Microwave photonic radar with a fiber-distributed antenna array for three-dimensional imaging.

A microwave photonic (MWP) radar with a fiber-distributed antenna array for three-dimensional (3D) imaging is proposed and demonstrated for the first time. Photonic frequency doubling, wavelength-division multiplexing and radio-over-fiber techniques are employed for radar signal generation, replication, and distribution. Based on the delay-dependent beat frequency division, parallel de-chirp processing is completed in the center office (CO), leading to multi-channel 2D ISAR imaging and further 3D reconstruction. The influence of the fiber transmission delay is discussed and the phase noise caused thereby is compensated in 3D imaging algorithm, improving the coherence between channels. An experiment of a Ku-band MWP radar with a transmitter (Tx) and 16 equivalent receivers (Rxs) is conducted and 3D imaging of three trihedral corner reflectors is achieved with a range resolution of 7.3 cm, a cross-rage resolution of 5.6 cm and an elevation resolution of 0.85°. The results verify the capability of MWP radar in high-resolution 3D imaging.

Three-Dimensional Imaging Method for Array ISAR Based on Sparse Bayesian Inference.

The problem of synthesis scatterers in inverse synthetic aperture radar (ISAR) make it difficult to realize high-resolution three-dimensional (3D) imaging. Radar array provides an available solution to this problem, but the resolution is restricted by limited aperture size and number of antennas, leading to deterioration of the 3D imaging performance. To solve these problems, we propose a novel 3D imaging method with an array ISAR system based on sparse Bayesian inference. First, the 3D imaging model using a sparse linear array is introduced. Then the elastic net estimation and Bayesian information criterion are introduced to fulfill model order selection automatically. Finally, the sparse Bayesian inference is adopted to realize super-resolution imaging and to get the 3D image of target of interest. The proposed method is used to process real radar data of a Ku band array ISAR system. The results show that the proposed method can effectively solve the problem of synthesis scatterers and realize super-resolution 3D imaging, which verify the practicality of our proposed method.