Key influencing factor analysis aims to identify influential patterns in interrelated variables. This paper proposes an anytime entropy‐guided factor‐combination analysis method for discovering feasible multifactor combinations in large discrete or discretized design spaces. The method uses negative factor removal entropy to prioritize dimensions and a best‐first search strategy to return valid combinations under a user‐specified time budget while preserving multidimensional interactions beyond linear projection methods. It targets engineering datasets in which discrete design choices jointly affect continuous responses, making it suitable for data‐driven RF, microwave, and millimeter‐wave computer‐aided design tasks such as antenna, circuit, and subsystem optimization. Experiments on real‐world and synthetic datasets demonstrate that the proposed approach can efficiently produce high‐quality factor combinations, achieving fast discovery on moderate‐scale data and maintaining practical efficiency on larger‐scale settings.
This letter presents the design of a compact integrated antenna operating across both FR1 and FR2 frequency ranges for 5G applications. The proposed structure, with overall dimensions of 0.58 lambda G & times; 0.66 lambda G & times; 0.01 lambda G, employs a common aperture shared by a slot antenna and a patch antenna. In the microwave band, the slot-based radiator exhibits a bidirectional radiation pattern, which is well suited for wide-area and orientation-independent connectivity in 5G IoT and sub-6 GHz communications. At millimeter wave frequencies, the patch radiator generates a broadside radiation pattern with moderate gain, enabling high-data-rate directional links such as device-to-device communication and vehicular communications. The proposed dual-band antenna achieves peak gains of 5.6 dBi in the microwave band and approximately 10.2 dBi in the millimeter wave band. The antenna provides wide fractional impedance bandwidths of 74% (3.3-7.2 GHz) and 23.8% (24-30.5 GHz), effectively covering several key 5G bands. Owing to its novel integrated structure, an isolation better than 30 dB is achieved in both bands. Furthermore, frequency-dependent beam scanning is observed in both operating bands. A prototype was fabricated, and the measured results show close agreement with simulations.
In this paper, a novel wideband band‐pass filter with a single notch is presented. Designed to cover the LTE 4G band (2.50–2.69 GHz), the 5G N77 (3.30–4.20 GHz), and N78 (3.30–3.80 GHz) bands, as well as the upper 6 GHz band (6.425–7.125 GHz), the proposed filter uses a grounded patch etched with meander line resonators exhibiting inverted symmetry. Unlike conventional symmetrical resonators, this design introduces a coupled, inverted‐symmetry resonator configuration integrated with a grounded patch. This proposed mechanism efficiently achieves a dual‐band response by incorporating a notch band and enhances the upper stop‐band rejection through the generation of two transmission zeros (TZs). The notch band of the proposed filter is allocated at 5.54 GHz to block the existing interference of the 5 GHz WI‐FI, with an insertion loss of 35.1 dB and 10‐dB notched fractional bandwidth of 17.33% (i.e., 4.93–5.89 GHz). This notch separates the wide bandwidth into two sub passbands, the first of which is allocated at 3.38 GHz with a 3 dB bandwidth of 68.63% (2.22–4.54 GHz) and the second sub passband, on the other hand, is assigned at 6.67 GHz with a 3‐dB fractional bandwidth of 14.39% (6.05–7.01 GHz). Additionally, two TZs are detected in the upper stop band at 8.83 and 9.46 GHz, respectively. Note that, because of its close proximity with the 5 GHz WI‐FI, the 5G N79 band (4.40–5.00 GHz) was not initially targeted. However, the compact designed filter is also covering part of it as well, making it an attractive device for 5G communication systems.
A multilayer log-periodic metasurface patch antenna (LPMPA) operating in the 4-9-GHz frequency range with broadside radiation is presented. This antenna array is characterized by its compact size and low profile. Each element of the LPMPA consists of a 2-D periodic structure of 4 & times; 4 square patches, which can be viewed as a metasurface. The array is excited through aperture coupling in the ground plane beneath the radiators. The proper phase progression of the currents for a broadside radiation of the LPMPA ' s elements in the active region is obtained by increasing the length of the feed line placed between adjacent radiators. The structure ' s stop-band caused by the excess of length between radiators is eliminated by increasing the characteristic impedance of the feed line to 70 Omega in the proximity of each slot. A prototype of the proposed antenna, consisting of four 2-D periodic structures, is fabricated and tested. The obtained results show a 76% fractional bandwidth with gain ranges between 8 and 13 dB.
This paper presents the design and implementation of a high-efficiency two-way Doherty power amplifier (DPA) for sub-6 GHz 5G New Radio (NR) applications, specifically targeting the n78 band (3.3-3.8 GHz). The proposed gallium nitride (GaN)-based DPA delivers a peak output power of 42.5 dBm, a gain of 13.3 dB, and a maximum power-added efficiency (PAE) of 83% at 3.5 GHz with VDD = 28 V under a 50-Omega matched load. Both amplifier branches employ CG2H40010F GaN HEMTs configured in Class AB (carrier) and Class C (peaking) modes to achieve efficient load modulation across the operating band. A key feature of the proposed design is an integrated input network based on an unequal Wilkinson power divider combined with a lambda/4 phase-delay section, which is system-level optimized to provide appropriate power division, phase alignment, and impedance matching for Doherty operation without requiring additional hybrid couplers. This compact structure minimizes insertion loss, improves amplitude-phase balance, and enhances Doherty load modulation performance across the 3.3-3.8-GHz range. The DPA is implemented on a Rogers RO4003C substrate and incorporates lambda/4 impedance inverters and a seventh-order postharmonic suppression network to achieve superior spectral purity, reducing harmonic components below -30 dBc. Full-wave electromagnetic simulations and experimental validations demonstrate strong agreement between measured and simulated results, confirming the effectiveness of the proposed architecture as a broadband, energy-efficient, and manufacturable solution for next-generation sub-6 GHz 5G base-station transmitters.
An ultra-wideband circular polarized (CP) antenna array with nonperiodic elliptical shape metasurface (MTS) for millimeter-wave (mm-w) applications is proposed in this paper. The element in this array uses fragmented elliptical patches as the MTS and features an elliptical notch microstrip patch beneath it, acting as the primary radiator. Characteristic mode analysis (CMA) was used to analyze the evolution process of the structure and demonstrate the working principle of divided by S11 divided by and axial ratio (AR) bandwidth broadening. Based on the proposed element, a 4 & times; 4 antenna array is designed to achieve higher gain. And the element and arrays are fabricated and measured to verify the design. The measured performance of the proposed element achieves an impedance bandwidth of 89%, covering the frequency range from 15.5 to 40.5 GHz, along with an AR bandwidth of 62.3% (16-30.5 GHz), and reaches a maximum gain of 8 dBi. For the antenna array configuration, the impedance bandwidth spans from 15 to 41 GHz, while the AR bandwidth extends over 17.7-33 GHz, and the peak gain reaches 17.9 dBi. This design highly appropriates for broadband applications in mm-w satellite applications.
This paper introduces a dual-frequency wideband inverse Class-F power amplifier (PA). This PA employs a dual-frequency biasing circuit to effectively prevent RF signals from entering the DC power supply. We combine the SRFT with the continuous inverse Class-F PA reactance space to design a wideband matching network. By moderately relaxing the third harmonic constraints in the low-frequency band to avoid spectrum conflicts, the proposed PA achieves high efficiency and wideband characteristics. After testing, the designed PA has a 57.4%-61.1% drain efficiency and 39.4-40.3 dBm output power in the 0.8-1.0 GHz range and a 58.5%-71.7% drain efficiency and 40.6-41.7 dBm output power in the 3.3-3.8 GHz range.
In this paper, we propose a broadband and wide-angle stable absorber based on screen-printing resistive film (SPRF) and impedance matching layer (IML). The proposed absorber consists of five layers: two IMLs, a lossy layer based on SPRF, a dielectric matching layer, and a metallic ground plane. Simulation and measurement results show that the reflection coefficient with |S11| less than -10 dB ranges from 4.5 to 19.3 GHz and 3.11 to 25.6GHz under normal incidence, respectively. Furthermore, the absorption band can maintain good stabilities under both TE and TM polarizations within 60 degrees of oblique incidences. The measured and simulated results agree well with each other, verifying the design principle and manufacturing process. The proposed SPRF-based and IML-loaded absorber with improved angular stabilities can be applied in stealth radome and interference suppression in the future.
This paper presents a tri-band CPW-fed two-element MIMO antenna designed for smart home Internet of Things (IoT) applications. The proposed antenna operates at 1.5, 2.4, and 5.8 GHz, with a wide upper-band response from 3.84 to 7.14 GHz, covering major IoT, Wi-Fi, Bluetooth, and sub-6 GHz wireless systems. The novelty of this work lies in the integrated antenna and compact decoupling design, which simultaneously achieves wideband operation, high isolation, and a small footprint. The antenna shows reflection coefficients better than -15 dB across all operating bands and interelement isolation below -28 dB, ensuring low mutual coupling. The design also provides low envelope correlation, a diversity gain close to 10 dB, and stable radiation characteristics. Measured and simulated results show good agreement. Owing to its compact size, strong isolation, and reliable MIMO performance, the proposed antenna is well-suited for next-generation smart home and IoT wireless devices.
This work introduces a new quad-band bandpass filter (BPF) and filtering power divider (FPD) based on half-mode substrate integrated waveguide (HMSIW) technology and metamaterial concept. To achieve a high level of miniaturization, multiple design approaches are jointly employed, including HMSIW implementation, evanescent-mode operation, stepped-impedance resonators (SIRs), fractal geometries, and the meandered technique. Using the aforementioned design strategies, quad-band HMSIW BPF and quad-band HMSIW FPD with equal power-splitting characteristics were developed. These circuits operate at center frequencies of 1.75, 3.3, 4.5, and 5.2 GHz and were thoroughly validated through simulation, fabrication, and experimental measurement. The passband center frequencies are readily tunable through dimensional adjustments. Experimental results closely match the simulated responses. Moreover, the proposed structures occupy an extremely small footprint, with an overall size below 0.009 lambda g2, clearly demonstrating the high level of miniaturization achieved. The proposed structures offer several notable benefits, including a highly compact footprint, low insertion loss, tunable passband characteristics, reduced manufacturing cost, straightforward integration with planar microwave circuits, acceptable return loss performance, and flexible tuning of the operating center frequencies.
A conformal, compact, and flexible patch filtering antenna with independently tunable radiation nulls is presented. By etching open-ended split-ring resonator (SRR) slots and meandered slots on a conformal microstrip patch, two independently controllable radiation nulls are introduced to enhance band-edge selectivity. The antenna is implemented on a flexible substrate, maintaining stable filtering performance and radiation null controllability under conformal conditions. The prototype is designed to operate at 2.37 GHz and conforms to a cylindrical surface with a radius of 70 mm. Two radiation nulls are achieved at 2.10 GHz and 2.47 GHz, respectively. The antenna exhibits an average in-band gain of over 7.1 dBi and out-of-band suppression exceeding 20.5 dB. The proposed design is particularly suitable for conformal antenna systems in smart helmets and unmanned aerial vehicles (UAVs)/robotic platforms, where low-profile integration onto curved surfaces and enhanced interference rejection are essential.
This paper presents a high-performance on-chip diplexer designed for K/Ka-band applications, fabricated via 130-nm SiGe BiCMOS across two distinct frequency bands: 17-21 and 27-31 GHz. A localized backside etching (LBE) technique is employed to create air cavities beneath the inductors, a method that fundamentally mitigates substrate-related losses and significantly enhances the inductor quality (Q) factor. The diplexer, based on a compact low-pass/high-pass filter topology, achieves low insertion loss and high interband isolation. Measured results demonstrate insertion losses of 2.2 and 2.4 dB for the low band and high band, respectively, and an isolation greater than 40 dB. This experimental validation proves the effectiveness of the LBE technique for realizing compact, high-performance RF front-end components in silicon-based technologies.
This paper presents an eight-element antenna array designed for triple-band multi-input multi-output (MIMO) operation in fifth-generation (5G) mobile terminals. Each antenna element comprises a triple open-loop structure on a metal frame and fed by a customized feed element. The triple open-loop design not only significantly miniaturizes the radiator but also provides wide bandwidth. The dimensions of the proposed antenna array are approximately 8.2 & times; 7 mm, with a small ground clearance of 8.2 & times; 0.3 mm. It fully covers 5G New Radio (NR) bands N41 (2.496-2.690 GHz), N77 (3.3-4.2 GHz), and N79 (4.4-5.0 GHz) at the three resonance frequencies. Several critical parameters-including bandwidth, reflection coefficient, isolation, total radiation efficiency, and envelope correlation coefficient-have been studied. An antenna prototype was fabricated and measured; excellent agreement between simulation and experiment confirms that the triple open-loop array is well suited for 5G handsets demanding compact, triple-band MIMO antennas.
This article presents the design, simulation, fabrication, and experimental validation of a three-port S-band waveguide circulator with nonstandard dimensions, implemented using commercially available aluminum tubes with internal dimensions close to WR-284. The device incorporates two Y-Gd ferrite disks polarized by permanent magnets and coaxial-to-waveguide probe-type transitions with rear short-circuit tuning. The transitions achieve |S11 | <-10 dB between 2.6 and 3.95 GHz, whereas the complete circulator assembly provides, at 3.1 GHz, |S11 | <-20 dB, an insertion loss of less than 1.8 dB, and an isolation between 17 and 30 dB. Continuous wave measurements at 10 W confirm stable operation at average power. The proposed approach demonstrates that nonstandard, low-cost waveguide structures can achieve performance comparable with conventional WR-284 circulators, offering a compact and cost-effective alternative for S-band RF systems.
An optimization technique that can be used to design high performance, wideband 90 degrees hybrid couplers is described. Optimization is performed not by using the traditional theoretical coupling factors, but rather by directly synthesizing the geometric dimensions of the hybrid in full-wave simulations. Simulated results thus include all secondary, nonideal transmission line and implementation effects, and can be optimized for the required equiripple results. The full-wave synthesis technique is explained in detail, and simulated results of a 2-18 GHz design with 0.5 dB magnitude imbalance improvement over any previous results are shown. It is also used to implement a unique 0.5-18 GHz 3 dB, 90 degrees tandem hybrid, of which measurements are presented showing near optimally minimized magnitude imbalance of 1.47 dB, loss of less than 1.8 dB, and phase imbalance below 8 degrees, over the complete ultrawideband bandwidth.
This paper proposes an efficient metasurface simulation method leveraging deep neural networks to mitigate the time-consuming and resource-intensive nature inherent in traditional numerical simulation techniques. The proposed approach harnesses convolutional neural networks (CNNs) to extract metasurface features and employs a transformer network for electromagnetic field prediction. To ensure precision, simulation data from the finite-difference time-domain (FDTD) method with coarse grid is incorporated as additional input to the transformer. By integrating CNNs and transformers with coarse mesh compensation data, the accuracy of optical response prediction is enhanced. Prediction outcomes demonstrate that the proposed method can predict the electromagnetic characteristics of the metasurfaces accurately and efficiently. The mean squared error is merely 1.35e-4. Furthermore, this method yields spectral results of the metasurface within a mere 3 s, marking a notable 100-fold increase in efficiency compared with traditional simulation software.
This research explores the utilization of the R & ouml;ssler chaotic attractor in designing a broadband electromagnetic absorber with superior performance across the 2-20-GHz frequency range. The study commences with an in-depth exploration of the parameters governing the R & ouml;ssler chaotic system, culminating in the generation of intricate three-dimensional spatial representations. Given the standardized thickness of 0.035 mm for the z-axis in the absorber structure, these three-dimensional models were carefully processed through iterative algorithms using Julia Fractal transformations. This process facilitated the derivation of two-dimensional chaotic patterns, which were subsequently subjected to rigorous simulations to evaluate their electromagnetic absorption properties. In the proposed absorber design, the chaotic patterns were developed using a resistive ink with an accurate thickness of 0.035 mm, integrated with an FR-4 substrate. To maximize absorption efficiency, the absorber backplane was coated with copper at a standardized thickness of 0.035 mm. A comprehensive parametric analysis was conducted to examine the influence of critical design factors, including substrate thickness, absorber dimensions, and polarization modes across varying incident angles, on the absorption characteristics. The findings emphasize the unique capabilities of the R & ouml;ssler chaotic patterned absorber, unveiling its exceptional potential for deployment in a range of contemporary applications. Significantly, this study signifies a pioneering endeavor in applying the R & ouml;ssler chaotic methodology to the design and optimization of metamaterial absorbers. This contribution not only strengthens the theoretical understanding of chaotic systems in electromagnetic applications but also establishes a novel framework for future advancements in the field.
In this paper, a new design and analysis of a highly compact metamaterial antenna array for radar applications operating in the S-band (2-4 GHz) is presented. To enhance the electrical and radiation characteristics of the proposed antenna, a slot was introduced into the radiating element, and a novel power divider was employed. The antenna structure incorporates a metamaterial complementary split-ring resonator (CSRR). The results show that at a resonant frequency of 2.55 GHz, the proposed antenna exhibits a reflection coefficient ranging from -32 to -10 dB. When the two-element array is assembled, the radiation gain increases to 6.4 dB, with an efficiency of 91.24%. Furthermore, the antenna array provides a complete 360 degrees coverage, enabling omnidirectional and continuous scanning. This feature is crucial for radar applications, as it ensures optimal target detection throughout the entire radar perimeter, without blind spots or interruptions.
In the rapidly evolving field of terahertz (THz) communications, the design and fabrication of efficient antennas pose significant challenges due to the inherent complexities of operating at such high frequencies. This paper presents a microfabricated THz antenna array featuring triangular-slot patches designed to enhance bandwidth, gain, and efficiency at THz frequencies from 0.70 to 0.95 THz. The design involves utilizing a coplanar waveguide (CPW) feed technique to simplify the microfabrication process, improving antenna integration by enhancing impedance matching and reducing transmission losses. To optimize the antenna geometry, a machine learning (ML)-assisted global optimization method, specifically the surrogate-assisted differential evolution algorithm, is used to improve bandwidth, gain, and tolerance to fabrication variations. The prototype is fabricated on a flexible polyimide substrate using electron beam lithography, with a titanium/gold (Ti/Au) metallization stack of 10/350 nm. The proposed design achieves a simulated impedance bandwidth of 37.5% (from 0.70 to 0.95 THz), a simulated radiation efficiency of 85%, and a simulated gain of 8.71 dBi, making it a potential candidate for short-range wireless communication applications. Owing to the unavailability of in-house measurement facilities at THz frequencies, the experimental validation could not be performed at this stage; however, the design process is supported by full-wave electromagnetic simulation along with an extensive optimization of every parameter using ML-enabled optimization, which are established as reliable and effective methods for antenna design and performance prediction. These results highlight its potential for compact, high data rate short-range THz systems.
In this proposal, an advanced integrated multiple-input multiple-output (MIMO) antenna system has been presented for next generation 5G-NR, high speed WLAN and X-band communications. The four radiators having comb-shaped geometry at the top edge are positioned orthogonally with each other. An adequate gap is maintained between the radiating ports of MIMO antenna to lower down the mutual coupling. A small fractal geometry is engineered at the bottom corners of the patch to receive size miniaturization, wide band performance and manufacturing advantage. In similar fashion, thin slots are introduced to excel the isolation. The ultrawide band response (1.6 GHz-11.35 GHz) could be achieved by introducing partial ground plane underneath each radiator. A commercially available Flame Retardant 4 substrate was utilized. The individual ground structures are interconnected using thin conducting strips, which play a dynamic role in system performance by providing high isolation between the MIMO elements. The proposed MIMO system is analyzed and confirmed based on various antenna responses such as diversity gain (DG) (>9 dB), mean effective gain (MEG) (-6 to -8 dB), channel capacity loss (CCL) (< 0.4 bits/s/Hz), and envelop correlation coefficient (ECC) (< 0.002 abs). The received reflection coefficient values from the MIMO antenna are compared with actual values. Both the responses are closely aligned with each other. This research supports SDG 9, SDG 11, and SDG 7 by advancing innovative wireless communication infrastructure, enabling sustainable and resilient smart city connectivity, and indirectly promoting energy-efficient network operations through high-isolation and efficient antenna design.
