Phase errors of phased array antenna (PAA) can cause pattern distortion. This letter presents an over-the-air (OTA) phased array calibration method by an iterative stochastic parallel gradient descent algorithm (SPGD algorithm). During the measurement, all the phased array elements are excited simultaneously, and an external receiving probe is placed to a given direction in the far-field for amplitude measurement, which is used as the fitness function. The basic principle is to find the optimal phases that maximize the fitness function by gradient operation. We numerically simulated and experimentally validated in a 4×4 uniform rectangular array (URA) at 2.6GHz. The experimental results show that the proposed method needs 6N∼7N measurements to calibrate an N -element PAA and its calibration accuracy is comparable to that of the well-known rotating element electric field vector (REV) method. The proposed method provides a new idea for fast and accurate OTA phase calibration for PAA.

Ning Ding, Dingkun Long, Guangwei Xu, Muhua Zhu, Pengjun Xie, Xiaobin Wang, Haitao Zheng. Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics. 2020.

Non-mechanical beam steering is required for holographic displays, free-space optical communication, and chip-scale LiDAR. Optical phased arrays (OPAs), which allow for inertia-free, high-speed beam control via electronic phase control, are an important research topic. The present study investigates the primary material platform for on-chip OPAs: Liquid crystal OPAs (LC-OPAs) employ electrically tunable refractive indices for low-voltage operation; lithium niobate OPAs (LN-OPAs) utilize high electro-optic coefficients for high-speed, low-power consumption, and large-bandwidth operation; and silicon-based OPAs (Si-OPAs) apply mature photonic integration to achieve high integration density and GHz-range steering. The paper thoroughly examines OPA basics, recent material-specific advancements, performance benchmarks, outstanding issues, and future prospects.

A silicon photonics-based optical phased array (OPA) is promising for realizing solid-state and miniature beam steering. In our work, a 1 × 16 silicon optical phased array (OPA) hybrid integrated with a III–V laser is proposed and demonstrated. The III–V laser chip is vertically coupled with a silicon OPA chip based on a chirped grating coupler with a large bandwidth. The coupling efficiency reaches up to 90% through utilizing the metal reflector underneath the silicon oxide layer. The one-dimensional antenna array comprising silicon waveguides with half-wavelength spacing enables beam steering with none high-order grating lobes in a 180° field of view. The measured beam steering angle of the hybrid integrated OPA chip is ±25°, without grating lobes, and the suppression ratio of the side-lobes is larger than 9.8 dB with phase calibration.

The increasing demand for long-range, high-resolution detection and high beam steering rate in optical sensors is driving the rapid advancement of light detection and ranging (LiDAR) architectures. A variety of LiDAR technologies have been developed, each targeting specific applications with varying degrees of success. However, LiDAR systems have been challenged by requirements on achieving long-range and high-precision distance detection, simultaneously. Frequency-modulated continuous-wave (FMCW) LiDAR employs the beat frequency signal, generated by transmitting and receiving chirped signals, to map distance-frequency relationship. Coherent beam combining (CBC) technology demonstrates high-power output and enables high-speed beam steering through fully electronic control. In this work, we present a LiDAR system that integrates a 64-Element two-dimensional fiber laser phased arrays (FLPA) based on CBC technology with FMCW. We conducted ranging experiments at a distance of 2.35 and 3.45 m with a resolution level of 0.26 m. This LiDAR can effectively enhance the imaging resolution and detection range by increasing the number of elements in the FLPA.