A novel broadband high-sensitivity optical E-field sensor is proposed in this letter. To solve the problem of bandwidth sensitivity, thin-film LiNbO ₃ (TFLN) is employed to fabricate the photonic device. Herein, the inductively coupled plasma (ICP) etching methodology using a mixture of Ar and C ₄ F ₈ is first introduced, which is more effective in etching and helps to sharpen the lateral angle of the LN ridge waveguide. The LF-shaped electrode is designed to improve the performance of the sensor with a bandwidth of 1 MHz to 20 GHz and a sensitivity of 1 mV/m. The volume of the sensor with the package is only 20×5×5 mm, which can be utilized in narrow spaces of the weak electromagnetic signal in the wideband frequency range.

The optical-frequency-comb-based (OFC-based) sampling method is of better efficiency than a heterodyne receiver when measuring non-cooperative signals over large frequency range. However, under-sampling during the down-conversion process often results in missing frequency information, necessitating multiple OFCs for recovery. This paper proposes a frequency-phase-mapping method with single OFC is proposed to recover the missing frequency information. Firstly, an asymmetric two-branch electro-optical-modulating structure is designed to acquire the phase difference caused by the time delay. Then, the acquired phase difference is mapped into the signal frequency by complex unit circle without 2π-blur. A dimension-expanding procedure is proposed by introducing multi-measuring to enhance the robustness performance. The influence of frequency range, signal-to-noise-ratio (SNR) and measuring times are analyzed in detail. The experiment indicates that the correct ratio of frequency recovery can reach 93.5% when the SNR is 20dB, frequency range is 1G-12GHz and the measuring times are 2, demonstrating the proposed method’s efficiency.

Microwave camera is a passive focal-plane microwave imaging system which is utilized for large-scale, wide-band electromagnetic interference (EMI) imaging. Microwave camera images the EMIs with their amplitude and location by the reflector and sensor array, like taking a photograph. This camera however only receives the power density of the EMIs within a wide band and the frequency information is aliased and abandoned. To address this issue, in this paper, we propose a frequency estimation method to recover the frequency of the wide-band EMI from its amplitude image without a need to add new hardware. For the developed imaging system, the proposed method realizes the frequency estimation in 3-6GHz frequency range with the resolution of 100KHz consistently in most of the central part of the field of vision (FOV). Our proposed method is also applicable to other passive imaging applications such as passive millimetre radar imaging and infrared imaging, to extract the related information of the detected objects.

Real-time routing for satellite communication of mega-constellations is a challenging task due to the large scale of network nodes, especially on devices with limited computation, such as onboard embedded systems. Hence, this paper proposes a fast-SPF method for mega-constellation backbone network routing. Firstly, inspired by the regularity and sparse characteristics of mega-constellations, the 4-degree percolation theory is proposed to describe the node search process. Then, dynamic minimum search and mapping methods are used to narrow down the traversal range. The proposed method performs equally well as the heap-optimized Dijkstra algorithm but with less memory space and dynamic access. The experimental results show that the proposed method can significantly reduce routing computation time, especially onboard, edge-computing, or other computation-limited devices.

Noncooperative electromagnetic radiation source sensing faces challenges such as wide bandwidth and an unknown number of sources, which hinder various applications like electromagnetic compatibility, radar detection, and passive positioning. Traditional sweep reception methods, based on antennas and superheterodyne receivers, struggle to meet real-time requirements. Optical undersampling sensing technologies enable rapid reception in ultrawideband. Frequency measurement in these systems, however, requires triple-comb or higher-dimensional information, introducing complexity and instability. The dual-comb-based frequency measurement method is further complicated by dead zones due to its underdetermined nature. In this article, we demonstrate, for the first time, the boundedness and reachability of the solution to the dual-comb ultrawideband frequency measurement problem. We propose a boundary determination method that ensures error-free solutions. Simulation and experimental results demonstrate that our method achieves 98% accuracy for a single source with seven octave bandwidths and over 90% accuracy for the coexistence of two-five sources. This method can achieve accurate measurement with only a 5 dB signal-to-noise ratio (SNR) and exhibits high robustness. Our work clearly defines the theoretical limits of frequency measurement for dual-comb undersampling systems, significantly enhancing both test accuracy and engineering practicability. This method can be widely applied to frequency measurement and signal estimation in RF and optical systems, paving new high-speed, accurate and robust pathways in microwave photonics metrology and ultrawideband signal processing.

The ultrawideband (UWB) reception and detection of microwave electric fields are crucial in various fields, including cognitive radio, radio navigation, radar imaging, and the Internet of Things. However, the receiving bandwidth of antennas is constrained by the impedance matching principle of transmission lines, which focuses on maximizing received power. In this work, we introduce a novel concept of a microwave photon receiving antenna (MPRA) based on the voltage matching principle, demonstrating a significant enhancement in the receiving bandwidth of Vivaldi antennas. We bond an electro-optic (EO) sensing photonic chip made of thin-film lithium niobate (TFLN) to the Vivaldi surface mount using gold wire to achieve optimal voltage matching. The resultant MPRA exhibits gains exceeding 0 dBi across the 0.4-20 GHz frequency range, with peak gains surpassing 10 dBi between 1-18 GHz and gains ranging from 15 to 21 dBi within the 1.7-15.5 GHz band. By leveraging optical fiber for signal transmission, the MPRA strengthens the receiving system against strong electromagnetic interference while enhancing long-distance signal propagation. This concept and its demonstration represent promising advancements in ultrawide-band antenna technology, offering valuable insights for future antenna design and improvements.