Suspended Substrate Research Articles

Spatial patterns of larval settlement and early post-settlement survivorship of Mytilus galloprovincialis in a Galician Ría (NW Spain). Effect on recruitment success

Larval settlement and recruitment play an important role on the population dynamics of marine benthic invertebrates, and are key factors in the management of aquaculture industries. In order to check the current strategies of mussel seed gathering from collector ropes in the Ria of Ares-Betanzos (NW Spain), this work analyses the seasonal and spatial variability of larval settlement and recruitment of the mussel Mytilus galloprovincialis, as well as the relationship between settlement and recruitment. Our results highlight the importance of the hydrographic characteristics of the Ría de Ares-Betanzos on the spatial distribution of larval settlement and on the early post-settlement mortality, which determines recruitment success. The spatial distribution of larval settlement, with higher abundances in the northern-shore but significant larval retention in the southern culture areas, is in agreement with the positive subtidal circulation of this embayment and the larger residence times in the southern shore. The positive subtidal circulation of the Ría favours larval transport from the culture areas located in the south to the northern shore, while the larger residence times allow larval retention in the southern shore. The strong linear relationship between settlement and recruitment suggest density-independent mortality and allowed estimating recruitment abundances and short-term survival rates. The highest and lowest post-settlement mortalities were registered at the most external and sheltered locations respectively, suggesting that the vulnerability to the hydrodynamic stress may be the main cause of early post-settlement mortality of mussel juveniles on suspended substrates. Our results confirm that the sheltered culture polygons located in the inner area of the Ría of Ares-Betanzos are favourable environments for the recruitment of Mytilus galloprovincialis spat, supporting the current strategies of seed gathering from collector ropes in the Ría of Ares-Betanzos.

Microfluidically Tunable Microstrip Filters

A new approach for the development of tunable and reconfigurable microstrip (MS) devices is proposed. The basic idea consists of using a suspended substrate with an integrated network of plastic tubes, which can be selectively filled in with a high-permittivity dielectric fluid, e.g., water. The local change of the substrate effective permittivity achieved in such a way enables one to change, in a controlled and reversible manner, the electrical length of certain elements of MS circuits. As a proof-of-concept, tunable stub resonators based on suspended and inverted MS lines are designed and characterized in frequency and time domains. The same principle is then applied for the development of a fourth-order bandpass filter with 40% fractional bandwidth operating at 5 GHz. A tunable range of 19.5% with the insertion loss of 0.6 dB is demonstrated. The performance of the stub resonators and filter is validated successfully via prototyping.

Compact Dual-Band Suspended Microstrip Slot Antenna with an Antipodal Parasitic Element for WLAN Applications

In this paper, a dual-band microstrip slot antenna over a suspended substrate with an antipodal parasitic element is proposed for wireless local area network systems operating at 2.4, 5.2, and 5.8 GHz. The antenna is composed of multi layers of flame retardant-4 (FR4) and air/foam substrates. The foam/air substrate is included a coaxial single-feed pin and the FR4 substrate is comprised of a modified T-shaped patch and an antipodal modified U-shaped parasitic element with a modified slot around it. The slot antenna configuration improves the compactness, the impedance bandwidth, and the radiation pattern. The realized antenna is proportionately small in size (17 × 20 mm2) and experimental result shows that the antenna covers 2.39---2.5 and 5.1---6.05 GHz with the 10-dB return loss bandwidth. Furthermore, the antenna has good radiation patterns in both x---z and y---z planes over the desired frequency ranges.

P-i-n-Diode-Based Four-Channel Switched Filter Bank With Low-Power TTL-Compatible Driver

The design of a four-channel switched filter bank in the S- and C-band using p-i-n-diode switches is described. Narrowband filters (3.2%-3.5%) are designed on suspended substrate stripline. The biasing circuit allows the switches to be driven with transistor-transistor-logic-compatible voltages and minimum biasing current. The average insertion loss measured is 3.6 dB corresponding to a Q-factor of 580. Spurious responses were suppressed from dc to roughly 19 GHz.

Coupled nanowire-based hybrid plasmonic nanocavities on thin substrates.

We theoretically analyze nanowire-based hybrid plasmonic nanocavities on thin substrates at visible wavelengths. In the presence of thin suspended substrates, the hybrid plasmonic modes, formed by the coupling between a metal nanowire and a dielectric nanowire with optical gain, exhibit negligible substrate-mediated characteristics and overlap better with the gain region. Consequently, the confinement factor of the guided hybrid modes is enhanced by more than 42%. However, the presence of significant mirror loss remains the main challenge to lasing. By adding silver coatings with a sufficient thickness range on the two end facets, we show that the reflectivity is substantially enhanced to above 50%. For a coating thickness of 50 nm and cavity length of about 4 μm, the quality factor is above 100.

Rigorous Full-Wave Analysis of Rectangular Microstrip Patch Antenna on Suspended and Composite Substrates

In this paper, Galerkin's method in the Fourier transform domain is applied to the determination of the resonant frequencies and half-power bandwidth of rectangular microstrip patch on composite and suspended substrates. Using Galerkin's method in solving the integral equation numerically, the complex resonant frequency of the microstrip antenna on suspended and composite substrates is studied with sinusoidal functions as basis functions, which show fast numerical convergence. The validity of the solution is tested by comparison of the computed results with experimental data. Finally, numerical results for the effects of suspended and composite substrates on the resonant frequency and half-power bandwidth are also presented.

A Capacitive Fed Microstrip Patch Antenna with Air Gap for Wideband Applications (RESEARCH NOTE)

In this paper a microstrip antenna on a suspended substrate with capacitive feed is presented. capacitive feed is created by a slot within the rectangular patch around the feed point. The proposed antenna exhibits a much higher impedance bandwidth of about 47% (S11 < −10 dB). Effects of key design parameters such as the air gap between the substrate and the ground plane, the gap width between radiator patch and feed point, and the location of the feed point on the input characteristics of the antenna have been investigated and discussed. A prototype of the antenna is also fabricated and tested, to verify the design. Measured characteristics of the antenna are in good agreement with the simulated results.

PLANAR BANDPASS FILTER WITH 100-DB SUPPRESSION UP TO TENFOLD PASSBAND FREQUENCY

This paper proposes a miniature microwave bandpass fllter. It comprises quasi-lumped suspended substrate stripline resonators of a new type. Their common substrate consists of two contiguous dielectric layers. Every resonator in the fllter has three parallel strip conductors. Two of them are placed on the outer substrate surfaces and the rest is placed inside the substrate. The fllter of the sixth order was designed with the use of special optimization rules that are universal for all resonator fllters. The substrate of the fabricated fllter was made of RT/Duroid 5880 (r = 2:2, tan- = 0:002) with thickness of 0.127mm. It has dimensions of 12mm £ 45:5mm. The measured passband has a center frequency of 1.01GHz, 3-dB fractional bandwidth of 11%, and minimum insertion loss of 1.4dB. The 100-dB upper stopband extends up to 10.5GHz.

Design of Subharmonic Mixers above 100 GHz

This paper presents the design and simulation of several fixed-tuned sub-harmonic mixers cover frequencies from 110 GH to 130 GHz, 215 GH to 235 GHz, 310 GH to 350 GHz, and 400 GH to 440 GHz. Among them, 120 GHz, 225 GHz, 330 GHz subharmonic mixers are designed with flip-chipped planar schottky diode mounted onto a suspended quartz-based substrate, the 225 GHz and 425 GHz subharmonic mixers are GaAs membrane integrated, and the 115 GHz subharmonic mixer has been fabricated and tested already.

Miniature bandpass microwave filter with interference suppression by more than 100 dB in a wide rejection band

A new planar resonator design in which a single conductor is replaced by three parallel stripe conductors located one above the other on a suspended two-layer substrate is proposed. It is shown that the resonator longitudinal sizes can be significantly reduced and, at the same time, the resonator intrinsic Q factor and frequencies of higher oscillation modes can be increased. A fourth-order bandpass filter with a central frequency of the transmission band (relative width 5%) of 1 GHz has been developed and fabricated. This filter has a −100-dB rejection band up to frequencies exceeding 10 GHz. The filter is enclosed in a metallic case with an internal size of 38 × 12 × 7.5 mm. It is shown that a similar filter fabricated in accordance with low-temperature cofired ceramic (LTCC) technology has a −40-dB rejection band up to 30 GHz, with sizes reduced to 5.0 × 4.25 × 1.24 mm.

Eigenwaves in multilayer strip structures

Strip lines of different types are the basis for integrated circuits (chips) operated in the microwave range. The up-to-date technology of manufacturing such chips, which is characterized by close spacing of individual elements and the presence of dielectric super- and sublayers, makes it necessary to allow for interelement coupling and the multilayer character of the medium, when calculating strip lines. Thus, in order to construct mathematical models of the elements of microwave chips, one should solve the problem of finding the system of eigenwaves in multilayer guiding strip structures. In [1], an efficient numerical-analytic method is proposed for calculation of eigenwaves in a shielded microstrip line. It is based on the projection method of solving special integral equations with the use of the Chebyshev basis which allows for the boundary features of the solution explicitly. This method makes it possible to obtain numerical results with high accuracy even for a fairly small number of basis functions [2]. In this work, this method is generalized for the multilayer strip guiding structures considered in [3] and applied to construction of the mathematical model of the connected microstrip lines on a suspended substrate. A universal, independent of the number of layers, way to obtain the main calculated relationships is proposed. In this case, the algorithms of finding the characteristics of multilayer strip structures are identical to the corresponding algorithms for microstrip lines on a single-layer substrate. Therefore, the algorithms, which are developed for microstrip lines, and the computer codes, which implement them, can be used for calculation of multilayer strip structures with minor adjustments.

Characteristics of Equilateral Triangular Patch Antenna on Suspended and Composite Substrates

A computer-aided design oriented cavity model is proposed in this article to predict the effect of composite and suspended substrates on the characteristics of an equilateral triangular patch antenna. The present model is very simple, fast, accurate, and valid for an entire range of permittivities and thicknesses of composite and suspended substrates as well as a single-substrate patch antenna. No design guide line or experimental results are available in the open literature to predict the characteristics of an equilateral triangular patch antenna on composite substrate. Also, the effect of a suspended substrate on input impedance, bandwidth, and gain of an equilateral triangular patch antenna has not yet been investigated, so commercial softwares (HFSS [Ansoft Corp., 2012] and CFDTD [Artech House, 2004]) was employed to validate the present model for a suspended and composite substrate triangular patch antenna. The computed values of a triangular patch on single substrate are compared with different theoretical and experimental values available in the open literature, and the present model shows very close agreements with the experimental results. This model is very useful for designing the microwave integrated circuit on semiconductor materials with εr ≥ 10.

Electrical modelling and design insight of a vertically movable gate field effect transistor for physical sensor applications

A novel electrical modelling for a vertically movable gate field effect transistor (VMGFET) for sensing applications is conducted. Presented is the manipulation of threshold voltage and drain current of the VMGFET as a function of the effective charge density and the air gap between the gate and the substrate body. The usage of the VMGFET in depletion mode, while operating in the saturation region, is proposed to prevent an electrostatic attraction between the suspended gate and substrate and to have a linear response of drain current over a varying air gap. The sensitivity of the VMGFET is simulated and shows a constant slope by changing the air gap under the operating conditions, such as working in depletion mode and operating in the saturation region. The sensitivity independence of the gate position is desirable when the VMGFET is applied for physical sensor applications.

Fast and accurate model of equilateral triangular patch antennas with and without suspended substrates

AbstractA set of closed‐form expressions based on cavity model and equivalent resonant circuits are proposed to compute accurately the resonant frequency, input impedance, bandwidth, and gain of an equilateral triangular patch antenna (ETMPA) with and without suspended substrates. The computed values for wide range of antenna parameters and feed locations of an ETMPA without suspended substrates are compared with different experimental and theoretical values available in open literature. The present model shows very close agreement with experiments. The experimental and theoretical values of input impedance, bandwidth, and gain of an ETMPA on suspended substrate are not available. So, we have employed a commercial simulator (HFSS) to validate the present model with suspended substrate. The present model is very fast, simple, and more close to the experiments compared to other theoretical models and full wave analysis. This model is very useful for designing the MIC on semiconductor materials with εr ≥ 10. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2663–2668, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27129

SUSPENDED SUBSTRATE STRIPLINE BANDPASS FILTERS WITH SOURCE-LOAD COUPLING STRUCTURE USING LUMPED AND FULL-WAVE MIXED APPROACH

This paper presents the design of two suspended substrate stripline (SSS) bandpass fllters (BPFs), both with a source-load coupling structure embedded to create a transmission zero (TZ) near each side of the passband edges. For the flrst BPF, the physical circuit layout is proposed flrst and followed by the establishment of an equivalent LC circuit. The optimization of element values of the LC circuit using a circuit-level simulator leads to quick adjustment of the structural parameters of the physical circuit layout with the aid of a full-wave simulator. For the second BPF, the ingenious equivalent LC circuit modifled from that of the flrst one is proposed for bandwidth enhancement, which is achieved by exciting two extra loaded resonances in the passband. With the element values of the LC circuit optimized, proper reshaping the physical circuit layout from that of the flrst BPF is easily accomplished. The presented lumped and full-wave mixed approach is very e-cient in that the circuit- level simulator is used to the largest extent and the time-consuming full-wave simulator is employed only at the later stage of the design. Experiments are conducted to verify the design of the two SSS BPFs and agreements are observed between the measured and simulated data.

Circuit Model of Multilayer Microstrip Step Discontinuity Using Single-Layer Reduction Formulation

New closed-form models for the microstrip step discontinuity to compute shunt capacitance (Cp) and series inductance (Ls) is reported for the substrate 2.3 ≤ ϵr ≤ 40.0 or more. The model is extended to the multilayer (composite and suspended substrate) microstrip step discontinuity. The average deviation for normalized Cp is 5%, and normalized Ls are 2.9 against the results extracted from Sonnet. For the multilayer step discontinuity, the average deviation in the present model for Cp is 5.2%. The method of moment analysis gives an average deviation of 13.53% for Cp and 5.3% for Ls against the results of Sonnet. Comparison with Sonnet indicates that the static model for simple and multilayer case is valid for h/λ ≤ 0.42.

Two-stage UASB design enables activated-sludge free treatment of easily biodegradable wastewater

A two-stage lab-scale UASB reactor, incorporating a selector-type UASB prior to the main reactor was operated at 37 degrees C with an easily biodegradable food wastewater having a COD of 3,000 mg/L. Varying the hydraulic retention time from 25 to 5 h, the removal of COD by the two-stage process was higher than 95%. Effluent soluble COD was consistently below 75 mg/L and the methane production rate close to theoretical values. The selector UASB removed the majority of the organic load (70-90%) at high organic loading rate, i.e. between 6 and 30 g/(Ld) and the granular sludge developed was characterized by dense microbial colonies, high volatile suspended solids' content and high substrate degradation efficiency. Design of a two-stage process, incorporating a selector and a second UASB reactor, was able to achieve stable and complete substrate degradation at overall loading rates of the order of approximately 10-15 g/(Ld).

A BROADBAND SUSPENDED MICROSTRIP ANTENNA FOR CIRCULAR POLARIZATION

In this paper we propose a circularly polarized (CP) microstrip antenna on a suspended substrate with a coplanar capacitive feed and a slot within the rectangular patch. The antenna has an axial ratio bandwidth (< 3 dB) of 7.1%. The proposed antenna exhibits a much higher impedance bandwidth of about 49% (S11 < -10 dB) and also yields return loss better than -15 dB in the useful range of circular polarization. Measured characteristics of the antenna are in good agreement with the simulated results. The radiation patterns indicate good cross polarization rejection and low back lobe radiations. The design proposed here can be scaled to any frequency of interest.

Investigation of the coupling coefficients of stripline resonators in combline filters on a suspended substrate

Expressions for the frequency-dependent coupling coefficients of codirectional resonators used in a miniature design of a stripline filter on a suspended substrate are derived. The obtained expressions fully reflect the specific features of the frequency response of the analyzed structure. It is shown that the numerical analysis of a 1D model of this device performed in the quasi-static approximation provides sufficiently good agreement with experimental results. The influence of the design parameters of the analyzed structure on the frequency-selective properties of band-pass filters designed on the basis of this structure is theoretically investigated, and the capabilities for a substantial improvement of the selectivity of such devices are demonstrated.

ANALYSIS OF PERIODICALLY LOADED SUSPENDED SUBSTRATE STRUCTURES IN MILLIMETER WAVE

Abstract—This paper presents a comprehensive study on the hybrid mode analysis of a periodic structure in a Suspended Microstrip and Broadside-coupled Suspended Stripline. The analysis has been use of Floquet’s theorem in special harmonics to express the field equations in various sub regions of the periodic loaded suspended substrate. Their characteristic equation is derived, using the Galerkin’s procedure. The unknown electric field distribution in the substrate region, corresponding to one unit cell of the periodic structure is specified in terms of suitable basis functions. The characteristic of slow wave properties, resonance behavior and the passband-stopband characteristics are at the millimeter wave frequencies as a various structural parameters are presented.