate, each of the elements including a-resonant cavity and a mechanism for feeding the cavity with an electromagnetic signal., The cavity is formed in a multi-layer structure between a ground plane and a layer of metallization. A radiating slot or slots are provided in the layer of metallization. A first layer of dielectric material is disposed within the cavity. The feed mechanism is a microstrip feed disposed in the first layer of dielectric material parallel to a plane of a portion of the substrate over which an associated element is disposed. A layer of foam is disposed between the layer of dielectric material and the ground plane. Second and third parallel layers of dielectric material are included in each element. The second layer is disposed adjacent to the ground plane. A layer of element interconnection circuitry is disposed between the second and third layers of dielectric material. A transmit/receive module or circuitry for each element is secured to the third layer of dielectric material. The substrate may be conformal or conformable, as well as rigid. An arrangement is included for steering a beam transmitted or received by the antenna.