Aeu-International Journal of Electronics and Communications最新文献

An ultra-low power capacitor-less LDO with feedforward compensation technique based on the small-signal gain stage and composite transient enhancement structure is proposed. The feedforward compensation technique based on the small-signal gain stage reaches a low frequency zero ,by utilizing the compensating effect of the zero to relieve the adverse effects of the pole, thereby enhancing the stability and performance of the circuit. Furthermore, the small gain stage can adjust the quiescent current consumption,contributing to a significant reduction in system energy consumption. The proposed composite transient enhancement structure can reduce the transition time of the circuit, adjust the gain of the circuit under different operating conditions to achieve precise gain control and improve the transient performance of the system. The proposed LDO is designed using SMIC 0.18um CMOS process. The simulation results show the total quiescent current is 0.94$uA$ and the current efficiency is up to 99.99%. The extremely low FoM value of 0.04 represents a good transient performance. Synthesizing the comparison of various parameters, the superiority of this design can be clearly concluded.

Due to the large degrees of freedom (DOF) by generating difference coarray, nonuniform arrays have great potential in direction of arrival (DOA) estimation. However, some existing nonuniform arrays (e.g., (sparse) nested arrays) still have comparatively strong mutual coupling in physical array domain, whereas the others (e.g., coprime arrays) have holes or only used part available in difference coarray domain, for the performance loss of DOA estimation. To address these issues, we propose two kinds of dual-spread arrays which achieve more and continuous DOF by exploiting correlation matrix reconstruction, rather than the generation of difference coarray. All inter-antenna spacings of the proposed arrays are larger than half-wavelength, resulting in extended aperture and reduced mutual coupling. An ESPRIT-based estimation method is further provided for unique DOA estimation with high-accuracy and low-complexity. The analyses of mutual coupling and computational complexity are provided in detailed. The theoretical analyses and simulation results show the superiority of the proposed arrays and method over the existing techniques.

The Internet of Things (IoT) based wireless devices are mainly designed for rapid indoor millimeter-wave (mmW) communication systems. These systems often require high gain mmW antennas within a wideband MIMO framework. This work presents a high performance quad element pin-loaded multiple-input multiple-output (MIMO) antenna array for mmW communications that can be utilized within IoT-enabled smart environment. The novelty of these antenna elements lies in the incorporation of unique flower-shaped slots and shorting pins in each patch of a two-element antenna array. Moreover, a four-port MIMO antenna system is created by arranging the two element arrays in an orthogonal configuration. By employing this pattern diversity technique and incorporating shorting pins in each individual element, the adverse mutual coupling effects between adjacent elements are effectively mitigated. Experimental validation of the MIMO array prototype confirms the minimum isolation of 34 dB and high port isolation of 72 dB over the operating bandwidth from 26.31–30.25 GHz (3.96 GHz). Notably, these features together with lower correlation values and higher diversity gain, make it a good choice for mmW-based IoT devices in smart environments.

The paper suggests that optimum Chebyshev filters present an excellent choice for microwave filter design, as this approximation offers minimum return loss in the half-power passband, provides a maximum cutoff slope, and maintains low sensitivity in the passband. A comparative analysis is conducted with the chained-function filters to demonstrate the efficacy of this approximation, since chained-function filters also utilize Chebyshev polynomials to shape the filter’s characteristic function. The optimum Chebyshev filter, along with two chained-function filters, each of the sixth-degree, are realized, simulated, and compared as lowpass stepped impedance filters with a half-power passband of 1 GHz. After a detailed comparison, it is concluded that the optimum Chebyshev filter outperforms, or at least matches, the performance of the chained-function filters. This suggests that the optimum Chebyshev filter can effectively replace chained-function filters in all applications, offering a superior solution.

This paper proposes a circularly polarized planar wide-angle scanning phased array radar. The structure of the proposed array element is a windmill-type patch with an octagon-shaped series power divider. The proposed array exhibits a low axial ratio because the element has a wide 3-dB axial ratio beamwidth and the array topology uses the sequential rotation technique. Test results show that the proposed 8 × 8 uniform planar array can realize two-dimensional circularly polarized scanning from −60° to +60° in the working band of 3.43–3.48 GHz. The coverage gains of θ = ±60° are about 3 dB lower than the gain when the main beam points at θ = 0°. Moreover, in the scanning mentioned above airspace, the scanning beam axial ratio is below 0.5 dB in the xz-plane (φ = 0°) and yz-plane (φ = 90°) and below 1.4 dB in the D-plane (φ = 45°). Another notable feature is the single-layer structure, and its profile is only 0.08λ₀ at the center wavelength. This good low- axial ratio and low-profile characteristics make the proposed array potentially applicable to low-orbit satellite communications.

Upper extremity impairments are a common consequence of stroke, necessitating thorough rehabilitation monitoring and kinematic assessments to facilitate motor recovery. The Box and Block Test (BBT) and Sollerman Hand Function Test (SHFT) are two widely utilized and recommended tools for objectively measuring upper limb dexterity and evaluating fine motor skill rehabilitation in patients. However, these tests rely on specific equipment and therapist attendance, making the process time-consuming and clinic-dependent. This paper introduces a computer vision-based hand rehabilitation assessment suite specifically designed for mobile devices, such as smartphones and tablets, which serves as a virtual alternative to traditional methods while also incorporating an interactive exergame. Our application faithfully integrates the original tests’ guidelines and procedures into an engaging computer vision experience, utilizing advanced technologies like MediaPipe Hands for precise hand and finger tracking. This innovative solution obviates the need for additional computer peripherals such as smart gloves or VR headsets, as well as physical equipment like wooden boxes and blocks, relying solely on the built-in camera of everyday mobile devices. In addition, we address several technical challenges encountered in our approach and outline future directions for score normalization and feature expansion, ensuring the continued improvement and efficacy of our hand rehabilitation assessment suite.

A wideband dual-polarized high-efficiency transmitarray antenna utilizing the isolated metal elements is proposed. First, a dual-polarized isolated metal element supported by a substrate frame is introduced. Each array element is isolated from adjacent elements by gaps. To realize the element, a substrate frame is used to completely fill the gaps and support the elements. As a result, the limitation of metal connections is overcome, and the transmitarray bandwidth is significantly enhanced. Based on equivalent circuit of the element, its wideband operating mechanism is revealed. Then, to reduce the manufacturing difficulties and costs while maintaining electrical performance, PCB technology is applied to the transmitarray fabrication, integrating the elements and the substrate frame. Finally, a wideband dual-polarized substrate-based metal transmitarray is designed, fabricated and measured. The measured results of the prototype indicate that its gain at the center frequency 10.2 GHz is 26.9 dBi, its 1-dB gain bandwidth is 23.4%, its efficiency is 56.1% and its lowest efficiency across the 1-dB gain bandwidth is 38% at 12.4 GHz. To the best of our knowledge, this is the first time a wideband two-layer substrate-based metal transmitarray has been proposed and implemented.

This study presents a novel four-element MIMO antenna system designed for the millimeter-wave (mmWave) spectrum. Each MIMO antenna element features a meandered V-shaped radiating structure fed by a 50$\Omega$ microstrip line and a partial ground plane with a square notch printed on a 0.254-mm thick RO5880 substrate. The characteristic mode analysis (CMA) of the antenna is done, which reveals that the antenna efficiently utilizes Mode 2, while Modes 1 and 4 also contribute to the resonance, resulting in a wideband response within the mmWave spectrum. A four-element pattern diversity MIMO configuration is developed to evaluate its suitability for MIMO communication, incorporating a connected ground-structure decoupling network to enhance isolation. The MIMO system achieves over 20 dB isolation between elements, with an impedance bandwidth ranging from 20.2 to 33.05 GHz and a peak gain of 6.6 dBi at 28 GHz. Fabrication and measurement validate the design, showing strong agreement with simulations. The MIMO performance metrics, including envelope correlation coefficient (ECC), diversity gain (DG), mean effective gain (MEG), total active reflection coefficient (TARC), and channel capacity loss (CCL), are within acceptable limits, suggesting that the proposed MIMO antenna system is a promising candidate for future mmWave applications.

A wideband 32-element vehicular 3D-MIMO system is proposed by utilizing eight-element MIMO antenna for Internet-of-Vehicle/Vehicle-to-Everything. The eight-element MIMO antenna consists of four sets of two identical antenna elements are arranged 90⁰ symmetrically on an octagon-shaped substrate cross-section area of 0.4374 ${\lambda }_0^2$. A combination of ground stubs between two same oriented antennas is loaded with shared ground at the bottom of the same substrate for better matching and low correlation, which are fed through the tapered microstrip line. Similarly, dual I-shaped stubs interconnected with shared ground for high isolation between a pair of corner elements. The proposed antenna achieved measured impedance bandwidth range (S_ij ∈ i = j <  − 10 dB) of 3.03–15.33 GHz with a maximum mutual coupling (S_ij ∈ i ≠ j) value of − 15.5 dB. Furthermore, a set of eight-element MIMO antenna with extended ground is vertically orthogonally symmetrically rotated around the central axis, forming a 32-element 3D-MIMO antenna and its found results are almost close to eight-element antenna with an enhanced peak gain value of 12.1 dBi. The performances of the 3D-MIMO antenna with radome and large metallic sheet are also examined. The satisfactory results observed in the 3D system-in-package highlight its capability for advanced vehicular communication.

This work presents a 60 GHz continuously adjustable mm-wave cross-coupled voltage − controlled oscillator (VCO) utilizing an innovative frequency doubling technique in 40 nm CMOS technology. The extraction of the second harmonic is performed through a transformer from the tail of the 30 GHz fundamental VCO. The primary side of the transformer serves a dual purpose, functioning both as a filter for the second harmonic and as a balun simultaneously. The circuit incorporates a MOS varactor along with a four-bit binary weighed capacitor bank to achieve coarse and fine frequency tuning respectively. Post Layout simulation results indicate that the VCO spans a broad tuning range of 12.3 GHz, covering frequencies from 52.7 to 64.98 GHz. Phase noise (PN) remains below −96.3 dBc/Hz at a 1 MHz frequency offset within all bands Power consumption, including the output stage, is 21.8 mW from a 1.1-Volt supply. The VCO provides more than −13 dBm output power in all frequency bands and occupies a chip area of 0.53 $m{m}^2$.