Suspended Substrate Research Articles

A proposal for design of 2 – 4 GHz wideband bandpass filter using suspended substrate stripline for passive radar systems

This article proposes a solution to design of front-end bandpass filters which finds application in wideband receivers for passive radar systems. The structure employs suspended substrate stripline as base transmission lines, dual-frequency resonators, and broad-side coupling patterns to render a wideband, steep cutoff and low-loss bandpass filter that aims at replacing lossy microstrip-based or bulky waveguide-based filters. The structure is able to scale to different operating frequency ranges in electronic warfare systems.

A novel eight-way power combiner on suspended substrate stripline for Ku-band applications

This work proposes a novel 8-way power combiner implemented using suspended substrate stripline technology for Ku-band applications. The equivalent circuit of the design is analyzed to obtain parameters for the physical realization of the structure. The combiner is well matched at both input and output ports with VSWR better than 1.6:1, achieves low insertion loss of less than 1dB and isolation of more than 16.8 dB over the range from 12 GHz to 18 GHz. The structure is also able to handle high thermal dissipated power due to its housing, hence, suitable to find application in high power-amplifier subsystems.

Micro-heater embedded Ni-SnO2 ordered nanoporous films: On-chip fabrication for fast, sensitive, and selective gas sensing towards multiple VOCs for air quality monitoring

The ability to simultaneously detect multiple volatile organic compounds (VOCs) is crucial for assessing indoor air quality and addressing significant health hazards. In this study, we present a sacrificial template approach for on-chip fabrication of two-dimensional (2D) Ni-doped SnO2 nanoporous sensing films on micro-heater substrates. The technical analysis shows that the resulting honeycomb-like ultrathin Ni-SnO2 sensing layer on a suspended substrate maintains perfect structural integrity and consistency. The Ni-SnO2 sensors exhibit exceptional characteristics, including a ppb-level detection limit, high sensitivity, fast response/recovery time, and signal repeatability for typical VOCs, while operating at a low power consumption of 25 mW. Additionally, the Ni-doping enhances the sensors' cross-sensitivity to various forms of VOCs, while causing a discernible response inhibition towards flammable or exhaust gases. Furthermore, X-ray photoelectron spectroscopy (XPS) and in-situ Raman spectra reveal a Ni2+-substitution induced surface adsorbed oxygen species enrichment mechanism for sensing enhancement. Thus, the developed Ni-SnO2 sensors hold promise as future candidates for reliable air quality assessment by real-time monitoring of overall concentrations of multiple VOCs.

Compact beamforming network for producing multiple orthogonal beams in a limited field of view phased array antenna

AbstractDue to the advent of high-throughput communication satellites in a geostationary orbit, the development of multiple beam phased array antenna (MBPAA) technology has become a necessity. This paper presents the design and implementation of the constituent unit of a beamforming network (BFN), which feeds an MBPAA with interleaved sub-arrays. The proposed BFN generates multiple orthogonal sub-beams with a very tiny angular distance between adjacent sub-beams in a limited field of view. The BFN consists of sub-array beamforming networks (SABFNs) with unequal number of beam ports and antenna ports, which can feed both the arrays lateral elements and the interleaved core sub-arrays for pattern shaping and side-lobe level reduction. A microwave circuit for this SABFN has been designed and fabricated in C-band. The microstrip lines have been printed on the two sides of a suspended substrate. This technique leads to size reduction of the circuit by twice a value compared to a conventional microstrip circuit. Measurements have been compared to simulations, and good conformity has been observed. The insertion loss in the path of beam ports to the antenna ports is 3.5 dB for a relative bandwidth of 10%.

Recruitment of Oysters by Different Collection Devices at a Longline Shellfish Farm in the Central Adriatic Sea

In 2020–2021, a trial to recruit flat oysters was implemented at a longline farm in the central Adriatic, whereby the efficiency recruitment (n. oyster/dm2) of different suspended substrates was evaluated. Two lantern nets (50 cm diameter; 145 cm h) had different substrates composed of 8 mm wide wrinkled ribbon and empty oyster shells positioned in the upper levels of the lanterns. The tumbling evaluation and the presence of mud were also considered. The efficiency recruitment was similar between the wrinkled ribbon and the oyster shell. Recruitment was in the same proportion on the external rough part of the shells as on the internal smooth part of the shells. No significant differences were shown when comparing the different substrates in terms of recruitment efficiency.

Study and Design of A Dual Mode Resonant Band-Pass Filter Suspended Substrate Stripline for 5G Communications

Study and Design of A Dual Mode Resonant Band-Pass Filter Suspended Substrate Stripline for 5G Communications

A High-Gain Wideband Microstrip Patch Antenna With Folded Ground Walls

This letter proposes an approach to improve the gain of a microstrip patch antenna on a suspended substrate without compromising its bandwidth. The ground plane of the antenna is folded upward to form sidewalls parallel to the nonradiating edges. The distance from the patch edges and the height of the sidewalls are determined to maximize the radiation performance of the resultant antenna. This approach results in a peak gain better than 12 dBi and impedance bandwidth of around 45 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> . Simulation studies indicate that sidewalls parallel to radiating edges degrade the antenna performance.

Differences in Mercury Concentrations in Water and Hydrobionts of the Crimean Saline Lakes: Does Only Salinity Matter?

Of significant scientific and public concern is the high toxicity, significant bioaccumulation, and magnified concentration within the food web of mercury (Hg). Hg content both dissolved and in suspended forms in water as well as in biomass of different hydrobiont taxa was studied in 18 saline lakes in Crimea from 2012 to 2021. The impact of different factors (salinity, seasonality, anthropogenic activities, geological background, etc.) was analyzed. The generalization of data for all lakes showed that the average concentration of Hg in dissolved form was 129 ng L−1, varying over a wide range. The content of Hg in total suspended substrates was an average of 151 ng L−1, and the total content of Hg in lake water averaged 291 ng L−1. Geological background and anthropogenic activities can determine the total Hg content in lakes. In most lakes, a significant positive correlation was noted between the concentration of one, two, or all three indicators of Hg content and the month of the year, with indicators increasing from winter through to autumn. When analyzing the entire data array, a significant positive correlation was found between the concentration of the suspended form of Hg and salinity; such correlation between the concentration of the dissolved form of Hg and salinity was absent. The highest average Hg concentrations in biomasses were noted in Artemia and were the lowest in plants. Geological background and human activity contribute to high Hg content in lakes. Hydrobionts can significantly influence the distribution and behavior of Hg, being an important factor of its cycle in the lakes.

Dual polarized designs of square microstrip antenna for GSM and LTE applications

SummaryTo obtain the polarization agility in wireless applications, the dual polarized wideband or multi‐band antennas are required. In this paper, modified designs of square microstrip antenna by employing overlap offset parasitic patches are proposed for the dual polarized wideband and multi‐band response. Due to the optimum spacing in between the fundamental TM1045 and TM01135 modes along with TM11 mode, on a total substrate thickness of 0.075λg, the proposed design yields bandwidth of more than 550 MHz (&gt;50%), exhibiting the dual polarized characteristics. A similar design is presented on a thinner suspended substrate. Here, on the substrate thickness of 0.035λg, it yields impedance matching at higher order TM20 mode, which along with TM1045, TM01135, and TM11 modes exhibits triple band response. An impedance bandwidth of 3.4%, 17%, and 4.7% is realized in the three bands with a broadside gain of more than 6 dBi. The proposed design satisfies the requirements of GSM 810/GSM900/LTE applications. In each design, simulated results have been experimentally verified that show close agreement.

Mapping the complex refractive index of single layer graphene on semiconductor or polymeric substrates at terahertz frequencies

Assessing experimentally the main optical parameters of graphene (e.g. complex refractive index, carrier density, mobility) in the far-infrared (0.1–10 THz) is important for quantum science, due to the possibility to devise miniaturized devices (frequency combs, random lasers), components (optical switches, spatial light modulators, metamaterial mirrors and modulators) or photonic circuits, in which graphene can be integrated with existing semiconductor technologies to manipulate their optical properties and induce novel functionalities. Here, we combine time domain terahertz (THz) spectroscopy and Fourier transform infrared spectroscopy to extract the complex refractive index of large (∼1cm2) area single layer graphene on thin (∼0.1-1 µm) polymeric suspended substrates, flexible and transparent films, and high reflectivity Si substrates in the 0.4–1.8 THz range. We model our data to extract the relevant optical (refractive index, absorption coefficient, penetration length) electronic (Fermi velocity) and electrical (carrier density, mobility) properties of the different graphene samples.

Design of novel compact SISL filters with multiple TZs based on patch resonators

AbstractThis letter presents two compact filters using patch resonators based on the substrate integrated suspended line (SISL) technology platform. First, a bandpass filter (BPF) with multiple coupling schemes is designed by using a shorted‐stub‐loaded patch resonator. Two shorted stepped‐impedance resonators are working together to form the third‐order BPF. A 98.18% size reduction is achieved, and five transmission zeros (TZs) are produced by introduced mixed electric and magnetic coupling, cross‐coupling, and source to load coupling. Then, the SISL dual‐band bandpass filter (DBBPF) with six TZs is designed by using an improved slotted patch resonator. By adopting the patterned suspended substrate structure, the implemented DBBPF, featured with self‐packaging, achieves a fractional bandwidth of 52% and 10%, centered at 0.95 and 3.25 GHz with insertion losses of 0.57 and 2.89 dB, respectively.

Vertical monolithic integration of wide- and narrow-bandgap semiconductor nanostructures on graphene films

We report monolithic integration of indium arsenide (InAs) nanorods and zinc oxide (ZnO) nanotubes using a multilayer graphene film as a suspended substrate, and the fabrication of dual-wavelength photodetectors with the hybrid configuration of these materials. For the hybrid nanostructures, ZnO nanotubes and InAs nanorods were grown vertically on the top and bottom surfaces of the graphene films by metal-organic vapor-phase epitaxy and molecular beam epitaxy, respectively. The structural, optical, and electrical characteristics of the hybrid nanostructures were investigated using transmission electron microscopy, spectral photoresponse analysis, and current–voltage measurements. Furthermore, the hybrid nanostructures were used to fabricate dual-wavelength photodetectors sensitive to both ultraviolet and mid-infrared wavelengths.

Theoretical and experimental investigation of two-layer circular patch antenna excited by a coaxial probe

AbstractIn this article, we present two efficient closed-form models to examine thoroughly the dependence of resonant frequency, quality factor, probe reactance, input impedance, bandwidth, and gain on parameters such as patch radius, probe location, substrate electrical parameters, and air gap of a coax probe-fed circular patch antenna. The implementation of these models is very easy and the computation cost is very low. The proposed models show excellent agreements with experimental and simulation results. We have also investigated experimentally the gain patterns of a suspended substrate circular patch antenna.

In situ tunable droplet adhesion on a super-repellent surface via electrostatic induction effect

SummaryIn this paper, we report a finding that substrate affects the adhesion of charged super-repellent surfaces. Water droplet impacting on a super-repellent surface produces surface charge, whose expression depends on the substrate. The charged super-repellent surface is sticky to droplets for a suspended substrate made of dielectric materials, while it has low adhesion for a conducting substrate or stage attached at the bottom because of electrostatic induction. Theoretical analysis and simulation are conducted to elucidate the mechanism of substrate effect on surface adhesion. Finally, we develop a new approach to reversibly tune the adhesion of super-repellent surface by combining surface-charge-induced adhesion increase and electrostatic-induction-regulated express of net surface charge. As a proof-of-concept experiment, we demonstrate that droplet sorting and manipulations can be realized by using this controllable surface adhesion tuning approach, which has potential applications in advanced lab-on-a-drop platform.

Performance analysis of 65 nm CMOS LNA using SSL technique for 5G cellular front-end receivers

This paper presents a performance analysis of a wideband low noise amplifier (LNA) that utilizes a 65 nm CMOS Samsung mm-wave process. The proposed CMOS LNA designed with new built-in techniques will overcome the challenges faced by device parasitic and electromagnetic (EM) losses. A suspended substrate line (SSL) is characterized and analyzed with its dual-band operation and achieves excellent EM compatibility. The traditional EM losses in bulk active and passive components have been incurred using built-in techniques to provide better linearity of LNA. The proposed mm-wave LNA enables it’s each family component to avoid leakage of EM waves and its interconnected parasitic losses in layout. An SSL based parallel-series network is optimized to achieve a wide bandwidth of 26 GHz to 34 GHz. The full design of LNA achieves the highest peak gain of 25 dB by using proper 50 Ω matching constraints over the wideband response of 27.8 GHz to 32.5 GHz. The fabricated chip of LNA is given a supply voltage of 1.2 V, and the calculated chip area is 0.35*0.22 mm2. The simulation and measurement results demonstrate the minimum noise figure of 2.5 dB and achieve the highest stability factor in the desired band of operation. The LNA also measured linearity with a 1 dB compression point where input power of −19dBm has obtained at 30.5 GHz.

A Dual-Band Coupled Line Power Divider Using SISL Technology

A coupled-line based dual-band power divider using substrate integrated suspended line (SISL) for WLAN application is proposed in this brief. Two-section cascaded coupled line in each output path is used for dual-band response. One coupled line loaded at the input port is to improve the frequency selectivity. Two lumped resistors placed between two pairs of the two-section coupled line are used for isolation enhancement. Multi-layer SISL structure is introduced to realize tight broadside coupling, as well as for low loss, miniaturization and self-packaging. To further reduce the dielectric loss, the suspended substrate is cut out in specific pattern. The proposed dual-band power divider (DBPD) is analyzed using the even- /odd- mode method, the S-parameters are derived, and the design procedure is exhibited. For verification, a DBPD prototype working at 2.45 / 5.13 GHz is implemented. The measured results agree well with the simulated ones. The two passbands are from 1.7 GHz to 3.1 GHz and from 4.6 GHz to 5.5 GHz, with fractional bandwidth (FBW) of 58.3% and 17.8%, respectively. The measured return loss and isolation are both better than 15 dB in both passbands.

An Ultra-Wideband Stripline Bandpass Filter with a Noise Suppression Level of More than 100 dB

An ultra-wideband bandpass filter formed by cascading of a novel high-pass filter (HPF) and a low-pass filter (LPF) on suspended substrates with a two-sided pattern of strip conductor has been investigated. The high selectivity of the HPF is ensured by the transmission zeros near the passband, the number of which is equal to the filter order. A second-order HPF has been designed on a 0.5-mm-thick substrate with a permittivity of e = 9.8 using the numerical electrodynamic analysis of a 3D model of the filter. The experimental HPF prototype has a cutoff frequency of fb = 0.25 GHz at a level of –3 dB and a passband that extends to 5 GHz. The ultra-wideband bandpass filter formed by cascading of the LPF and the designed HPF has a fractional bandwidth of Δf/f0 = 150% with a central frequency of f0 = 1 GHz. It has the broad and deep high-frequency stopband, which extends to a frequency of 7.8f0 at a suppression level of –100 dB.

180° hybrid using a novel planar balun on suspended substrate for beam forming network applications

In this paper, a 180° hybrid consisting of a broadband balun and a T-junction in-phase power divider is proposed. The 180° hybrid is intended for operation in the C-band. The balun resembles a center tapped magnetic transformer where the coils are replaced by broadside-coupled lines. This new technique allows magnetic couplers to be realized by planar structures at microwave frequencies. The planar balun is broadband, and the size reduction is considerable. The broadside-coupled lines are on a suspended substrate. The proposed structure can be used in the beam forming networks of the multiple-beam antennas. It also prevents cross connections in the conventional beam forming networks. The planar balun is analyzed by the signal flow graph method. The scattering parameters of the 180° hybrid are calculated by the multiport connection method. Some design formulas for the construction of the balun are presented. The 3-dimensional model of the planar 180° hybrid is simulated by a full-wave simulator. Measurement results of the fabricated hybrid approve the simulation results. The 180° hybrid exhibits a relative bandwidth of 45% centered at 4.5 GHz. In the operating band, the amplitude and phase imbalance of the output ports are <0.6 dB and <10°, respectively.

A Highly Selective Stripline Lowpass Filter with More Than 100-dB Wide Stopband Attenuation

A new miniature design of a highly selective lowpass filter based on a suspended substrate with a two-sided stripline pattern has been developed. The filter frequency response slope (cutoff attenuation rate) and stopband attenuation depth are determined by transmission zeros, the number of which is equal to the filter order. An experimental prototype of a fifth-order lowpass filter on 0.5-mm-thick alumina substrate with dielectric permittivity e = 9.8 has been synthesized with the aid of numerical electrodynamic analysis of a three-dimensional model. The cutoff frequency of the filter passband at a –1-dB level is fc = 1.75 GHz. The stopband width at a –100-dB attenuation level reaches 4.4fc.

Reduction of Beam Squinting and Cross-Polarized Fields in a Wideband CP Element

Achieving wide circularly polarized (CP) bandwidth in a simple probe-fed microstrip antenna is essential for many practical applications. Existing knowledge guides exploring a thick substrate-based patch design. However, it suffers from two major inherent issues: squinting of beam and high cross-polarized (XP) radiation. No solution is available so far. This letter successfully addresses both issues by imposing restriction on the fringing characteristics as well as modal fields of a suspended substrate circular patch. Engineered ground plane bearing different strategic defects has been explored leading to about 50% correction in beam squinting with reference to antenna boresight and 2–8 dB reduction in a peak XP level. Realistic design, physical insight, and the experimental validation ensure its huge potential for practical applications.