Achieving Full Grating-Lobe-Free Field-of-View with Low-Complexity Co-prime Photonic Beamforming Transceivers

Abstract: Integrated photonic active beamforming can significantly reduce the size and cost of coherent imagers for LiDAR and medical imaging applications. In current architectures, the complexity of photonic and electronic circuitry linearly increases with the desired imaging resolution. We propose a novel photonic transceiver architecture based on co-prime sampling techniques that breaks this trade-off and achieves the full (radiating-element-limited) field-of-view (FOV) for a 2D aperture with a single-frequency laser. Using only order-of-N radiating elements, this architecture achieves beamwidth and side-lobe level (SLL) performance equivalent to a transceiver with order-of-N-squared elements with half-wavelength spacing. Furthermore, we incorporate a pulse amplitude modulation (PAM) row-column drive methodology to reduce the number of required electrical drivers for this architecture from order of N to order of square root of N. A silicon photonics implementation of this architecture using two 64-element apertures, one for transmitting and one for receiving, requires only 34 PAM electrical drivers and achieves a transceiver SLL of -11.3dB with 1026 total resolvable spots, and 0.6 degree beamwidth within a 23x16.3 degree FOV.