This paper introduces a 12-element asymmetric mirror-coupled loop antenna for integration into 5G smartphones. The proposed antenna includes six identical asymmetrically mirrored (AM)-coupled building blocks, each consisting of two gap-coupled loop antennas, with each building block dimensioning a mere 12×7 mm². The unique architecture of the proposed antenna yields an isolation performance exceeding 14 dB without the necessity for ancillary decoupling elements and effectively covers the dual-band 5G mobile frequency bands of 3.3-3.6 GHz and 4.8-5.0 GHz. The antenna was optimized using simulation software HFSS, and the results indicate an antenna's envelope correlation coefficient of less than 0.016 and an efficiency range of 72%-81%. Finally, the performance of single-hand and double-hand handset smartphone modes is discussed, which still exhibit good radiation and MIMO performance under both modes, demonstrating their stability in practical applications. Simulation and measurement results indicate that the proposed 12-element MIMO antenna holds great promise for 5G smartphone applications.

In a number of wireless communication systems with multibeam antennas, the distance from the antenna to subscribers in different parts of the service area varies significantly. Such systems include high-altitude platform station communication systems, communication systems based on low Earth orbit and medium Earth orbit satellites, and several others. If such a system uses an antenna with identical beams, the throughputs of communication lines in different cells can differ by more than an order of magnitude due to the variation in distance. To equalize throughputs across all cells within the service area, an antenna with different beams can be employed. The gain of these beams should be proportional to the squared slant ranges to the centers of the served cells. The gain of a beam can be modified by altering its size and shape. This paper proposes a method for service area partitioning in communication systems that accounts for the slant range to subscribers. It determines the shapes and profiles of the ideal contoured beams and presents optimized contoured beams for a real antenna.

In the landscape of wireless communication, smart antennas, or adaptive array antennas, have emerged as vital components, offering heightened gains and spectral efficiency in advanced communication systems such as 5G and beyond. However, augmenting network coverage, capacity, and quality of service remains a pressing concern amid advancing communication technologies and escalating user demands. Array antennas with reduced sidelobe levels, high directivity, and increased beam steering capabilities are sought after to address these challenges. This paper explores convex optimization as a potent tool for array synthesis problems, offering robust performance and solution efficiency. By formulating optimization problems as convex programming, sidelobe reduction challenges can be efficiently addressed. The paper presents a comprehensive investigation into convex optimization-based approaches for array pattern nulling, assessing their performance and computational efficiency in various scenarios. Numerical examples demonstrate the efficacy of the proposed methods in maintaining the main lobe, controlling sidelobe levels, and placing nulls at interfering directions, thereby advancing the state-of-the-art in smart antenna technology.

A new dual-polarized compact crossed-notched dielectric resonator antenna (DRA) array with high-gain and wideband performance is proposed for low-band massive multiple-input multiple-output (MIMO) applications at the 700 MHz band of 5G new radio (5G NR) technology. The DRA element consists of three dielectric layers with relatively high relative permittivity constants (ε_r1 = 15 for the bottom and top layers and ε_r2 = 23 for the middle one) for a compact antenna. Characteristic mode analysis (CMA) of a rectangular DRA reveals that two pairs of degenerate modes, namely M2/M3 and M4/M5, resonating at 0.4 and 0.6 GHz respectively can be used to achieve dual polarizations with a proper feeding strategy. By jointly reshaping the conventional DRA along with adding a notch into the middle dielectric layer the two pairs of degenerate modes are merged to produce a broad bandwidth with a compact size of 0.2λ_max × 0.2λ_max (λ_max being the wavelength at low-frequency point). The measured results show an impedance bandwidth of 13.15% (710 MHz-810 MHz) and an isolation of less than -17 dB. Furthermore, the antenna exhibits a good radiation pattern over the working band with a high gain of 7 dB. Finally, the proposed element is tested in a massive MIMO system of 3×4. The results exhibit a wideband of 17.7% and high isolation of more than 12 dB along with a stable gain of 5 dBi within the operating band.

In this paper, a diamond-shaped broadband high-gain microstrip patch antenna based on a folded floor structure is proposed. The overall dimensions of the antenna are 108 mm × 100 mm × 25 mm. Additionally, it contains a radiating microstrip patch, a folded ground plane, and a capacitive feed strip. The broadening of the antenna's operating band is achieved by enhancing the microstrip radiating patch and the capacitive feed band. The original rectangular structure was transformed into a rhombic structure, enabling the radiating patch to absorb the current more effectively and achieve a better impedance match for the antenna operating around 5 GHz. The radiation performance of the antenna is maximized by utilizing the folded floor structure. Measured results show that the impedance bandwidth of the antenna is about 61.5% (2.84 GHz-5.36 GHz), covering 5G dual bands. Meanwhile, the peak gain reaches 12.6 dBi, and the average gain reaches 10.7 dBi.

Multi-resonator gap-coupled design of coaxially fed half-hexagonal microstrip antennas is proposed in 900 MHz frequency range. It yields an impedance bandwidth of 32 MHz (3.28 %) on a thinner FR4 substrate (~0.01λ_g). Reduction in patch area in the gap-coupled design is achieved by employing the ground plane slots. Slots reduce the fundamental mode resonance frequency on each patch, thereby realizing wideband response in a lower frequency region. With impedance bandwidth of 26 MHz (3.4%), slot cut ground plane design provides patch area reduction by 38.13% and frequency reduction by 21.8%. Enhancement in the broadside gain on a thinner lossy substrate in the gap-coupled designs is achieved by integrating a cavity-back structure, which provides gain increment by nearly 2.5-3 dBi. Thus, the proposed work outlines a technique that enhances the bandwidth and reduces the patch size with an increment in the gain, on a thinner lossy substrate. An experimental verification for the obtained results is carried out that shows a close agreement.

In this paper, a mode control technology of a slotline resonator is proposed and utilized to guide the design of the slotline resonator. With this method, characteristic modes generated by the slotline resonator are more controllable. With characteristic mode analysis, which is the core of this technology, the desired and unwanted modes of the slotline resonator are easy to be analyzed, controlled, and further used to expand the stopband bandwidth. By applying this technology, a multi-mode slotline resonator with a T-shaped coupling structure (MMSR-T) is proposed by modifying a multi-mode slotline resonator (MMSR), and its unwanted modes out of the passband are more controllable without influencing the expected modes in the passband. Based on the proposed MMSR-T, a balanced bandpass filter (BPF) is proposed, which consists of a U-shaped microstrip/slotline transition as the input/output structure, a T-shaped slotline feeding structure as a feeding terminal, and MMSR-T as the filtering unit. Through the mode analysis and design of MMSR-T, ultra-wide differential-mode (DM) stopband, high common-mode (CM) suppression, and high DM selectivity are obtained in this design. The measured results agree well with the theoretical predictions and simulated results. The effects of mode control technology on stopband extension are proven.

To solve the problem of antenna miniaturization and mutual interference between the communication band of the UWB system and other wireless communication system bands, this paper proposes a UWB monopole antenna which has frequency notch characteristics. By applying two pairs of Split Ring Resonator (SRR) structures on a CPW transmission line, a coupling resonance is generated in a specific frequency band, and the antenna has a dual frequency notch and a wide band notch function. The measured results show that the antenna has good band-notch characteristics in the frequency ranges of 3.3 GHz to 4 GHz and 5.1 GHz to 6.2 GHz, suppressing ultra-wideband interference between WiMAX (3.3 GHz~3.8 GHz) and WLAN (5.15 GHz~5.35 GHz and 5.725 GHz~5.825 GHz) in a wireless communication system. The volume of the antenna is 40 mm × 36 mm × 1 mm, and the measured results are compared with the simulated model results. Besides, the measured and simulated results have a good consistency.

A novel compact dual-band antenna based on dual-cap metasurface (MS) is proposed. By etching circumferential circular ring slots on one side of the substrate and large cruciform slot on the other side, the dual-cap MS operates in two frequency bands. In addition, by placing the dual-cap MS at the back of a circular ring planar antenna which serves as a reflector, the impedance characteristic of the antenna in lower band and gain both in two bands are improved. The results show that this dual-cap MS antenna operates in the Wireless Local Area Network (WLAN) bands of 2.43-2.6 GHz and 5.48-6.05 GHz. Moreover, the maximum gains in lower and upper bands can reach 6.9 and 5.8 dBi, respectively.

In order to achieve miniaturization and high performance in microwave filters, this paper proposes two double-layer bandpass filters with different structures, both equivalent to square-coupled topologies. These filters employ dual-cavity single-mode and single-cavity dual-mode substrate-integrated waveguide resonators. In this configuration, the upper layer comprises two single-mode resonators connected to the input and output feed lines, while the lower layer contains dual-mode resonators coupled to the upper layer's single-mode resonators through two slots on the middle metal layer. A comprehensive analysis is conducted on the impact of primary parameters on filter characteristics and transmission zero positions. The second filter is fabricated and tested, yielding results consistent with simulation outcomes. The center frequency of the filter is 4.77 GHz, with a 3 dB bandwidth of 0.16 GHz (relative bandwidth: 3.35%). Additionally, its rectangularity coefficient at 10 dB approximately equals one, an ideal value for practical applications.

The rapid expansion of wireless communication systems has spurred a growing demand for adaptable multiple-input multiple-output (MIMO) antennas capable of accommodating diverse frequency bands and operational environments. This paper presents a compact quad-port wide-band tuning-reconfigurable MIMO antenna tailored specifically for 5G applications operating within the sub-6 GHz spectrum. The proposed design enhances isolation levels (>18 dB) and augments pattern diversity by utilizing four orthogonal radiating elements. Integrating a C-shaped monopole element with a matching stub facilitates frequency tuning via a varactor diode, ensuring a consistent radiation pattern. The lower and upper resonant bands could be fine-tuned by adjusting the varactor diode's reverse-biased voltage within the allowed range of 0.5 to 10 V. These bands are 4 to 5.18 GHz and 5.45 to 6.65 GHz, respectively. The proposed antenna system's four C-shaped elements are placed on a 40 × 40 mm² ground plane and mounted on a Rogers RT5880 substrate that is 0.8 mm thick with a relative permittivity of 2.2. This design is well suited for various wireless applications and cognitive radio networks due to its compatibility with sub-6 GHz frequency bands and wide-band tuning capabilities.

A compact, spectacle shaped, tri-band, metamaterial inspired antenna is designed for ISM, WiMax, WLAN, Wi-Fi 6E 6 GHz, Aeronautical Radio navigation and Radio-Location Applications. The radiating electrical length is modified by two successive CSRR structures to mitigate the current and create a band notch at 3.9 GHz as well as 5.5 GHz. The proposed prototype is designed on low cost FR-4 material. Antenna performance parameters are investigated on a four-layered phantom model. The results obtained reveal that the antenna works well on free space as well as at the close proximity to human tissues.

Surrogate models have been gradually promoted in electromagnetic compatibility (EMC) simulation in recent years, and two typical application scenarios are uncertainty analysis and electromagnetic optimization design. The surrogate model can simulate the forward EMC simulation process as accurately as possible with relatively few sampling points. The choice and number of sampling points will directly determine the accuracy of the surrogate model. The purpose investigated by uncertainty analysis and electromagnetic optimization design is different. How to choose appropriate sampling strategies is worth discussing, but there are fewer studies in the field at this stage. This paper applies a cascaded cable crosstalk example to explore the accuracy of the surrogate model under different sampling strategies, which provides a theoretical level of guidance for the application of the surrogate model in EMC simulation. The study enables the surrogate model to be better suited for two application scenarios: uncertainty analysis and electromagnetic optimization design.

The proposed multi-resonant monopole antenna has a compact design and operates between 2.9 and 6 GHz, effectively covering the full 5G sub-6 GHz spectrum (N77/N78/N79) as well as WLAN frequency ranges. This Miniaturized Multi-resonance Monopole Planar Antenna (MMMPA), having dimensions 25 × 16 × 1.6 mm³ (L x W x h), is ideally suited for wireless communication devices and systems. The antenna achieves triple resonances, encompassing the frequency bands from 2.9 to 6 GHz, through an inventive construction consisting of rectangular patch, U slots, key-shaped slots, split ring resonators, and annular rings forming an electromagnetic band-gap (EBG) structure. A strong degree of agreement and correlation amongst the simulation and measurement findings attests to the antenna's dependable operation. Even though the patch size was reduced by around 65%.

The conventional synchronous generator model accurately represents only the stator circuit. However, when considering transient effects on rotor quantities such as rotor voltage and current, accurate predictions can be achieved by properly incorporating the field and damper considerations with the stator circuits in an equivalent model. Besides, it has been observed that simulated responses obtained using the conventional model with calculated machine parameters frequently do not align well with the actual measured responses, especially for the rotor winding. This paper analyzes the effect of the d and q axis parameters of synchronous machines, focusing on accurately determining these parameters, particularly the Canay inductance. It investigates the impact of precise determination of these parameters from the time constants of the direct axis operational inductance on transient response and stability. Through simulation studies on a high order model synchronous generator system, the paper compares transient performances with and without considering Canay inductance, shedding light on its effects.

We propose a 3-band iteration method to transfer knowledge learned from RGB (red, green and blue) data pretrained models to the hyperspectral domain. We demonstrate classification of a Multi-spectral Choledoch database for cholangiocarcinoma diagnosis. The results show quicker and more stable training progress: 92%+ top-1 accuracy in the initial 3 epochs. Some advanced training techniques in the RGB computer vision field can be easily utilized and transferred to the hyperspectral domain without adding more parameters to the original architecture. The computational cost and hardware requirements remain the same. After voting, the highest top-1 accuracy on the validation set reached 95.4%, and the highest top-1 accuracy on the test set reached 94.3%. We can directly use our models trained on high-dimensional spectral images to test and infer on RGB color images. We visualized some results by Grad-CAM (Gradient-weighted Class Activation Mapping) on RGB test data, and it shows the transferability of knowledge. We trained the models solely on classification task on spectral data, and these models showed their ability to predict on RGB images with different fields of views. The results indicate good segmentation even when the model has never been trained on any segmentation task.

In order to prolong the service life of lithium batteries, the charging process is usually divided into two stages: first constant current (CC) charging, and then constant voltage (CV) charging. This letter proposes a three-coil structure wireless power transfer (WPT) system to realize inherent CC and CV characteristics and automatic CC-CV transition function. During charging, the proposed system can operate in S-S-LCC tank for CC charging and in S-S-S tank for CV charging, respectively. Different from the previous closed-loop control, hybrid topology switching and dual-frequency switching methods, the proposed method has automatic CC-CV transition function due to the special circuit structure. Therefore, the communication links, state-of-charge detection circuits and open-circuit protection circuits are omitted, which ensures the high reliability and low cost of the system. Finally, a verification experimental prototype with a rated power of 480 W is built to verify the feasibility of the proposed system.

A compact four-port dual-band compact multiple-input multiple-output (MIMO) antenna system with reduced mutual coupling is proposed in this paper. The dual-band antenna operates in the frequency range covering 3.1-3.6 GHz (5G NR, n78) and in the newly introduced 5G midband spectrum of 5.925-7.125 GHz (5G NR, n96). The proposed MIMO antenna system is compact with dimensions 65 × 65 × 0.8 mm³ and has isolation ≤ -20 dB among all ports. The single monopole antenna is loaded with multiple resonant branches designed and optimized with impedance bandwidths of 14.92% at 3.35 GHz and 18.46% at 6.5 GHz. Impedance bandwidth, polarization diversity, and mutual coupling between elements for the designed four-port MIMO antenna system are measured. The proposed design is fabricated using an FR4 epoxy substrate, and the measured gain values are 3.9 dB and 4.8 dB for 3.3 GHz and 6.5 GHz, respectively, with nearly omnidirectional radiation pattern.

In the paper, a dual-band circularly polarized (CP) antenna with wide axial-ratio and gain beamwidths is proposed for high-precision BDS applications. The radiator is consisted of four groups of dipoles, eight metal columns, and a reflector. The half-power beam width (HPBW) can be effectively increased by bending a portion of the dipole into an arc and loading a series of metal columns on the ground. Besides, a reactive impedance structure (RIS) is inserted serves as a reflector to improve the axial ratio beamwidth (ARBW) and obtain unidirectional radiation. At the same layer of the dipoles, a four-feed network is presented to provide stable quadrature-phase excitation. For validation, the designed antenna is manufactured, where the overall size is 0.48λ₀ × 0.48λ₀ × 0.12λ₀. Measurement results suggest that the proposed antenna is capable of operating efficiently within the frequency range of 1.17-1.22 GHz (4.2%) and 1.5-1.65 GHz (9.5%), which covers BDS B1 and B2 band. Moreover, at four main planes, the measured 3-dB ARBW/HPBW are more than 121°/121° and 150°/198° at 1.207 GHz and 1.561 GHz, separately. Consider that the proposed CP antenna exhibits wide overlapped beamwidth and small size, it is conducive to high-precision positioning in BDS applications.

This paper introduces a 5G multi-frequency antenna design method based on multi-objective sequential domain patching. By etching helical metamaterials on radiation patches and loading asymmetric electric-inductive-capacitive metamaterials on the transmission line side, the antenna structure is designed and optimized using electromagnetic simulation software, HFSS, and MATLAB. The resulting multi-frequency antenna operates across multiple frequency bands: n1, n41, 3.5G, and 4.9G. To ensure antenna performance and radiation efficiency, the antenna multi-frequency bands are precisely controlled. The experimental results show that the error between each operating frequency band and target frequency bands of the antenna is within 7.2%. Compared with conventional antenna design methods, the use of metamaterials and intelligent algorithms to optimize the structural parameters and loading positions of metamaterials can improve antenna performance while shortening the design cycle. Overall, this research offers novel insights into the design of 5G high-performance antennas.