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Additive manufacturing (AM) is making a big leap in the manufacturing technology world primarily due to its unique capability to produce parts in a layer-by-layer fashion from the digital 3D model with immense versatility in terms of design complexity. In addition, AM does not require any additional tooling and can produce parts with minimal to no material loss. Despite these technological advantages, AM is not making inroads to its potential, mainly due to a lack of fundamental understanding of all the AM processes and cohesive efforts in standardization, metrology (the science of measurement), qualification and certification. As a result, AM produces parts with higher complexity and features yet lacking dimensional accuracy, precision, the required level of tolerances and intended material properties. Particularly, the process-specific standardized metrology and inspection methods for the parts made by AM play a major role in imparting the desired quality and subsequently facilitate the process of certification of the AM part. Considering this, the present article provides (1) a comprehensive review of generic metrology and in-situ, real-time inspection methods that are currently utilized for the parts produced from conventional manufacturing processes in use, as well as (2) a comprehensive review of metrology and in-situ, real-time inspection methods currently and/or may be utilized for the parts produced from AM processes. In addition to these, the appropriate metrology and inspection methods are recommended here for various AM processes. NSWC Corona, the leading agency for the U.S. Navy’s Metrology and Calibration (METCAL) program, is playing an important role towards addressing these AM metrology challenges.

The challenges of high heterogeneous multi-layer reservoirs were a driver for ADNOC to establish new well completion requirements. Based on this, the well completion strategy was revised in order to improve the completion design for a Dual Oil Producer (DOP) initially well planned without accessibility into the upper drain. The solution was successfully implemented by drilling the well having a Multilateral Dual String Level 5 Completion System to have full reservoir isolation and mechanical accessibility to TD in both drains.A major approach was implemented giving the utmost importance to all operational risks concerning drilling and completion. The design relies on the Latch Coupling (LC) pre-installed with the production casing as the foundation for the successful drilling and cementing the upper drain liner and for different completion runs. Thus, a level 5 multi-lateral completion coupled with Inflow Control Devices and Pre-perforated Liner in the upper and lower lateral respectively was successfully deployed.The main advantages of this technology compared to the initial proposal are:Brings effectively two single wells from one slot of the wellhead tower as it provides independent access & control for enhanced reservoir management (well stimulation, production logging and water shut-off). Substantial cost savings due to the utilization of one slot only. Conventional single designs need two slots to deliver equivalent completion requirements. The completion technology meets the Well Integrity Policy & Completion Guidelines stated by ADNOC to have full accessibility to all drains.This is the first Level 5 configuration installed in UAE integrated with a lower completion. The design enhances the benefits of the multilateral construction by providing full mechanical & pressure isolation at the junction throughout the life of the well. Furthermore, accessibility to both laterals from surface without the use of a re-entry deflector or any constraints was deemed to be paramount for a successful well construction.

The findings presented in this paper are a result of unclassified literature research of different types of biosensors within a larger context of biological warfare. This paper discusses different ...

The theorem proposed in the original article ( IEEE Microw. Wireless Compon. Lett. , vol. 25, no. 3, pp. 145–147, Mar. 2015.) regarding the replacement of six quarter-wavelength lines of conventional rat-race coupler (RRC) using asymmetric two-port networks (TNs) is absolutely correct. This letter will further illustrate the concept of single-frequency equivalence of the conventional RRC using asymmetric TNs.

We have performed a design optimization of a stiffened panel with curvilinear stiffeners using an artificial neural network (ANN) residual kriging based surrogate modeling approach. The ANN residual kriging based surrogate modeling involves two steps. In the first step, we approximate the objective function using ANN. In the next step we use kriging to model the residue. We optimize the panel in an iterative way. Each iteration involves two steps-shape optimization and size optimization. For both shape and size optimization, we use ANN residual kriging based surrogate model. At each optimization step, we do an initial sampling and fit an ANN residual kriging model for the objective function. Then we keep updating this surrogate model using an adaptive sampling algorithm until the minimum value of the objective function converges. The comparison of the design obtained using our optimization scheme with that obtained using a traditional genetic algorithm (GA) based optimization scheme shows satisfactory agreement. However, with this surrogate model based approach we reach optimum design with less computation effort as compared to the GA based approach which does not use any surrogate model.

A novel uniform theory of diffraction (UTD)-type diffraction coefficient for a straight edge in a cylindrically curved screen valid for both convex and concave side wave incidence is obtained via uniform asymptotic theory of diffraction (UAT) formulations. The proposed curved screen UTD-type coefficient (CSUTD) allows uniform description of the fields at all aspect angles including the grazing incidence case, where UTD coefficient-based predictions deviate sharply from available measurements, when it is applied to the problem of monostatic radar cross section (RCS) of cylindrically curved plate.

An asymmetric structure is in general never equivalent to a quarter-wavelength (symmetric) transmission line. However in this letter a theory has been derived, wherein each of the six quarter-wavelength transmission lines of a conventional rat-race coupler can be replaced by any arbitrary asymmetric structure connected in identical orientation. The theorem exploits the mirror-symmetry of a rat-race coupler, even when the asymmetric structure is used as its building block. It is also observed that every asymmetric structure has an equivalent frequency independent symmetric representation when used in a rat-race coupler. Asymmetric-T has been used as an example of the asymmetric-structure to demonstrate the accuracy of the theory and has been compared with that of the conventional and existing asymmetric-T based couplers.

The preparation and complex permittivity and permeability measurement of a new U-type of hexaferrite microwave absorbing material (Ba4 Mg2 − x Mn x Fe36 O60) is reported for different value of x in range 0 ≤ x ≤ 2. Complex permittivity and permeability values of hexaferrite pellets are measured using a vector network analyser (VNA) in X-band. The reflection loss of the materials is computed for different values of x and thickness using the measured permittivity and permeability values. The optimum reflection loss is found to be −43 dB for hexaferrite pellet (x = 0.5) at a thickness of t = 1.7 mm. Microwave absorbing paint pellets are prepared by mixing hexaferrite powder with polyimide solution and their complex permeability and permittivity are also measured using a VNA. Using these measured values, radar cross-section reduction simulation for artillery shells has been carried out using electromagnetic simulation software in the 8–10 GHz frequency range. A maximum radar cross-section reduction of 15 dB has been observed for a 30 mm artillery shell at 9 GHz.

This paper presents a computation of the absolute free space capacitance and electrostatic body potential of a spacecraft using moment method with triangular patch modeling. Expressions are derived numerically and the moment integral is evaluated. The capacitance of a square plate is computed to validate the approach. Finally, the free space capacitance of a typical spacecraft is computed for various configurations and body potential is evaluated. The derived expressions are simple and suitable for developing the charging analysis tool. As this approach is more general, it can be easily applied to any practical spacecraft configuration.

A novel application of signal-interference technique to branch-line coupler design is proposed for miniaturization and wideband harmonic passband suppression. The coupler's second, third and fourth harmonic passband responses are attenuated due to a pole at each of these harmonics. Design equations and graphs are provided using lossless transmission line model. A prototype coupler, having a compact (λ g /6)2 area, that is 44.4% of the (λ g /4)2 conventional coupler area, is fabricated in microstrip form for validation purposes. The input matching, isolation, amplitude and phase balance bandwidths of the proposed coupler are comparable to those of the conventional coupler.

Although there are closed-form solutions for calculating the Probability of False Accept (PFA) and the Probability of False Reject (PFR) of normally distributed measurement errors, there lacks solutions for non-normal distributions. Extending our knowledge to measurement errors that do not follow the normal distribution is beneficial to lowering the risk of having a high PFA or PFR. This research finds that the Uniform Distribution is generally not useful for assessing PFA and PFR.

In this paper, simple shunt open-stub units are used to design a compact balun with suppressed harmonic response. The stopband response of shunt stubs has been utilized to suppress the harmonic passbands. Design guidelines are presented with equations and graphs based on transmission line model. To validate theoretical predictions, an experimental prototype microstrip balun, with suppressed harmonic passbands up to six times the operating frequency, and occupying only 25% of the conventional balun circuit area is presented.

A novel application of a dual-transmission line is proposed to design a lowpass filter (LPF). The proposed structure uses only transmission line elements to produce an equiripple LPF response with sharp roll-off. Design equations are derived using a lossless transmission line model. Controlling the electrical lengths, three transmission-zeros are realized in the stopband to obtain a sharp roll-off rate and wide stopband bandwidth. A single unit microstrip LPF with a 3-dB cut-off frequency at 1.0 GHz having a roll-off of 135 dB/GHz along with a stopband bandwidth of 69.5% is designed for validation.

In this article, we demonstrate that the compact bandstop filter (BSF) configuration consisting of an edge-coupled microstrip line connected in parallel to a transmission line section can produce multiple transmission zeros in the stopband. A lossless transmission model is used to derive the condition for two, three, or four transmission zeros. A prototype BSF at 2 GHz achieving a wide 20 dB stopband bandwidth of 92.8% with sharp rejection along with a better than 30 dB return loss in the passband is fabricated for validation purposes. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2265–2268, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26258

This article presents the design of harmonic suppressed compact microstrip balun, using shunt open-stubs. Two approaches using Π-shaped and T-shaped open-stub configurations are investigated. Because of the stopband effect of the open-stubs, the harmonic passband responses are suppressed effectively. A compact-size balun is realized because both kinds of structures have slow wave characteristics. To validate theoretical predictions, two prototype baluns operating at f0 = 1 GHz, showing size reduction up to 75% and no spurious passband up to 4f0 compared with the conventional design are fabricated in microstrip form. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.

Finite edge geometrical theory of difiraction (FEGTD) approach is a new and latest improvement in GTD technique. This FEGTD technique is applied to the E-plane horn radiation problems with spherical source excitation. The radiation patterns obtained with the FEGTD approach are found to be in good agreement with measured results.

In this letter, explicit transmission zero conditions, for the ultra-wide bandstop filter (BSF) with five transmission zeros, are derived using even-odd mode, analysis. The BSF topology is obtained by folding the two connecting transmission lines in a conventional optimum BSF to compose a stub-loaded coupled-line section and using λ g/2 end open-stubs. A necessary and sufficient condition is explored for the crucial coupled-line section to produce three transmission zeros. Further, it is shown that the same five zeros BSF stopband bandwidth and rejection level performance is obtained with compact three zeros BSF (without λ g/2 open-stubs) with improved passband flatness and return loss.

A simple design of a sharp-rejection microstrip bandpass (BPF) filter is presented. By creating multiple transmission zeros in the lower and upper stopbands, sharp rejection characteristics are obtained. The basic filter unit consists of a single parallel coupled-line section and an open-ended stub. A lossless transmission line model approach is used to derive the design equations for frequency responses and transmission zero positions. The bandwidths are controllable by the zero locations that in turn are controlled by varying the impedances of the configuration. To validate theoretical predictions, two prototype BPFs operating at lower band 2.4 GHz of WLAN are fabricated in microstrip form.

In this article, the design of a broadband branch-line coupler (BLC) with reduced size and suppressed harmonic passband response is presented. The proposed approach can be used to replace the low impedance λ/4 lines of the conventional BLC by an equivalent structure almost λ/12 in length. The main advantage of the proposed BLC is that, it has approximately the same bandwidth as that of a conventional BLC. A prototype broadband coupler having fractional bandwidth >50% at 1.1 GHz and of size less than one third of a conventional three-section wideband BLC topology is realized. In addition, at least 20 dB suppression of up to fourth harmonics is achieved. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.

In this article, a single coupled-line configuration is presented for the design of compact, sharp-rejection, wide-stopband low-pass filters. The proposed filter topology consists of parallel coupled-lines shorted at the middle. The filtering action results from the generation of three transmission zeros brought about by cross coupling. Design equations and guidelines to adjust both bandwidth and the rejection depth are provided. Theoretical predictions are validated in microstrip line by fabricating a two-unit prototype filter having better than 25 dB stopband, which is at least five times the filter cut-off frequency. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1402–1405, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25166

The earlier geometrical theory of diffraction (GTD) approach to the H-plane horn radiation problem is reconsidered with spherical source excitation. Corner diffraction terms are included to provide a GTD model for the finiteness of the horn edges. A new heuristic corner slope diffraction (CSD) coefficient for a finite edge in a conducting plane is presented. The H-plane horn pattern, obtained with the addition of the corner diffraction and the new CSD terms to the earlier infinite edge GTD approach, is found to be in better agreement with measured results compared to earlier GTD formulations.

In this article, a novel transmission line (TL) shunt stepped impedance open stub configuration has been presented to design a dual-band bandstop filter with impedance controlled center frequencies and bandwidths. Design guidelines are derived using lossless TL model. The high-impedance lines required for TL sections facilitate convenient meandering that makes the geometry compact. To validate theoretical predictions, a prototype filter operating at two bands 1.5 and 3.4 GHz has been fabricated. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2274–2277, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24635

In this letter, a design of a compact, dual-band, rat-race coupler is presented. The dual-band characteristics are obtained by using two shunt open-stubs with the conventional coupler. The proposed design can cover a wide range of frequency ratio of the dual bands within the fabrication limit of a low and high impedance microstrip line. Frequency variations of the bandwidths of this coupler in terms of isolation, matching, amplitude, and phase imbalance are also discussed. Theoretical prediction has been verified in the microstrip line by fabricating a dual-band coupler at the 900/1900-MHz mobile bands. Experimental results agree well with the theoretical predictions. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 277–281, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23063

Testing electronic equipment for radiated emissions requires the accurate calibration of EMI sensor. The performance of the sensor depends on its Antenna Factor (AF), which is the ratio of the incident electric field on the antenna surface to the received voltage at the load end across 50Ω resistance. The theoretical prediction of the AF of EMI sensors is a very attractive alternative if one takes into consideration the enormous expenditure and time required for calibrating a sensor experimentally. In this work, FDTD is developed to predict the performance of rectangular waveguide for EMI sensors.

In this study, a novel transmission line configuration has been proposed to design a sharp-rejecting, compact bandstop filter with wide rejection-bandwidth. Signal interference technique is used to obtain transmission zeros, which provide the sharp rejection characteristic. Rejection bandwidth is controlled by the characteristic impedances of transmission lines. Filter is analyzed using transmission line model. Theoretical predictions have been verified by the measurements of two compact filters fabricated in microstrip line. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1244–1248, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23335

In this paper, analysis of a rat-race coupler having three equal arms of arbitrary electrical length is presented. All of these couplers have lower characteristic impedances than the conventional 1.5-lambda coupler and some of them have smaller electrical lengths. Bandwidths in terms of isolation, matching, amplitude, and phase imbalances are also discussed. A reduced-size rat-race coupler of length 19lambda/18 at the operating frequency of 0.9 GHz has been fabricated in the microstrip line. Experimental results agree well with the theoretical predictions.

An accurate antenna factor (AF) is highly desirable for radiated emission and/or normalized site attenuation measurements. An AF is often measured in the presence of a perfectly conducting ground plane and reflectors. For a receiving antenna; the ground plane or reflectors affects the electromagnetic field by altering the magnitude and distribution of the incident field. It also introduces mutual coupling between the antenna and its image beneath the ground. These effects can cause a different measured AF when the same antenna is polarized horizontally or vertically in respect with ground, or calibrated at a different height. Using a monopole antenna: we conduct a numerical analysis to quantify the influence of the ground and reflector on the AF.

Electromagnetic Interference (EMI) is becoming a crucial issue in the era of modern electronic systems. For EMI measurement, it is required to place a sensor to receive the radiation from the equipment in a suitable test environment. The performance of the sensor depends on its Antenna Factor, which is the ratio of the incident electric field on the antenna surface to the received voltage at the load end across 50 Ω resistance. FDTD is one of the efficient numerical techniques to solve radiation and scattering problem in any environments. To the best of the knowledge of the authors no literature is available where FDTD is used to evaluate the Antenna Factor. Here, in this work we applied FDTD to predict the performance of dipole antenna when it is used as a EMI sensor. The results presented here for free space environment are compared with published results.

A new method, with branches having an equivalent series inductance using defected ground structure, is proposed for size reduction and harmonic suppression of branch-line coupler. The proposed structure is 35% of the conventional branch-line coupler at 1 GHz and the measured third harmonic signal is less than −30 dB. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1966–1969, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21830

This paper presents the analysis of linear tapered waveguide. Voltage-standing-wave-ratio (VSWR) is obtained from transmission matrix of the taper waveguide. Taper section is divided into number of section having uniform length. Transmission matrix of taper waveguide is found by multiplication of transmission matrix of each section. Transmission matrix of each section is obtained as the product of three matrices. One is of the initial length of transmission line,second one is due to discontinuity and third one is of the final length of transmission line. Transmission matrix of discontinuity is obtained by two methods. One is by equivalent circuit of step discontinuity and another is by moment method. The results are seen to be in good agreement with (1,2) and (3).

This paper describes the performance of different loaded wire antennas (e.g., inverted L, T, I and C-shaped antennas) as electromagnetic interference (EMI) sensors. Loaded wire antennas in transmitting mode are widely used for low frequency communication. However, while using these antennas as EMI sensors, the extra loading is likely to introduce the reception of cross-polarized component of incident electric field and investigation on this has not yet been performed. This paper highlights the results of the initial investigation on the performance of these loaded antennas as EMI sensors in terms of the Antenna Factor for the desired and cross-polarized component of incident electric field. The Method of Moments with Pulse basis function and Point-matching technique has been used to evaluate the current distribution on the antenna surface and hence the Antenna Factor.

The findings presented in this paper stem from the survey of unclassified literature on additive manufacturing (AM)/3D printing technologies and their metrology (science of measurements). AM technologies allow engineers to design and build parts more freely than ever before. They also help to make production more distributed and eliminate obsolescence. This paper introduces different types of AM, as well as metrology challenges that NSWC Corona, the leading agency for the US Navy's Metrology and Calibration (METCAL) program, needs to address. It discusses potential uses, process limitations and metrology related to three popular categories of AM technologies; material extrusion (e.g., fused deposition modelling), powder bed fusion (e.g., selective laser melting) and directed energy deposition (e.g., laser-engineered net shaping). Powder bed fusion and directed energy deposition have proved capable of firearm and aerospace-grade manufacturing. AM technologies demonstrate huge promise and may revolutionise design, manufacturing, logistics, maintenance and acquisition in the Navy. However, there are still multiple hurdles to overcome before AM becomes an effective component in the military toolset. As AM continues to advance, the only way to ensure these new technologies fit as reliable pieces of the warfighter arsenal is to prioritise the development of corresponding measurement techniques and calibration schedules.

The ratio of incident electric field at the surface of receiving antenna to the received voltage at the antenna terminal when terminated in 50 ohms load is known as the antenna factor. It is an important parameter of a sensor used for EMI measurements. To determine electromagnetic radiation from an electronic component it is required to evaluate the field strength at a certain distance from it using the sensor. If the antenna factor of the receiver and the received voltage are known then the field can be found out applying simple relations. In this paper a simple and useful Method of Moment-based theoretical technique is described to evaluate the antenna factor of wire antenna. The wire is considered as perfectly conducting with radius much less compared to the wavelength of operation. The wire is divided in large number of small segments. A point matching technique is applied to evaluate the surface current distribution due to the incident electric field. The output impedance is found out from the short ...

A novel application of shunt open-stubs at the feed points of a center fed coupled-line hairpin resonator is presented for the design of compact lowpass filter (LPF) with very wide stopband. The transmission zeros of the basic unit are minimally affected by its association with the stubs. The stopband bandwidth and filter roll-off rates achieved here are larger than those achieved earlier. A prototype microstrip LPF having a very wide stopband up to nine times the filter cutoff frequency is fabricated.

This letter presents the design of a compact bandstop filter (BSF) operating at two frequencies. The proposed BSF consists of open-ended stepped impedance resonators (OSIR) and an end-shorted parallel-coupled microstrip line (E-PCML). The OSIRs are used to achieve the impedance-controlled stopband positions. The wide BSF bandwidths are achieved through enhanced coupling of the E-PCML. Explicit design guidelines are derived using a lossless transmission line model. To validate theoretical predictions, a prototype dual-band BSF operating at 900 MHz and 2,100 MHz with fractional bandwidths of 72% and 36%, respectively, is implemented in microstrip.

In this letter, a modified optimum bandstop filter (BSF) design is presented. Broad stopband and sharp rejection characteristics are achieved by realizing three transmission zeros near the passband edges. Stopband rejection depth and bandwidth can be controlled by the impedances of the configuration. A lossless transmission line model analysis is used to derive design equations. Further, a compact geometry is chosen by replacing the low impedance section with its equivalent dual-high impedance lines, which facilitates convenient folding. To validate the theoretical prediction, a single unit sharp-rejecting prototype BSF having a 20 dB rejection bandwidth of 126% at 1.5 GHz has been fabricated.

We present the design of a compact microstrip lowpass filter with a wide stopband which is up to ten times the cutoff frequency. The filter is based on a coupled-line configuration and shunt open stubs. The open stubs create additional transmission zeros, which are used to extend the stopband of the filter without any additional components or cascaded units. A prototype lowpass filter with a 3 dB cutoff frequency of 0.428 GHz and a 15 dB stopband extended up to 4.77 GHz is fabricated to validate the theoretical predictions.

In this article, a compact microstrip coupled-line configuration has been presented to design a wideband bandstop filter with three transmission zeros. These transmission zeros are utilized to obtain sharp rejection characteristics. A loss-less transmission line model is used to obtain the filter design parameters. To validate the theoretical prediction, a single section sharp-rejecting, compact, bandstop filter having a 20-dB rejection bandwidth of ∼100% at 1.5 GHz has been fabricated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2955–2957, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23819

In this letter, a novel transmission line configuration has been proposed to design a sharp-rejection, bandstop filter (BSF) with wide rejection bandwidth. The rejection bandwidth and the level of rejection are controlled by the characteristic impedances of the transmission lines. Design equations are obtained by using a lossless transmission line model. The proposed design has been verified in microstrip line by fabricating a prototype BSF of -20 dB fractional bandwidth of 100% at a stopband center frequency f0 = 1.5 GHz. The filter structure is simple and easy to fabricate.

A compact unit of parallel coupled transmission line is presented for design of a compact, sharp-rejection, wideband bandstop filter (BSF). The rejection depth and bandwidth can be easily controlled by the coupled-line parameters. A lossless transmission line model is used for filter analysis. Design equations and graphs are presented in order to facilitate the design procedure. Theoretical prediction is verified in microstrip line by fabricating a prototype single section coupled-line BSF.

In this article, a new configuration has been proposed for miniaturization of a branch-line 90° hybrid coupler. The present coupler is obtained by replacing the low impedance series arms of a conventional coupler by their equivalent parallel high impedance lines. This arrangement facilitates meandering, used to realize a compact geometry. The main advantage of the proposed coupler is that it has approximately the same bandwidth as that of a conventional one. A prototype coupler area is 45.3% of that of a conventional branch-line coupler. The design is validated by full-wave electromagnetic simulation and measurement. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1135–1137, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23320

A new compact microstrip low-pass filter (LPF) is presented using a novel rectangular patch compact microstrip resonant cell (RPCMRC) and square-head defected ground structure (DGS). It exhibits wide, high stopband, and sharp rejection. A demonstration LPF having 3 dB cutoff frequency of 2.65 GHz was fabricated and measured. Measured rejection is better than 20 dB from 2.8 to 16 GHz. Electrical length of the filter is less than 20% of the guided wavelength at 3 dB cutoff frequency. Measured passband to stopband attenuation slope is more than 56 dB/GHz. Good match between experimental and simulated results are obtained. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 798–800, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22259

A novel compact microstrip low-pass filter (LPF) is proposed using open circuit stubs and square patches alongwith complementary split ring resonator (CSRR). It exhibits wide stopband and sharp rejection. A demonstration LPF, having 3-dB cutoff frequency of 1.45 GHz, was fabricated and measured. Measured passband to stopband attenuation slope is more than 355 dB/GHz. Measured rejection greater than 20 dB extends over more than 13.75 times of the 3-dB cutoff frequency. Electrical length of the filter is less than 12% of the guided wavelength at 3-dB cutoff frequency. Experimental and simulated results agree well. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2865–2867, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22825

Brownian dynamics simulations have been carried out on a binary colloidal mixture of particles of two different diameters interacting via a Derjaguin-Landau-Verway-Overbeek potential. As the screening length is increased a transition from liquid to crystal (at a volume fraction φ=0.2) or a glassy state (at φ=0.3) is observed. Below a certain effective temperature T⋆, the temporal evolution of the mean-squared displacements shows a marked subdiffusive behavior at intermediate and long times. The supercooled liquid with φ=0.3 shows a staircase profile indicating strongly cooperative jump motion which is corroborated by the behavior of van Hove self-correlation functions and the non-Gaussian parameter. The van Hove distinct correlation function, in the β relaxation regime, shows a factorization property in accordance with the mode-coupling theory predictions. The most interesting result is the observation of cooperative hop and subsequent hop-back motion at temperatures close to the glass transition.

Complementary split ring resonators are used to design compact, low insertion loss (IL), low pass filter with sharp cut-off. A prototype filter implementing area is 0.23 lambdagtimes0.09lambda g, lambdag being the guided wavelength at 3-dB cut-off frequency (fc) 1.887GHz. Maximum IL is within 0.5dB up to 1.717GHz and 20-dB stopband extends up to 3.4fc

In this letter, complementary split ring resonators (CSRR) are proposed to design bandpass filters (BPFs) having wide controllable 3-dB fractional bandwidth (FBW). FBW can be varied between 10% and 100%. In addition, filters have the advantages of compactness, sharp rejection, low insertion loss (IL), and low cost. Two prototype fabricated filters of FBW 10.8% and 81.6% show a maximum passband IL of 1.2dB. Filter occupying area is less than 0.25lambdagtimes0.15lambda g, where lambdag is the guided wavelength at the midband frequency

A new compact defected ground structure (DGS) is proposed for the microstrip line. The structure is compact in microstrip line direction. Here, this DGS is used to design a compact low pass filter (LPF) that is at least 26.3% more compact lengthwise than other reported compact structures and has sharper transition knee.

In this letter, a novel compact structure is proposed for bandpass filter (BPF) design. The structure is realized using only one resonator. The resonator is excited by two open microstrip stubs. Further, ground plane aperture technique is used to obtain wide bandwidth. 3-dB fractional bandwidth can be varied between 1.0 and 90.0% with good in band as well as out of band filter characteristics. The filter has the advantages of compactness, wide bandwidth, low insertion loss (IL), and ease of fabrication. A prototype fabricated filter of FBW 45.1% and passband center frequency f0 = 3.795 GHz shows a maximum passband IL of 2.0 dB. The basic BPF occupying area is less than 0.22 λg × 0.23 λg, where λg is the guided wavelength at f0. A simple stub modification extends its upper stopband at least three times the upper cutoff frequency. Good agreement between measurements and simulations are obtained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 29–31, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22039