Microwave photonic I/Q mixer for wideband frequency downconversion with serial electro-optical modulations.

In this paper, we propose a serial electro-optical (EO)-modulation-based microwave photonic in-phase and quadrature (I/Q) mixer and investigate its performance for wideband frequency downconversion. The proposed I/Q mixer uses two EO modulators and a programmable optical processor in a serially cascaded structure, which ensures good phase stability and flexibility to achieve high-performance broadband frequency downconversion. A proof-of-concept experiment is carried out in which the frequency downconversion of the RF signals in the range from 10 to 40 GHz is demonstrated with an average image rejection ratio of 38.

Deep-learning-based time-frequency domain signal recovery for fiber-connected radar networks.

A deep-learning-based time-frequency domain signal recovery method is proposed to deal with the signal distortion in fiber-connected radar networks. In this method, the deteriorated signal is converted to the time-frequency domain, and a two-dimensional convolutional neural network is used to conduct signal recovery before inverse conversion to the time domain. This method can achieve high-accuracy signal recovery by learning the complete features in both time and frequency domains.

Photonics-based 3D radar imaging with CNN-assisted fast and noise-resistant image construction.

Photonics-based high-resolution 3D radar imaging is demonstrated in which a convolutional neural network (CNN)-assisted back projection (BP) imaging method is applied to implement fast and noise-resistant image construction. The proposed system uses a 2D radar array with each element being a broadband radar transceiver realized by microwave photonic frequency multiplication and mixing. The CNN-assisted BP image construction is achieved by mapping low-resolution images to high-resolution images with a pre-trained 3D CNN, which greatly reduces the computational complexity and enhances the imaging speed compared with basic BP image construction.

Photonic scanning receiver for wide-range microwave frequency measurement by photonic frequency octupling and in-phase and quadrature mixing.

A photonic scanning receiver with optical frequency scanning and electrical intermediate frequency envelope detection is proposed to implement wide-range microwave frequency measurement. This system applies photonic in-phase and quadrature frequency mixing to distinguish and measure the signals in two frequency bands that mirror each other. Combined with the photonic frequency octupling technique, the proposed system has a frequency measurement range that is 16 times that of the sweeping range of the electrical signal source.

Deep neural network-assisted high-accuracy microwave instantaneous frequency measurement with a photonic scanning receiver.

A microwave instantaneous frequency measurement system with a photonic scanning receiver is proposed in which deep neural network (DNN)-assisted frequency estimation is used to deal with the system defects and improve the accuracy. The system performs frequency-to-time mapping by optical-domain frequency scanning and electrical-domain intermediate frequency envelop detection. Thanks to the optical frequency multiplication, the system can measure high frequency signals in a large spectral range.