This invention relates to reducing the complexity and cost of antenna arrays and is more specifically concerned with reducing the complexity of an antenna apparatus (10). It provides an antenna array (62) made up of a vertical stack of horizontal linear structures (74) each having several groups of neighboring array antenna elements (78), the groups (74) having variable numbers of the antenna elements (78) each connected to a transmit/receive module (66). The advantage of this configuration is that less communication modules (66), such as transmit/receive modules, are required to operate the antenna array (62), reducing the weight, power consumption and cost of an antenna apparatus (10) incorporating such an antenna array (62) without significantly limiting the capability and/or performance of a system compared to a conventional solution.