Slot Cut Research Articles

E -Band Low-Profile, Wideband 45° Linearly Polarized Slot-Loaded Patch and Its Array for Millimeter-Wave Communications

A series of E-band low-profile wideband antenna arrays with 45° and ±45° dual linear polarizations is presented for high-speed millimeter-wave communication applications. The array element consists of a corner-fed patch with a tilted slot cut at its edge, which suppresses unwanted modes in order to generate the desired 45° linear polarization. Comparing to a traditional 45° tilted patch, the proposed element gets rid of the bending feedline and realizes a higher isolation level between adjacent patches in the side-by-side arrangement. For proof-of-concept demonstration, a $2 \times 8$ array with 45° linear polarization was fabricated and measured, exhibiting a good agreement between simulation and measured results. The proposed array prototype possesses a −10 dB impedance bandwidth of 10.6% (74.3–82.5 GHz). Moreover, a dual $1 \times 8$ array with ±45° dual polarization is also presented, showing a bandwidth of 9.7% (74.4–81.9 GHz) and a high isolation level of greater than 25 dB. The proposed E-band planar arrays own the advantages of low profile, i.e., $\sim 0.067\lambda _{0}$ , single layer, low fabrication cost, simple structure, wide operational bandwidth, i.e., ~10%, and polarization flexibility. They represent promising candidates for high-speed E-band communications.

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow.

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer coefficient as a function of the liquid flow rate in a transparent pipe. With certain amendments, the approach is extended to gas-liquid flows, with a particular emphasis on the effect of a single elongated (Taylor) air bubble on heat transfer enhancement. A non-invasive thermography technique is applied to measure the instantaneous temperature of a thin metal foil heated electrically. The foil is glued to cover a narrow slot cut in the pipe. The thermal inertia of the foil is small enough to detect the variation in the instantaneous foil temperature. The test section can be moved along the pipe and is long enough to cover a considerable part of the growing thermal boundary layer. At the beginning of each experimental run, a steady state with a constant water flow rate and heat flux to the foil is attained and serves as the reference. The Taylor bubble is then injected into the pipe. The heat transfer coefficient variations due to the passage of a Taylor bubble propagating in a vertical pipe is measured as function of the distance of the measuring point from the bottom of the moving Taylor bubble. Thus, the results represent the local heat transfer coefficients. Multiple independent runs preformed under identical conditions allow accumulating sufficient data to calculate reliable ensemble-averaged results on the transient convective heat transfer. In order to perform this in a frame of reference moving with the bubble, the location of the bubble along the pipe has to be known at all times. Detailed description of measurements of the length and of the translational velocity of the Taylor bubbles by optical probes is presented.

Free Streamline Hydrodynamic Analogy for a Linear Elastic Antiplane Slot Problem with Perfectly Plastic Ligaments at Its Ends

It is shown that a two-dimensional analogy exists between an inviscid incompressible fluid flow around two finite-length flat plates (Riabouchinsky problem) and that of a straight slot cut in a linear elastic plate having rounded ends that are on the verge of yielding plastically. For the plates, a uniform flow at infinity is assumed in a direction perpendicular to the side-by-side parallel lines that constitute the two-dimensional geometry of the plates. Correspondingly, the slot has a boundary condition at infinity of a uniform shear traction in the antiplane direction. In the fluid flow problem, two free streamlines form at both ends of the flat plates, while in the slotted plate problem, the rounded ends of the traction-free slot surfaces constitute ligaments of perfectly plastic material. The specific shape of the rounded ends of the slot problem can be inferred by analogy with the fluid flow problem.

UWB Slotted Circular Disc Monopole Antenna with Inverted U Shaped Defected Ground Plane for Brain Cancer Detection

In this paper the new design of UWB inscribed slotted circular disc monopole antenna is used in the detection of brain cancer is presented. The proposed antenna design consists of circular patch and the bandwidth is increased to cover the UWB frequency range of 3.2 GHZ to 10.6GHZ by embedding square shaped slot cut at the centre and a pair of inverted U shaped cut in the ground plane which gives a defected ground structure that provides the fractional bandwidth more than 110%[3.2 -10.6GHZ]. The proposed antenna is designed and fabricated for brain cancer detection. FR4 substrate is used with printed circular monopole radius of 15mm and with finite ground plane of (60mm x 50mm). It is designed with thick substrate with the thickness of h=1.6mm and high dielectric constant of Iµr=4.4. The voltage standing wave ratio is of (1-1.5). The proposed antenna design provides minimum return loss, better fractional bandwidth, satisfactorily radiation pattern.

Characterization of inverse diffusion flames in vitiated cross flows via two-photon planar laser-induced fluorescence of CO and 2-D thermometry

Two-photon, planar laser-induced fluorescence (PLIF) of carbon-monoxide (CO) and two-dimensional thermometry employing two-color, hydroxyl radical (OH) PLIF are used to characterize atmospheric-pressure inverse diffusion flames. These flames are important tools to aid the understanding of secondary reaction zones that may form in gas turbine engines when film-cooling air reacts with fuel-rich packets from the combustor. For the experiments performed in the present study, exhaust from a propane–air well-stirred reactor is channeled to a test section where three different film-cooling geometries are used to create inverse diffusion flames: (1) a single row of normal cooling holes, (2) a slot cut at an angle of 30° with respect to the wall, and (3) an 5×11 array of cooling holes. It is found that CO and H2 concentrations of a few percent can lead to secondary reaction zones and that different cooling-hole geometries can produce dramatically different secondary reaction-zone shapes. These secondary reaction zone flames have Damköhler numbers greater than unity and are diffusion limited. The PLIF measurements show regions where CO is consumed, OH produced, and the temperature perturbed. For film-cooling flows that remain attached to the wall, the secondary reaction zone is also close to the wall and can cover a relatively long axial length. For film-cooling flows that separate from the wall, the secondary reaction zones protrude farther into the cross flow then quickly mix with the cross flow. By comparing the CO, OH, and temperature fields, three characteristic regions of flows with secondary reaction zones are identified: the injection region where cooling air displaces the vitiated cross flow, the secondary reaction zone region, and the mix-out region where all of the oxygen has been consumed and mixing with the vitiated cross flow controls the local composition and temperature.

The microwave Hall effect measured using a waveguide tee

This paper describes a simple microwave apparatus to measure the Hall effect in semiconductor wafers. The advantage of this technique is that it does not require contacts on the sample or the use of a resonant cavity. Our method consists of placing the semiconductor wafer into a slot cut in an X-band (8–12 GHz) waveguide series tee, injecting microwave power into the two opposite arms of the tee, and measuring the microwave output at the third arm. A magnetic field applied perpendicular to the wafer gives a microwave Hall signal that is linear in the magnetic field and which reverses phase when the magnetic field is reversed. The microwave Hall signal is proportional to the semiconductor mobility, which we compare for calibration purposes with d.c. mobility measurements obtained using the van der Pauw method. We obtain the resistivity by measuring the microwave reflection coefficient of the sample. This paper presents data for silicon and germanium samples doped with boron or phosphorus. The measured mobilities ranged from 270 to 3000 cm2/(V s).

Statistical analysis on the bandwidth of a dual frequency textile antenna

A novel dual frequency, wide band textile antenna has been proposed. A slot cut out of a regular rectangular patch revealing a vertical dumbbell-shaped conducting region resonates at global positioning system (L1 and L3) and time division duplex long term evolution fourth generation bands. The radiation efficiencies of the antenna at the lower and upper resonant frequencies are 96 and 88%, respectively. The antenna is fabricated using double side silver coated conductive fabric on a denim substrate and experimentally validated. The textile antenna resonates from 1.435 to 1.81 GHz and from 2.755 to 3.19 GHz. The antenna has a bandwidth of 375 and 435 MHz, that is, fractional bandwidth of 25.08 and 12.6% at the lower and upper bands, respectively. The fabricated antenna is then subjected to bending, shear, stretching deformations and their effects on the bandwidth of the antenna are analysed using analysis of variance method. The significant factors and their percentage contribution on the bandwidth are also determined using the F-test. Finally, an empirical equation is derived for the designed antenna to compute the bandwidth and the results are validated.

On the Design of Slot Cut Circularly Polarized Circular Microstrip Antennas

Circularly polarized microstrip antenna is frequently realized by cutting the slot inside the patch and feeding it along the diagonal axis. In the reported literature, procedure to design them at any given frequency is not available. In proposed work, circularly polarized slot cut circular microstrip antenna at 900 MHz is discussed. By studying the surface current distributions at two orthogonal modes, formulations in their resonant length are proposed. The frequencies calculated using them closely agree with simulated results. Using proposed formulation, procedure to design circular polarized antennas at different frequencies is presented that gives circular polarized response. Thus, proposed work will be helpful to design similar circular polarized circular microstrip antenna at any desired frequency.

A stacked sierpinski gasket fractal antenna with a defected ground structure for UWB/WLAN/RADIO astronomy/STM Link applications

ABSTRACTAn aperture coupled stacked Sierpinski gasket fractal antenna with a defected ground structure is proposed in the current article for ultra wide band (UWB) and wireless local area network (WLAN) applications. The radiating structure is formed of two Sierpinski gasket fractal patch antenna layers on two layers of FR4 substrate stacked one over the other. This stacked structure is fed by a third (bottom) layer also of FR4 substrate, with ground layer at its top and the feed line with a stub, at the bottom. The top ground layer has a ‘†’ shaped slot cut in it to provide a wideband behavior to the antenna, and the feed line is designed with a stub to provide circular polarization to the EM fields radiated by the proposed antenna. The antenna is designed using CST Microwave Studio version 2010 assuming perfect boundary conditions. The proposed antenna shows a dual band wideband behavior with an impedance bandwidth of 630 MHz (4.75–5.38 GHz) and 400 MHz (6.8–7.2 GHz) with a gain of 5.85 dB and 9.5 dB at the center frequencies of the two bands, respectively. The antenna is capable of covering two UWB bands from (4.75–5.28) GHz and (6.8–7.2) GHz, a radio astronomy band from (5.01–5.03) GHz and IEEE 802.11a band from (5.15–5.35) GHz. The prototype of the proposed antenna is tested using a VNA and an anechoic chamber to validate against the simulated results. The proposed antenna has volumetric dimensions of 6 × 6 × 0.483 cm3 which makes it a suitable choice for RF front end circuits. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2786–2792, 2015

Radiation and Scattering of Electromagnetic Waves by a Multielement Vibrator–Slot Structure in a Rectangular Waveguide

A problem of radiation and scattering of electromagnetic waves by a structure, consisting of a narrow transverse slot cut in the broad wall of a rectangular waveguide and two vibrators with a variable surface impedance located inside the waveguide and interacting with one another, is solved. A solution of integral equations for electric currents at the vibrators and equivalent magnetic current in the slot is derived using the generalized method of induced electro-magneto-motive forces (EMMF). Conditions needed to achieve maximum slot radiation coefficient are defined. Computed and experimental graphs of electrodynamic characteristics of the vibrator–slot structure for different vibrator locations and for the various surface impedance distributions along the vibrators are presented.

Compact broadband modified triangular microstrip antennas

Slot cut compact shorted 60° sectoral microstrip antenna and its complementary configuration are proposed. The slot optimises the spacing between higher order TM1/4,1 and fundamental TM1/4,0 modes to yield broadband response. On air substrate of thickness 0.105λ 0, shorted 60° sectoral patch antenna yields a bandwidth (BW) (VSWR ≤ 2) of more than 600 MHz (821–1428 MHz, ∼54%), whereas its complementary configuration yields BW of more than 480 MHz (655–1142 MHz, >50%). The proposed antennas show a broadside radiation pattern with a gain of more than 3 dBi over the complete BW.

Dual Polarization Slotted Miniature Wideband Patch Antenna

An ordinary patch antenna can be modeled as a simple resonance LC parallel circuit. This means that the resonant frequency may be lowered if the patch has slot cuts to increase the inductance L without affecting the parallel C. This communication presents a novel design of miniaturizing: a square patch with 4-C shaped slots of two polarizations. The antenna is miniaturized to λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> /8 size but with excellent port isolation of more than -30 dB. It has two polarizations, with a simulated bandwidth of about 6.9%. The T-probes are used to feed the 4-C slot-cut patches to widen the bandwidth. A lumped circuit feeding for the 4-C slot-cut patch antenna is also introduced. The lumped components can replace the single-stubs of the T-shaped proximity feed and thus maintain the miniature size. Although our design has a low radiation efficiency of ~ 20%, it provides a low-cost solution that is useful for applications of short-range two-way communications (e.g., antenna of wireless mouse). The idea can be used to simplify the industrial transceiver design.

Slot Cut Ultra Wide Band Antennas

The ultra wide band antennas are required in applications where larger bandwidth for the transmitting signal is needed. They cover wide bandwidth in the range from 500 MHz to the frequencies above 8000 MHz. In this paper, a review of various techniques to realize ultra wide band microstrip antennas (MSA) is presented. They are realized by using different techniques like basic planar monopole antenna and the variations of the same by using different shapes of radiating monopole antenna, like, bi-conical, Bowtie, etc. They are also realized by using modifying the feeding strip shape or by cutting the slot inside the patch. The ultra wide band (UWB) response has also been realized by using fractal shapes in the radiating monopole antenna. Towards the end of paper, the scope of future work is proposed, wherein the exact formulation of resonant length is needed for planar monopole antenna at its fundamental and higher order modes as well as the explanation for the ultra wide band response in terms of operating modes in slot cut and fractal geometries.

Analysis of Broadband L-probe fed Microstrip Antennas

suspended microstrip antenna on thicker substrate is realized by using non-contact L-probe feeding technique. The guidelines for selecting total L-probe length are not available in the reported literature. In this paper, an analysis of broadband L-probe fed variations of microstrip antenna like, circular microstrip antenna, annular ring microstrip antenna, rectangular microstrip antenna, E-shaped microstrip antenna and half E-shaped microstrip antenna, is presented. It was observed that, total L-probe feed length nearly equals quarter wavelength at the resonance frequency of equivalent patch. Further using this quarter wavelength approximation, L-probe fed rectangular and circular microstrip antennas were re- designed at different frequencies which results into the broadband response with formation of loop inside the VSWR = 2 circle. The comparison between two non-contact feeding techniques of microstrip antenna, namely proximity feed and L-probe feed is presented. The two have similar performance in terms of bandwidth and radiation pattern, with proximity feeding technique to be the simplest method to be implemented in thicker substrates. Keyword microstrip antenna, Circular microstrip antenna, Annular ring microstrip antenna, E-shaped microstrip antenna, Broadband microstrip antenna, L-probe feed upon the ratio of vertical strip length to its horizontal length for the given patch substrate thickness. The design guidelines for properly selecting the strip vertical and horizontal lengths are not reported in the available literature. In this paper, various reported broadband designs of L-probe fed RMSA, U- slot cut CMSA, annular ring MSA, E-shaped MSA and half E-shaped MSAs are discussed. Further using their optimized designs the formulation for total L-probe length in terms of operating wavelength of the resonance frequency of the radiating patch is proposed. The total L-probe length was found to be around quarter wave in length at the patch resonance frequency. Using this approximation, RMSAs and CMSAs were re-designed at different frequencies. This results in broader BW with formation of loop in the impedance locus inside the VSWR = 2 circle. For RMSA, the comparison between the non-contact proximity feeding and L-probe feeding technique is presented. It was observed that in terms of operating BW and radiation pattern characteristics, both these techniques yields nearly the same performance, however as against L-probe feeding, the proximity feeding is simpler to implement especially in thicker substrates. The proposed study was carried out using IE3D software (18) and to validate the simulated results, measurements were carried out using finite square ground plane of side length 40 cm. The input impedance response was measured using R & S vector network analyzer.

Slot cut printed elliptical UWB monopole antenna

ABSTRACTA novel compact ultra‐wideband slot cut elliptical printed monopole antenna is proposed. The measured bandwidth (BW) from 1.6 GHz to more than 22 GHz (&gt;170%) has been obtained. The gain, radiation efficiency and radiation patterns, over the entire BW, remain similar to that of a printed elliptical monopole antenna with reasonable agreement between simulated and measured results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:631–635, 2014

Dual Band Dual Polarized Slot Cut modified Circular Microstrip Antenna

new broadband and dual band circular slot cut modified circular microstrip antenna is analyzed and proposed. The parametric study to analyze the effects of circular slot which realizes broader bandwidth is presented. The circular slot creates two additional resonant modes near the fundamental TM11 mode resonance frequency of the equivalent circular patch and yields bandwidth of 202 MHz (8%). The polarization of the two modes which realizes broadband response was found to be orthogonal, which leads to the principal plane variations over the bandwidth. Further by using this concept, a circular slot cut dual band and dual polarized circular slot cut circular microstrip antenna in 1000 MHz frequency band is proposed. The proposed antenna yields dual frequency response with orthogonal polarization and variable frequency ratio with bandwidth of 2% at the dual frequencies.

ENERGY CHARACTERISTICS OF A SLOT CUT IN AN IMPEDANCE END-WALL OF A RECTANGULAR WAVEGUIDE AND RADIATING INTO THE SPACE OVER A PERFECTLY CONDUCTING SPHERE

A mathematical model of a spherical antenna excited by a slot cut in an impedance end-wall of a semi-inflnite rectangular waveguide was built using a rigorous solution of the problem. Control of energy characteristics is accomplished by changing impedance distributed on the end-wall of the waveguide section. If the waveguide is excited by the wave H10, the wavelength tuning reaches (30{ 35)%, i.e., about a half of the wavelength range of single mode waveguide regime.

Broadband and Dual Band Modified Rectangular Microstrip Antennas

The more frequently used technique to realize broadband and dual band microstrip antenna is by cutting the slot at an appropriate position inside the patch. In this paper, an in-depth analysis of dual band rectangular slot cut rectangular microstrip antenna and plus shaped slot cut broadband rectangular microstrip antenna is presented. The dual band slot cut antenna is reported to be resonant at 3640 and 4080 MHz. Through the analysis it was observed that the slot modifies the resonance frequencies of TM11 and TM02 mode of the rectangular patch and optimizes the impedance at them to realize dual frequency response. Further when an additional horizontal slot is cut inside the above rectangular slot which realizes plus shaped slot, it further reduces TM02 mode resonance frequency and along with the TM11 patch mode, yields broadband response. The proposed analysis gives an insight into the functioning of the slot cut patch antennas operating at higher order modes as well as it will help them in designing them in given frequency band.

Analysis of Broadband E-shaped Microstrip Antennas

The broadband E-shaped microstrip antenna is realized by cutting pair of rectangular slots on one of the radiating edges of rectangular microstrip antenna. While designing an Eshaped antenna at given frequency, the slot length is taken to be nearly quarter wave in length. However this simpler approximation does not give closer results. In this paper, first a comparison of slot frequency calculated by using quarter wavelength approximation against simulated data for an optimized E-shaped antenna, is presented, which shows larger error. Further a detailed analysis to study the effects of slot on broadband response in E-shaped microstrip antenna is proposed. It is observed that slots do not introduce any additional mode but reduces the resonance frequency of higher order orthogonal TM02 mode of the patch and along with fundamental TM10 mode yields broadband response. The slot also modifies the surface current distribution at TM02 mode thereby yielding broadside radiation pattern over complete bandwidth without any variations in the directions of principle planes. Further an analysis of rectangular slot cut rectangular patch is also presented. The rectangular slot reduces orthogonal TM01 mode frequency of the patch and along with its TM10 mode, yields broadband response. The proposed analysis gives an insight into the functioning of widely used E-shaped antenna, and it will help in designing them in given frequency band.

Proximity fed Broadband Microstrip Antennas

broadband microstrip antenna is realized by fabricating the patch on lower dielectric constant thicker substrate in conjunction with proximity feeding technique. Using thicker substrates, a formulation for an edge extension length and design guidelines for strip dimensions in proximity fed broadband antennas, are not available. In this paper, first by designing suspended rectangular and circular microstrip antennas on different substrate thickness and at various frequencies in 800 to 6000 MHz frequency band, graphs for an edge extension length are developed. Using them an edge extension length at given frequency and substrate thickness is calculated. The suspended patches were further designed using edge extension length graphs which give closer result with the desired frequency. Further by using proposed equations, proximity fed microstrip antennas were optimized at various frequencies in 800 to 6000 MHz frequency band. Using these optimized designs, a formulation for coupling strip parameters is proposed. By using proposed formulations for edge extension length and strip parameters, proximity fed antennas were re-designed at different frequencies in 800 to 6000 MHz frequency band. In all the configurations, broadband response with formation of loop inside VSWR = 2 circle is obtained. Also by using the proposed formulation, design procedure for proximity fed U-slot cut rectangular microstrip antenna is explained. The U-slot cut antenna gives bandwidth of more than 450 MHz at center frequency of around 1000 MHz. The proposed formulations can be used to design broadband antennas using thicker substrate at any given frequency. Keywordsctangular microstrip antenna, Circular Microstrip Antenna, Equilateral triangular microstrip antenna, Edge extension length, Proximity feeding, Broadband microstrip antenna coupling strip which is either placed below or in the plane of the patch. A larger BW is realized due to electromagnetic coupling between the patch mode and the strip. This method yields broader BW for thickness more than 0.060. The BW of MSA is also increased by cutting a slot inside the patch (4 - 8). Further increase in the BW of slot cut MSA is realized by using proximity feeding technique (9). In proximity feeding method, for the given patch and strip substrate thickness, design parameters are, the strip dimensions and its position below or in the plane of the patch. In the available literature on proximity feeding, the design guidelines for given substrate thickness and operating frequency are not available. In this paper, design formulations for broadband proximity fed MSAs on thicker substrates are proposed. First by designing rectangular MSA (RMSA) and circular MSA (CMSA) at a given frequency and for different substrate thickness in 800 to 6000 MHz frequency band, plots for an edge extension length against substrate thickness are developed. Using them an edge extension length at any given frequency and substrate thickness is calculated. By using the proposed graphs, patch was re-designed at different frequencies in the above frequency band. It gives patch resonance frequency at nearly the same desired value with an error less than 2%. Further broadband proximity fed RMSA, CMSA and equilateral triangular MSA (ETMSA) were designed at different frequencies in the 800 to 6000 MHz frequency band. Using their optimum designs, the formulations for strip dimensions and its position below the patch for the given patch substrate thickness is proposed. Using edge extensions graphs and the formulation for strip dimensions, proximity fed RMSA, CMSA and ETMSA were re-designed at different frequencies in 800 to 6000 MHz frequency band. A broadband response with the formation of loop inside the VSWR = 2 circle is obtained. Using proximity fed formulations, a detail design procedure for proximity fed U-slot cut RMSA is also presented. It gives broadband response with BW of more than 450 MHz (>45%). The above study was carried out using IE3D software followed by experimental verifications (10). In IE3D simulations an infinite ground plane was used. In measurements the antennas were fabricated using the copper plate having finite thickness and were supported in air using the foam spacer support placed towards the antenna corners. The antenna was fed using N-type connector of 0.32 cm inner wire diameter. At all the frequencies, measurements were carried out using R & S vector network analyzer (ZVH 8 model) using finite square ground plane of side length 100 cm. This larger ground plane simulates the effect of infinite ground plane. The radiation pattern was measured in minimum reflection surroundings with required minimum far field distance between reference antenna and antenna under test (11). The antenna gain was measured using three antenna method (11). The proposed