Large Frequency Ratio Research Articles

3-D-Printed Encapsulated Dielectric Resonator Antennas With Large Operation Frequency Ratio for Future Wireless Communications

3-D-Printed Encapsulated Dielectric Resonator Antennas With Large Operation Frequency Ratio for Future Wireless Communications

Highly miniaturized dual-band bandpass filter with wide bandwidth and large center frequency ratio

The design of a miniaturized dual-band bandpass filter featuring a broad bandwidth and a high center frequency ratio is demonstrated in this article. A novel symmetrically loaded shunt coupled line with dual stepped impedance stubs has been investigated for the first time and it is utilized to realize a dual-band bandpass filter with seven transmission zeros. The transmission zeros frequencies of the filter response have been theoretically verified using even-odd mode analysis. For experimental validation purposes, a dual-band filter with a center frequency ratio of 4.06 covering 5G applications is implemented using Rogers RT/duroid 5870 substrate and tested. The tested filter has wide 3 dB fractional bandwidths of 53.8% and 17.9% in the first and second passbands, respectively, and has a compact topology of 0.20 × 0.09 λg 2. The full-wave simulated and tested magnitude and group delay responses of the proposed filter are in good congruence.

Compact Tri-Band Shared-Aperture Antenna With Large Frequency Ratio for 5G Mobile Terminals

Compact Tri-Band Shared-Aperture Antenna With Large Frequency Ratio for 5G Mobile Terminals

Dual-band high-gain shared-aperture antenna with large frequency ratio hybridizing Fabry-Perot cavity and folded transmitarray

Dual-band high-gain shared-aperture antenna with large frequency ratio hybridizing Fabry-Perot cavity and folded transmitarray

An Integrated DRA-Based Large Frequency Ratio Antenna System Consisting of a MM-Wave Array and a MIMO Antenna for 5G Applications

An Integrated DRA-Based Large Frequency Ratio Antenna System Consisting of a MM-Wave Array and a MIMO Antenna for 5G Applications

Dual-Band Large-Frequency Ratio Power Divider Using Mode Composite Transmission Line for 5G Communication Systems

In this paper, a novel kind of mode composite transmission line (MC-TL) is proposed, and a dual-band power divider with a large frequency ratio using this novel MC-TL for 5G communication systems was developed. The proposed MC-TL was developed using spoof surface plasmon polaritons (SSPPs) and a corrugated substrate-integrated waveguide (CSIW) transmission line, which supports both a surface plasmon mode and TE10 mode, independently. The surface plasmon mode operates in the grooves of the surface metal layer, while the TE10 mode works in the substrate between two metal layers. These two parts can transmit different modes at independent frequencies. This structure can be used in dual-band transmission lines with a high frequency ratio. The characteristics and design of the MC-TL (SSPPs and CSIW) are analyzed and illustrated. The MC-TL was fabricated and measured to demonstrate its performance. Moreover, based on the proposed MC-TL, a dual-band power divider with a large frequency ratio (operating at 3 GHz and 28 GHz simultaneously) was also designed and fabricated. It can cover the frequency of a fifth-generation communication system perfectly. The measured outcomes align closely with the simulated results, demonstrating robust agreement and showcasing excellent transmission capabilities.

Analytical optimization and performance evaluation of non-traditional tuned mass damper for stochastic base excited structures considering dual solutions

Compared with traditional tuned mass damper (TMD), non-traditional tuned mass damper (NTMD) has higher damping efficiency in some conditions. Nevertheless, the analytical optimization problem of NTMD has not been well solved; especially, multiple optimal solutions are not discussed. In this study, the closed-form optimal expressions of the NTMD using tuning stiffness are derived based on H 2 norm optimization. And the vibration mitigation performance of the NTMD is evaluated considering dual-solutions situation subjected to typical ground motion and impulse excitation. Different from solving the unique optimal frequency ratio, there exist two sets of optimal stiffness and damping ratio derived using tuned spring elements for given mass ratio, and the effective mass ratio is also limited as 1/3. The vibration mitigation or isolation performance and robustness of H 2 optimized NTMD with higher stiffness ratio are far superior to NTMD with lower stiffness ratio. NTMD using larger optimal tuning stiffness ratio also can be seen as an optimized form of Maxwell model using additional mass. Hence, using a large stiffness, namely, a large frequency ratio to design NTMD is recommended, which is different from traditional TMD. The case of NTMD with large stiffness can be adopted when the demands of practical engineering are not met using the optimal parameters of small stiffness. And a compromise scheme can also be provided, which are the combination with a larger mass ratio but is less than the maximum limit value 1/3 and a not very large stiffness ratio but is exceeded 0.5 according to demands of practical engineering.

Independent dual-band absorptions with large frequency ratio and large bandwidth ratio from composite metamaterials of water pyramids over Helmholtz resonators

We demonstrate the perfect trapping of electromagnetic fields at dual frequencies through composite metamaterials of a water pyramid cascaded meta-surface loaded with a Helmholtz resonator array. More specifically, the water pyramid cascaded meta-surface functions as an ultra-wideband absorber at the frequency range of 6.6–100 GHz with more than a 175 % relative bandwidth, while operating as a transparent screen at lower frequencies for the Helmholtz resonators. On the other hand, the Helmholtz resonator array will absorb electromagnetic fields at 100 MHz with the Q factor of 63 and the total thickness of 1/160 wavelengths, while performing as the ground for the water pyramids. The proposed design, integrating the water pyramid cascaded meta-surface with a Helmholtz resonator array for the independent dual-band absorptions with a large frequency ratio and large bandwidth ratio, should pave the way for building up more advanced energy-harvesting meta-devices.

A Large Frequency Ratio Dual-Band Integrated Bandpass Filter Based on MCSICL Structure

In this paper, a dual-band integrated bandpass filter (DI-BPF) based on a mode composite substrate integrated coaxial line (MCSICL) is proposed for a large frequency ratio. The low-frequency bandpass filter is formed by incorporating an SICL line and a gap into the MCSICL, operating in the fundamental mode of the MCSICL. The high-frequency bandpass filter is formed by introducing grounded vias into the MCSICL, operating in the first high-order mode of the MCSICL. To guide the design, the equivalent circuit models of the low- and high-frequency bandpass filters are built. Based on the equivalent circuit models, the DI-BPF is synthesized for a large frequency ratio. The transitions from the DI-BPF to ground coplanar waveguides (GCPWs) are designed for the low- and high-frequency bandpass filters. The DI-BPF with the transitions is fabricated by the printed circuit board (PCB) process. Measurement results indicate a large frequency ratio of 23.16, with the isolation between the low- and high-frequency bandpass filters exceeding 30 dB from dc to 50 GHz.

An Aperture-Shared Vehicular Antenna With Large Frequency Ratio and Pattern Diversity for Future 5G Millimeter-Wave and DSRC Applications

An Aperture-Shared Vehicular Antenna With Large Frequency Ratio and Pattern Diversity for Future 5G Millimeter-Wave and DSRC Applications

Dual-Wideband Dual-Frequency Antenna With Large Frequency Ratio for 5G Applications

Dual-Wideband Dual-Frequency Antenna With Large Frequency Ratio for 5G Applications

Singly-Fed Large Frequency Ratio Composite Dielectric Resonator Antenna for sub-6 GHz and mm-Wave 5G Applications

Singly-Fed Large Frequency Ratio Composite Dielectric Resonator Antenna for sub-6 GHz and mm-Wave 5G Applications

A Dual-Band Dual-Polarized Antenna With High Aperture Reuse Efficiency and Large Frequency Ratio for Modern Wireless Communications

A Dual-Band Dual-Polarized Antenna With High Aperture Reuse Efficiency and Large Frequency Ratio for Modern Wireless Communications

Design of Singly Fed Dual-Band Antenna With a Large Frequency Ratio by Introducing a Monopole Mode to Yagi–Uda Antenna

Design of Singly Fed Dual-Band Antenna With a Large Frequency Ratio by Introducing a Monopole Mode to Yagi–Uda Antenna

Joint Microwave and Millimeter-Wave Antenna Design for UAV-Enabled Communications

Wireless communications aided by unmanned aerial vehicles (UAVs) have emerged as a promising technology for serving numerous terminal devices of the Internet of Things (IoT). To support such a broad range of emerging applications, millimeter-wave (mm-Wave) is an effective solution because it has the characteristics of high transmission efficiency, wide frequency band, and very low latency. Meanwhile, a UAV-assisted communication system also requires a global positioning system (GPS) reception (1.575 GHz) and ground control unit (2.4 GHz). This paper investigates a highly integrated multi-band antenna design to operate at the microwave (μ-Wave) and mm-Wave bands for robust and flexible UAV communications. Each antenna operating band utilizes the technology of a substrate-integrated waveguide (SIW) cavity-backed antenna. By strategically engineering an mm-Wave antenna into a 2.4 GHz band antenna to share the aperture, besides showing high aperture reuse efficiency with a large frequency ratio, the proposed antenna has also maintained the geometrical advantages of compactness, planar configuration, and ease of integration with other circuits. Furthermore, the proposed antenna can provide flexible radiation patterns with upper/lower-space signal coverage according to the mission demands of the UAV. Experimental results of the prototype show that the antenna can fully cover the 1.575 GHz, 2.4 GHz, and fifth-generation (5G) mm-Wave bands of n257, n258, and n261. Multiple bands and stable radiation characteristics indicate the proposed antenna's suitability for deploying a UAV-supported wireless network.

Fatigue damage characteristics of a flexible cylinder under concomitant excitation of time-varying axial tension and VIV

Flexible cylindrical structures are susceptible to the concomitant excitation of vortex-induced vibration (VIV) and time-varying axial tension in offshore engineering. The structural instability caused by the simultaneous excitation can lead to severe fatigue damage, threatening the safe application of cylindrical structures. In this paper, experimental research was conducted on a long flexible cylinder with an aspect ratio of L/D = 350 to investigate its fatigue characteristics under the concomitant excitation. The reduced velocity Vr ranged from 1.34 to 26.71. The axial tension excitation was characterized by three axial tension amplitude ratios Tv/Tc = 0.1–0.3 (where Tv is the tension amplitude and Tc is the constant tension) and six axial tension frequency ratios fv/f1 = 0.5–4.0 (where fv is the tension frequency and f1 is the fundamental frequency of the cylinder). The S–N curve method and the linear accumulative damage theory were employed to estimate the fatigue damage. The effects of reduced velocity, excitation amplitude and excitation frequency on the fatigue damage characteristics were discussed in terms of the fatigue damage distribution and maximum fatigue damage. The effect of the tension excitation on the fatigue damage is more pronounced at low reduced velocities (Vr ≤ 5.34) when the VIV is not excited, since the axial tension can excite the mode vibration. The fatigue damage area and maximum fatigue damage are significantly enhanced with the increase of the tension amplitude ratio and frequency ratio due to the occurrence of higher-order mode vibrations. The effect of axial tension excitation on the fatigue damage of the cylinder is more pronounced in the in-line (IL) direction than in the cross-flow (CF) direction. However, for a small amplitude ratio (Tv/Tc = 0.1), the tension excitation is only noticeable with a large frequency ratio (fv/f1 = 4.0). On the other hand, as the reduced velocity increases, the VIV of the cylinder is excited and dominates the fatigue characteristics. The accumulative fatigue damage distribution is aggravated with the increase of reduced velocity. The time-varying axial tension has a negligible effect on the fatigue damage distribution features and the maximum fatigue damage values of the cylinder. Nevertheless, under certain circumstances, the axial tension excitation can slightly alleviate the fatigue damage in some regions along the cylinder.

Wide stopband QMSIW diplexer with large frequency ratio and flexible specification

AbstractIn this letter, a wide stopband quarter‐mode substrate‐integrated waveguide (QMSIW) diplexer is proposed. By using coupling feeding lines and QMSIW cavities, the two passbands of the diplexer can be controlled independently by their respective QMSIW bandpass filters. In comparison to other counterparts, the proposed diplexer provides flexible passband specification, compact size, and high isolation. The design exhibits a wide 20‐dB stopband up to 3.2f0, a frequency ratio of 1.6, and a high isolation level larger than 42.2 dB across the passbands.

Design of a Dual-Band Dielectric Resonator Antenna Array for Millimeter-Wave Communication

This paper presents a dual-band dielectric resonator antenna (DRA) with a large frequency ratio at millimeter-wave band. A large frequency ratio of 2.36 is formed by the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">111</sub> mode and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">131</sub> mode working at 16 GHz and 38 GHz, respectively. These two modes of DRA are excited by a microstrip-fed slot. A 1×4 DRA array is then constructed to achieve high gain in the millimeter-wave range. In addition, this design also features easy fabrication and wideband characteristics achieved through the use of printing circuit board (PCB) technology. The impedance bandwidths of 13.3 – 19 GHz (35.3%) and 36.3 – 40 GHz (9.7%), and the gain of 10.6 and 14.2 dBi can be realized in these two bands, respectively. The good agreement between measurement and simulation suggests that this design has promising potential for application in millimeter-wave communication.

A dual‐band filtering crossover with large frequency ratio for microwave and millimeter‐wave applications

AbstractModern wireless communication systems require components that can support microwave and millimeter‐wave bands simultaneously. However, it is difficult for the existing dual‐band crossover configurations to achieve a frequency ratio larger than 5. In this letter, a dual‐band filtering crossover with a frequency ratio larger than 10 is presented for the first time. To implement such a large frequency ratio, a microstrip filtering crossover operating at microwave band and a substrate integrated waveguide filtering crossover operating at millimeter‐wave band are combined through the aperture coupling mechanism. As the two elements almost have no influence on each other, a high degree of design freedom over two bands can be obtained. For demonstration, a dual‐band filtering crossover operating at 2.4 and 28 GHz was designed, fabricated, and measured. Measured results are in good agreement with simulated ones, which validates the proposed structure.

A MIDAS multinomial logit model with applications for bond ratings

In multinomial classification analysis, the issue of mixed-frequency data is becoming increasingly common. To solve the multiclassification problem in a mixed-frequency data environment with a large frequency ratio, we combine the restricted mixed data sampling (MIDAS) method with a multinomial logit (MLogit) model to construct a MIDAS-MLogit model. The MIDAS-MLogit model imposes functional constraints on high-frequency variable parameters and fully uses high-frequency information to complete multiclassification tasks in a mixed-frequency data environment. Through extensive Monte Carlo simulations, we prove that this novel MIDAS-MLogit model has better classification performance than conventional MLogit and U-MIDAS-MLogit models for solving multiclassification problems with a large frequency ratio. In addition, we use the MIDAS-MLogit model to predict the ratings of corporate bonds issued by Chinese-listed companies from 2008 to 2021 and find that its prediction accuracy outperforms several competitive models. We further verify the validity of the MIDAS-MLogit model for different periods, including the global financial crisis, the post-financial crisis, and the pandemic. The results show that all three models perform well during the global financial crisis, but the MIDAS-MLogit model predominates the post-financial crisis and pandemic periods. The empirical results also show that covariates from bond, corporate, and financial environment levels have varying effects on corporate bond ratings.