Operating Frequency Range Research Articles

넓은 입력전력 범위를 갖는 S-대역 광대역 고조파 응답기

This paper presents a through-type harmonic transponder for S-band nonlinear radar. To increase the operating frequency range, a 2-stage L-shaped matching network was configured for the input and output matching networks. In previous studies, conventional harmonic transponders were configured with λ/4 stubs in the input and output matching networks to minimize the influence of these networks because the impedance mismatch suppresses the second harmonic and fundamental signals. However, in this design, a λ/4 open stub was utilized at the output and configured with the output matching network to alleviate the insertion loss of the additional open stub. For verification, the proposed circuit was implemented with the circuit size of 37.6 mm×16.1 mm. The measurement results show that the conversion gain is maintained over −15 dB for frequencies between 2.8~3.8 GHz at −5.5 dBm and −17.5~11 dBm at 3.1 GHz of input power.

DEVELOPMENT AND MODELING OF THE ANTENNA SYSTEM THE DIRECTION FINDER UNMANNED AERIAL VEHICLE

The article is devoted to the design the proposed construction of the antenna system for the direction-finding complex of the UAV. The experimental part is represented by the results of mathematical modeling the behavior of the antenna in different parts the operating frequency range. The effectiveness of the adopted design solutions was evaluated in comparison with analogues of leading companies in the world. Based on the results of the research, the areas of application the antenna as part of the built-in functional mobile UAV direction finding systems were determined.

A Wide-Range Four-Phase All-Digital DLL with De-Skew Circuit

A four-phase all-digital delay-locked loop (ADDLL) with a de-skew circuit for NAND Flash high-speed interfaces is proposed. The proposed de-skew circuit adopts a fall-edge-judgment phase adjuster and a three-stage digitally controlled delay line to align the system input clock and 0∘ output clock of the four-phase DLL over a wide frequency range, thus solving the four-phase offset caused by clock skew. A parallel-cascade configuration is proposed to solve the variable phase alignment problem caused by mode switching, thus effectively improving the phase-locked accuracy. The proposed circuit is fabricated in the 0.13 μm CMOS process with a 0.072 mm2 core area. The chip testing results show an operating frequency range from 26 MHz to 1.55 GHz and a typical alignment error of approximately 17 ps.

A Dual Port Hybrid Super-wideband MIMO Antenna with Diminished CCL and High BDR for IoT Applications

In this work, a simple hybrid dual port skull-shaped super wideband Multiple Input Multiple Output (MIMO) antenna with improved isolation is designed and analyzed. Each antenna element consists of a skull-shaped radiator along with a rectangular notched chamfered Defective Ground Plane structure (DGS). The proposed antenna’s impedance bandwidth and radiation characteristics are improved by the triple elliptical inclined slot and DGS together. To accomplish the proposed MIMO configuration, the antenna elements are further organized in a linear arrangement. Deteriorated isolation characteristics, which are the key bottleneck for such MIMO schemes, are significantly improved in the proposed design by using a corrugated T-shaped strip decoupling plane. This 2-port MIMO antenna is placed on top of a glass epoxy FR4 substrate and has an overall dimension of 45 × 50 × 0.787 mm3 (0.20λ × 0.19λ × 0.003λ). The proposed MIMO antenna is fabricated and the experimental results are verified with the simulation results. The results indicate that the proposed antenna covers an operational bandwidth of 48.75 GHz (1.25–50 GHz) with a fractional bandwidth of 190.24% and offers an isolation of less than −20 dB throughout the frequency range of operation. The proposed MIMO has an extremely high bandwidth dimension ratio (BDR) of 5092 among the reported antennas. An optimal performance has been achieved with a lower value of Envelope Correlation Coefficient (ECC) ≤ 0.02, high multiplexing efficiency, extremely lower Channel Capacity Loss (CCL) of 0.2, and omnidirectional radiation characteristics. These design metrics show the potential of our antenna to operate for eMBB (Enhanced Mobile Broadband) applications which includes 5G, Augmented reality, and etc.

Reliability-based topology optimization for fundamental frequency maximization with frequency band constraints

Resonance can be avoided by preventing the structural natural frequencies from falling within the operating frequency range. However, structural natural frequencies are influenced by uncertain parameters, such as material properties and geometric sizes. Therefore, it is essential to consider these uncertainties during the conceptual design phase. To address this problem, a novel reliability-based eigenvalue topology optimization model under frequency-band constraints is established, in which the uncertainties of the material properties and structural size are considered. Owing to the high computational costs of dealing with frequency-band reliability constraints, a frequency-band constraint shifting method (FBCSM) is proposed to ease the heavy computational burden without sacrificing accuracy. In addition, the sensitivities of simple and multiple eigenfrequencies with respect to the design and random variables are derived. The “bound formulation” and “robust formulation” are used to reduce the gray elements and checkerboard phenomenon. Four examples are used to determine the effectiveness of the proposed reliability-based eigenvalue topology model and FBCSM. The results confirmed their superiority in terms of validity and efficiency.

New ASDEX Upgrade ICRF antenna vacuum feedthrough: Optimization status

A new design concept aims to improve the voltage stand-off by using two repositioned 9-inch Al2O3 windows, to avoid/reduce the neutron impact on the ceramic by moving the window far from antenna, and to reduce the nearby E-fields by optimizing the shape of the conducting structures. New RF windows position is found to be close to the voltage node and determined from the standing wave patterns at the most used frequency of 36.5 MHz. The return loss coefficient S11 is between -30 and -55 dB for the whole operating frequency range. The calculated power losses for the new RF window structures are less than 0.13 kW each at 1 MW of incident power. Modelling shows maximum E-field less than 1.9 kV/mm in a torus and private vacuum of the feedthrough. The dimensions, E-fields and transmission make this design relevant to a possible DEMO ICRF system.

Photonic system for Doppler-frequency-shift and Angle-of-arrival simultaneous measurement using dual-parallel Mach–Zehnder modulator

A simple photonic system is proposed to measure the Doppler frequency shift (DFS) and Angle of arrival (AOA) of microwave signals simultaneously. The echo signals received by the two antennas are fed into two sub-MZM of a dual-parallel Mach–Zehnder modulator (DPMZM) respectively, and the reference signals are sent into one of the sub-MZM. The introduction of reference signals makes it easier to determine the direction of DFS. After the reference signal and echo signal pass through the low-speed PD, the beating signal is obtained. The value and direction of the DFS can be derived from the frequency of the down-converted signal. And the measurement of AOA can be calculated from the power of the output signal. The experimental results show that the echo signal measurement errors of DFS are less than ±0.5 Hz in the operating frequency range of 20 GHz, and the power sensitivity is less than -40 dBm. AOA has measurement errors of less than ±1.5° in the range of 0 to 90°. In addition, by adding only one test branch, the system can achieve the unambiguous measurement of AOA in the range of ±90°.

Hydroacoustic Bottom Soil Profiling Device with Synthetic Aperture

Introduction. Acoustic profiling is a conventional method for studying the geological structure of the seabed. To this end, a low-frequency acoustic profiler with an operating frequency range of 1…14 kHz can be used. However, under lower operating frequencies, the difficulty of achieving the required resolution arises. The problem of improving the angular resolution of a hydroacoustic device, particularly in the direction of the carrier movement, remains to be a priority task in the search and detection of objects on the seabed, as well as the study of the bottom soil structure. Angular resolution can be improved through several approaches, including an algorithm for synthesizing the antenna aperture based on the law of the phase change of the reflected signal. This approach is relevant in the design of highresolution hydroacoustic tools.Aim. To demonstrate the possibility of constructing a bottom soil profiling device, as well as the possibility of increasing its angular resolution based on an algorithm for synthesizing the antenna aperture of an acoustic profiler.Materials and methods. The study employed the groundwork data obtained for side-scan sonars with a synthetic aperture in terms of constructing an antenna device and the methods of radio-wave excitation developed for radar systems.Results. The possibility of synthesizing the antenna aperture for an acoustic profiler of the bottom soil was studied. An algorithm for synthesizing the antenna aperture was investigated along with phase distortions of the trajectory signal and their influence on the sonar image. The fundamental principles of processing the trajectory signal were considered.Conclusion. An approach to increasing the resolution of an acoustic profiler when performing search and survey tasks is proposed. The proposed design of the acoustic part of a profiling device can be used in the development of search and survey hydroacoustic devices with a high angular resolution.

Investigation of a Tunable Microwave Photonic Filter Based on an Acetylene Reference Cell

Introduction.Recently, the development of tunable microwave photonic filters has attracted great scientific and practical interest. Such microwave photonic filters are a good alternative to traditional electrical solutions, due to low losses, wide operating frequency range and such filters can be easily integrated into various telecommunication systems. By using an acetylene reference cell and a laser with tunable wavelength can make it possible to create tunable microwave photonic filter with wide operating frequency range.Aim.Investigation of the characteristic of a tunable microwave photonic filter based on an acetylene reference cell, as well as research possible solution to reduce losses in filter bandwidth; numerical simulation of microwave photonic filter characteristics.Materials and methods.Experimental study was carried out on an experimental prototype of a tunable microwave photonic filter. The filter consisted of a laser with a tunable wavelength, a phase modulator, an acetylene reference cell, an optical fiber connecting the gas cell with a photodetector, and a photodetector. Theoretical study was carried out by modeling of the transmission characteristics of the microwave photonic filter.Results.Experimental transmission characteristics of a tunable microwave photonic filter were obtained. The tuning of the filter bandwidth by tuning laser wavelength was studied. Modeling of transmission characteristics of microwave photonic filter was performed. Possible solution to reduce losses in filter bandwidth was proposed.Conclusion.A tunable microwave photonic filter based on an acetylene reference cell is proposed. Losses in the filter bandwidth was about −30 dB. Using high-power laser and a photodetector with a high photocurrent can reduce losses in the filter bandwidth.

Demonstration of Non‐contact Out‐of‐Plane Vibration Energy Harvesting Using an Electric‐Double‐Layer Electret

This paper reports demonstration results of non‐contact out‐of‐plane vibration energy harvesting using an electric‐double‐layer electret (EDLE). Unlike contact types or non‐contact in‐plane types, the proposed operation type can be useful in terms of expanding the operating frequency range and simplifying the device structures. A demonstration system is developed, and power generation is confirmed using an EDLE with a surface potential of −1 V under an atmospheric condition. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Spectral Analysis of a SPR Sensor based on Multilayer Graphene in the Far Infrared Range

In this paper, we present a spectral analysis of a Surface Plasmon Resonance (SPR) sensor based on multilayer graphene (MLG) operating as a terahertz refractometer. This device's structure is based on Kretschmann configuration, and the graphene layers are modeled as surface impedances with conductivity described by the Kubo model. The structure's electromagnetic response is obtained from the Generalized Coefficients Model, considering TM excitation performed in a frequency range from 1 to 4Thz. In this approach, we evaluate the sensor response for two, three, four and five layers of graphene, equally doped. To verify the effects of MLG doping, we varied the chemical potential by 0.35eV and 0.70eV. As a result, we present the plasmonic response of the device, verifying the operating frequency range for each case of multilayer graphene. In addition, the sensitivity, FWHM and Figure of Merit (FOM) are calculated to describe the sensor performance in each demonstrated case. From the results presented, we verified that the increase in doping reduces the sensitivity of the sensor, however, it improves its FOM. The validation of the proposed model was carried out from simulations in a software based on the Finite Element Method.

Development of a microwave resonant waveguide slot antenna with in-phase slot excitation

The object of research in the work is the process of radiation of electromagnetic waves of a resonant waveguide-slot antenna with in-phase excitation of slots. The subject of research is the wave parameters and directional properties of a resonant slotted waveguide antenna with in-phase slot excitation. The existing problem is that it is necessary to ensure highly directional properties of the antenna with electrical control of its wave parameters at high transmitter power. This problem is due to the fact that to solve the problem of developing equipment for radio control, and radar of aircraft, highly directional antennas of small sizes are required. To solve this problem, the paper proposes the design of a simple and cheap version of a microwave resonant waveguide-slot antenna with in-phase slot excitation.
 As a basis for developing a resonant slotted waveguide antenna, the authors chose a standard R48 rectangular waveguide, which is a classic in the theory of directional systems in the microwave range. This is due to the fact that in order to calculate and study a microwave resonant waveguide-slot antenna with in-phase excitation of slots, the authors used well-known elements of the theory of aperture antennas. The design of a resonant slotted waveguide antenna consists of a rectangular waveguide, an exciter, and a feeder. The radiation surface of the antenna is a wide wall of a standard R48 rectangular waveguide along the central axis, of which slots are symmetrically cut in a checkerboard pattern. The exciter is made in the form of a metal pin inside a rectangular waveguide near the short-circuited wall. This pin acts as an asymmetric vertical vibrator that excites electromagnetic waves in a rectangular waveguide. The antenna is tuned to the maximum radiation power mechanically by moving the short-circuited wall of the rectangular waveguide. The pin feeds a feeder based on a coaxial cable with a characteristic impedance of 75 ohms.
 The developed resonant waveguide-slot antenna with in-phase excitation of slots operates in the frequency range of 4.0–6.0 GHz. In the frequency range of 4.0–5.45 GHz, the value of Voltage Standing Wave Ratio (VSWR) varies from 1.08 to 2.1. In the frequency range of 5.45–6.0 GHz, the Voltage Standing Wave Ratio (VSWR) value varies from 2.1 to 6.55. The directivity of the antenna in the operating frequency range is not less than 90. The width of the main lobe of the antenna pattern in the horizontal plane is not more than 3.1°. The antenna gain in the operating frequency band is at least 100. The efficiency is at least 90 % with a maximum generator signal power of 10 kW.

Ventilated acoustic meta-barrier based on layered Helmholtz resonators

The performance of a multilayer sound attenuating metamaterial with ventilation capacity based on arrays of wall-embedded Helmholtz resonators is investigated analytically, numerically and experimentally. Each cell of the barrier front wall is a Euclidian polygon, such as square or hexagon. One thickness layer of the barrier cell contains a parallel array of 4 (for square cell) or 6 (for hexagon) Helmholtz resonators connected via the axial ventilation duct element. Multiple layers of resonators can be connected in sequence with the extension of the ventilation channel. The sound attenuation performance of the barriers is investigated first using the lumped parameter theory and transfer matrix method (TMM), and numerically using the finite element (FE) simulations solving the Helmholtz equations in frequency domain. These results indicate that the sound attenuation in audible range (300–2000 Hz) can be meaningfully improved using several layers with a unique peak resonance frequency assigned to each corresponding layer, with each additional layer improving the total attenuation. However, it is acknowledged that the previously studied fundamental trade-offs between the total barrier thickness, ventilation capacity, operational frequency range and integral sound attenuation do apply to the proposed design as well. Nevertheless, it is suggested that the simplicity of both structural design and theoretical methods of performance estimations make the suggested barrier a good candidate for applications with a well known desired attenuation spectrum. The impedance tube experiments validate the sound blocking performance and show a reasonable agreement with the numerical predictions.

FEM-Inclusive Transfer Learning for Bistable Piezoelectric MEMS Energy Harvester Design

In this article, a bistable piezoelectric MEMS energy harvester is presented to operate in a low-frequency range, around 100–200 Hz. The proposed design has an M-shaped structure with a couple of proof masses to not only lower the operating frequencies but also enlarge the frequency bandwidth. This specific structure has multidegrees of freedom, making it fit for a bistable piezoelectric energy harvester on the MEMS scale. An artificial neural network (ANN) is used to tackle this design in order to facilitate the optimization process and determine proper physical dimensions. To improve the accuracy and boost the training process of deep neural network (DNN), we utilize a transfer learning technique in this work. The analytical modeling and finite-element modeling (FEM) simulation data have been used for the DNN model training. Here, a DNN is first trained with a large dataset computed from the lumped-parameter model, and then, the trained network is transferred to a new DNN model for another round of training with a small dataset of highly accurate FEM simulation data samples to further reduce the estimation error. It is shown that the new model can estimate the device features with over 94% accuracy, which is considerably higher than the regular DNN. Next, the trained model is used as a performance estimator in a genetic algorithm (GA) to optimize the topology of the device to improve the operating frequency range and the generated voltage. An optimized design with a total volume of 1.02 mm3 was fabricated by the micromachining process. Our experimental results confirm that the proposed transfer-learning-based method can not only reduce the prototype’s first and second resonant frequencies to 123.8 and 175.7 Hz, respectively, but also enhance the generated power up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.83 ~\mu \text{W}$ </tex-math></inline-formula> under 0.2-g input acceleration.

A Simple Design of Water-based Broadband Metamaterial Absorber for THz Applications

A simple water-based broadband metamaterial absorber has been proposed for the terahertz region. The absorption bandwidth is extended based on large frequency dispersive permittivity and high relative dielectric loss of water. The simulated result indicates that the absorption of the proposed structure achieves over 90% in the frequency range from 0.6 to 10 THz at a normal incident angle. Moreover, the performance maintains high over 80% with a wide incident angle up to 60o for transverse electronic (TE) mode and over 90% up to 700 transverse magnetic (TM) mode in the entire operating frequency range. Therefore, the designed absorber has a potential candidate for broadband THz applications.

Design and simulation of a novel miniaturized printed antenna with ultra-wideband and high gain for millimeter-wave wireless applications

The goal of this work is to create a new patch antenna array with a standard gain, broadband, unidirectional radiation pattern, and high efficiency, making it a viable contender for millimeter-wave wireless applications. This study begins with a simple single-patch antenna that has four key components to provide effective matching and a wide impedance bandwidth: elliptical lateral edges, vertical stubs, slots expressed in concavity, and notches. The ground plane was defect-free, and the patch was printed on a Rogers RT5880 substrate. The performance of the proposed antenna can be improved using array topologies of 1×2 and 2×2 patches, for which a corporate feed network was built for excitation. The suggested 2×2 array antenna with a compact size of 18x16.1 mm2 achieved a gain of 13.8 dB, 92% efficiency, a return loss of-34.8 dB, and an ultra-wide bandwidth of 12.2 GHz (ranging from 39.9 to 52.1GHz) at a resonant frequency of 43.2. It’s a novel compact 2×2 array antenna appropriate for miniature devices is suggested using CST studio software, which gathers all qualities together, including high-gain, radiation efficiency, and ultra-wideband. The planned antenna operating frequency range runs from 27 to 58 GHz, which encompasses multiple frequency bands, such as V, Q, and Ka.

Novel low‐profile stacked edge grounded rectangular dielectric resonator antenna with compact size for UWB applications

AbstractIn this paper, a low‐profile stacked dielectric resonator antenna (DRA) is proposed for ultra‐wideband applications. To improve the performance of the proposed antenna, techniques such as stacking of two dielectric materials, air gap slots, edge grounding technique, and the partial ground plane is employed. The measured impedance BW of the proposed antenna is 106% at the center frequency of 7.7 GHz (3.65–11.8 GHz). The analysis of field lines shows that the fundamental TEx111 mode is preserved at the first resonant frequency of 4.4 GHz. The maximum gain achieved over the operating frequency range is 6.38 dBi. The design is compact in its nature with a miniaturization capability of 66% of its volume. The proposed design is structurally simple, has a low weight, and has a high radiation efficiency of more than 90% in the operational range.

Preventing loss of synchronism of droop-based grid-forming converters during frequency excursions

This short communication addresses the risk of synchronisation loss during frequency excursions for droop-based grid-forming converters when active power limitations are considered. The synchronising capability of this control approach is based on the converter’s active power exchange, which is used to generate the internal frequency of the converter control. The power available in the resource or converter ratings can impact the synchronising capability during frequency deviations. The analysis is restricted to droop-based grid-forming converters, but it could be extended to other active-power-based synchronising methods. A droop-based control is proposed to extend the operation frequency range of grid-forming converters. The performance of the suggested method is also compared to alternative ones presented in the literature. Finally, the proposed control is validated in the IEEE 9-bus system with different VSC penetration levels through EMT simulations developed in PSCAD.

Scalable Antenna Arrays Featuring Stable Radiation Pattern in Multioctave Bandwidth

This article proposes a novel concept of antenna arrays operating in the multiple-octave frequency range. The antenna arrays ensure steady half-power beamwidth (HPBW) in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{N}$ </tex-math></inline-formula> :1 bandwidth (BW) due to the proper placement of radiating elements and appropriate signal switching between them. The proposed arrays consist of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N+1$ </tex-math></inline-formula> centered subarrays that are electrically similar at successive frequencies. The antenna arrays are fed by networks composed of power dividers and directional filters responsible for gradual RF power shift from the elements operating at the lowest frequency to the elements operating at the highest frequency. The directional filters utilize the same properly scaled switching function for every frequency octave in the operational frequency range. The presented concept has been verified by the design of antenna arrays operating over 1.2–4.8 (4:1 BW) and 1.2–9.6 GHz (8:1 BW) frequency ranges.

Integrated lightweight gradient honeycomb metastructure with microwave absorption and mechanical properties: Analysis, design, and verification

Integrated lightweight metastructures with microwave absorption and mechanical properties are of great significance in practical applications, but so far relevant study is still lacking. In this paper, an integrated lightweight gradient honeycomb metastructure (GHM) was proposed using 3D printing and screen printing technologies. Using the equivalent circuit method (ECM), we provided an in-depth analysis of how to broaden the absorption bandwidth and derived the mathematical formula of the equivalent resistance of the hexagon loop. The simulation results reveal that the proposed metastructure has the characteristics of broadband absorption, polarization insensitivity, oblique incidence stability, and radar cross section (RCS) suppression in the operating frequency range. The measured results are in good agreement with the simulation ones. In addition, the compression test results show that the metastructure has good compression strength. This work provides a route to achieve integrated metastructures with thin, lightweight, excellent absorption and mechanical properties.