Sai Zhu

Traditional electronic phased array radars are constrained by electronic bottlenecks, resulting in inherent limitations including large form factor, fixed operational parameters, and narrow instantaneous bandwidth, which fail to meet the stringent requirements of next-generation high-performance radar systems. Optical true time delay (OTTD) technology based on integrated optical waveguides emerges as a core solution for realizing broadband, compact optically controlled beamforming systems. Traditional silicon-based waveguides suffer from severe mode competition (delay jitter > ±0.05 ps), energy leakage (transmission loss > 0.5 dB/cm) and large beamforming angle fluctuation (>0.3°) in OTTD systems, failing to meet the picosecond-level delay accuracy and broadband beam squint-free requirements of next-generation phased array radars. Thus, a customized mode-selective waveguide design for OTTD systems is urgently required. To address these critical challenges, this study proposes an OTTD-customized mode-selective integrated optical waveguide design tailored for OTTD systems, with three distinct innovations: (1) A systematic OTTD-oriented mode classification and selection methodology is established—instead of a conventional single-mode design, the fundamental TE₀ mode is identified as the optimal operating mode through Finite-Difference Time-Domain (FDTD) simulation, (95% TE polarization fraction and 2.0553 effective refractive index at 1548.39 nm, which cannot be achieved by other guided modes for OTTD applications). (2) The wavelength-dependent transmission characteristics of the TE₀ mode are quantitatively characterized, revealing a linear correlation between the effective refractive index (2.05–2.10) and wavelength (1500–1550 nm), alongside a controllable group delay range of 1.4315–1.4395 ps—this precise linear model fills the gap of lacking OTTD-specialized delay calibration theory in conventional waveguide research. (3) An OTTD-optimized practical mode selection criterion for OTTD applications is proposed by modifying the standard guided-vs-leaky condition for asymmetric waveguides: the effective refractive index of the operating mode must exceed the substrate refractive index with a fabrication tolerance margin (n_eff > 1.44 ± 0.02 for SiO₂ substrate) to mitigate leakage and adapt to OTTD picosecond-level delay precision. This criterion is validated through system-level beamforming experiments (rather than only device-level simulation), and the designed waveguide achieves a mode suppression ratio (MSR) of >30 dB for leakage modes and a transmission loss of <0.2 dB/cm, which is significantly superior to conventional single-mode waveguides in OTTD systems. Experimental results indicate that the angle fluctuation of the beamforming system is less than 0.08°, which is significantly superior to the 0.3° fluctuation observed in traditional silicon waveguide OTTD systems. This work provides a technical solution for improving the performance of optical phased array radar and laser radar and has broad engineering application prospects in microwave photonics and optical communication fields.

In the field of modern optical communication, radar signal processing and optical sensors, true time delay technology, as a key means of signal processing, can achieve the accurate control of the time delay of optical signals. This study presents a novel design that integrates a 2 × 2 Multi-Mode Interference (MMI) structure with a Mach–Zehnder modulator on a silicon nitride–lithium niobate (SiN-LiNbO₃) heterogeneous integrated optical platform. This configuration enables the selective interruption of optical wave paths. The upper path passes through an ultralow-loss Archimedes’ spiral waveguide delay line made of silicon nitride, where the five spiral structures provide delays of 10 ps, 20 ps, 40 ps, 80 ps, and 160 ps, respectively. In contrast, the lower path is straight through, without introducing an additional delay. By applying an electrical voltage, the state of the SiN-LiNbO₃ switch can be altered, facilitating the switching and reconfiguration of optical paths and ultimately enabling the combination of various delay values. Simulation results demonstrate that the proposed optical true delay line achieves a discrete, adjustable delay ranging from 10 ps to 310 ps with a step size of 10 ps. The delay loss is less than 0.013 dB/ps, the response speed reaches the order of ns, and the 3 dB-EO bandwidth is broader than 67 GHz. In comparison to other optical switches optical true delay lines in terms of the parameters of delay range, minimum adjustable delay, and delay loss, the proposed optical waveguide digital adjustable true delay line, which is based on an optical switch and an Archimedes’ spiral structure, has outstanding advantages in response speed and delay loss.

The existing array antenna reliability evaluation method based on the n/k system is analyzed. As the failed T/R module’s influence on the array antenna’s performance is not considered, the reliability of the array antenna is overestimated. To improve the accuracy of the array antenna reliability evaluation, the performance changes caused by T/R failures in different locations are considered. The reliability evaluation method considering the performance changes is established. The performance and probability of the array antenna’s state are calculated, and accurate reliability is obtained by calculating all the available state’s probabilities. The complexity of the reliability evaluation method is analyzed, and the reliability evaluation method for large-scale array antennae is established. The large-scale array antenna is divided into several subarrays. The performance and reliability of each subarray are analyzed, and the array antenna’s reliability is calculated through subarrays. The array antenna’s performance changes are considered with the proposed method, the overestimation problem of the existing reliability evaluation method is solved, and the accuracy of the array antenna reliability evaluation is improved.

The reliability of phased array antenna can be improved with the self-repairing technology, and the existing self-repair method based on the TR module reconfiguration has problems such as slow calculation speed and difficulty in calculating the elements’ mutual coupling, which is difficult to meet the application requirements. In this paper, a novel phased array antenna structure with self-repair ability is proposed. Based on the embryological electronics (embryonics), a novel phased array antenna structure with TR cell as the basic unit is constructed. The faulty TR cell can be detected and removed, and its influence on the phased array antenna’s performance can be eliminated. The function and connection of faulty TR cell can be implemented by the normal TR cells and idle TR cells, the performance of phased array antenna can be repaired in real-time. TR cell, TR cell array and input/output switching control module are designed. The simulation tests show that, the phased array antenna with various fault conditions can be repaired in real-time based on the proposed structure, and the performance of phased array antenna can be repaired to the initial normal state with enough idle TR cells in array. Even without the idle TR cell, the performance of phased array antenna with fault can be improved through the self-repair. A new way for the design of phased array antenna design with self-repair ability is provided.

Radar is known as an important sensor in modern warfare. The complex electromagnetic environment of the battlefield has adverse effects on the survivability and working ability of the radar battlefield. Clutter is the main interference in radar signal processing. It is the key for radar development, test and performance detection to simulate the clutter environment that radar is facing. This paper summarizes the research status of radar clutter simulation technology, and highlights the clutter simulation method based on reverberation chamber. It is also pointed out that there is still a long way to go for the mechanism analysis and experimental research of radar clutter simulation in reverberation chamber.

With the fast development of electronic industry,the techniques of testing electronical system have varied from traditional functional test to structured test accordingly.The principel of functional test is presented in this paper and the representative techniques of structured test, as in-circuit test(ICT),boundary-scan test(BST),build-in self-test(BIST) and scan-path test,are explored subsequently.Finally,the developmenting trends in the future are looked forward to.

To surmount the problem that radar equipment fault detection data to be hard get, support vector domain description is be used to diagnose radar fault, and have established the kind of classification model based on a classification. This model uses few fault sample and the sample under normal state to establish fault classification model, realizes the fault diagnosis of fault identification and complete radar equipment. Finally, through diagnose fault of logarithm magnifying circuit to verify the feasibility of this method, and reach a good diagnosis result.

Fault dictionary method is a kind of very practical fault diagnosis method. But large scale and complex circuits, the fault dictionary is huge, and the speed of fault searching affects the efficiency of real-time diagnosing. In this paper, a new method that the faults are classed and many son fault dictionaries are built with BP nerve networks organize the search index is introduced. This method using the BP nerve network's ability that could accurately describe the relation between input data and corresponding goal organizes the index in a multilayer binary tree with many BP nerve networks. Through this index, the seeking scope is reduced greatly, the searching speed is raised, and the efficiency of real-time diagnosing is improved.