Top Layer Of Substrate Research Articles

An in‐band full‐duplex antenna for 2.4 GHz WLAN using differential‐feed based neutral coupling for isolation enhancement

AbstractThis article introduces a unique design approach for a compact in‐band full‐duplex (IBFD) antenna with good isolation in a wider bandwidth at the 2.4 GHz WLAN. The meander slot baluns are innovatively constructed in the feeding network, one balun on the top substrate layer and the other on the bottom substrate layer of the ground, to realize double differential feeding and polarization diversity. The metallic vias that connect one of the baluns in the feeding network with the co‐radiating patch further reduce the antenna's overall size. The balun's neutral coupling characteristics of differential potentials, which reduce the leakage currents by creating null potential, and differential filtering, which suppresses the leakage currents by non‐coupling fields, generate high isolation in the antenna. The designed balun offers a stable differential feed with a trivial magnitude and phase imbalances of (0.04–0.06) dB and , respectively. The antenna offers a minimum isolation of 78 dB with a wider bandwidth of 130 MHz. The far‐field measurement shows broadside radiation with low cross‐polar levels of less than −32 dB. A prototype is fabricated on FR‐4 substrate layers with an overall size of (0.8 × 0.8 × 0.012) ( is the free space wavelength of the frequency GHz) to validate the proposed design performance. The measured results of the prototype properly correlate with the simulated results.

How does microorganism in different zones cooperatively promote N2O emissions from SWIS during freeze-thaw?

Subsurface wastewater infiltration systems (SWIS) are environmentally-friendly technologies for domestic wastewater treatment, where pollutants are removed by physical, chemical and biological reactions. However, SWIS also produce nitrous oxide (N2O), a potent greenhouse gas. Distribution of dissolved oxygen and nitrogen in SWIS determines denitrification process, which affects microbial activity and N2O release degree in different layers of system. Top layer of SWIS substrate is exposed to environmental factors such as freeze-thaw (FT), which changes microbial community structure in different substrates. Exact mechanisms of microbial-mediated N2O emissions in SWIS are still unclear despite extensive research. Therefore, this study simulated FT process using in-situ SWIS, to investigate how FT disturbance affects microbial community structure and N2O release in SWIS profiles. Results showed that after the ninth freeze-thaw cycle, FT stimulated anaerobic bacteria activities such as Euryarchaeota, accounting for 78.4 % of total Euryarchaeota population in middle (60 cm) and 33.97 % in the lower layer. Under low oxygen conditions, NO2−-N accumulation in middle and lower layers provided a sufficient nitrogen source for Euryarchaeota. Canonical correlation analysis (CCA) showed Euryarchaeota was significantly correlated with N2O emissions in middle and lower layers during FT, contributing 31.68 %–32.01 % and 61.78 %–65.15 %, respectively. These results suggested that FT disturbance enhanced denitrification by anaerobic bacteria in middle and lower layers of SWIS, significantly increasing N2O emissions. However, specific pathways and mechanisms of N2O production by Euryarchaeota remain to be elucidated in future studies.

Alteration and interrogation of ultra-thin layer of silicon by reactive molecular ion implantation

We report the engineering of ultrathin top layer of Si substrate by low energy (14 keV) reactive ion bombardment. The physicochemical nature of the layer is interrogated and the optical properties are explored. Irradiation of nitric oxide (NO+) and mixture of carbon monoxide & nitrogen (CO+ + N2+) ions on Si surface at normal incidence leads to formation of multiple chemical phases of Si with varying ion distribution within the layer. It is found that the chemistry of the topmost layer (∼5 nm) is massively modified by the reactive projectiles, while implanted rich layer is formed at a depth of 25 to 37 nm followed by an intermediate amorphous Si layer of 20 nm thickness. The Ultra Violet-Infrared (UV-IR) response of the modified layer reveals high sensitivity in the UV region. The change in optical bandgap, estimated from Kubelka-Munks theory, indicates the presence of multiple direct and indirect bandgaps. The potential applications of such chemically modified multi-layered ultra-thin Si are addressed here.

High Performance Multiple Passband Substrate Integrated Plasmonic Filters

We proposed a new variety of substrate integrated plasmonic filters (SIPFs) with multiple passband characteristics based on the concept of spoof surface plasmon polaritons (SSPPs). By etching a periodic interdigital structure array on the top metal layer of substrate integrated waveguide (SIW), we can achieve high-efficiency microwave SSPP transmission with an insertion loss of 1 dB in the passband of 7.4-12.5 GHz, and a high rejection level of 27 dB in the rejection bands. By introducing antisymmetric C-ring resonators (ASCRs) in the filter structure, the passband number and bandwidth of the filter can be flexibly manipulated. To validate the proposed design, four SSPP filters prototypes are fabricated and tested, showing good filtering performances with a high transmission coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}21\mathbf {&gt;}-$ </tex-math></inline-formula> 1 dB) and low reflection coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}11\,\,\mathbf { &lt; } - $ </tex-math></inline-formula> 12 dB) in their passbands, and a high rejection level over 15 dB between them. By changing the geometric parameters of ASCR, the number of passbands can be increased from 1 to 3, and the passband center frequency and bandwidth can be engineered accordingly. The proposed SSPP filters with good multiple passband characteristics may have great potential applications in microwave wireless integrated plasmonic circuits and communication systems.

Combining the good tribological properties with the high adhesion strength of the amorphous carbon films in situ grown on PI

Polyimide (PI) is widely utilized in the modern industry because of its excellent heat resistance, dielectric properties, radiation resistance and chemical stability. However, PI will appear wear failure due to different working environments in the application of various friction components. In order to ensure the normal function of Pi-based parts and reduce the wear of PI materials, it is necessary to deposit amorphous carbon film with high adhesion strength and wear resistance on PI substrate. In this experiment, we treated polyimide surfaces with carbon plasma to prepare the amorphous carbon films with in situ transition layers. The microstructure, mechanical properties and tribological properties of the amorphous carbon films were studied. The results showed that the hardness and wear resistance of the PI surface were greatly improved by the amorphous carbon film with in situ transition layer. More importantly, the in situ transition endowed the film high adhesion strength on the PI substrate. The roles of the carbon plasma in the deposition process of the amorphous carbon, namely, the deposition effect, and the induction effect, referring to the effect on the top layer of PI substrate, were systematically analyzed. This work realizes the purpose of protecting the PI surface with the amorphous carbon film with high adhesion strength, and also provides a new idea for improving the adhesion between hard coating and flexible substrate.

A Novel Compact Highly Isolated UWB MIMO Antenna with WLAN Notch

This paper presents a compact Multiple Input Multiple Output (MIMO) antenna with WLAN band notch for Ultra-Wideband (UWB) applications. The antenna is designed on 0.8 mm thick low-cost FR-4 substrate having a compact size of 22 mm × 30 mm. The proposed antenna comprises of two monopole patches on the top layer of substrate while having a shared ground on its bottom layer. The mutual coupling between adjacent patches has been reduced by using a novel stub with shared ground structure. The stub consists of complementary rectangular slots that disturb the surface current direction and thus result in reducing mutual coupling between two ports. A slot is etched in the radiating patch for WLAN band notch. The slot is used to suppress frequencies ranging from 5.1 to 5.9 GHz. The results show that the proposed antenna has a very good impedance bandwidth of |S11| < −10 dB within the frequency band from 3.1–14 GHz. A low mutual coupling of less than −23 dB is achieved within the entire UWB band. Furthermore, the antenna has a peak gain of 5.8 dB, low ECC < 0.002 and high Diversity Gain (DG > 9.98).

Growth and characterization of nitrogen-polar AlGaN/AlN and demonstration of field effect transistor

This study proposes a nitrogen-polar (N-polar) Al x Ga1−x N/Al0.9Ga0.1N/AlN structure that can generate a large amount of two-dimensional electron gas to enhance the device development of samples. Additionally, we have analyzed the critical thickness of N-polar AlGaN/AlN based on the theoretical calculations of three different values of film thickness. The metalorganic vapor-phase epitaxy method is used to grow N-polar Al x Ga1−x N/Al0.9Ga0.1N/AlN on sapphire substrates. The substrates with a misorientation angle of 2° along the m-axis and a-axis directions are selected to determine the effect of the off-cut angle on sample flatness and current–voltage characteristics. Furthermore, we determine the effect of Al contents on N-polar Al x Ga1−x N/Al0.9Ga0.1N/AlN under the optimum growth conditions of the growth thickness of the top layer of AlGaN and sapphire substrate. The results indicate that the current throughput increases with a decrease in Al content. Lastly, we have fabricated the N-polar AlGaN/AlN heterostructure field effect transistor (FET) to demonstrate the static FET characteristics.

Surface Alloying During Pb Underpotential Deposition on Au(111)

The surface alloying during Pb underpotential deposition (UPD) on Au(111) films was studied using electrochemical techniques. This UPD system has been known for its unusual stress behavior associated with surface alloying during epitaxial monolayer (ML) formation. The characteristic cyclic voltammetry of Pb UPD on Au(111) exhibits an anodic peak at the most positive potentials that does not have a symmetric cathodic counterpart. The peak can be associated with the surface structural changes due to the Pb dealloying from the top substrate layer. Two electrochemical approaches were used to study the surface transformations: i) extended polarization (up to 60 min) at high Pb coverage of 0.85 ML, and ii) repeated cycling 1150 times between the potentials corresponding to 0.25 ML and 1 ML Pb coverages. In both approaches, it was observed that with the increased time of polarization or number of potential cycles, the prominent UPD peaks gradually reduced in magnitude, became broader and lost their original double-peaks structure. At the same time, the dealloying (the most anodic) peak shifted positive about 0.1 V and increased in magnitude. Quantitative analysis of the changes estimated the coverage of Pb alloying with a surface of 0.28–0.30 ML.

Double-Sided Sapphire Optrodes with Conductive Shielding Layers to Reduce Optogenetic Stimulation Artifacts.

Optrodes, which are single shaft neural probes integrated with microelectrodes and optical light sources, offer a remarkable opportunity to simultaneously record and modulate neural activities using light within an animal's brain; however, a common problem with optrodes is that stimulation artifacts can be observed in the neural recordings of microelectrodes when the light source on the optrode is activated. These stimulation artifacts are undesirable contaminants, and they cause interpretation complexity when analyzing the recorded neural activities. In this paper, we tried to mitigate the effects of the stimulation artifacts by developing a low-noise, double-sided optrode integrated with multiple Electromagnetic Shielding (EMS) layers. The LED and microelectrodes were constructed separately on the top epitaxial and bottom substrate layers, and EMS layers were used to separate the microelectrodes and LED to reduce signal cross-talks. Compared with conventional single-sided designs, in which the LED and microelectrodes are constructed on the same side, our results indicate that double-sided optrodes can significantly reduce the presence of stimulation artifacts. In addition, the presence of stimulation artifacts can further be reduced by decreasing the voltage difference and increasing the rise/fall time of the driving LED pulsed voltage. With all these strategies, the presence of stimulation artifacts was significantly reduced by ~76%. As well as stimulation suppression, the sapphire substrate also provided strong mechanical stiffness and support to the optrodes, as well as improved electronic stability, thus making the double-sided sapphire optrodes highly suitable for optogenetic neuroscience research on animal models.

Two-Material-Filled Ridge Half-Mode Substrate Integrated Waveguide for Monomode Bandwidth Enhancement

In this letter, a two-material-filled ridge half-mode substrate integrated waveguide (2M-RHMSIW) is proposed for monomode bandwidth (MMB) enhancement. The cutoff frequency of the dominant mode decreases with the permittivity of the material filling in the bottom layer increasing. The cutoff frequency of the second mode increases as the permittivity of the material filled in the top layer decreases. Therefore, the proposed structure uses low-permittivity material for the top substrate layer and high-permittivity material for the bottom substrate layer, to widen the MMB. In addition, a series of air holes are drilled in the top substrate layer to reduce its effective permittivity, which further widens the MMB. A prototype of the proposed structure is fabricated under PCB process, which MMB is from 2 to 14 GHz.

Circularly Polarized Millimeter Wave Frequency Beam Scanning Antenna Based on Aperture-Coupled Magneto-Electric Dipole

Based on the newly suggested wideband circularly polarized (CP) aperture-coupled magneto-electric dipole (MED), a millimeter-wave (mm-wave) frequency-scanned array (FSA) is proposed in this article. The MED is printed on two substrate layers. The electric dipole is two metal patches with perturbation structure, while the magnetic dipole is two rows of metal vias passing through the top substrate layer. The electric and magnetic dipoles, fed by a coupling slot, excite CP wave. By loading an arc-shaped vias row (AVR) at both ends of the magnetic dipole, the CP bandwidth with axial ratio (AR) less than 3 dB is extended to 40.9%. A new compact wideband transition from the rectangular waveguide (RWG) to the substrate integrated waveguide (SIW) is suggested as the feed structure for the CP FSA. A slow wave structure is etched on the ground of SIW to widen the beam scanning range. A 16-element array is designed and measured. The measured results show that the beam scanning range is 56° over 23–33 GHz band with a peak gain of 19.5 dBi. The CP mm-wave FSA has the advantages of wide scanning angle, low profile, and easy fabrication.

Miniaturised ultra-wideband rectangular shaped slot antenna for ground penetrating radar applications

Abstract In the proposed work, a miniaturised ultra-wideband tapered slot planar antenna with the aim of gain enhancement, working bandwidth containing lower frequency range, and improving antenna efficiency is presented. The proposed antenna consists of a slotted patch printed on the top layer of FR4 substrate with three 50-Ω resistors connected in the slotted arms and bottom layer consists of an optimized ground plane with a non-uniform parasitic patch which is used to achieve circular polarization in the frequency range of 2.4–2.6 GHz. The measured impedance bandwidth of the proposed antenna is 0.3–4 GHz with a peak gain of 3.2 dBi. The overall antenna efficiency is 83% and radiation patterns of the proposed design on different frequencies are shown to confirm the proposed antenna result, especially at lower frequencies. The proposed antenna can be used for the detection of artifacts in the deeper ground known as ground-penetrating radar applications.

An active microfluidic sensor based on slow-wave substrate integrated waveguide for measuring complex permittivity of liquids

In this paper, a microfluidic sensor based on slow-wave substrate integrated waveguide (SW-SIW) is proposed to measure the complex permittivity of liquids and it achieves an ultrahigh quality factor of 51156, which is much higher than previous reported designs. The proposed sensor consists of three-layer dielectric substrates and an active circuit. The traditional SIW has the fundamental mode of TE101, whose electric field is concentrated inside the SIW structure. The SW-SIW, which is evolved from traditional SIW structure, has the characteristic of relatively small electrical size due to large equivalent capacitance and the capability to confine the electrical field density further. The internal rows of blind via holes are connecting the top layer of second substrate to the bottom layer of third substrate. In order to further reduce the electrical size, an air cavity is formed in second substrate around blind via holes as it can increase the equivalent capacitance of SW-SIW resonator. The air cavity has an important impact on the resonant frequency of the sensor, and the electrical size could be reduced by enlarging the air cavity. In this paper, an appropriate air cavity is adopted with comprehensive consideration of detection sensitivity and electrical size. The polydimethylsiloxane (PDMS) microfluidic substrate is embedded in first substrate. When the resonator is excited, the electric field is confined above the surface of blind vias. The electric field varies with the volume fraction of aqueous solution injected into the microfluidic channel, and the resonant frequency and quality factor alter correspondingly. The variations in the resonant frequency and quality factor are applied to retrieve the complex permittivity of liquid samples. The proposed sensor is fabricated and tested, it has a dimension of 0.678λ0 × 0.432λ0 (λ0 is the wavelength in free space at 3.7 GHz), and the peak sensitivity and unloaded quality factor are about 2.5 % and 51156, which are improved by 67 % and 5015 % than traditional SIW sensor, respectively. In particular, the sensitivity of measuring loss tangent of liquid sample is improved by several times to hundreds of times with the loss tangent range from 0.1 to 0.9 than other reported sensors. The measured data has a good agreement with the reference complex permittivity.

Optofluidic lenticular lens array for a 2D/3D switchable display.

In this paper, we propose an optofluidic lenticular lens array (OLLA) for a two-dimensional/three-dimensional (2D/3D) switchable display. The OLLA includes a bottom substrate layer with lenticular lens structure, a microfluidic layer with microchannels, and a top substrate layer with inlets as well as outlets. A micro gap is formed between the lenticular lens of the bottom substrate layer and the top substrate layer. When air is in the micro gap, the OLLA behaves as a lenticular lens array, which can realize 3D display. When fluid is filled in the micro gap, because the refractive index of the fluid is the same with the lenticular lens structure, the OLLA equivalents to a transparent flat panel, which can realize a 2D display. Experiments verify that a switchable 2D/3D display prototype based on this OLLA and a smartphone achieves both high-resolution 2D display and high-quality 3D display.

On-chip terahertz bandpass filter based on substrate integrated plasmonic waveguide

In this paper, we propose and demonstrate a terahertz bandpass filter based on substrate integrated plasmonic waveguide (SIPW) using the standard 0.25-μm InP DHBT fabrication process. In this design, a Yagi-Uda antenna-like subwavelength array with effective asymptotic frequency reduction, is etched on the top metal layer of substrate integrated waveguide (SIW) to support a spoof surface plasmon polaritons (SSPPs) mode. The bandpass transmission with unique dispersion characteristics of the SIPW can be easily engineered by tuning the SIW and the SSPPs geometric parameters to independently adjust the low-cutoff and high-cutoff frequency, respectively. The simulated results show that, from the frequency range of 208 GHz to 265 GHz, the transmission coefficients is less than 2 dB, and the in-band reflection coefficients is better than 20 dB. To further verify the proposed design, a similar bandpass filter with geometry size scaled up operating in microwave frequency range is fabricated and measured. The measured results show that the great bandpass features and high-efficiency propagation are validated. In the passband of 13.5 GHz to 18.4 GHz, the reflection coefficients is better than 10 dB and the maximal transmission coefficients is 2 dB. Our work presents a novel 0.25-μm InP DHBT-based bandpass filter with dimensions of 900 μm × 285 μm in the terahertz range using SIPW for the first time, which may have extensive potential applications in integrated terahertz plasmonic devices.

A NEW MIMO SLOT ANTENNA FOR 5G APPLICATIONS

A new MIMO slot antenna is proposed in this paper, the proposed antenna consists of tuning stub with certain dimensions in the top layer of the FR-4 dielectric substrate to increase the matching between the feed line and slot in the ground plane, this antenna feeds with 50-ohm characteristic impedance microstrip feed line. The dimensions of the proposed antenna are (50×50×1.6) mm2, the FR-4 epoxy substrate has a relative dielectric constant of ɛr=4.3, the tangent loss of tan (δ) =0.025. A bandwidth of 9.083 GHz (25.917–35) GHz and gain (6.33) dBi compatible with 5G applications are achieved with this antenna. To get the desired gain and bandwidth, several slots are etched on the ground, Using CST tools, the simulation results are collected. And the proposed antenna is manufactured in the Ministry of Science and Technology's- Electronic Manufacturing Center, a reasonable agreement is reached between simulation and measured performance.

Where is the best site for loading nanoparticles in a membrane? To achieve a high flux and cephalexin separation simultaneously

In this research, with the aim of achieving a high flux and rejection of cephalexin antibiotic simultaneously, separate modifications were performed on the membrane top layer (selective layer) and substrate layer (support layer). Fe3O4 (Fe) and ZrO2 (Zr) nanoparticles were synthesized for modifying the PAN support layer, while Fe3O4/ZrO2 (FZ) nanoparticles were synthesized for modifying the PA top layer. In this regard, five types of nanocomposite membranes were synthesized: In order to regulate the porosity of the support layer, PAFe2@PAN and PAZr2@PAN membranes were synthesized which showed more pores number compared to PAPAN membrane. In order to enhance the surface hydrophilicity, FZ2@PAPAN membrane was synthesized, which showed around 16% lower contact angle and 58% greater roughness compared to PAPAN membrane. In order to compensate for the roughness developed on the membrane surface, concurrent modifications were performed on the top and support layers; the FZ2@PAFe2@PAN and FZ2@PAZr2@PAN membranes were synthesized, which separated cephalexin by 91% and 95.8%. Comparison of the performance of the synthesized membrane with that of commercial FILMTEC (NF270-2450) membrane showed that the cephalexin rejection (95 ± 1) and flux recovery (99 ± 1) of FZ2@PAZr2@PAN are almost the same as cephalexin rejection (98 ± 1) and flux recovery (96 ± 1) of commercial membrane. From permeation point of view, FZ2@PAZr2@PAN membrane at transmembrane pressure of 4 bar and cross flow velocity of 0.5 m/s had a water flux of 49 L/m2.h and cephalexin flux of 38 L/m2.h, while NF270-2450 at the same condition had a water flux of 42 L/m2.h and cephalexin flux of 25 L/m2.h.

A Novel MIMO Patch Antenna for 5G Applications

In this paper, a new MIMO patch antenna is proposed, the proposed antenna consist of patch with certain dimensions in the top layer of FR-4 dielectric substrate, and ground plane in the bottom of it, this antenna is feeding by microstrip feed line with 50-ohm characteristic impedance. The dimensions of the proposed antenna are (50 × 50 × 1.6) mm3, the FR-4 epoxy substrate has relative dielectric constant εγ=4.3, loss tangent tan (δ) =0.025. This antenna is realized a bandwidth of 4.337 GHz (24.22 – 28.557) GHZ and gain (3.68) dBi which is compatible with 5G applications. Some modifications were done in the ground plane and some of slots are etched on the patch to achieve the desired gain and bandwidth, all dimensions of these slots were chosen by using sweep parameter method to achieve the optimum value of them. The simulation results are obtained using CST software. And the proposed antenna is manufactured in the Electronic Manufacturing Center at the Ministry of Science and Technology, also the vital parameters are measured, a good agreement between simulation and measured results are achieved.

Broadband and high gain multilayer multiresonator elliptical microstrip antenna

In this study, a low cost, broadband and high gain multilayer multiresonator microstrip antenna (MSA) is designed. It consists of one metallic fed patch at the bottom layer and two circular patches (1B2 T) are printed on the bottom side of the top FR4 substrate layer, which is air suspended. Two configurations with the bottom patch of circular and elliptical shapes are compared. The elliptical 1B2 T MSA provides better bandwidth (BW), i.e. 53.4% with peak gain of 9.8 dBi. The antenna design parameters are selected to provide maximum BW with uniform gain. The elliptical 1B2 T MSA is further enclosed in a metallic cavity, which improves the BW, gain and front to back (F/B) ratio of the antenna. The elliptical 1B2 T MSA with cavity enclosure is fabricated and tested. Experimental results are in agreement with simulated ones. The elliptical 1B2 T MSA with cavity provides 55.7% BW with peak gain of 12.1 dBi and F/B of >18 dB. The proposed antenna can be used in GPS, 2G, 3G, 4G and Wi-Fi frequency bands applications.

Design of a novel miniaturized bandstop frequency selective surface exhibiting polarization insensitivity and enhanced oblique stability

In this article, a miniaturized 2.5-dimensional frequency selective surface (FSS) bandstop filter operating at 2.4 GHz is presented. The proposed FSS contains meander lines as well as metallic patches on top and bottom layer of FR-4 substrate, and vertical vias are employed to connect the top and the bottom layers. The proposed configuration significantly reduced the size of unit cell to 0.040λ0 × 0.040λ0 (where λ0 is the free space wavelength) at the desired frequency of 2.4 GHz. Additionally, this element arrangement assists in achieving fractional bandwidth of 140%. The measured −10 dB bandwidth is from 1 to 4.5 GHz. The proposed FSS is polarization insensitive and highly angularly stable (up to 75°). The equivalent circuit model (ECM) of this FSS and related surface current distribution are also provided to understand its working mechanism. The design performance validation has been carried out through the construction and testing of a functional prototype. The full wave simulation, the ECM, and the measured results depict a promising agreement.