Broadband Gain Research Articles

Design and fabrication of reconfigurable, broadband and high gain complementary split-ring resonator microstrip-based radiating structure for 5G and WiMAX applications

Frequency reconfigurability and high gain are the two essential parameters of any antenna design, and these two parameters are successfully achieved in the antenna presented in this manuscript. The two RF switching diodes are used to alter the charge distribution over the patch region to achieve frequency reconfigurability. The fabrication carried out using the FR-4 material keeps the antenna cost low. The performance of the presented work is analyzed in terms of reflectance coefficient, total gain, bandwidth, directivity, fractional bandwidth, and normalized directivity. The novelty in the presented work is the filling of copper and liquid-based split-ring resonators in superstrate regions over the patch area to identify the performance improvement. The presented design provides the maximum frequency reconfigurability of 550 MHz, a minimum reflectance coefficient of −44.821 dB, and a maximum bandwidth of 462 MHz. The addition of superstrate layers will enhance the gain and maximum gain of 3.49 dB. The presented novel work will provide the multiband behavior which targets the different wireless communication applications like 5G communication and WiMAX.

Phase control in glass-composite for three-dimensional active waveguide with broadband response

Broadband optical amplification is crucially important for expanding the transmission capacity of optical communication system and resolving the issue of internet traffic. A major challenge is the development of broadband gain materials. Herein, a heterogeneity engineering strategy is proposed for constructing all-inorganic transparent composite with tunable and ultrabroadband luminescence. The composite is characterized by the glass matrix homogeneously embedded with highly dense nanocrystalline domains with the optimal crystallinity of ~63.7%. Notably, the formation dynamics and phase configuration of the composite can be controlled. As a result, the interesting optical response with tunable and ultrabroadband near-infrared luminescence from 1000 to 1800 nm can be realized. In addition, the embedded high density crystalline domains gift the composite with the excellent antilaser damage behavior and three-dimensional smooth active waveguide can be directly written by using femtosecond laser. This unique feature allows the creation of the integrated waveguide array device and the potential for broadband optical amplification is demonstrated. Results suggest that the proposed heterogeneity engineering strategy can not only be extended for exploitation of active composite system, but also development of three-dimensional broadband photonic devices with high integration level.

A 95 × 40 Gb/s DWDM transmission system using broadband and flat gain amplification of promoted parallel EDFA

A 95 × 40 Gb/s DWDM transmission system using broadband and flat gain amplification of promoted parallel EDFA

A broadband single-layer substrate integrated waveguide cavity-backed slot array antenna with improved gain

ABSTRACT A single-layer substrate-integrated waveguide (SIW) cavity-backed slot array antenna with broad impedance bandwidth and improved gain is presented in this paper. In the element design, a multi-branch slot and a pair of inclined slots are designed on the top layer of the SIW as radiating structure and the grounded coplanar waveguide feeding structure are used for impedance matching, which ensures that the triple special resonant modes with the odd TE120 mode, the half TE120 mode, and a hybrid mode can be excited successfully to obtain broad impedance bandwidth and high gain, because of its low order and adjacent working frequencies points. Following this, an array antenna consisting of four elements and a four-way microstrip feeding network using only single-layer substrate structure is simulated and fabricated. The measured impedance bandwidth of the four-element array antenna achieves up to 34.4% and the measure peak gain at desired frequency band is 14.4 dBi with an aperture efficiency of 71.1%. The measured results prove that the proposed design has advantages of simple structure, broadband, and high gain, which is expected to be applied in high-speed vehicular communication system.

Role of Thermally Occupied Hole States in Room‐Temperature Broadband Gain in CdSe/CdS Giant‐Shell Nanocrystals

AbstractGrowing CdSe/CdS nanocrystals from a large CdSe core, and employing a giant CdS shell, a continuous, broadband gain spectrum, covering the spectral range between the CdSe and the CdS band edge, is induced. As revealed by k·p calculations, this feature is enabled by a set of closely spaced S‐, P‐ and, for larger CdSe cores, D‐state hole levels, which are thermally occupied at room temperature, combined with a sparse density of electron states. This leads to a range of bleach signals in the transient absorption spectra that persist up to a microsecond. By extending a state‐filling model including relevant higher‐energy states and a Fermi–Dirac distribution of holes at finite temperature, it is shown that thermal occupancy can lower the gain threshold for excited states. Inclusion of Gaussian broadening of discrete transitions also leads to a smoothening of the gain threshold spectrum. Next to a direct measurement of the gain threshold, a method is also developed to extract this from the gain lifetime, taking advantage that population inversion is limited by Auger recombination and recombination rates scale with the exciton density as 〈N〉·(〈N〉 − 1). The results should be readily extendable to other systems, such as perovskite or III–V colloidal nanocrystals.

Broadband and high gain circularly polarised truncated corner square patch metasurface antenna using aperture CPW feed

Broadband and the high gain circularly polarised antenna are designed in a single-layered planar substrate. An array of 3 × 3 truncated corner square patches are designed as a metasurface antenna on one side of the substrate and the metasurface antenna is fed by a stub-loaded uniform aperture CPW feed on another side of the substrate. In the metasurface antenna, the size of the central patch is increased for improving the bandwidth of impedance bandwidth and 3 dB axial ratio. Furthermore, the amount of truncation is reduced in the patches surrounding the central patch to enhance the bandwidth of impedance bandwidth and 3 dB axial ratio bandwidth. The designed metasurface antenna has achieved an impedance bandwidth of 38.2% (4.5–6.63 GHz) with an axial ratio bandwidth of 13% (5.0–5.7 GHz). Moreover, the antenna has a peak gain of 10.36dBic. The simulation and measurement results are compared.

Raman gain control in optical fibers with orbital-angular-momentum-induced chirality of light.

Stimulated Raman scattering is a particularly robust nonlinearity, occurring in virtually every material because its spectral linewidth and associated frequency shift do not typically depend on phases or directions (i.e. wavevectors) of the interacting light beams. In amorphous materials such as glass fibers, Raman bandwidths are large, enabling its use as a broadband gain element. This ubiquity makes it a versatile means for achieving optical amplification or realizing lasers over a large range of pulsewidths at user-defined colors. However, this ease of deploying the effect also presents itself as a stubborn source of noise in fiber-based quantum sources or parasitic emission in fiber lasers. Here, we show that orbital angular momentum carrying light beams experiencing spin-orbit interactions yield novel phase-matching criteria for Raman scattering. This enables tailoring its spectral shape (by over half the Raman shift in a given material) as well as strength (by ∼ 100×) simply by controlling light's topological charge - a capability of utility across the multitude of applications where modulating Raman scattering is desired.

Design of a broadband U-slot loaded E-shaped patch antenna using characteristic mode analysis

This article introduces a characteristic mode analysis (CMA) based broadband and high gain microstrip patch antenna by embedding U-slot into an E-shaped patch in a single-layer radiating structure. The design and analysis of the antenna utilize the CMA to obtain the inherent modal currents induced in the E-shaped radiator. Out of possible radiating intrinsic modes, an undesired higher-order mode (HOM), adjacent to the upper band of the E-shaped patch, is efficiently excited with a secondary radiating slot (U-slot) to increase the bandwidth. Additionally, the U-slot creates another HOM with proper polarization and broadside radiation. Consequently, the overlapping of these new excited modes with the primary operating band of the E-shaped patch exhibits a broader bandwidth of 64.7% (4.7–9.2 GHz) and a peak gain of 10.6 dBi with an overall dimension of 1 . 4 λ 0 × 1 . 4 λ 0 × 0 . 1 λ 0 ( λ 0 being the free-space wavelength at a centre frequency of ≃ 7 GHz). The fabricated prototype agrees well with the simulation results, and the radiation patterns remain consistent over the entire bandwidth. Due to planar and broadband features, the proposed antenna is suitable for low-cost WLAN, Wi-Max, Wi-Fi 6E, and sub-6 GHz applications.

Dual Circularly Polarized 3-D Printed Broadband Dielectric Reflectarray With a Linearly Polarized Feed

A broadband dual circularly polarized (dual-CP) reflectarray based on 3-D printed dielectric materials is proposed in this article. A novel 3-D dielectric array element that enables the broadband linearly polarization (LP) to CP transformation is proposed. The unit cell consists of two orthogonal dielectric cuboids that adjust the phases of the two orthogonal LP waves independently and then combine them into a CP wave. The innovative unit cell design provides an extra degree of freedom in varying the geometries of the array elements in all three dimensions, which enables us to independently control the phases of the two LP waves. This maintains an equal amplitude and 90° phase difference condition across the entire reflectarray surface, realizing a broadband and high gain LP–CP reflectarray. The placement of the feed is also optimized to achieve the highest aperture efficiency. Finally, an off-set reflectarray was designed and fabricated using lost-cost 3-D printing. The reflectarray is able to provide both left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP), with just an LP feed. The measurements agree well with simulated results where the maximum realized gain and directivity at 34 GHz are measured as 27.9 and 28.1 dBi, respectively. The measured 3 dB gain bandwidth and aperture efficiency are 30% and up to 38%, respectively. More importantly, a broad 3 dB axial ratio (AR) bandwidth greater than 40% has been achieved for both LHCP and RHCP, covering almost the entire frequency band of interest, ranging from 26 to 40 GHz.

Two-band optical gain and ultrabright electroluminescence from colloidal quantum dots at 1000 A cm−2

Colloidal quantum dots (QDs) are attractive materials for the realization of solution-processable laser diodes. Primary challenges towards this objective are fast optical-gain relaxation due to nonradiative Auger recombination and poor stability of colloidal QD solids under high current densities required to obtain optical gain. Here we resolve these challenges and achieve broad-band optical gain spanning the band-edge (1S) and the higher-energy (1P) transitions. This demonstration is enabled by continuously graded QDs with strongly suppressed Auger recombination and a current-focusing device design, combined with short-pulse pumping. Using this approach, we achieve ultra-high current densities (~1000 A cm−2) and brightness (~10 million cd m−2), and demonstrate an unusual two-band electroluminescence regime for which the 1P band is more intense than the 1S feature. This implies the realization of extremely large QD occupancies of up to ~8 excitons per-dot, which corresponds to complete filling of the 1S and 1P electron shells.

Design a Broad-band High flatness Gain Low Noise Amplifier for radar Applications

Design a Broad-band High flatness Gain Low Noise Amplifier for radar Applications

Broadband Optical Amplification of Waveguide Cut‐Off Mode in Polymer Waveguide Doped with Graphene Quantum Dots

AbstractGraphene quantum dots (GQDs) showing a wide‐range tunability in their emission wavelength are promising materials for next‐generation optoelectronic applications. However, there are few studies on optical amplification functionalities for broadband emission of GQDs. Here, the authors demonstrate a broadband optical amplification of GQDs mixed with a polymer matrix. The GQD particles prepared by microwave‐assisted hydrothermal method show a large variation in their dimension and a broadband emission with a large Stokes shift. In a form of polymeric thin film, the GQDs exhibit amplified spontaneous emission (ASE) signal showing the broadband gain of ≈370–650 nm and the gain coefficient up to ≈4 cm–1. Cut‐off mode propagation is the origin of ASE signal generation. The optical amplification performance is found to be associated to the photoluminescence quantum yield, which is improved by the GQDs passivation with the polymer matrix. These results demonstrate that the GQDs are a promising active material as a wideband optical amplification medium.

High gain Vivaldi antenna from 26 up to 40 GHz for 5G applications

AbstractWe propose a directive broadband and high gain Vivaldi antenna in the Ka‐band (26–40 GHz) for 5G applications. To increase the gain of this antenna, we use a substrate lens and the quasi‐substrate integrated waveguide structure with the aim of reducing reflected waves and emphasizing the traveling waves. With this method, the gain is increased by 4.5 dBi in average and 7.5 dBi in the peak. The antenna has a good impedance matching in the whole band.

W-Band 광대역 저잡음 증폭기 설계

This paper presents a W-band broadband low noise amplifier (LNA). The proposed LNA was designed and verified using a 100 nm GaAs pHEMT. To achieve broadband low noise and gain characteristics, peak gain distribution was employed. The LNA comprised four gain stages and a shunt inductor at the input stage to prevent the device damage. The LNA achieved a 16.2 dB gain and 5.5 dB noise figure in an area of 1.78×0.743 mm2

Design of low RCS high gain CP slot antenna using polarization conversion metasurface

ABSTRACT In this work, a circularly polarised (CP) slot antenna based on linear polarisation conversion metasurface (PCM) is proposed for broadband radar cross-section (RCS) reduction and gain improvement. The proposed metasurface is designed using the chequerboard alignment of PCM unit cells and its mirrored ones to meet the phase cancellation principle required for RCS reduction. An improved loading technique of the PCM consisting of rearrangement of the PCM unit cells across the radiating slot is employed to enhance the gain of the proposed antenna. The measured results show that the operating bandwidth of the proposed antenna is in the range of 9.8–10.8 GHz. The maximum gain achieved is 2.4 dB more than the reference antenna while the 3-dB axial ratio bandwidth (ARBW) obtained is 9.8–10.6 GHz. The proposed antenna achieves an average RCS reduction of 11 dB in the frequency region of 6–18 GHz in comparison to the reference antenna.

Design and Fabrication of Low Polarization Dependent Bulk SOA Co-Integrated With Passive Waveguides for Optical Network Systems

Low polarization-dependent semiconductor optical amplifiers (SOA) co-integrated with passive circuits via an easy fabrication process are highly demanded in optical communication systems. However, despite several SOAs have been reported, co-integration of polarization-independent bulk SOA with passive waveguides in the InP platform to generate complex systems remains an issue. In this work, we design, simulate, fabricate and characterize a low polarization-dependent SOA based on a bulk active layer that is co-integrated with passive waveguides and exhibits its potential application to realize photonic integrated circuits. Simulation results are in good agreement with the experimental results. Based on the simulation results, the designed SOAs with the length of 300 μm, 750 μm, and 1500 μm cover broadband with 3-dB bandwidth of around 65 nm, 40 nm, and 37 nm, respectively. Characterization of SOAs with different lengths between 300 μm and 1500 μm co-integrated with passive waveguide has been performed. Broadband gain and polarization-dependent gain (PDG) less than 2 dB is measured for 300 μm SOA. Also, at 1550 nm, output saturation power of 12.8 dBm is achieved at the current density of 11.6 kA/cm². For the longest SOA with 1500 μm length, the higher gain of 16 dB with PDG lower than 2.5 dB and saturation power of 7.4 dBm at the wavelength of 1588 nm and current density of 4.1 kA/cm² are achievable. Thus, one could design SOA based photonic circuits with higher gain and saturation power and low PDG by exploiting different SOA lengths and design at the wavelength of interest, opening to potential application in photonic integrated circuits like low-loss and polarization-insensitive switches.

Broadband near-infrared emission in Bi-Tm co-doped germanium silicate glasses

• Broadband luminescence in the waveband region of 1000–2000 nm is realized. • The origin about the emission bands at 952, 1156, 1428 and 1800 nm is discussed. • The energy transfer mechanism between bismuth and thulium is proposed. Broadband gain materials are of considerable interest for the next generation telecommunication system because of their potential for realization of the optical amplification in the whole telecommunication low-loss window. One of the major challenges is to extend the operation waveband of the gain materials. Here, we report the synthesis and spectral analysis on the Bi-Tm co-doped germanium silicate glasses. Various characteristic emission bands at 952 nm, 1156 nm, 1428 nm and 1800 nm are analyzed and their origins are identified. By tuning the excitation wavelength, the broadband near-infrared emission in the 1000–2000 nm with smooth shape and full width at half maximum of ∼450 nm is achieved. The physical mechanism based on the energy transfer between Bi n m + and Tm 3+ is proposed for explain the interesting luminescence phenomenon. The results provide valuable reference for exploration of the novel broadband gain materials for fiber amplifier.

High Gain Broadband Power Amplifier Design Based on Integrated Diplexing Networks

This letter presents an enhanced gain broadband power amplifier (PA) design approach that is based on using an integrated diplexer with a phase compensation network to combine PAs of narrower bandwidths (BWs) over a wider overall bandwidth PA. The input and output matching networks of each amplifier are individually synthesized using a wideband matching network. The diplexer is designed using a lowpass/highpass topology approach. The separate amplifiers are integrated with the proposed diplexer, resulting in extended bandwidth and enhanced gain. For verification purposes, a broadband PA is designed and implemented over the frequency range of 2–4 GHz. Measurements demonstrate that the output power varies between 40.1 and 41.2 dBm with a drain efficiency (DE) of 61%–75%. The proposed design achieves a high small-signal gain of 12.5–15.3 dB. The reported saturated power gain is 10.1–11.2 dB.

PbS quantum dots and BaF2:Tm3+ nanocrystals co-doped glass for ultra-broadband near-infrared emission [Invited

With the rapid growth of optical communications traffic, the demand for broadband optical amplifiers continues to increase. It is necessary to develop a gain medium that covers more optical communication bands. We precipitated PbS quantum dots (QDs) and BaF2:Tm3+ nanocrystals (NCs) in the same glass to form two independent emission centers. The BaF2 NCs in the glass can provide a crystal field environment with low phonon energy for rare earth (RE) ions and prevent the energy transfer between RE ions and PbS QDs. By adjusting the heat treatment schedule, the emission of the two luminescence centers from PbS QDs and Tm3+ ions perfectly splices and covers the ultra-broadband near-infrared emission from 1200 nm to 2000 nm with bandwidth over 430 nm. Therefore, it is expected to be a promising broadband gain medium for fiber amplifiers.

A New Approach for Designing and Analysis of High Flat Gain Broadband Low Noise Amplifier Using Real Frequency Technique

This paper introduces a high flat gain broadband Low Noise Amplifier (LNA) design approach, which is based on using a new methodology of Real Frequency Technique (RFT). To get this done, the optimum matching network has been designed with second-order LC lumped elements to minimize the Noise Figure (NF) and maximize the Transducer Gain (GT) based on selecting the optimum (ZS, ZL) LNA terminations that have been used over a 2.1-4.2 GHz. The design has demonstrated a high stable gain in the range of 19.19 –18.73 dB with ± 0.2 dB gain flatness over the specified band. Moreover, the NF has been obtained at 0.68 – 0.82 dB and a stable operation throughout a broad bandwidth. Furthermore, the proposed method results have been compared with an analytical methodology which is based on computing equivalent input and output circuits for the transistor model using its scattering parameters. For the verification purpose, the performances of the synthesized amplifier are compared using MATLAB platform and ADS simulation software. The output results have a good agreement with the proposed method outcomes, which makes this method a new promising technique for the high flat gain broadband LNA design.