We propose and demonstrate a novel linearly frequency modulated (LFM) signal generation method using synchronized lasers in a heterodyne-beating scheme, featuring simple operation, large bandwidth and flexible reconfiguration. A hybrid synchronization mechanism combining the advantages of optical phase-locking and digital signal processing mechanisms maintains the phase coherence between lasers when the wavelength is sweeping. The ability of phase coherence maintaining provides attractive benefits in flexible reconfigurability of beat signal parameters and high scalability of signal bands. A dual-laser synchronization system is established, and an LFM waveform with reconfigurable bandwidth, central frequency and pulse duration is produced. Additionally, an ISAR imaging experiment is carried out. Results show the potential of the proposed method in multifunctional/multiband radar applications.

A dual-band reconfigurable microwave photonic transceiver chip for synthetic aperture radar is proposed and demonstrated on silicon photonic platform. Study deep into material level is conducted to establish the relation between nonlinear mechanisms in silicon and the performance of the system-on-chip. Guided by the theoretical model, rational paralleled photonic circuit architecture and a series of control strategies, including waveform predistortion, linearity optimization and thermal crosstalk compensation, are put forward to realize a practical and high-performance photonic radar transceiver. RF characterizations indicate that the chip is capable to generate broadband C-band or Ku-band radar signal with low phase deviation on the order of 10 ^-7 . It can also conduct stretch processing in both bands with high spurious free dynamic range exceeding 100 dB·Hz ^2/3 . A radar system taking the photonic chip as core is established to serve the function of two-dimensional imaging. Resolutions at centimeter level and high peak to side lobe ratios are achieved and in consistent with theoretical values. To the best of our knowledge, this work realizes superior analog frequency-conversion signal processing and imaging quality in comparison with previous works.

An active integrated broadband photonics multi-beamformer using optical true-time delay induced Blass matrix is designed and demonstrated. The multi-beamformer is constructed on a standard silicon-on-insulator platform, incorporating on-chip modulator array and photodetector array alongside a broadband multi-beamforming network. The network utilizes a Blass matrix architecture based on optical true-time delay to precisely control the power and delay of input microwave signals. Furthermore, wavelength division multiplexing technology achieved by multi-wavelength lasers is used to decouple the signals from different channels, enabling the simultaneous multi-beamforming. Radio-frequency characterizations indicate that the active integrated broadband photonic multi-beamformer is capable of covering the frequency range up to Ku-band and realizes five beams directed at 0${}^{\circ }$, $\pm$ 20${}^{\circ }$, and $\pm$ 40${}^{\circ }$ by 4 input channels. Experimental measurements demonstrate good agreement with designed parameters, validating the compatibility and feasibility of this beamformer for large-scale antenna arrays in radar and wireless communications systems.

The photonic frequency-interleaving (PFI) technique has shown great potential for broadband signal acquisition, effectively overcoming the challenges of clock jitter and channel mismatch in the conventional time-interleaving paradigm. However, current comb-based PFI schemes have complex system architectures and face challenges in achieving large bandwidth, dense channelization, and flexible reconfigurability simultaneously, which impedes practical applications. In this work, we propose and demonstrate a broadband PFI scheme with high reconfigurability and scalability by exploiting multiple free-running lasers for dense spectral slicing with high crosstalk suppression. A dedicated system model is developed through a comprehensive analysis of the system non-idealities, and a cross-channel signal reconstruction algorithm is developed for distortion-free signal reconstruction, based on precise calibrations of intra- and inter-channel impairments. The system performance is validated through the reception of multi-format broadband signals, both digital and analog, with a detailed evaluation of signal reconstruction quality, achieving inter-channel phase differences of less than 2°. The reconfigurability and scalability of the scheme are demonstrated through a dual-band radar imaging experiment and a three-channel interleaving implementation with a maximum acquisition bandwidth of 4 GHz. To the best of our knowledge, this is the first demonstration of a practical radio-frequency (RF) application enabled by PFI. Our work provides an innovative solution for next-generation software-defined broadband RF receivers.

An integrated sensing and communication (ISAC) system enabled by a photonic integrated broadband multi-beamformer is proposed and demonstrated. The integrated multi-beamformer, which employs an optical true-time-delay induced Blass matrix framework for reception, is capable of simultaneously synthesizing five squint-free beams directed at distinct angles across the entire Ku-band spectrum. Benefiting from space division multiplexing endowed by multi-beamforming, the system performs simultaneous broadband radar sensing and high-speed wireless communication. A proof-of-concept experiment on the ISAC system utilizing the photonic broadband multi-beamformer has been conducted, demonstrating simultaneous high-resolution microwave imaging with a 1 GHz bandwidth and wireless communication with a 2.4 Gbps data rate. The experiment validates the ISAC system architecture based on an integrated photonic multi-beamformer and highlights its promising potential for an advanced multimodal information system.

A photonic signal generation scheme based on recirculating frequency-shifting and channelized sub-band stitching is proposed to synthesize high-quality multi-octave broadband linear frequency-modulated (LFM) signals. The scheme employs a hierarchical two-stage approach to expand the bandwidth of a narrowband seed signal. First, recirculating frequency-shifting generates and stitches frequency-shifted signals to obtain a broadband sub-band waveform with first-stage bandwidth expansion. Then, multiple broadband sub-band signals in different channels are precisely aligned and stitched to achieve secondary bandwidth extension, effectively breaking the octave-spanning limitation. The partitioned-channel structure ensures superior spurious suppression performance. A proof-of-concept experiment is designed to demonstrate the generation of a 5–17 GHz cross-octave LFM signal with a 12 GHz bandwidth, a relative bandwidth of 1.09, and an in-band spurious suppression ratio (SSR) of 35 dB, covering the C, X and Ku bands. To verify system flexibility, signals with varying center frequencies and bandwidths are generated without any hardware modification. To assess the practicality of the generation in an actual imaging system, microwave imaging experiments are also conducted. To the best of our knowledge, the proposed ultra-wideband generation has the best SSR in the generation of cross-octave signals, which holds significant application value for high-quality, high-resolution radar imaging.