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.

A novel multiband fusion method based on a modified RELAX algorithm (MRA) is proposed. In the MRA, a maximum difference criterion is applied to the singular values of echoes’ Hankel matrix to improve the accuracy of calculating the number of scattering centers. In addition, a transformation process is put forward to merge the frequency-dependent factor (FDF) term, which is in the geometrical theory of diffraction (GTD) model, into the phase term of the echo to simplify the model. Moreover, a matching relationship for the correspondence between the FDF values and the cost function is established to effectively increase the estimated precision of the FDF. Therefore, based on the MRA, exact estimations of the incoherent errors among subband echoes are achieved, and then a fused full-band echo (FBE) with high estimation accuracy is produced. Using all the fused FBEes, high-resolution, anti-non-Gaussian colored clutter microwave imaging is realized. The effectiveness of the proposed method is validated with the simulated and real-data experimental results in a simulated non-Gaussian colored clutter environment.

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.

Fiber transfer delay (FTD) variations influence the coherence of distributed radars with fiber networks, resulting in a performance degradation in target detecting and imaging. To measure and compensate for the variation, a phase-derived ranging based FTD measurement using a composite signal is proposed. The composite signal comprises a sinusoidal component and a linear frequency modulation (LFM) component. As the composite signal passes through a fiber under test (FUT), the sinusoidal component generates a phase shift that corresponds to the FTD. The phase shift can be represented by two parameters: the number of complete periods of 2π that can be estimated by using the LFM component, and a phase shift less than 2π that be measured employing the sinusoidal component. When using the proposed measurement system to measure FTD variations in a distributed radar, only an additional sinusoidal component is needed, which minimizes interference with radar signals. Moreover, the proposed measurement system can share core function modules such as signal generation and process modules with distributed radars, which enhances the compatibility and reduces the overall complexity. Experiments are carried out to measure a variable optical delay line and a long optical fiber. The experiment results verify the feasibility of the measurement system and show that a measurement range of more than 15 km, an accuracy of ±0.1 ps and a measurement time of 105 ms can be achieved.

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.