Passive Angle of Arrival Detection Using Antenna Array and Photonic Integrated Circuit

In this work, angle-of-arrival (AoA) detection using a radio frequency (RF) 2-D planar antenna array receiver coupled to a photonic integrated circuit (PIC) is demonstrated. Optical upconversion identically preserves the RF phase-front information received by the antenna array and relays each upconverted RF signal to the linear array of inputs of a beamforming PIC. To convert from the 2-D planar array to a linear optical fiber array without loss of phase information, array-beamspace (AB) mapping is used in the signal routing. In the PIC, an optical spatial Fourier transform operation is performed via a star coupler, similar to the action of a Rotman lens. The signal measured at each output of the star coupler corresponds to a unique beam location in the RF beamspace. By applying AB mapping to the linear output array, the azimuth and elevation of the received signal can be fully recovered. This article presents the system architecture of the passive AoA detection system, as well as the steps to create an AB mapping scheme. The experimental results are presented for a 30-element triangularly spaced array for multiple source locations and multiple simultaneous sources. The PIC-based approach demonstrates a major reduction in latency as well as size, weight, and power (SWaP) for passive AoA detection.