Electronics Letters最新文献

This paper introduces the subarray partition based on the sparse array weighted K-means clustering method, which extends the conventional K-means clustering method through the inclusion of a weight matrix approach. This matrix is derived by recording the frequency of each element's occurrence across multiple independent sparse arrays, thereby generating a frequency matrix. The performance of SWKCM is demonstrated through simulations and comparisons with four similar methods. To assess the effectiveness and superiority of the SWKCM, it is applied to the subarray partition of a 40×40 uniform planar phased array and compared with the other four methods. The simulation results show that the proposed SWKCM method maintains comparable sidelobe suppression capabilities to those of KCM, achieving a normalized peak sidelobe level of -43.1076 dB. Furthermore, compared to the K-means clustering method, the sparse array weighted K-means clustering method significantly enhances the stability of subarray partition outcomes, as evidenced by a reduction in the peak sidelobe level standard deviation from 1.0991 to 0.8104, resulting in a 26.3% decrease in variability.

Antenna chambers are RF-shielded enclosures which are required for antenna and radio performance measurements. Typically, anechoic chambers (ACs) are used for measuring directional metrics (e.g. antenna pattern, effective isotropic power etc.), while reverberation chambers (RCs) are widely used for non-directional measurements (e.g. antenna efficiency, total radiated power etc.). When a device under test requires both types of measurements, testing needs to be conducted sequentially in an AC and an RC. This leads to significant time inefficiencies due to the need to set up and calibrate two separate measurement setups in two different chambers. To address these issues, this letter proposes a programmable chamber framework capable of electronically switching between AC and RC modes by programming the reflective intelligent surface-enabled sidewalls. This framework is highly attractive for the industry as it supports both directional and non-directional measurements within a single chamber. The letter outlines the conceptual framework, discusses design considerations, and presents preliminary experimental validation of reflective intelligent surface-enabled sidewall with the designed phase-setting configurations to emulate the radio absorber sidewall of an AC and the metal plate sidewall of an RC. The experimental results demonstrate the effectiveness and potential of the proposed approach.

Decoding of spatial information from place cells is currently limited to individual brain regions, severely constraining the understanding of the brain's spatial navigation mechanisms. In this study, synchronized detection of dual-brain region spatial encoding was conducted using brain–computer interface (BCI). Therefore, an implantable microelectrode array (MEA) was developed tailored for the simultaneous detection of neuronal activities in the CA1 of the hippocampus and the Barrel Cortex (BC) of the somatosensory cortex in rats as BCI. The MEA was improved by modifying the nanocomposite PtNP/PEDOT:PSS to improve their electrical properties (reducing impedance from 1.82 ± 0.17 MΩ to 3.4 ± 0.3 kΩ), facilitating neural recordings in freely behaving rats. The neural activities were obtained from the CA1 and the BC simultaneously and validated the existence of place cells in both brain regions. This study highlighted the potential of PtNP/PEDOT:PSS-modified MEA as BCI in concurrently detecting neural activity associated with spatial encoding in two brain regions, offering novel perspectives on the processing of tactile stimuli and the formation of cognitive maps for navigation.

The line of sight (LoS) probability is a key factor for the channel modeling of air-to-ground (A2G) communication. However, the existing LoS probability models do not account for the effects of airframe shadowing (AS) and building density, which can cause serious link obstruction and performance loss due to the six-dimensional (6D) mobility and self-body of unmanned aerial vehicle (UAV). In this article, a new LoS probability model is proposed that considers the AS and building density for different UAV heights. Adding to this, the AS is derived in terms of UAV framework and 6D mobility. Next, the machine learning (ML) based graph neural network (GNN) method is developed to learn the features and structure of the urban environment and predict the LoS probability. Then, the GNN model is trained and evaluated based on the ray tracing (RT) data to establish the relationship between model parameters and UAV heights under the building density and AS factors. The interpretation and explanation of the proposed GNN model and prediction are also discussed in this article. It is shown from the simulation analysis that the GNN model accurately captures the effects of AS, building height distributions, and UAV heights, with high accuracy compared to the baseline 3GPP, GCM and NYU models.

The integrated communication and jamming system is proposed by exploiting the diversity gain and flexible deployment of unmanned aerial vehicle (UAV)-based distributed multiple input multiple output technology, which is expected to gain higher spectral efficiency and system scalability. This paper designs transmit beamforming of multiple UAVs so that they can simultaneously impose jamming signal to jamming targets and communication signal to communication users at the same frequency. The aim is to maximize the total jamming effect of all jamming targets while achieving a certain communication rate of communication users by optimizing the transmit beamforming matrices. Two cases are considered in which the UAV swarm works in clock synchronization and clock asynchronization. Specifically, the problem is formulated into a non-convex optimization in the synchronous case. A near optimal solution is derived by decoupling the beamforming matrix into multi-user interference suppression matrix and single-user beamforming matrix. In the asynchronous case, the transmitter–receiver matching relation needs to consider and multiple optimization variables are highly coupled, penalty factors and intermediate variables to convert the optimization problem to convex programming are introduced. The simulation results show that the proposed beamforming design algorithm coordinates the communication and jamming signal rationally and outperforms the conventional beamforming design algorithms.

In this letter, we address the problem of designing the joint waveform of radar detection, wireless communication and jamming. In the current most powerful filter-bank multi-carrier comb spectrum framework, a parameter-agile time–frequency structure between symbols is elaborated to improve the uncertainty of waveform generation architecture. Furthermore, a novel composite modulation strategy that combines intra-symbol chaos-based radar frequency modulation and inter-symbol chaos-based phase modulation is proposed for a substantial jamming performance improvement. Simulation results verify that the proposed joint waveform produces a superior jamming performance while satisfying the requirements of radar detection and wireless communication.

Based on the principle of weight superposition, a modified Madelung model is proposed. By combining the signal delay response characteristics (SDRC), a dynamic model and its inverse model are established to describe and compensate for the rate-dependent hysteresis phenomenon of the piezoelectric actuators (PEAs). The effectiveness of the proposed method is verified by experiments, and the results show that the hysteresis nonlinearity of the PEA is basically eliminated, with the normalized root-mean-square error of 0.64% under the excitation of multi-frequency superposition signal.

With the development of processes and reduction of transistor size, transistor sensitivity to voltage changes has increased. Traditional SRAM bit cells struggle to function properly at low voltages, and the lengthy write time necessitated by the write conflict problem will inevitably result in write failure. As ultra-low-voltage SRAM has emerged as a significant direction of research for SRAM, this paper proposes an ultra-low-voltage 9T SRAM bit cell that is conflict-free. By circumventing write conflicts and enabling rapid writing, the bit cell demonstrates its superiority, particularly at ultra-low voltages, by eliminating the requirement for peripheral write-assist circuitry to accomplish chip writing. To assess the performance of the conflict-free 9T bit cell, simulation experiments are conducted utilizing the 28 nm process model. Simulation results indicate that the 9T bit cell proposed in this paper requires only 66% of the writing time of the traditional 6T cell. This enables the cell to accomplish fast writing and more stable writing performance.

The floating-gate transistor is commonly employed as a non-volatile memory device, leveraging a floating node at its gate to store electrical charge over extended periods. This stored charge effectively alters the threshold voltage of the transistor. Utilizing standard CMOS technologies, floating-gate transistors can be designed and fabricated using conventional CMOS processes. This study focuses on characterizing the performance of a PMOS-based floating-gate transistor, specifically fabricated using the open-source Skywater 130 nm process. The modulation of charge on the floating node is explored through both hot-electron injection and Fowler–Nordheim tunnelling, providing insight into the resolution of these programming mechanisms. Additionally, the study includes a preliminary analysis of the retention time of the programmed charge in these devices. This work contributes to the open-source electronics community by detailing the design and programming techniques of floating-gate transistors developed with an open-source process design kit, and makes the corresponding FG cell designs available for public use.

Research on the physical memristive system is vital for realizing widespread applications of the memristor in practical engineering. In this article, a family of the asymmetric generalized passive voltage-controlled memristive system (AGPVCMS) is proposed; also the mathematical model of the AGPVCMS is established and its remarkable memristive characteristics are analysed. Especially, the AGPVCMS only consists of the diode bridge and LR filter, however it can enhance its asymmetry as well as display various asymmetrical pinched hysteresis loops in the voltage–current plane, via expediently changing the number of the diodes on different bridge arms. In addition, the effectiveness of the AGPVCMS is verified by the consistency between theoretical and experimental results.