In this paper, a novel structure of a reconfigurable Electromagnetic Band Gap (EBG) layer is presented for direct antenna Amplitude Shift Keying (ASK) digital modulation. Therefore, the modulation process, in this paper, is realized without the need to include conventional parts like filters, mixers or power amplifiers. Beside many advantages, the proposed modulation process offers cost, complexity, and weight reductions to suit many modern applications including 5G systems. The reconfigurable EBG layer has two statuses: ON and OFF. Each status produces a certain level of gain enhancement. Via controlling the reconfigurable EBG statuses, the amplitude of the transmitted wave can be controlled. The results show such a system design can modulate the electromagnetic signals directly by varying the gain from 2 dBi for logic_0 (OFF) to 11 dBi for logic_1 (ON). For this, a mathematical model based on ray tracing analysis is conducted to explain the principle of operation of the proposed EBG layer. The antenna and EBG structures fabrication as a system is realized and tested experimentally. The measurements show good agreements with the proposed mathematical model and CST MWS simulations.