Fuzz button connectors are extensively used in vertical interconnection for high-density integrated circuits. However, fuzz buttons operating in harsh environments for extended periods are subject to degradation, which may directly affect the communication systems reliability. In this work, the specific effects of fuzz button degradation on its electrical properties are studied by theoretical and experimental analysis. The surface morphology and contact states of the metal wires inside the degraded samples are observed to analyze the degradation mechanism. The equivalent circuit models for the transmission channel with fuzz buttons before and after degradation are developed to evaluate signal reflection and transmission loss. The equivalent impedance networks of the fuzz button interconnections with slight and severe degradation levels are proposed and the corresponding parasitic electrical parameters of the equivalent impedance networks are also calculated and analyzed. Finally, fuzz buttons with different degradation levels are obtained by accelerated tests and the experiment tests are conducted to validate the equivalent circuit model results. The results of experimental test and equivalent circuit model are compared and show good agreement. The research results provide a better understanding of the electrical characteristics of degraded fuzz buttons and theoretical guidance for improving electronic system reliability.

Ball grid arrays provide a small size and high-density package, which may lead to crosstalk in complex working environments. Of specific interest in this current work, the impact of failed ground solder balls on crosstalk in microwave circuits using ground-signal-ground structure was evaluated by simulations and measurements. In the 3-D electromagnetic model, two single-ended signal transmission channels were developed to analyze the effects of failed solder balls and the distance between two soldering areas on the signal transmission performance and crosstalk. Based on the frequency distribution of resonance points and structural characteristics of the soldering area with failed ground solder balls, an inductive coupling model was proposed to quantify the impact of above-mentioned factors on signal crosstalk. The results obtained from 3-D electromagnetic and equivalent circuit models are in good agreements. Experimental tests were then conducted to verify the simulation results.

This work presents a cost-effective optical frequency comb generator (CEOFCG) solution for generating multiple, equally spaced carriers in wavelength-division-multiplexing coherent optical fiber communication systems (WDM-COFCS). It enables the replacement of multiple laser sources with a single continuous-wave laser, eliminating the need for additional amplification and filtering setups. The CEOFCG provides stable multicarrier spacing, broad phase coherence, and compatibility with advanced modulation formats, enhancing the performance of WDM-COFCS. Digital signal processing (DSP) techniques, including digital filtering, detection, and impairment compensation, contribute to high transmission and spectral efficiency (SE). The results demonstrate the potential of CEOFCG in achieving cost reduction, complexity reduction, high SE, and optimal utilization of optical fiber bandwidth, particularly in higher-order QAM-based COFCS.

Intelligent fault diagnosis of rolling bearings under variable-speed operation is still difficult to achieve, since it is hard to learn speed-invariant fault representation and maintain the geometric structure of the fault discriminator under different operating conditions. To address this issue, this paper proposes a Hybrid Transformer-based Dynamic Projection Network (HTPNet) method for cross-condition bearing fault diagnosis. A Transformer-based feature extractor with learnable patch embedding captures long-range temporal dependencies from raw vibration signals to generate informative features. A class-specific hypernetwork learns dynamically the projection matrices, which project features into adaptive low-dimensional subspaces, and orthogonality regularization stabilizes the projections and decorrelates features. We propose the Gradient Reversal Layer for adversarial domain adaptation to learn condition-invariant representations and all-class projection scoring for making reliable predictions on unlabeled target domains. The purpose of this optimization is a unified objective that improves the feature discrimination, the consistency of the projections and the domain alignment. Experimental results on both HUST and CWRU datasets reveal that HTPNet consistently outperforms other state-of-the-art methods in terms of diagnostic accuracy, robustness to operating condition variations, additive noise, and feature interpretability.

High-order, broadband OAM-vortex beams have great potential to increase the information-carrying capacity of wireless systems, but their practical application is constrained by issues with low gain, limited bandwidth, and low mode purity in higher-order modes. To address these requirements, in this paper, we propose a symmetric transmit unit cell that achieves full 360-degree phase coverage with acceptable transmission loss and a uniform configuration suitable for dual-polarized applications, which consists of four conductive layers interleaved with substrate layers. Experimental testing of higher-order modes on the manufactured transmissive prototype verifies broadband vortex-beam formation, which is consistent with the simulation results. Across the 26.5 to 40.5 GHz frequency span, the proposed design demonstrates a consistently high OAM-vortex mode purity exceeding 86% and covering 46.6% of the OAM bandwidth. It is also observed that the fabricated prototype achieves a peak realized gain of 21.7 dBi for the +2 mode, resulting in an aperture efficiency of 13.6%. With the implementation of the proposed transmitarray prototype, future wireless systems can attain significantly improved information-carrying capacity.