LAUSR

Spatial field digital modulation (SFDM) is a newly proposed technique, which directly modulates information in the spatial distribution of the electromagnetic (EM) field. In this letter, we propose an orbital angular momentum (OAM) based SFDM system. Furthermore, a demodulation method called the spatial matched filtering criterion is developed. The introduction of the spatial matched filter simplifies the architecture of the receiver and makes the practical system implement more viable. An experimental testbed is then built to measure the state isolation and the corresponding bit error rate (BER) performance of the OAM-SFDM system. We realize the SFDM signal transmission at a communication distance of 1.5 m with a practical analog-demodulation OAM-SFDM system. The results of the numerical simulations and the experimental measurements both verify the validity of this demodulation method. Moreover, it has been confirmed that the predictable phase information brought about by OAM waves plays a prominent role in the demodulation process.