An innovative virtual digital antenna beam (VDAB) forming approach based on orthogonal coding waveforms

Traditionally the radiation beams of phased array antennas are formed by linearly shifting the phases of the transmitted waveforms from the antenna array elements, and the antenna beams can be scanned from one direction to another by subsequently changing the waveform phases [1, 2]. Digitally forming receiving antenna beams can be implemented by digitally filtering the received signals at array elements and have been widely used. However, digitally forming virtual transmitting beams or both transmitting and receiving beams has been very technically challenging. Yet there are many potential advantages for employing virtual transmitting beams rather than real phased array antenna beams. For example, in forming virtual transmitting antenna beams, the radiation energy of the antenna is not physically focused in any particular direction and thus is very difficult to be detected. As a result, the virtual radiating system can operate in a ‘silent’ mode with an extremely low probability of interception (LPI). Because the virtual radiation beam is formed through digital filtering of the received signals, the formed beams are more accurate and concentrated for intended radiation direction compared with phased array antenna beams. In addition, with virtual radiation systems, multiple transmitting-receiving beams can be generated simultaneously. In this work, we propose an innovative approach to forming virtual digital antenna beams (VDAB) by transmitting and processing orthogonal coding waveforms. The principle and architecture of the proposed system will be introduced and some simulated results will be presented to demonstrate the feasibility of the new systems.