Dual-band Operation Research Articles

Adjustable THz Absorber Exploiting Nested Graphene Disk-Ring

This work introduces a THz dual-band absorber with the capability of being tuned via external stimulation. A nested disk-ring graphene pattern is proposed on top of the lossless substrate while the other side of the substrate is coated by a thick layer of gold. The proposed absorber is modeled using an equivalent circuit model (ECM) and also simulated by the full wave method. A perfect match between the circuit model and numerical full wave simulation highlights the developed circuit modeling. Since the circuit modeling can reduce CPU time and need memory considerably. The impedance-matching concept interpretations are discussed in detail. Ample simulation results show the dual-band operation of the proposed absorber at 2THz and 10THz, while an interesting tuning capability is provided by changing chemical potentials. Such a simple and adjustable wave absorber is in demand for numerous applications ranging from medical imaging to indoor communication.

A dual-band wideband high-gain slot loaded microstrip patch antenna

This paper presents a dual-band, wideband, high-gain microstrip patch antenna applied to 5G band. The antenna consists of two rectangular radiation patches of different sizes, connected by a microstrip line and fed by a coaxial line. The dual-band is achieved by both rectangular radiation patches producing dual target resonant frequency points. This antenna provides the freedom for adjusting both resonant frequencies independently. To increase the antenna bandwidth, long slots are loaded at specific positions on each rectangular patch, allowing for dual-mode resonance radiation in each frequency band. This antenna operates in a shorted-edge resonant mode, where metal grounding holes added on the patch act as shorting walls. The size of a radiation patch is only half that of a standard resonant mode patch, making this antenna compact in size. Measurement results show that the antenna has an impedance bandwidth of 4.98–5.56 GHz (11.0%) and 5.74–6.62 GHz (14.2%), which completely cover the 5G band of China (5.18–5.52 GHz and 5.74–5.82 GHz). The maximum measured realized gain is 8.1 dB in the low-frequency band and 10.2 dB in the high-frequency band. This antenna offers advantages of dual-band operation, broadband, low-profile, high-gain, which is suitable for 5G band applications with targeted coverage requirements.

An Optimization Design Method for Dual-Band and Wideband Patch Filtering Power Dividers

This paper proposes a new automatic design method based on continuous and binary optimization for dual-band and wideband filtering power dividers (FPDs). The designs utilize an optimization process to manipulate the multiple modes of a patch radiator. In this way, both dual-band and wideband operations can be achieved. Meanwhile, the filtering property is also taken into consideration during the optimization, which finally produces power dividers with filtering functions. The design process is highly automatic to minimize manual calculations and simulations. Finally, a dual-band filtering power divider whose center frequencies are 2.4 GHz and 6 GHz and a wideband filtering power divider operating from 3.7 GHz to 5.25 GHz are designed and fabricated for validation.

Dual-band 5G MIMO antenna with enhanced coupling reduction using metamaterials

This article introduces a miniaturized dual-band multiple input multiple output (MIMO) antenna with wide bandwidth and high isolation. The design incorporates ground plane modifications and utilizes metamaterials to achieve dual-band operation in the millimeter wave spectrum for 5G applications, specifically operating at the 28/38 GHz frequency bands. The proposed antenna maintains its dual-band functionality despite its compact size of 3.8 times 3.7 times 0.787 text {mm}^3 (without the feed line). The antenna is fabricated on a Rogers RT5880 substrate with a thickness of 0.787 mm and with relative permittivity varepsilon _r = 2.2. The MIMO system comprises two symmetric radiating elements positioned in close proximity, resulting in mutual coupling levels of - 20 dB and - 12 dB at 25 GHz and 37 GHz, respectively. Modifications are made to the ground length to enhance the isolation at the higher frequency band while embedding metamaterials effectively reduces the coupling at the lower frequency band. The incorporation of metamaterials leads to an enhanced bandwidth from 3.8 to 4.8 GHz in the desired lower band (24–28.8 GHz) and from 3.8 to 4.2 GHz in the higher band (36.6–40.8 GHz). The proposed system can operate across the 28/38 GHz bands using a compact design, thus offering reasonable isolation, an envelope correlation coefficient below 0.0001, and a significant diversity gain (> 9.99 dB). These attributes emphasize the system’s suitability for 5G millimeter-wave cellular communications.

Arbitrary ratio power splitter based on shape optimization for dual-band operation

Arbitrary ratio power splitters (ARPSs) are essential components in integrated photonics. However, most existing ARPSs are limited to operating within a single wavelength band. To address this limitation, in this paper, we propose a 1 × 2 ARPS capable of operating in multi-wavelength bands using the shape optimization method. Harnessing a compact footprint of 14 μm × 1.7 μm, a series of dual-band ARPSs (DBARPSs) with varying power splitting ratios (PSRs) are designed. Within the wavelength ranges of 1280–1340 nm and 1520–1580 nm, all of the DBARPSs have an excess loss of less than 0.55 dB, with PSR deviations falling within the range of −0.5 dB to 1 dB. The practical viability is confirmed through a fabricated DBARPS with a 3 dB PSR. Experimental results show that the PSR deviation is within −0.8 dB to 1 dB, while the excess loss remains below 0.54 dB within the bandwidths of 1280–1340 nm and 1520–1580 nm. Additionally, the same design methodology is extended to develop a high-performance 1310/1550 nm wavelength demultiplexer. The resulting device showcases remarkable performance, with insertion loss below 0.7 dB and extinction ratios higher than 17 dB across the specified wavelength ranges. Experimental outcomes align closely with the design objectives, underscoring the dual-band operational capability and robust generality of the approach outlined in this paper.

Dual-band transmission polarization conversion metasurface and its reconfigurable-phase design

Although abundant transmission polarization conversion metasurfaces (T-PCMs) have been reported, a dual-band T-PCM has only received little attention. Moreover, a reconfigurable-phase design of the T-PCMs is limited to a single-frequency band operation. There is hardly any literature to integrate dual-band and reconfigurable-phase features into a T-PCM. Herein, a dual-band T-PCM is presented based on the Fabry-Pérot-like resonant cavity. Particularly, the T-PCM meta-atom contains dual anisotropic patches distributed in different layers, and the novel dual-patch structure introduces multiple current modes to implement dual-band operation. Further, a reconfigurable-phase design of the dual-band meta-atom is performed, and four PIN diodes are embedded in each meta-atom to realize a 1-bit reconfigurable phase. In this way, the T-PCM meta-atom can simultaneously achieve high-efficiency 90° polarization rotation and 1-bit dynamic phase manipulation in 2.3–3.0 GHz and 4.4–7.5 GHz. By changing the encoding of the T-PCM, both cross-polarized transmission and beam manipulation are demonstrated in two divided bands. A sample is fabricated and measured to validate our design, and the results confirm the simulations. With the advantages of ingenious design and a clear operation mechanism, the novel dual-patch structure can be extended to the terahertz and optics regimes.

Dual-band transmissive linear to circular polarization converter with angular-stable and orthogonal polarizations

Abstract A dual-band angular-stable transmissive linear to circular polarization converter based on metasurface is proposed and demonstrated in this work. The converter consists of three layers. The top and bottom layers are formed by an array of double split-ring layers. The unit cell of the central layer contains a square loop nesting a slant dipole. The split-rings create two resonances, enabling dual-band operation. The slant dipole and square loop are useful for improving the quality of circular polarization conversion. It is shown that the proposed polarization converter converts the incident linearly polarized wave into circularly polarized wave with opposite polarization modes over the frequency ranges of 8.77–10.58 and 17.59–19.88 GHz. The angular stability is up to 60° for 3 dB axial ratio. Moreover, the thickness of unit cell has a wavelength below 0.06 at the lower band. Compared with other designs in the literature, the structure bears merits of wideband response, high angular stability, and low-profile property within dual-band operational region. To validate the design, a sample prototype was designed, fabricated, and measured. The measured results are in good agreement with the simulated ones.

Transparent Dual-Frequency CMUT Arrays for Photoacoustic Imaging.

The opaque ultrasound transducers used in conventional photoacoustic imaging systems necessitate oblique light delivery, which gives rise to some disadvantages such as inefficient target illumination and bulky system size. This work proposes a transparent capacitive micromachined ultrasound transducer (CMUT) linear array with dual-band operation for through-illumination photoacoustic imaging. Fabricated using an adhesive wafer bonding method, the array consists of optically transparent conductors [indium tin oxide (ITO)] as both top and bottom electrodes, a transparent polymer [bisbenzocyclobutene (BCB)] as the sidewall and adhesive material, and largely transparent silicon nitride as the membrane. The fabricated device had a maximum optical transparency of 76.8% in the visible range. Furthermore, to simultaneously maintain higher spatial resolution and deeper imaging depth, this dual-frequency array consists of low- and high-frequency channels with 4.2- and 9.3-MHz center frequencies, respectively, which are configured in an interlaced architecture to minimize the grating lobes in the receive point spread function (PSF). With a wider bandwidth compared to the single-frequency case, the fabricated transparent dual-frequency CMUT array was used in through-illumination photoacoustic imaging of wire targets demonstrating an improved spatial resolution and imaging depth.

Design of Multiband, Reconfigurable Coplanar Meander Antenna for WLAN Applications

This paper presents the implementation of Reconfigurable, Planar Meander Antenna operates at 2.45 GHz and 5.12 GHz for WLAN applications. In the proposed work the planar meander antenna is designed using FR4 substrate. In the meander antenna the varactor diodes are incorporated in the appropriate arm positions to achieve reconfigurability. In this, reconfigurability is accomplished using frequency tuning. Also, the principle of reconfigurability in meander antenna focuses size reduction and dual band operations. The meander structure is characterized for its operating frequency. A parametric study is done for finding the resonance in the appropriate arm positions of the meander antenna. The varactor diodes fixed meander antenna is tested using network analyzer. The comparison is made for the antenna designs of with and without varactor diodes for the establishment of reconfigurability. The effects of active components are ignored. The proposed antenna design is validated for its concurrence in both simulation and experimentation. The arm and the behavior of the frequency tuning is tested using the network analyzer. The reflection coefficient is -23.66dB and -18.41dB at 2.45 GHz and 5.1 GHz respectively. The overall size of the meander antenna is reduced by 76%. VSWR of the proposed antenna is 1.

MEMS-Switched Triangular and U-Shaped Band-Stop Resonators for K-Band Operation.

Triangular resonators re-shaped into Sierpinski geometry and U-shaped resonators were designed, linking them with single-pole-double-through (SPDT) RF MEMS switches to provide frequency tuning for potential applications in the K-Band. Prototypes of band-stop narrowband filters working around 20 GHz and 26 GHz, interesting for RADAR and satellite communications, were studied in a coplanar waveguide (CPW) configuration, and the tuning was obtained by switching between two paths of the devices loaded with different resonators. As a result, dual-band operation or fine-tuning could be obtained depending on the choice of the resonator, acting as a building block. The studied filters belong to the more general group of devices inspired by a metamaterial design.

Design and Analysis of a Low-Profile Dual-Band Circularly Polarized Monopole Antenna Based on Characteristic Mode Analysis

This paper presents the design of a simple dual-band circularly polarized monopole antenna using characteristic mode analysis. First, a dual-band elliptically polarized “L”-shaped monopole antenna with a partial ground is designed; then, a rectangular stub and a parasitic structure on the ground plane are implemented to achieve dual-band CP operation. To enhance impedance bandwidth and generate circular polarization in the upper band, the rectangular stub is attached to the “L”-shaped strip. The parasitic structure is employed for simultaneous dual-band CP radiation. Characteristic mode analysis is undertaken to predict the performance of the antenna before excitation. The modal analysis which is undertaken before excitation shows the natural modes that can be excited by the antenna structure to generate a dual-band CP response. The analysis gives approximate bandwidths that can be achieved by the antenna even before excitation. The overall dimension of the antenna is 0.379 λ 0 × 0.379 λ 0 × 0.015 λ 0 , where λ 0 is the corresponding free-space wavelength at 5.7 GHz. The measured -10 dB impedance bandwidth (ZBW) is realized to be 75.9% (4.5 GHz–10 GHz). The measured 3 dB axial ratio bandwidths (ARBW) at the lower and upper bands are 6% (5.6 GHz–5.95 GHz) and 28% (6.65 GHz–8.82 GHz), respectively. The proposed antenna features a simple and compact structure for Wi-Fi, WLAN, WiMAX, and C band applications.

A dual operating (27/38 GHz) high performance 2 × 4 MIMO antenna array for 5G new radio applications

This article presents an unique configuration of Multiple-Input Multiple-Output (MIMO) antenna array for functioning at 27/38 GHz millimeter-wave 5G new radio (NR) frequency bands applications. The suggested antenna is constructed with four MIMO elements, containing total of eight identical patches arranged in a 2 × 4 array configuration. The array also includes a separate non-connected rectangular ground plane with an overall dimension of 32.4 × 32.8 × 0.8 mm3. The single radiating patch elements are designed using spline resonator with H-shaped structures. The prototype model is realized using low cost FR-4 substrate and the obtained measurement results validate the analyzed simulated results. The suggested MIMO array antenna offers dual band operation with an impedance bandwidth of 8400 MHz covering 22 to 30.4 GHz and 8500 MHz ranging from 36.1 to 44.6 GHz. The proposed antenna achieves a peak gain of 8.75 dBi when operating at 27 GHz and 18.59 dBi at 38.1 GHz. Furthermore, it shows circular polarization characteristics by offering the axial ratio values significantly lower than 3 dB at 27 GHz and 38.1 GHz frequency bands. Additionally, the results indicate the favourable values of the diversity performance parameters with reference to Mean effective gain (MEG), Envelope correlation coefficient (ECC), Diversity gain (DG), Total active reflection coefficient (TARC), and Channel capacity loss (CCL). Moreover, it demonstrates high isolation (<−20 dB) within the desired bandwidth. These superior characteristics make it compatible for 5G NR frequency bands N257(26.5-29.5 GHz), N258 (24.5-27.5 GHz), N259 (39.5-43.5 GHz) and N260 (37-40 GHz), enabling its use in various countries including the China, European Union, Sweden, Korea, Japan, United States of America, Canada and Australia.

A novel dual-sense polarization reconfigurable dual-band microstrip antenna

In this paper, a novel dual-band, dual-sense, polarization reconfigurable dual coupled line square microstrip patch antenna is proposed. It comprises of a diagonal edge truncated square microstrip patch with a dual coupled line structure. The dual-band operation is realized by using dual coupled lines. They also aid in generating dual-sense of circular polarization (CP) at two resonances. The diagonal edge truncated square patch consists of four PIN diodes along with the bias circuit. It realizes a dual-sense of polarization reconfiguration like right-handed circular polarization (RHCP)/left-handed circular polarization (LHCP), linear polarization (LP)/LHCP, RHCP/LP at lower resonance f1 = 2.4 GHz and higher resonance f2 = 2.6 GHz respectively for different states of the diodes. The proposed antenna is designed, simulated, fabricated, and experimentally tested for validation. The experimental results of −10 dB reflection coefficient, 3 dB axial ratio for CP, gain, and radiation pattern characteristics at the two bands are acceptable and are found to be in concurrence with simulation results in all the states. The proposed antenna would be useful for multifunctional wireless communication applications.

A Compact Dual-Band ACS-Fed Frequency Independent Hook Loop Antenna for WLAN Applications

ABSTRACT Presented in this paper is a simple, small-sized, and hook-shaped monopole antenna fed by an Asymmetric Coplanar Strip (ACS) for different dual-band operations. The antenna operates at 3.5 and 5.2 GHz; hence, serving WiMAX and WLAN applications. Dual resonances were attained by integrating a quarter-wavelength strip with a C-shaped half-wavelength loop strip. The proposed antenna footprint is 20 × 7.9 mm2. Based on the achieved outcomes and the antenna compactness, it can be highly nominated for use in 3.5/5 GHz wireless communications applications and wireless gadgets.

A dual-band dual-polarized low-side-lobe transmitarray using independent amplitude and phase controllable elements

In this paper, a novel transmitarray (TA) element with independent control capability of amplitude and phase under dual-band dual-polarized operation is proposed. By changing the physical size of the TA element, the phase variation of the element can cover 360° at two bands. Moreover, the phase change of the frequency band is less than 30° when the phase of the other band is changed. Meanwhile, a higher maximal transmission amplitude can be maintained when varying the phase. Amplitude modulation is achieved by rotating the TA element. Utilizing the proposed TA element, a dual-band dual-linear polarization (LP) TA with low side lobe level (SLL) operating at 12.5 GHz and 14.25 GHz is designed. The SLL can be decreased by amplitude modulation of the elements. The measured peak gains of the proposed TA are 25.96 dBi and 25.89 dBi at 12.5 GHz and 14.25 GHz. In addition, the measured SLLs of the yoz/xoz planes are −22.4 dB/−22.4 dB and −22.5dB/−22.3 dB at 12.5 GHz and 14.25 GHz, respectively. The proposed TA shows good SLL performances and great application potential in satellite communication systems.

Plasmonic metafibers electro-optic modulators

Digitalizing optical signals through electric driving signals, electro-optic modulators (EOMs) are one of the cardinal elements in modern optical communications. Most of current EOM devices are targeting on-chip integrations, which routinely suffer from high coupling losses, complex optical alignments and single-band operations. In this study, we for the first time integrate a lumped EOM device on the endfaces of a single-mode optical fiber jumper for fast amplitude modulations. Profiting from ultrathin and high quality-factor plasmonic metasurfaces, nanofabrication-friendly and highly efficient EO polymers and coupling-free connections with fiber networks, our EOM is demonstrated to allow dual-band operations (telecom O band and S band) and high-speed modulations (~1 GHz at a bias voltage of ±9 V). This work offers an avenue to ‘plug-and-play’ implementations of EO devices and ultracompact “all-in-fibers” optical systems for communications, imaging, sensing and many others.

A K-/Ka-Band Diplexer-Integrated Simplified Rotary Joint Using Gap Waveguide Technology

This letter introduces a new <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$</tex-math> </inline-formula> -/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band diplexer-integrated simplified rotary joint. The stator and rotor are arranged to construct a guided-wave structure based on gap waveguide (GW) technology, which supports a stable rotation without leakage. A bandpass filter (lower band channel) and a two-path high-pass filter (upper band channel) are designed on the stator to form a diplexer to enable the wideband dual-band operation. A coaxial probe-based common port is located at the center of the rotor to achieve a smooth signal transmission in both bands. For demonstration, a prototype operating at 17.7–21.2 GHz ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$</tex-math> </inline-formula> -band) and 27.5–31 GHz ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band) is designed, fabricated, and measured. Experimental results show that the rotary joint has the maximum insertion loss of 0.4 and 0.9 dB in the two passbands. During the rotation, the insertion loss variation is less than 0.2 dB, guaranteeing a stable performance.

Theoretical Design of a Dual-Band TE01/TE02 Mode Gyrotron Traveling Wave Tube

A dual-band (K/Ka) TE01/TE02 mode gyrotron traveling wave tube is presented in this article. To suppress parasitic oscillations, a lossy-dielectric-loaded interaction circuit is employed. The particle-in-cell simulation results show that when it operates in K-band, the operating mode is the TE01 mode, with a peak output power of 87.1 kW, a saturated gain of 42.74 dB, and a −3 dB bandwidth of 0.7 GHz, and when it operates in Ka-band, the operating mode is the TE02 mode, with a peak output power of 62 kW, a saturated gain of 60.76 dB, and a −3 dB bandwidth of 2 GHz. Moreover, in the operating frequency range of the Ka-band, the overall gain is greater than 57 dB. To meet the requirements of dual-band operating, a dual-state magnetic injection gun is designed, a dual-mode coaxial cavity input coupler is proposed, and a dual-band output system is developed. All of these components showed excellent performance in simulations.

A high-gain dual-band shared-aperture array integrating zero-order-resonance patch and higher-order metasurface antenna

This letter proposes a high-gain shared-aperture array for vehicular communications which integrates the hybrid zeroth-order-resonance (ZOR) patch and the higher-order metasurface antenna (MA). In terms of each array element, four hybrid ZOR patches with shorting pins form a metasurface which is fed by slot coupling. Different from some reported designs which have more high-frequency elements than low-frequency ones, the whole array is composed of 4 times 4 hybrid ZOR patches operating in C band (4.74–5.12 GHz) and 2 times 2 MAs working in Ku band (13.0–14.0 GHz). Such a layout brings that the designed array has the benefit to reduce Ku-band loss. Measure results validate the dual-band operation and show that the antenna has its peak gains of 12.7 dBi and 17.2 dBi in these two bands, respectively, which can support vehicle-to-base station and vehicle-to-satellite communications.

Compact Sub 6 GHz Dual Band Twelve-Element MIMO Antenna for 5G Metal-Rimmed Smartphone Applications.

In this paper, a twelve-antenna system is designed for 5G smartphones with metal frames. The system is compact and operates on dual bands within the sub-6 GHz frequency range using multiple-input multiple-output (MIMO) technology. Two sets of six-antenna units are included in the system, arranged in a diagonal mirror-image configuration, and positioned at the center of the circuit board's longer edges. The profile height of each of the six-antenna units is only 3 mm, and the overall array dimensions are 105 × 3 × 3.1 mm3. A single antenna unit is 15 × 3 × 3.1 mm3 (0.173 λ × 0.035 λ × 0.036 λ, where λ equals the free-space wavelength of 3450 MHz). The arrangement of the antennas in the six-antenna units is parallel, with a 3 mm separation between adjacent antennas. The antenna structure comprises of an inverted L-shaped feed branch and two inverted L-shaped short-circuit branches integrated into part of the metal frame. The proposed array can form multiple resonance paths, achieving dual-band operation at 3300-3600 MHz and 4800-5000 MHz. The measured isolation of this twelve-antenna system within the operating frequency band is over 10 dB, and the measured antenna efficiency is greater than 36%. Therefore, the system is suitable for use in smartphones with high screen-to-body ratios and metal frames.