RF-Photonic Spatial-Spectral Channelizing Receiver

Abstract

As mobile beam-bandwidth-product requirements accelerate, millimeter-wave (mmW) bands have been opened to telecommunications networks to enable wider channel bandwidths, while Massive Multiple-Input Multiple-Output (mMIMO) technology has been implemented to concurrently address multiple devices at the same frequency from a single base station. Such space-division multiplexing can be combined with spectral multiplexing to enable a very large number of concurrent users, but currently is implemented through computationally intensive digital beamforming networks. We show that a radio-frequency (RF) photonic receiver system, previously shown to be capable of sorting signals into respective spatial-spectral 'bins' is further capable, through an injection-locked tunable optical local oscillator (TOLO), of recovering the data upon each signal in the RF scene. The TOLO is combined in free-space with an up-converted optical sideband and the combined optical field impinges upon an array of photodetectors, each corresponding to separate points in k-space, defined by unique combinations of angle-of-arrival (AoA) and carrier frequency. Using this free-space LO insertion, we demonstrate simultaneous recovery of multiple spatially co-located data streams with resilience to interference.