Discretely-sampled partial aperture receiver for orbital angular momentum modes

Spatial modes, such as orbital angular momentum (OAM) modes, are of interest for creating high spectral-efficiency line-of-sight wireless links in propagation environments with limited diversity gain. Four-element receive arrays have been designed using a Monte-Carlo method so as to enable the simultaneous reception of four different OAM modes. A test-bed operating in the 5GHz band has been developed to validate the principle experimentally. The test bed's transmitter is an eight-element uniform circular array, which allows the generation of OAM modes with mode numbers l = ϵ {±3, ±2, ±1,0}. The receiver is a four element array, and all elements in the transmit and receive arrays have a dedicated programmable phase shifter to facilitate rapid adjustment between modes.