Desired Frequency Band Research Articles

Design of Leaky Wave Antenna for V2V Communications

In this article, a low-profile, microstrip-based, periodic leaky wave antenna has been proposed for vehicle-to-vehicle (V2V) communications. The leaky-wave structure, loaded periodically with stepped impedance resonator stubs operates in the 5.4–6.2 GHz frequency band, which includes the WAVE (Wireless Access in Vehicular Environments) band (5.85–5.925 GHz) required for automated vehicular communications. The S11 obtained in the spectrum is below −12.68 dB. While the majority of the antennas designed for V2V communications produced omnidirectional patterns, the structure proposed in this work yields a directional pattern, preventing unnecessary outages of signals. The periodic structure gives an added advantage of beam scanning, resulting in a wider, yet directive coverage in the desired frequency band. A backward beam scan from −13˚ to −31˚ is obtained in the frequency range of 5.4–6.2 GHz with a gain variation of around ±0.6 dB only.

Magnetic Bimetallic Heterointerface Nanomissiles with Enhanced Microwave Absorption for Microwave Thermal/Dynamics Therapy of Breast Cancer.

Microwave thermotherapy (MWT) has shown great potential in cancer treatment due to its deep tissue penetration and minimally invasive nature. However, the poor microwave absorption (MA) properties of the microwave thermal sensitizer in the medical frequency band significantly limit the thermal effect of MWT and then weaken the therapeutic efficacy. In this paper, a Ni-based multilayer heterointerface nanomissile of MOFs-Ni-Ru@COFs (MNRC) with improved MA performance in the desired frequency band via introducing magnetic loss and dielectric loss is developed for MWT-based treatment. The loading of the Ni nanoparticle in MNRC mediates the magnetic loss, introducing the MA in the medical frequency band. The heterointerface formed in the MNRC by nanoengineering induces significant interfacial polarization, increasing the dielectric loss and then enhancing the generated MA performance. Moreover, MNRC with the strong MA performance in the desired frequency range not only enhances the MW thermal effect of MWT but also facilitates the electron and energy transfer, generating reactive oxygen species (ROS) at tumor sites to mediate microwave dynamic therapy (MDT). The strategy of strengthening the MA performance of the sensitizer in the medical frequency band to improve MWT-MDT provides a direction for expanding the clinical application of MWT in tumor treatment.

Optimization of plasma parameters for effective attenuation of microwaves in specified frequency range

AbstractIn this article, a plasma‐metal model is studied as an electromagnetic absorber for stealth application. Epstain distribution is considered for plasma and the electromagnetic reflection of the structure is analyzed by the Green's function volume integral equation method. The attenuation of microwaves in plasma depends on microwave frequency, plasma electron density, spatial distribution of plasma, collision frequency, and plasma thickness. Using a metaheuristic optimization method, it is possible to change the parameters simultaneously in the specified domains to obtain conditions for which microwaves can be absorbed effectively in the specified frequency. In this paper, optimized plasma parameters related to ideal attenuation in desired frequency band are determined by this method. The advantage of this method is that the intervals related to the plasma parameters are selecting according to the practical conditions and in many cases prevent the production of high volume with high density plasma to achieve effective attenuation. The proposed method can be useful for designing adjustable devices in stealth applications. Proper management of power consumption in these devices is one of the results of adjustment.

Tunable double-layer dual-band metamaterial with negative mass density

Due to the huge structure and low efficiency of acoustic metamaterial (AM) with local resonance, a tunable dual-band AM with nested double layer hollow tube (NDLHT) is presented here, which is achieved by adjusting the inner or outer layer tube’s lengths or diameters to modulate the frequency band with the negative mass density. In addition, an accurate resonant frequency formula for OE-CE (Open End-Close End) NDLHT was derived based on the principle of standing wave resonance. The theoretical calculated resonant frequencies exhibit in good agreement with the simulated frequencies. Thus, the structural unit can then be actively constructed in the desired response frequency range using the geometric parameters that were obtained from this theoretical formula. This type of the nested AM with negative mass density has the advantages of high space utilization, active design, programmed modelling, customized production, 3D quantitative printing and is easily combined with other structure units with negative modulus to prepare AM with double negative in the desired frequency band.

An efficient, compact, wide-angle, wide-band, and polarization-insensitive metamaterial electromagnetic energy harvester

This paper introduces a metamaterial energy harvester that is compact, highly efficient, and capable of operating at wide angles. The proposed design has an outer ring resonator housing inverted T-shaped resonators, and it can operate at two distinct frequencies, 3.2 GHz and 5.4 GHz. The structure's impedance is carefully designed to align with that of free space, ensuring efficient capture of incident electromagnetic power with minimal reflection. This enables the resistor load to receive power in the most efficient manner. Based on the simulation findings, the proposed harvester exhibits a notably higher conversion efficiency of around 97 %. To ensure the accuracy and reliability of the simulation outcomes, we fabricated a 3x3 cell array of the proposed design and conducted experimental tests within an anechoic chamber. The simulation and experimental results exhibit a strong correlation. Existing metamaterial-based energy harvesting designs frequently confront size, absorption band, and polarization sensitivity limitations. Our compact design is distinguished by its ability to accomplish near-unity absorption and greater power conversion efficiencies at the desired frequency bands. This makes it an ideal option for energy harvesting systems for wireless sensor networks prioritizing efficiency and size.

A Co-Planar Waveguide Ultra-Wideband Antenna for Ambient Wi-Fi RF Power Transmission and Energy Harvesting Applications

This study proposes an ultra-wideband antenna for ambient radio frequency (RF) energy harvesting applications. The antenna is based on a co-planar waveguide (CPW) transmission line and incorporates a rectangular slot as an antenna harvester. The proposed antenna utilizes an evolutionary design process to achieve impedance matching of the 50 Ω CPW feeding line over the desired frequency bands. A parametric study investigates CPW elements and rectangular slot size. The harvester antenna is then connected to the primary rectifier circuit of the voltage doubler to examine the signal characteristics. The antenna covers the Industry, Science, and Medicine (ISM) Wi-Fi bands of 2.45 GHz and 5 GHz, achieving a realized gain of 3.641 dBi and 4.644 dBi at 2.45 GHz and 5 GHz, respectively. It exhibits a relatively broad frequency ranging from 2.16 GHz to 6.32 GHz, covering the ultra-wideband fractional bandwidth (FBW) of 105%.

The Design and Investigation of a Super Wideband Antenna with Dual-Band Notch Characteristics for MIMO Application

A printed monopole super wideband (SWB) antenna is presented in this paper. It consists of a beveled-shaped radiator and a tapered ground plane. It is investigated that tapering of the radiator and ground plane enhances the impedance matching and results in broad impedance bandwidth. The experimental result depicts that the antenna achieved 164.9% impedance bandwidth from 2.6 to 27.27 GHz. Furthermore, to prevent the interference caused by communication systems within the ultra-wideband (UWB) range, dual-band rejection at Wi-MAX (2.7–4 GHz). and X-band (8.5–12 GHz) are introduced by etching an H-shape and two back-to-back C-shaped notches in the radiator and feedline, respectively. The measured result demonstrates that both slots effectively reject the desired frequency bands with a small shift in the lower frequency edge from 2.41 to 2.6 GHz. In addition, the proposed antenna application is shown in the two elements MIMO system where a bowtie decoupling structure is utilized to improve the isolation. It is found that the presence of a decoupling structure improves the isolation by up to 60%. To characterize the diversity performance, parameters such as Diversity Gain (DG), Envelop Correlation Coefficient (ECC), Channel Capacity Loss (CCL), and Mean Effective Gain (MEG) are calculated and all are found in the acceptable limit.

A Low-Profile Compact Broadband CP DRA for RF Energy Harvesting Applications

In this letter, a low-profile circularly polarized (CP) chamfered rectangular dielectric resonator antenna (RDRA) is designed and investigated for radio frequency energy harvesting (RFEH) applications. The proposed modified RDRA comprises of dielectric resonator (DR) made up of Alumina material (ε r = 9.9) mounted on the PEC ground plane. Dual unequal triangular-shaped vertical slits are engraved on the rectangular DR for generating the orthogonal modes with CP characteristics. The optimized antenna offers an impedance bandwidth (IBW) of 51.4% (2.25–3.81 GHz) and axial ratio bandwidth (ARBW) of 14.8% (3.25–3.77 GHz), respectively. The peak realized gain and maximum radiation efficiency are 7.18 dBi and 97.8% in desired frequency bands. Due to the wide impedance and AR bandwidths with realized gain and radiation efficiency, the optimized antenna is suitable for integration with a rectifier circuit for RF energy harvesting applications. A rectifier circuit with a single shunt diode topology is also designed for rectification purposes. The rectifier achieved 67.16% RF-DC power conversion efficiency (PCE) at 3.5 GHz and 5dBm input power. At 0dBm input power, the rectifier achieved 60.26% PCE. The effective input power range, during which the PCE maintains above 50%, is calculated to be 15.2 dBm from −3.5 to 11.7 dBm.

Design of a wideband highly efficient GaN HEMT power amplifier for multiband applications

AbstractA distributed basic matching network (MN) designed method that can achieve multioctave bandwidth and highly efficient power amplifier (PA) for multiband applications is presented in this letter. The distributed network unit with a left-rotating T-type structure is employed to construct the wideband MN, whose topology and circuit parameters are acquired through optimization. Finally, the impedance realized by the designed MN falls into the target impedance region obtained by using multi-harmonic bilateral pull technique in the desired frequency band. For the proof of the method, a broadband highly efficient PA has been designed, fabricated, and measured using commercialized GaN high electron mobility transistors (HEMT). The measured results show that the implemented PA achieves a bandwidth of 137.8% from 0.7 to 3.8 GHz. The drain efficiency is between 59% and 70% with an output power of greater than 39 dBm and a gain ranging from 9 to 12.1 dB.

Dual Plane Monopulse Comparator Network System using Substrate Integrated Waveguide Hybrid Coupler

ABSTRACT This paper presents a new compact monopulse comparator network system (MCNS) using a modal substrate-integrated waveguide (SIW) hybrid coupler for the first time. The main objective of this research is to evaluate the performance of dual-plane MCNS based on return loss and coupling coefficients. A detailed analysis, design, and implementation of dual-plane MCNS is performed using the four modal SIW hybrid couplers. The sum and difference signals required by the monopulse antenna are generated with the proper orientation of couplers. The in-phase and out-phase characteristics of the couplers are generated using TE102 and TE201 orthogonal degenerate modes. A complete planar and compact SIW structure has a footprint of 58.2 mm × 58.2 mm. MCNS is fabricated on a single-layer Rogers RO4003 substrate with a permittivity of 3.55 and thickness of 0.787 mm using a photo-lithographic process. MCNS provides excellent return loss characteristics at all input and output ports. It measured the isolation better than 20 dB for all output ports in the desired frequency band. It achieved good coupling between all input and output ports. Simulation and measured results show that at 10 GHz, MCNS gives better performance parameters and can be used in monopulse antenna.

Receiver Design in Full-Duplex Joint Radar-Communication Systems

Full-duplex (FD) integrated sensing and communication (ISAC) has great potential in future vehicular networks. However, the FD requirement and the ISAC functions make the receiver processing extremely complicated, particularly when multiple transmissions are uncoordinated. In this paper, we study frequency-hopping (FH) based receivers in an FD ISAC system, where the arrivals of backscattered signals from one node may overlap with those of signals from another node. To mitigate the interferences caused by the overlapping signals, we consider two receiver options based on either conventional communications or frequency-modulated continuous-wave radars, and two signal modulations based on either fast FH or un-slotted ALOHA FH. Based on the different signal modulations, we develop two parameter estimation schemes via using FH-decoding and dechirp operations, respectively. To further improve the sensing accuracy, we proceed to propose an iterative algorithm, which refines the estimates of all parameters via using short-time-Fourier transform and maximizing the received power in desired frequency bands. After obtaining all channel parameters in sensing, bilateral communications between two nodes are realized by differential phase-shift keying. Finally, simulation results are provided and verify that the proposed FD ISAC can obtain parameters in high resolution and realize robust communication links.

Circularly polarized differential intra-oral antenna design validation and characterization for tongue drive system

Assistive devices are becoming increasingly popular for physically disabled persons suffering tetraplegia and spinal cord injuries. Intraoral tongue drive system (iTDS) is one of the most feasible and non-invasive assistive technology (AT), which utilises the transferring and inferring of user intentions through different tongue gestures. Wireless transferring is of prime importance and requires a suitable design of the intra-oral antenna. In this paper, a compact circularly polarized differential intra-oral antenna is designed, and its performance is analysed within heterogeneous multilayer mouth and head models. It works at 2.4 GHz in the Industrial, Scientific, and Medical (ISM) band. The footprint of the differential antenna prototype is 0.271 λgtimes 0.271 λgtimes 0.015 λg. It is achieved using two pairs of spiral segments loaded in diagonal form near the edges of the central rotated square slot and a high dielectric constant substrate. Its spiral-slotted geometry further provides the desired swirling and miniaturization at the desired frequency band for both mouth scenarios. Additionally, corner triangular slits on the radiating patch assist in tuning the axial ratio (< 3 dB) in the desired ISM band. To validate the performance of the proposed in-mouth antenna, the measurement was carried out using the minced pork and the saline solution for closed and opened mouth cases, respectively. The measured − 10 dB impedance bandwidth and peak gain values in the minced pork are from 2.28 to 2.53 GHz (10.39%) and − 18.17 dBi, respectively, and in the saline solution, are from 2.3 to 2.54 GHz (9.92%) and − 15.47 dBi, respectively. Further, the specific absorption rate (SAR) is estimated, and the data communication link is computed with and without a balun loss. This confirms that the proposed differential intraoral antenna can establish direct interfacing at the RF front end of the intraoral tongue drive system.

Compact Ultra-­Wideband Planar Inverted F Antenna on Laminated Paper­-Based Substrate with Reduced Specific Absorption Rate

This paper presents a laminated paper-based Planar Inverted F Antenna (PIFA) for wireless body area network (WBAN) applications. The major challenges like providing adequate thickness, uniformity of surface, and water wet ability associated with paper substrate have been transcended in this antenna design by laminating the substrate with a transparent sheet. The simulated and measured reflection coefficients of the fabricated antenna in free space and on human arm are remarkably good, validating the prototype’s utility. It can operate effectively in GSM, WMTS, GPS, DCS, ISM, WiMAX, HIPERLAN, WLAN, and UWB frequency bands with S11 less than -10 dB and the gain ranging from 0.94 to 9.53 dB (free space) and 1.03 to 6.07 dB (on-body). The electrical size of the proposed antenna is 0.16 λg x 0.12 λg at 0.7 GHz with a group delay below 2.3 ns over the desired frequency bands. The performance characteristics are also investigated on-body and it encompasses most of the desired frequency bands for the body area network. This paper also analyses the specific absorption rate (SAR) of the designed antenna by placing it on a tissue-layered human arm model, which is 0.64 Watt/kg, complying with the SAR safety guidelines.

Low-profile frequency-reconfigurable antenna for 5G applications

The demand for higher data rates has increased in recent years. The reconfigurable antenna that operates in the millimeter-wave spectrum (23.5 GHz – 29.64 GHz) was developed. This design is obtained by merging a half-circle radius of 3.97 mm, and a half-ring inner radius of 4 mm. The shape is similar to the round bottom flask. Two PIN diodes are used in this design to achieve frequency reconfigurability to meet the wideband mobile communication need of the future 5G. The suggested antenna, built on Roger RT5880 substrates and properties of ε = 2.2 and δ = 0.0009, has been used as the antenna substrate. For all the resonant bands, the suggested antenna has a voltage standing waves ratio (VSWR) &lt; 1.11. From 84 % to 92 %, the suggested structure radiation efficiency is calculated. A small antenna element has an excellent end-fire radiation pattern in the desired frequency bands. The antenna shows three reconfigurable bands, 25.17, 26.75, and 27.64 GHz, and gain (2.77-4.4) dBi. The suggested antenna is well suitable for future fifth-generation (5G) networks because of its notable features of small overall size (9.8×13×0.787) mm 3 , wide bandwidth, and frequency reconfigurability.

Combined Open-Slot and Monopole 8 × 8 High-Isolation Broadband MIMO Antenna System for Sub-6 GHz Terminals

In this article, an 8 × 8 MIMO antenna system with multidecoupling structures is proposed for the fifth-generation (5G) terminal applications. First, an antenna element consisting of an L-shaped open slot with dimensions of 5.6 × 5 mm2 and two bent-L-shaped monopoles with dimensions of 12.7 × 6.1 mm2 is introduced. Due to coupling feed technology, the initial open slot owns a wide bandwidth from 3.62 GHz to 4.82 GHz. For broadening the bandwidth of the initial antenna element, two bent-L-shaped monopoles are added to the open slot to adjust the input impedance. By optimizing the parameters of monopoles, the proposed antenna element has been finally determined and the bandwidth of the antenna element has been broadened (2.82 GHz to 5.23 GHz). Second, a dual antenna pair is constructed by placing the two antenna elements with an edge-to-edge distance of 27 mm in a mirror image placement; the 8 × 8 MIMO antenna system is brought about by symmetrically disposing four such antenna pairs with an edge-to-edge distance of 47 mm. Moreover, the isolation of two closely placed antenna elements is achieved by the parasitic strip-loading technique and defective ground techniques. Due to the decoupling techniques used in the 8 × 8 MIMO antenna system, the average isolation has been optimized from 13.2 dB to 21.9 dB and the total efficiency of each antenna element has been improved from a worst 20% to over 45%. Besides, the calculated mean efficiency gain is less than 1 dB, and the calculated envelop correlation coefficient (ECC) is lower than 0.01 for desired frequency bands. Furthermore, the proposed 8 × 8 MIMO antenna system has the measured broadband bandwidth from 3.28 GHz to 5.05 GHz (covering N77, N78, and N79 bands) and a compatible dimension for ultra-thin mobile phones. The simulated results of this work are all obtained from EM software CST STUDIO SUITE 2019. In general, the proposed 8 × 8 MIMO antenna system with a high-isolation property provides a hopeful solution to 5G ultra-thin mobile phones.

A Miniaturized Dual-Band Diplexer Design with High Port Isolation for UHF/SHF Applications Using a Neural Network Model

In this paper, a compact dual-band diplexer is proposed using two interdigital filters. The proposed microstrip diplexer correctly works at 2.1 GHz and 5.1 GHz. In the proposed diplexer, two fifth-order bandpass interdigital filters are designed to pass the desired frequency bands. Applied interdigital filters with simple structures pass the 2.1 GHz and 5.1 GHz frequencies and suppress other frequency bands with high attenuation levels. The dimensions of the interdigital filter are obtained using the artificial neural network (ANN) model, constructed from the EM-simulation data. The desired filter and diplexer parameters, such as operating frequency, bandwidth, and insertion loss, can be obtained using the proposed ANN model. The insertion loss parameter of the proposed diplexer is 0.4 dB, and more than 40 dB output port isolation is obtained (for both operating frequencies). The main circuit has the small size of 28.5 mm × 23 mm (0.32 λg × 0.26 λg). The proposed diplexer, with the achieved desired parameters, is a good candidate for UHF/SHF applications.

Bearing fault-induced feature enhancement via adaptive multi-band denoising model

To accurately extract the bearing fault-induced impulse features from the vibration signals corrupted by heavy noise and large-amplitude random impulses, an adaptive multi-band denoising model based on the Morlet wavelet filter and sparse representation is put forward. First, to locate the desired frequency band associated with fault components, the Morlet wavelet filter is employed to band-pass the signal from the perspective of the frequency-domain. Herein, an improved Protrugram-based index, termed as windowed envelope spectral kurtosis, is designed as the objective function to choose the optimal center frequency and the bandwidth of the Morlet wavelet filter. Furthermore, benefitting from the time-domain characteristics of the vibration signal, the in-band noise is eliminated by sparse representation. One of the critical parameters (resonance frequency) of the wavelet atom used in the sparse representation dictionary is directly taken as the center frequency of the Morlet wavelet filter, which makes full use of the information derived from the filter, and thus significantly improves the calculation efficiency. Finally, the recovery signal is demodulated by the Hilbert transform to extract the fault characteristic frequency. The effectiveness and superiority of the proposed method are demonstrated through a complete analysis of the simulated, experimental, and engineering signals, as well as a comparison with such prevalent methods as Kurtogram, individual sparse representation, and Morlet wavelet filter combined with the maximum correlation kurtosis deconvolution.

A Simulation Study of Triband Low SAR Wearable Antenna

The proposed paper presents a flexible antenna that is capable of operating in several frequency bands, namely 2.45 GHz, 5.8 GHz, and 8 GHz. The first two frequency bands are frequently utilized in industrial, scientific, and medical (ISM) as well as wireless local area network (WLAN) applications, whereas the third frequency band is associated with X-band applications. The antenna, with dimensions of 52 mm × 40 mm (0.79 λ × 0.61 λ), was designed using a 1.8 mm thick flexible kapton polyimide substrate with a permittivity of 3.5. Using CST Studio Suite, full-wave electromagnetic simulations were conducted, and the proposed design achieved a reflection coefficient below −10 dB for the intended frequency bands. Additionally, the proposed antenna achieves an efficiency value of up to 83% and appropriate values of gain in the desired frequency bands. In order to quantify the specific absorption rate (SAR), simulations were conducted by mounting the proposed antenna on a three-layered phantom. The SAR1g values recorded for the frequency bands of 2.45 GHz, 5.8 GHz, and 8 GHz were 0.34, 1.45, and 1.57 W/Kg respectively. These SAR values were observed to be significantly lower than the 1.6 W/Kg threshold set by the Federal Communication Commission (FCC). Moreover, the performance of the antenna was evaluated by simulating various deformation tests.

Capsule Endoscopic MIMO Antenna With Radiation Pattern and Polarization Diversity

This article presents a novel compact dual-element capsule endoscopic multiple-input-multiple-output (MIMO) antenna at a 915 MHz industrial, scientific, and medical (ISM) band. Both radiating elements of the MIMO antenna system are circularly polarized (CP) at the desired frequency band (915 MHz). In fact, Antenna- 1 operates at left-handed CP (LHCP) and Antenna- 2 operates at right-handed CP (RHCP), enabling polarization diversity at 915 MHz. Moreover, the radiating elements radiate in two opposite directions; thus, they enable pattern diversity. The performance of the proposed antenna system is analyzed in a realistic human phantom. Reactive slots in the patch antennas are incorporated to achieve compactness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi \times $ </tex-math></inline-formula> (4.7) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm{ 2}}\,\,\times0.13$ </tex-math></inline-formula> = 9.01 mm3) and CP characteristics. Furthermore, a rectangular slot on the ground plane is introduced to reduce the mutual coupling between the radiating elements. The proposed antenna has compact dimensions of 9.01 mm3, a peak realized gain of −24.6 dBiC, and a high isolation level of 29.7 dB within the whole band. The specific absorption rate (SAR), link margin (LM) and main MIMO channel parameters are investigated which show good results. The key features of this antenna are its compact size, high isolation level between the antennas, and polarization and pattern diversity.

Four-Port 38 GHz MIMO Antenna with High Gain and Isolation for 5G Wireless Networks

In this paper, a 38 GHz 4-port multiple-input multiple-output (MIMO) antenna with considerable isolation and gain enhancement for 5G applications is introduced. The suggested antenna element is a monopole antenna composed of a circular patch with a rectangular slot etched from it and a partial ground plane is used to extend the desired frequency to operate from 36.6 GHz to 39.5 GHz with a center frequency of 38 GHz. The high isolation is achieved by arranging the four elements orthogonally and adding four stubs to reduce mutual coupling between elements at the desired frequency bands. The gain improvement is also introduced by placing a frequency selective structure (FSS) which is designed at the same frequency bands of the antenna under the suggested MIMO antenna to act as a reflector. The proposed four-element MIMO with the FSS prototype is built and tested in order to confirm the simulated results. The suggested antenna operated from 37.2 GHz to 39.2 GHz with an isolation of less than 25 dB across the obtained frequency range. The peak gain of the antenna is enhanced from 5.5 dBi to around 10 dBi by utilizing the FSS structure; furthermore, the back radiation is enhanced. The MIMO performance is validated by extracting its parameters and comparing with the simulated results. The results extracted from the simulation and the measurement show satisfactory matching along with the target band, indicating that the proposed structure could be used for 5G communications.