Dual Band Research Articles

Dual emitting carbon nanoparticles for tunable white light emission

Eco-friendly, biomass derived single component luminescent materials with dual emission bands hold immense potential in white light emitting devices (WLED). Compared to WLED fabricated from different color emitting carbon nanoparticles, self-reabsorption and degradation will be negligible in single system white light emitting materials which guarantees stability in long run. Herein, we report a facile, inexpensive and sustainable direct thermal decomposition method to synthesize carbon nanoparticles with dual emission bands. Addition of PVP could efficiently enhance the red emission band of carbon nanoparticles. The excitation dependent broad blue-green emission and excitation independent narrow red emission helps to obtain white light emitting carbon nanoparticles. Upon change in excitation wavelength from 410 nm to 370 nm, white light emissions are obtained with tunable CCT value from 2648 K to 8980 K respectively. By virtue of this tunable warm to cool white light emission, single system WLED can be designed suitable for both indoor and outdoor applications.

Sound trapping and waveguiding in locally resonant viscoelastic phononic crystals

We describe the trapping and absorption of audible sound in centimeter-scale claddings of two-dimensional, locally resonant phononic crystals. In a square lattice of local resonators consisting of steel cores and cellulose shells, embedded in a viscous foam, dual acoustic-range band gaps extending from about 200 to 2850 text { Hz} are achieved. The spectral range consists of a low-frequency, local resonance gap, separated from a higher frequency Bragg resonance gap, by narrow bands of slow-sound modes. We demonstrate that thin claddings of such phononic crystal, of only three unit cells in thickness, can effectively prevent sound transmission, by a combination of reflection and absorption, over much of the audible spectrum. Moreover, frequency-selective sound transmission can be enabled by engineering waveguide channels that transmit sound through the local resonance gap, the Bragg gap, or both. This offers a path to sound-sculpting claddings that can surround a noise-generating source. The viscoelastic foam in our cladding is treated using a fractional Voigt model, capable of describing experimentally observed responses.

Compact dual band 4-port MIMO antenna for 5G-sub 6 GHz/N38/N41/N90 and WLAN frequency bands

In this investigation, a dual-band 4 port MIMO antenna is designed, fabricated and measured. The MIMO design consists of perturbed hexagonal patch along its periphery on the top of the substrate and the connected ground plane on the bottom. The MIMO design has an overall dimension of 50 × 50 × 0.8 mm3. The proposed antenna structure demonstrates the dual frequency band of 2.47–3.38 GHz and 4.94–7.24 GHz, respectively covering the 5G sub-6 GHz/WLAN/HiperLAN band applications. Moreover, the radiation efficiency, gain and far-field patterns are also presented across both the operating bands. The antenna diversity parameters which include ECC, DG, MEG, CCL and TARC are studied and found excellent for the MIMO antenna implementation. The channel loss of the proposed 4 × 4 MIMO antenna is calculated and found 21.54 b/s/Hz at SNR of 20 dB. The proposed design is modeled in CST Microwave Studio and the results are compared with the fabricated prototype antenna for the practical implementations.

Dual Band Metasurface Integrated With Wideband Power Combiner for RF Energy Harvesting

This letter presents a novel dual-band metasurface (MS) structure with a Chebyshev transformer-based wideband power combiner for RF energy harvesting (RFEH). The unit cell (UC) of MS formed by embedding an electric-inductive capacitive resonator (EICR) in a single square loop (SSL) provides dual-band characteristics at 2.2 and 4.6 GHz, respectively. The wideband power combiner in corporate feed architecture, represented by the circuit schematic, channels the power to a 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega$</tex-math> </inline-formula> load, mimicking the input impedance of any standard rectifier. The system is studied using numerical simulation followed by fabrication of the prototype and its validation with experiment. The proposed system provides close to 90% radiation to ac conversion efficiency at 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega$</tex-math> </inline-formula> load in dual-band.

Dual-Band Metasurface With Extreme Angular-Asymmetric Transmission and Frequency Selection Based on Resonant Coupling Effect

Asymmetric transmission plays an important role in many electromagnetic systems. Different to the asymmetric transmissions in full space, angular-asymmetric transmissions in half space support different characteristics for symmetrical oblique incidences, which has great potentials for antenna designs and wireless systems. By introducing guided wave modes and resonant coupling effect into metasurface design, this paper designs and demonstrates a dual band multi-functional metasurface with angular-asymmetric transmission and frequency selection under oblique incidences. At 8.7 GHz, the electromagnetic wave under 30° TM oblique incidence is absorbed, and the wave under -30° TM oblique incidence transmits, which presents an angular-asymmetric transmission. At 10.4GHz, both ±30° TM oblique incident waves can be transmitted, which presents a frequency selection function. The metasurface sample with optimized geometry parameters has been fabricated and measured, and the measurement agree well with the simulation results.

Microstrip dual band hybrid directional resonator antenna with volume reduction

This paper presents a novel design of a single-layer, horizontally polarized, dual-band, omni- and multi-directional hybrid dielectric resonator antenna (DRA) feeding through a 50 Ω coaxial connector. The proposed antenna consists of an FR4 substrate, a regular ground plane and a cross-shaped patch. The connector is placed at the middle point of the square ground plane. Above the microstrip patch, four similar solid dielectric resonator elements are placed diagonally. These DRA structures generate the TE111, hybrid HEM22δ modes and put up an ideal magnetic dipole and an electric quadrupole far-field radiation pattern. To verify the idea, an optimized antenna model is fabricated and tested. A reasonable agreement between the measured and simulated results is obtained. The measured impedance bandwidths of the TE111 and HEM22δ modes are 4.26 % (2.9–3.2 GHz) and 4.34 % (4.4–4.6 GHz), respectively. The proposed antenna has a stable omnidirectional radiation pattern at the first resonance frequency and a directional radiation pattern at the second resonance frequency and provides volume reduction.

Design of High-Efficiency Dual Band Power Amplifier Based on GaN HEMT

In this paper, a novel dual-frequency impedance converter is proposed, and a rigorous derivation process is given. Based on this, a 0.61/2.6 GHz dual-frequency and high-efficiency power amplifier is designed. The joint simulation results show that the designed power amplifier achieves a maximum power added efficiency (PAE) of 68.3% at 0.61 GHz and achieves a saturated output of 41.53 dBm; At 2.6 GHz, the saturated output power is 40.8b dBm, and the maximum PAE is 56.3%. The designed dual-frequency power amplifier has good working performance.

Novel Dual Band Frequency Selective Surface and its Applications on the Gain Improvements of Compact UWB Monopole Antenna

In this work, a highly directional ultra-wideband (UWB) microstrip patch antenna as a single-element is suggested. The proposed antenna’s gain is enhanced with a novel dual-band frequency selective surface (FSS) placed beneath it. The FSS design has a hexagonal structure with meander line inductances and a capacitance-like structure connecting all of the corners to the middle. There is no metallic layer on the other side of the substrate, which shows transmission zeros at 4.95 GHz and 12.7 GHz, and a modified U-shaped monopole antenna is developed. First, the performance characteristics of the antenna and FSS are analyzed from the simulation results, and they are validated experimentally after fabrication, followed by measurement. The compact configuration comprises an antenna loaded with the proposed FSS results S11 less than -10 dB from 3.15 GHz to 22.65 GHz, covering the UWB band together with the X, Ku-band with a bandwidth of 19.5 GHz (151.16% FBW). The antenna’s overall physical dimensions would be 38.8 mm×38.8 mm×25.2 mm (0.407λo×0.407λo×0.265λo), with λo denoting the lowest frequency’s free-space wavelength. The FSS loading results in a 9.9 dBi maximum gain at 10 GHz. The antenna’s small size increases bandwidth, and its high peak gain makes it ideal for use in real-time applications.

Design of a Crossed Dielectric Resonator-Loaded, Dual-Band Dual-Polarized Differential Patch Antenna with Improved Port Isolation and Gain

To meet the urgent requirement for more channel capacity in modern wireless communication systems, antennas with more operation bands are demanded. However, large amounts of antennas suffer from low radiation gains and low port isolation levels. In view of this, a differentially fed, dual-wideband, dual-polarized patch antenna is proposed in this paper. Compared with conventional crossed-feeding structures, the proposed crossed dielectric resonator (CDR) can provide extra resonances with improved isolation levels and radiation gain. Further, four shorting pins are introduced to the radiating patch to help improve the impedance-matching performance. In addition, the proposed antenna also has a very compact size of 0.46λ × 0.46λ × 0.12λ. Finally, a prototype of the proposed antenna is fabricated to validate the design concept. The measured results show that the proposed antenna generates dual wide bands of 1.86–2.52 GHz and 3.26–3.72 GHz for |S11| &lt; −10 dB. High radiation gains of 8.9 ± 0.9 dBi and 10.8 ± 1.2 dBi are also obtained, as well as high port isolation levels of better than 38.4 dB and 36.2 dB at the two bands. The excellent performance of the proposed antenna makes it a promising candidate for 4G/5G wireless communication systems.

A High Gain Circularly Polarized Dual Band Antenna Array Using Sequential Phase Rotation Technique for Wireless Applications

A High Gain Circularly Polarized Dual Band Antenna Array Using Sequential Phase Rotation Technique for Wireless Applications

A symmetric plus-shape resonator based dual band perfect metamaterial absorber for Ku band Wireless Applications

In this article, introduce a metamaterial for microwave absorber applications based on a variant of the symmetric plus-shape resonator. This MA has two absorption peaks, making it suitable for Ku frequency band use. The MA unit cell built on a cheap FR4 substrate. The unit cell's resonator is designed in the form of a four-plus-shape with an eight-square-point in one of the corners, and its dimensions have been tweaked to achieve maximum absorption peaks of 99.04%, and 99.90% at 12.32 GHz, and 16.00 GHz, respectively. Analysing the surface current, electric and magnetic fields, permittivity, permeability, and normalised impedance provides insight into the nature of metamaterial and absorber. The incidence and polarization angle insensitivity of the suggested dual-band absorber allows for pretty much constant absorbance efficiency when the angle is changed. Moreover, for both TE mode and TM mode, the developed metamaterial absorber demonstrates near unity absorption for polarization and oblique incident angles up to 90°. These are single negative metamaterial qualities. The fact that the patch as a whole is rotationally symmetrical is one of the most important factors in determining whether or not it will retain its polarization-insensitive quality. Because of its outstanding insensitivity performance and nearly perfect absorption, it could be a good option for use in Ku band applications.

Linear phased meta-material incorporated patch antenna array at sub-6 GHz for 5G base stations

ABSTRACT This article presented a four-element dual-band linear phased antenna array operating at sub-6 GHz. The single-element antenna was designed by mounting a double-negative single- layered Complementary Split Ring Resonator (SL-CSRR) on the patch and grounding with a rectangular slot and four SL-CSRR’s array; it was resonated at dual bands 3.43–3.56 GHz and 4.93–5.75 GHz and got size shrinkage of 80.45% with dimensions 0.35λx0.35λx0.028λ mm3. The proposed phased array antenna was resonated in 3.42–3.57 GHz and 4.86–5.74 GHz with central frequencies 3.49 GHz and 5.18 GHz, respectively, with respect to −10 dB impedance bandwidth. It was dimensioned with 0.35λx2.42λx0.028λ mm3. The isolation of > 16 dB, ECC < 0.1, DG ~ 10 dB, CCL < 0.15bits/s/Hz and MEG<-6 dB were achieved. The maximum gain of 8.4dBi and 10.4dBi and maximum efficiency of 81.14%, and 99.12% were achieved over the two resonated bands, respectively. The array antenna excited initially with 0° phase difference was radiated bi-directional beam focused to 0° and 180° in the pattern like a broadside array and with the change of phase difference, the structure capable to focus the beam to ± 90° like end-fire array at 3.49 GHz and it was capable to steer the beam to ± 48.6° at 5.18 GHz. These results demonstrated that the proposed phased array antenna is a good candidate to provide services at base stations for 5 G sub-6 GHz applications. The prototypes of the single-element antenna and four-element phased array antennae were fabricated and tested. The matching of simulation results with measurement one has a good commitment to similarity.

An optically transparent dual-band frequency selective surface for polarization independent RF shielding

This article reports on a compact dual band, Frequency Selective Surface (FSS) based spatial filter for Wi-Fi and WLAN shielding applications on a transparent glass surface with optical transparency of 70%. The unit cell comprises an outer square loop resonator with a disconnected and concentric annular ring resonator. To introduce frequency tuning and compactness T shape stubs are strategically loaded on these resonators and it is ensured that the mutual coupling remains minimal. The outer square resonator suppresses the 2.4 GHz band, and the inner circular ring resonator stops the 5.4 GHz band. The unit element is four-fold symmetric thus it offers complete polarization independence. A detailed parametric and electromagnetic field analysis has been conducted to elucidate the significance of different sections of the unit element. An equivalent lumped circuit model is also derived for the proposed unit element to better explain the underlying working mechanism. A finite prototype of 15 × 11 elements is fabricated on a soda lime float glass by using ordinary adhesive copper foils with a standard chemical etching process. Polarization independence and angular stability up to 45° are measured and compared with the simulated responses. The FSS shield offers frequency suppression up to 45 dB and 43 dB for 2.4 GHz and 5.4 GHz bands respectively. With high optical transparency, the design allows maximum light through it and causes no extra burden on energy consumption for indoor applications. The compact dual band design and the possibility of direct application on host surfaces like glass windows and doors make this design an excellent candidate for data security and privacy applications in secure installations with an esthetically pleasing outlook.

Dual nanocomposite materials that enhance the radiation characteristics of flexible circular antenna

A novel dual nanocomposite filled circular shaped flexible slot antenna is introduced for WLAN/WiMAX/5G/Wi-Fi applications. The circular radiating patch is given two slots that are filled with nanocomposite materials PANI/CCo and PDMS/AgNW, which enhances antenna radiation properties in both lower and upper band independently. The antenna is fabricated deploying a coplanar waveguide (CPW) fed system that encompasses a patch featuring a circular shape and CPW ground combined with a circular ring shape. The dual band is formed by introducing a narrow rectangular slot on the circular radiating patch and is designed for a mid-frequency 3.85 GHz, of two resonance frequencies. Different bending radii are used to evaluate antenna flexibility, and findings are in good match for a flat antenna. With good radiating qualities over the whole dual band, the suggested fabricated antenna covers the 2.4/5.2/5.8 GHz WLAN, 2.5/5.5 GHz WiMAX, 2.3/2.6 GHz 5G, 2.4/4.9/5.2/5.5/5.8 GHz Wi-Fi, and 5G SUB 6 GHz bands.

Miniaturized dual wideband MIMO antenna for implantable biomedical applications

AbstractA novel miniaturized multiple input multiple output (MIMO)‐based implantable antenna is designed to operate with dual bands, which are wide enough to cover three industrial, scientific, and medical (ISM) bands of 402–405 MHz, 902–928 MHz, and 2.4–2.48 GHz. The proposed antenna has an overall dimension of π × × 0.635 mm3 and uses an RT3010 substrate of thickness 0.635 mm. Each element of MIMO has a spiral structure made of meandered line to realize resonance at 915 MHz, while an arc is etched in each element for obtaining a band of 403 MHz. Semicircular slots are etched in each quadrant of the ground plane for better impedance matching at the higher band of 2.4 GHz. In a −10 dB fractional bandwidth of 95%, 45.36% is attained for the realized bands. Simulation in a skin phantom provides better impedance matching and mutual coupling of less than −15 dB in the three operating bands.

Dual-Band High-Efficiency Power Amplifier Based on a Series of Inverse Continuous Modes With Second-Harmonic Control

This letter proposes a design approach for a dual-band (DB) power amplifier (PA) based on a series of inverse continuous modes (SICMs). The approach possesses a wider fundamental and second-harmonic impedance space compared with inverse continuous class-F, and the dual bandwidths of the DB PA can be improved flexibly. In addition, a variable knee voltage is considered for predicting the output performance of the PA more accurately. A simple impedance control network only for the second-harmonic is exploited to improve PA efficiency. Simulation and measurement results indicate that the fabricated DB PA achieves drain efficiencies of 65%–80.9% from 2.43 to 2.70 GHz, and 65%–76.2% from 3.37 to 3.52 GHz, respectively, and the obtained output power exceeds 10 W in DBs.

Plasmonic dual-band waveguide with independently controllable band-notched characteristics

Abstract In this present paper, an investigation is conducted on a dual-band waveguide with independently controllable band-notched characteristics. The proposed slot structure, featuring a loaded gap, facilitates the operation of the plasmonic waveguide at two distinct frequency bands. Moreover, the working bandwidth of the waveguide can be flexibly adjusted through the use of varactors loaded across the gap. Notably, the dual band can be adjusted independently and flexibly by regulating the varactors. The measurement results demonstrate that the plasmonic filtering waveguide possesses excellent frequency selectivity and compact physical size, particularly concerning its real-time controllable notched-band response with the varactor voltages.

K-/Ka-Band Planar Shared-Aperture Beam-Scanning Array Antenna for Simultaneous Transmitting and Receiving Low Earth Orbit Satellite Communication Terminal

A planar shared-aperture beam-scanning array antenna for simultaneous transmitting and receiving (STAR) satellite communication is proposed. The antenna operates in dual working bands with right-handed circular polarization (RHCP) from 17.7 to 21.2 GHz and left-handed circular polarization (LHCP) from 27.5 to 31.0 GHz. For the K-/Ka-band shared-aperture beam-scanning array antenna, the main challenge is to simultaneously achieve a wide beam scanning range, low profile and high cross-band isolation. Compared to high-profile end-fire duplexing or filtering antennas, planar laminated antennas have a stronger coupling between two elements operated at different frequency bands. In this design, two embedded two-stage filters are proposed and integrated into the dual-band feeders. The minimum spacing between the elements is 1/4 wavelength, and both in-band wideband impedance matching and cross-band filtering are performed simultaneously. Firstly, two square lattices with a 45° rotation angle between them and a non-stacked topology are employed in the design of uniform arrays for both bands. This design is better suited for this filtering array. Secondly, to improve CP performance during the beam scanning, the Ka-band induced current on the K-band radiator should be suppressed. The rotary feed phase and the segmented patch are used to suppress the induced current and produce the reverse induced current in the small and large beam scanning area respectively. Finally, the equivalent circuits and chain matrices are used to design the filtering feeders. As a result, the dual cross-band isolations increase to 38 dB and 41 dB. The total profile is less than 3.2 mm, much smaller than the existing K-/Ka-band filtering antenna’s profile of 10 mm, and the proposed design also has a wide operating bandwidth and a large beam scanning range of ±60°.

Reconfigurable Compact Quad-port MIMO Antennas for sub-6 GHz Applications

This paper presents compact quad-port frequency reconfigurable multi-input multi-output (MIMO) antennas for 5 G applications that operate at sub-6 GHz. The proposed design provides more isolation (&gt;13 dB) and pattern diversity using four orthogonal radiating elements. C-shaped metal is used to extend the antenna's radiating elements by inserting one positive intrinsic negative diode (PIN) in the metal. The C-shaped metal and matching stub achieve frequency reconfigurability with a consistent radiation pattern. The PIN diode's switching characteristics allow the frequency to be shifted between two communication bands. One mode (diode ON) covers 2.5 and 5 GHz, while the second mode (diode OFF) covers another dual band of 3.5 and 5.7 GHz. Substrate dimensions are only 50 x 50 x1.6 mm3, making the proposed design compact. Antenna peaks at a gain of 4.18 dB and radiation efficiencies of 80 and 94% in the four frequency bands. The antenna design is appropriate for multi-functional wireless systems and cognitive radio applications since it spans frequency bands below 6 GHz and can be reconfigurable between wide and narrow bands.

Composition controllable multifunctionality of PVDF/PMMA/BaTiO3/OMMT based ternary and quaternary hybrid polymer nanocomposites

State-of-the-art engineered multifunctional nanocomposites composed of different polymer matrices and functional nanomaterials are in high industrial demand for advances in all-solid-state flexible device technologies. Within this framework, the host matrices of poly(vinylidene fluoride) (PVDF) and its blend with poly(methyl methacrylate) (PMMA), and the barium titanate (BaTiO3) and organo-modified montmorillonite (OMMT) clay mixed nanomaterial dispersed ternary PVDF/x wt% (BaTiO3+OMMT) and quaternary (PVDF+PMMA)/x wt% (BaTiO3+OMMT) hybrid polymer nanocomposites (HPNCs) are prepared through ultrasonicated homogenized solution casting method. The XRD patterns and FTIR transmittance spectra confirmed the composition dependent crystal phases of the PVDF and the heterogeneous polymer-polymer and polymer-nanomaterial interactions in these HPNC materials. The DSC measurements explained a huge alteration in the PVDF crystallite melting temperatures and also the degree of crystallinity of different HPNC materials. The UV–Vis absorbance of these hybrid materials depends strongly on their composition design and demonstrated dual energy band gaps attributed to host polymer matrices and the nanofillers. The dielectric permittivity dispersion in the broadband frequency range of 20 Hz − 1 GHz explains the contribution of several polarizations and relaxation processes in these complex composites, at 27 °C. Appreciably high dielectric permittivity (4 to 7) in the 20 Hz − 1 MHz range and low permittivity at the ultra high radio frequencies confirmed the promising nanodielectric characteristics of these hybrid materials. The interesting structure-property relationship, tunable energy band gaps, a wide range of composition controllable dielectric permittivity, and frequency dependent electrical conductivity revealed the usefulness of these HPNCs in making flexible-type innovative optoelectronic, capacitive energy storage, and microelectronic devices.