Band Operation Research Articles

Design of a Compact Wearable Antenna for IoT Enabled Bio-Telemetry in Diagnostic Health Monitoring System

The structure developed involves the etching of Moore’s curve onto a conventional rectangular patch and subsequently encasing it in a rectangular loop along with a defected ground structure. The proposed antenna exhibits dual-band Since the Internet of Things (IoT) enabled medical diagnostic system requires unprecedented precision and automation for better health care delivery, therefore in such systems, the performance of antennas for efficiently transferring data (vital functions of the human body) is an important task. To address these concerns, a mechanically robust, novel hybrid wearable on-body antenna inspired by Moore’s fractal based geometry and conventional rectangular loop for a diagnostic health monitoring system is proposed. with bandwidth ranging from 1.38 - 1.8 GHz and 2.25 - 4.88 GHz respectively, covering WMTS, ISM, and Personal Communication band besides covering a portion of UWB band also. The two operating bands of the antenna offer a fractional bandwidth of 38.5% and 73.7% respectively. It is observed that the average specific absorption rate (SAR) over the multi-layer phantom is 0.025 W/kg for an input power of ≈ 24 dBm. In comparison to the recently reported wearable antennas, the design proposed has a compact footprint of 0.135 λo x 0.093λo x 0.004λo besides offering a dual- band of operation, peak gain of 2.2 dBi, overall radiated efficiency of 95% and SAR below 0.025 W/kg. The design is fabricated using Rogers 5880 substrate (semi-flex) of thickness 0.75 mm.

Efficient ultra-broadband low-resolution astrophotonic spectrographs

Broadband low-resolution near-infrared spectrographs in a compact form are crucial for ground- and space-based astronomy and other fields of sensing. Astronomical spectroscopy poses stringent requirements including high efficiency, broad band operation (> 300 nm), and in some cases, polarization insensitivity. We present and compare experimental results from the design, fabrication, and characterization of broadband (1200 - 1650 nm) arrayed waveguide grating (AWG) spectrographs built using the two most promising low-loss platforms - Si3N4 (rectangular waveguides) and doped-SiO2 (square waveguides). These AWGs have a resolving power (λ/Δλ) of ∼200, free spectral range of ∼ 200-350 nm, and a small footprint of ∼ 50-100 mm2. The peak overall (fiber-chip-fiber) efficiency of the doped-SiO2 AWG was ∼ 79% (1 dB), and it exhibited a negligible polarization-dependent shift compared to the channel spacing. For Si3N4 AWGs, the peak overall efficiency in TE mode was ∼ 50% (3 dB), and the main loss component was found to be fiber-to-chip coupling losses. These broadband AWGs are key to enabling compact integrations such as multi-object spectrographs or dispersion back-ends for other astrophotonic devices such as photonic lanterns or nulling interferometers.

A Dual-Band 8-Antenna Array Design for 5G/WiFi 5 Metal-Frame Smartphone Applications.

This paper presents a dual-band 8-port multiple-input multiple-output (MIMO) antenna specifically designed for fifth-generation (5G) smartphones, featuring two open-slot metal frames. To enhance impedance matching and improve isolation between adjacent antenna elements, each antenna element employed a coupling feed. All simulation results in this paper come from Ansys HFSS. The operational frequency bands of the proposed antenna spanned 3.36-4.2 GHz for the lower band and 4.37-5.95 GHz for the higher band, covering 5G New Radio (NR) bands N78 (3.4-3.6 GHz) and N79 (4.4-4.9 GHz), as well as WiFi 5 (5.15-5.85 GHz). Notably, the antenna demonstrated outstanding isolation exceeding 16.5 dB within the specified operating bands. The exceptional performance positions the proposed antenna as a promising candidate for integration into 5G metal-frame smartphones.

Mutual coupling reduction of a two-port MIMO antenna using defected ground structure

In response to the escalating demand for high data rates and the expanding user base, multiple input multiple output (MIMO) technology has recently become of paramount importance in addressing the imperative for high-capacity communication systems aligned with emerging standards. In this paper, a single antenna element that achieves a wideband frequency coverage by adjusting the slots ‘dimensions and a satisfactory gain of 6.4 dBi is presented. To enhance the antenna's gain and capabilities, we introduced a MIMO antenna designed to operate within the frequency range of 36.8 to 40.9 GHz. The proposed MIMO antenna configuration consists of two-element arrays etched on a compact 25.94×26.76×1.3 mm³ Rogers RT/duroid 5880 substrate. While maintaining the operational band and enhancing gain, a critical challenge involving inadequate isolation between the two antenna elements is encountered due to the confined area. To effectively tackle this issue, a parametric study on the inter element distance between antennas is conducted and Defected Ground Structure (DGS) is implemented. This refinement results in a substantial 3.6 dB enhancement in isolation, which is found to be lower than -31 dB, a notable improvement in impedance matching, and a remarkable high gain of approximately 7.7 dBi is achieved. Besides, the analysis of the MIMO metrics demonstrates that they consistently fall within acceptable ranges, with the antenna showcasing an envelope correlation coefficient of approximately 0.005 and a commendable diversity gain of around 9.99 dB. The proposed antenna's combined attributes, including its compact, simple, and low-profile design, position it as a highly promising choice for 5 G communication system and future miniature devices intended for Internet of Things (IoT) applications.

In-band dual-polarization RCS reduction of waveguide slot array antenna integrated with AMC and PEC chessboard structure

An in-band low radar cross section (RCS) waveguide slot array antenna (WSAA) is proposed by using a chessboard structure composed of artificial magnetic conductor (AMC) and perfect electric conductor (PEC), which serves as the antenna radiator. The method for RCS reduction is the reflection energy cancellation. Standing wave array is used to achieve higher energy efficiency and more compact antenna structure. Experimental results show that the in-band monostatic RCS is sufficiently reduced with the chessboard structure application for both co- and cross-polarized incident waves, where 10-dB RCS compression is realized among the frequency range of 9.7–9.91 GHz for co-polarization and 9.5–9.85 GHz for cross-polarization with maximum RCS reductions of −13.3 dB and −11.9 dB, respectively. Meanwhile, the designed WSAA maintains the high gain characteristics of the original WSAA. The paper provides a simple, practical and effective strategy for stable RCS compression in the operation band of waveguide antenna array, which has potential applications in stealth platforms.

Dual-band and spectrally selective infrared absorbers based on hybrid gold-graphene metasurfaces

In this paper, we propose a dual-band and spectrally selective infrared (IR) absorber based on a hybrid structure comprising a patterned graphene monolayer and cross-shaped gold resonators within a metasurface. Rooted in full-wave numerical simulations, our study shows that the fundamental absorption mode of the gold metasurface hybridizes with the graphene pattern, leading to a second absorptive mode whose properties depend on graphene’s electrical properties and physical geometry. Specifically, the central operation band of the absorber is defined by the gold resonators whereas the relative absorption level and spectral separation between the two modes can be controlled by graphene’s chemical potential and its pattern, respectively. We analyze this platform using coupled-mode theory to understand the coupling mechanism between these modes and to elucidate the emergence and tuning of the dual band response. The proposed dual-band device can operate at different bands across the IR spectrum and may open new possibilities for tailored sensing applications in spectroscopy, thermal imaging, and environmental monitoring.

An ultrathin wideband linear-to-circular polarization conversion metasurface for X-band applications

A specialized ultrathin metasurface has been developed to transform a linearly polarized incident wave into a reflected wave with circular polarization across a wide range of frequencies. The unit cell consists of two modified L-shaped structures that convert the incident linearly polarized wave to a circularly polarized wave. The axial ratio bandwidth of the reflected wave ranges from 8.19 to 11.08 GHz, exhibiting a fractional bandwidth of 30%. The dimensions of the unit cell are 7 × 7 ×1.6mm3 (0.225λ×0.225λ×0.051λ) where λ represents the center frequency within the operational frequency band. The proposed design not only provides a wide bandwidth but also is ultrathin as the dimensions are much less than λ/12. Finally, the proposed metasurface is fabricated and tested. The results obtained are in significant concurrence with the simulated results. Hence, it can be used in various applications, including implementation in multi-beam antennas, beam-scanning antennas, wireless systems, weather monitoring, radar tracking, and navigation systems.

1.94 & 2.04 µm dual-band four-wavelength-switchable single-frequency narrow linewidth fiber laser using a novel fs-laser direct-written polarization-dependent four-channel filter

We present a dual-band four-wavelength-switchable single-frequency thulium-holmium co-doped fiber laser (THDFL) utilizing a novel band-switchable polarization-dependent four-channel filter (BS-PDFCF). The filter incorporates two high-birefringence fiber Bragg gratings (HB-FBGs) and an electrical-controlled optical switch (EC-OS). Specifically designed for operation in the 1.94 μm and 2.04 μm bands, two HB-FBGs are fabricated using femtosecond (fs) laser direct-writing technology in two segments of polarization-maintaining fibers via a point-by-point method. Each HB-FBG features two narrow-band reflection channels with perpendicular polarization directions. The EC-OS switches the operation band of the BS-PDFCF. A 1.2 m long dynamic ultra-narrow-band filter is employed in the THDFL to achieve single-longitudinal-mode oscillation. The THDFL achieves exceptional output performance, including four single-wavelength and two dual-wavelength operations, spectral wavelength and power fluctuations of ≤0.012 nm and ≤0.386 dB, respectively, OSNRs of >76 dB, RINs of ≤−142.48 dB/Hz@≥5 MHz, linewidths of ≤3.59 kHz@1.94 μm band and ≤5.46 kHz@2.04 μm band, and output power fluctuations of ≤0.109 dB in a measurement time span of 30 min.

A low profile circularly polarized metasurface-based ultra-wideband 4x4 MIMO antenna for 5G NR band FR2 frequencies

This article presents a polarization conversion metasurface-based low-profile ultra-wideband circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with high performance that is specifically designed for operating in 5G New Radio (NR) bands in frequency range 2 (FR2). For these frequency bands, the 4-port MIMO antenna is being proposed for the first time and is capable of being operated in all of the newly created radio frequency bands in the 5G FR2 region. The main advantage of the proposed configuration is that it requires no isolation/decoupling circuit and the antenna elements are placed orthogonal to their adjacent elements. The 4x4 MIMO antenna offers a good impedance bandwidth of 111.09 % ranging from (12.87–45.02) GHz below − 10 dB reflection coefficient with a minimum isolation of –23.77 dB and maximum isolation of −52.53 dB. The maximum peak realized gain of the 4x4 MIMO antenna without metasurface is 8.14 dBi in the operating band. An improvement of 47 % in the peak realized gain was observed after stacking the metasurface on top of the radiating patch. The proposed antenna produces a circular polarization (CP) in the desired operating band. The 3-dB axial ratio impedance bandwidth for the lower band in millimeter wave (mm-Wave) is 14.13 % ranging from (23.22 – 26.75 GHz) and for the upper band is 7.92 % ranging from (40.82 – 44.19 GHz). Initially, the proposed antenna is designed for a single element and it is extended for a 4-element MIMO with added 4x4 metasurface unit cells for improvement of gain and polarization conversion. The simulated and measured results are in good agreement. In addition to that, the envelope correlation coefficient (ECC), channel capacity loss (CCL), total active reflection coefficient (TARC), mean effective gain (MEG), and diversity gain (DG) are calculated and simulated for the proposed four-element MIMO antenna. The designed metsurface-based circularly polarized MIMO antenna covers all 5G new radio frequency bands in FR2 and hence the designed antenna is applicable for 5G NR band FR2 in mm-Wave communications.

Robust multi-band acoustic router by hybridizing distinct topological phases

The acoustic router, capable of guiding sound waves along specific paths, holds a significant value in both science and engineering. Compared to traditional methods of implementing acoustic routing, the recently developed concept of topological acoustics, with its nontrivial topological phases, offers the potential to achieve a robust acoustic routing device. However, current investigations primarily focus on individual topological phases within a single bandgap, thereby limiting the exploration of diverse topological phases in multiple bandgaps and their hybridizations. In this study, we utilize topological acoustics to construct a robust dual-band acoustic router, which is challenging to achieve with traditional acoustics. By calculating Chern and valley topological phases in different bands, we reveal the competitive relations between different topological phases in a specific bandgap. Furthermore, by modifying the boundary meta-atoms, we have increased the operational frequency bands and proposed a triple-band acoustic router.

State-constrained control strategy for safe navigation trajectory tracking of hovercraft based on improved barrier Lyapunov function

This study addresses the challenge of trajectory tracking control for underactuated hovercraft by utilizing an improved integral barrier Lyapunov function to ensure safe and efficient navigation in the presence of uncertain dynamics and environmental disturbances. The research introduces an improved barrier Lyapunov function tailored for both constrained and unconstrained systems by integrating prescribed performance control (PPC) with a log-type barrier Lyapunov function (LBLF). This function effectively limits tracking errors in both position and heading to within a predetermined range. To ensure the hovercraft's navigational stability at high speeds, the paper presents a novel, time-varying integral barrier Lyapunov function (IBLF) with both unilateral and bilateral asymmetric constraints, specifically designed to control surge speed and yaw angular velocity. This ensures the maintenance of surge speed above the critical resistance peak speed and keeps the yaw angular velocity within a secure operational band. The study also introduces a finite-time disturbance observer (FTDO) to estimate the system's uncertainties. Theoretical analysis confirms that the tracking errors are ultimately uniformly bounded, establishing Lyapunov stability. Simulation results substantiate the superiority and efficacy of the proposed control strategy.

Characterization of the optical gain at 1550 nm of erbium-oxalate single crystals

Erbium is well-recognized as a key element for optical amplification at the 1550 nm operation band. However, the limited solubility of this material in vitreous matrices sets a critical constraint to the achievable optical gain, which limits its applicability in photonic integrated platforms. One of the solutions to increase the concentration of erbium is to employ a crystalline structure instead of a glass. In this paper, we characterize samples of erbium and erbium-ytterbium oxalate single crystals synthesized using the gel diffusion method. X-ray diffraction spectra and thermogravimetric analyses reveal that the synthesis method indeed generated the expected compound, and the pump-and-probe experiments demonstrate an on-off gain coefficient of ≈ 6.5 dB/mm, making this material a high-potential candidate for the implementation of integrated optical amplifiers.

Dual-band GPS/LoRa antenna for internet of thing applications

This paper presents the design and characterization of a compact dual-band microstrip antenna for GPS and long range (LoRa) internet of thing (IoT) applications. The antenna operates at 868 MHz and 1.57 GHz and has a gain of 3.35 dBi and 5.08 dBi, respectively. The antenna design is optimized using CST microwave studio software (MWS®), and both simulation and measurement results are in close agreement. The antenna features a directional E-plane and omnidirectional H-plane radiation pattern in each band of operation. The proposed antenna’s compact size and dual-band capability make it suitable for IoT applications that require GPS and LoRa communication in a small form factor. The results presented in this paper demonstrate the feasibility and effectiveness of the proposed antenna design.

A novel differential‐fed frequency beam scanning antenna with low sidelobe

AbstractIn this letter, a novel differential‐fed frequency beam‐scanning antenna is introduced. This differential structure is achieved by leveraging quasi‐Yagi radiating elements within a four‐layered geometry. Within this configuration, the element is excited by a pair of out‐of‐phase slow‐wave meander lines, through which differential signals are transmitted. These lines can be seamlessly integrated with other differential circuits. To ensure robust coupling, a broadside coupling structure is incorporated between adjacent layers. To corroborate theoretical insights, a prototype was constructed and tested. Measurements have shown that the primary beam can be scanned from −33.5° to +32.6° on a lateral plane, covering an operational frequency band of 9–11 GHz. Throughout this frequency range, a consistent peak gain of approximately 16.4 dBi is observed for the antenna.

A Ku band low-voltage and low-power CMOS low-noise amplifier with bulk isolation techniques

Abstract In this paper, a broadband(12-18G) low-noise amplifier (LNA) using 65-nm CMOS technology for satellite communication is presented. This LNA was designed in a cascode common source with inductive degeneration topology. In addition, the bulk isolation technique is employed to make the proposed LNA have a higher gain. Furthermore, a two-stage cascaded configuration combined with inductive parallel peaking technology is utilized to make the LNA achieve a wide operating band. For validation, we design this LNA in a 65nm CMOS technology. The simulated results show that S21 of 17.7dB ± 0.5dB, the input/output return loss of -10dB to -33dB and -12dB to -23dB, respectively. It offers the minimum noise figure (NF) performance of 3.33dB, reverse isolation(S12) better than 60dB, and third-order input point (IIP3) of -22.8 dBm obtained over the band of interest. Excluding the output buffer stage, the LNA is consuming 5.1 mW at a supply voltage of 0.8V and its layout area occupies 0.205 mm2.

Wideband Low-Profile Fabry-Perot Cavity Antenna with Metasurface

A novel Fabry-Perot cavity (FPC) antenna with metasurface is presented, which can achieve broad bandwidth and low profile. Traditional FPC antennas, with rectangular microstrip antennas as feeds, have limited impedance bandwidth and struggle to make a compromise in the gain bandwidth and maximum gain value. To obtain wide bandwidth, the FPC antenna proposed in this paper utilizes a feed antenna loaded with parasitic patches. To widen impedance bandwidth and gain bandwidth and reduce the profile, a positive phase gradient partially reflective surface (PRS) and an artificial magnetic conductor (AMC) are located above and below the feed antenna, respectively. The phase property of the PRS and AMC also brings in a more smooth gain value curve. To further increase gain values, four metal reflector plates are located around the proposed antenna. The overall dimension of the antenna is 2.5λ0×2.5λ0×0.25λ0 (λ0 is the free space wavelength at 7.5 GHz). Simulated results show that the resonant cavity antenna proposed in this letter exhibits an impedance bandwidth of 13.3% (7–8 GHz) and a 3 dB gain bandwidth of 14.3% (7.02–8.10 GHz). The maximum gain in the whole operating band is 14.5 dBi. The measured results are in good agreement with the simulated ones.

Design of Enhanced Wide Band Microstrip Patch Antenna Based on Defected Ground Structures (DGS) for Sub-6 GHz Applications

In this paper a comprehensive comparative study of three distinct microstrip patch antenna (MPA) designs, each optimized for the sub-6 GHz applications, is presented. The initial design phase utilized a Rogers RT 5880 substrate with a permittivity (εr1) of 2.2 and a thickness(H1) of 1.42 mm. The proposed model achieved a resonance band ranging from 4.8 to 7 GHz, with a bandwidth of 2.2 GHz and a return loss (S11) of -20 dB. Subsequent enhancements involved integrating a Barium Strontium Titanate (BST) thin film (εr2 = 250, thickness(H2) = 0.005 mm), effectively shifting the operational band to 3.5-5.3 GHz. The final design iteration, which incorporated both BST and a Defective Ground Structure (DGS), represented a substantial advancement, achieving wideband operation from 1.8 to 6 GHz, expanding the bandwidth to 4.2 GHz, and improving the S11 to -25 dB. This integration also resulted in a compact antenna size of 30 x 26.5 x 1.42 mm³. These findings underscore the synergistic impact of BST and DGS in enhancing MPA design, marking a significant progression in antenna technology, vital for a range of wireless communication.

Design of dual circular polarized stacked patch antenna for BeiDou navigation satellite systems

In this article, a design of two-layered, dual circular-polarization (CP) and dual-band path antenna is presented for BeiDou navigation satellite (BDS) system applications. A single 50-Ω Co-axial probe feeding arrangement is employed to achieve dual-band operation and it feeds both the antennas simultaneously. This mode introduces the CP radiation on both upper (RHCP) and lower (LHCP) operation bands. The impedance bandwidth is further widened by accommodating two semi-circular stubs on the top patch. The fabricated and experimentally validated prototype radiates at 1.82 and 3.45 GHz (center frequency). The upper and lower operating band exhibits right and left-handed CP radiations, which constructs dual-band operation. The fabricated prototype has a physical size of πr2 × 0.024 λg with an antenna profile of 2.38 mm (0.024 λg). The experimentally validated upper and lower bands impedance bandwidth with |S11| < −10 dB are 21.1% and 11.1%, respectively. The fabricated prototype is a good candidate to use in BDS applications. [Q2

A low-profile high-isolation endfire MIMO antenna based on spoof surface plasmon polaritons for X-band applications

This work proposes a three-port, low-profile, coplanar endfire multiple-input-multiple-output (MIMO) antenna based on spoof surface plasmon polaritons (SSPPs). The proposed antenna comprises a coplanar waveguide (CPW)-fed SSPPs transmission line (TL). A transition to transform the CPW quasi-TEM mode to the SSPPs mode. The radiator section with asymmetric discontinuities converts the bounded SSPPs waves into radiating waves. The proposed MIMO antenna exploits the inherent feature of high isolation in the SSPPs TL due to its strong field confinement competency. Wider beamwidths for ample azimuth and elevation coverage with a stable pattern in the endfire direction are achieved in the 9.52–11.23 GHz operating band. In the operating band, the MIMO antenna has an average realized gain of 6 dBi. Mainly, it has high isolation below -35 dB (measured) in the operating range, a maximum envelope correlation coefficient (ECC) of 1.5 × 10−3, and a total active reflection coefficient (TARC) value below 0.3. The measured results are closely matched with the simulated ones in terms of S-parameters, radiation pattern, ECC, TARC, and CCL.

Design Procedure of Cascaded Multilevel Inverter for High-Power Amplifier in SONAR System

In recent years, there has been a trend toward expanding the operating frequency range and increasing the output power of Sound Navigation and Ranging (SONAR) systems to enhance their acoustic detection capabilities. However, due to this increase in operational power, the electrical capacity of amplifiers for SONAR system operation also increases, necessitating High-Power Amplifiers. When configured with a single amplifier, as in conventional methods, the volume of amplifiers increases due to volumetric increases in heat dissipation, components, and windings. These issues are detrimental to SONAR amplifier installation, mobility, maintenance, and equipment lifespan due to stress on individual components. Additionally, amplifiers for SONAR systems are comprised of power conversion devices, transformers for LC filters and matching, necessitating consideration of LC filters and matching transformers for enhancing voltage quality and efficiency to improve amplifier performance transmitted to SONAR transducers. However, previous research has focused on single-amplifier design methods, neglecting such considerations. Therefore, this paper proposes a design technique that overcomes the drawbacks of using the conventional design method by configuring multiple H-bridge inverters in a cascade format and utilizes one of the optimization algorithms, Particle Swarm Optimization (PSO), to derive amplifier design techniques that optimize component parameters for enhancing high-capacity amplifier performance. Subsequently, theoretical analysis, simulations, and experimental results comparing the proposed high-power amplifier design method with conventional single-amplifier design methods demonstrate similar error rates in operational frequency bands.