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This paper presents the design and development of planar triplexer slot antenna using substrate integrated waveguide (SIW) technology. The proposed antenna is realised using 'Y' shaped slot backed by SIW cavity. SIW cavity is excited by three separate feed lines for resonance at three different frequencies of 5.7 GHz, 6 GHz and 6.4 GHz with unidirectional radiation pattern and gain of 6.26 dBi, 5.87 dBi and 5.19 dBi, respectively. Average isolation of the three ports is better than 24 dB. All the simulations are carried out using high frequency structure simulation (HFSS) software. The proposed antenna is fabricated on RT Duroid 5880substrate and measured results show better performance. The developed antenna is small in size (0.79 λ × 0.78 λ), simple to fabricate and easy to integrate with planar technology making it suitable for C-band application. [ABSTRACT FROM AUTHOR]

Space-time block code and spatial multiplexing are promising approaches that exploit the multiple input multiple output (MIMO) channel to provide high diversity and multiplexing gain without sacrifice in bandwidth. In this paper, a hybrid MIMO scheme for orthogonal frequency division multiplexing systems is proposed to achieve various multiplexing gains according to the channel condition. The existing hybrid MIMO schemes are appropriate for limited integer multiplexing rates without taking into account the channel condition, whereas the proposed scheme can attain various multiplexing rates according to the channel condition. [ABSTRACT FROM AUTHOR]

This paper explores how an evaluative framework of resilience might be utilised to assess the impact of new digital technologies. This paper outlines key themes and indicators from recent literature on community-level and rural resilience and incorporates insights from work on digital inclusion and rural information and communication technologies to build a framework of rural community resilience. It then highlights a successful case study carried out by the Digital Engagement and Resilience project and describes some of the methodological challenges that can be encountered in cross-cutting evaluative work in a digital economy context. Finally, it contextualises this work in the current policy climate of rural digital agendas to stress the growing need for holistic and critical approaches to ‘resilience’. [ABSTRACT FROM AUTHOR]

A conventional energy harvester typically consists of a cantilevered composite piezoelectric beam, which has a proof mass at its free end while its fixed end is mounted on a vibrating base structure. The resulting relative motion between the proof mass and the base structure produces a mechanical strain in the piezoelectric elements, which is converted into electrical power by virtue of the direct piezoelectric effect. In this article, the harvester is provided with a dynamic magnifier consisting of a spring-mass system that is placed between the fixed end of the piezoelectric beam and the vibrating base structure. The main function of the dynamic magnifier, as the name implies, is to magnify the strain experienced by the piezoelectric elements in order to amplify the electrical power output of the harvester. With proper selection of the design parameters of the magnifier, the harvested power can be dramatically enhanced and the effective bandwidth of the harvester can be improved. The theory governing the operation of this class of cantilevered piezoelectric energy harvesters with dynamic magnifier (CPEHDM) is developed using the Generalized Hamiltons's Principle. Numerical examples are presented to illustrate the merits of the CPEHDM in comparison with the conventional piezoelectric energy harvesters (CPEH). The obtained results demonstrate the feasibility of the CPEHDM as a simple and effective means for enhancing the magnitude and spectral characteristics of CPEH. [ABSTRACT FROM AUTHOR]

We present a theoretical study on optoelectronic properties ofn-type monolayer MoS2under long-wavelength light radiation. The optical conductance for such material system is evaluated using the energy-balance equation derived from the Boltzmann equation in the presence of linearly polarized radiation field. Forn-type monolayer MoS2, the optical absorption in terahertz bandwidth can be achieved via intra spin-conserved transitions and inter spin-flip transitions at K and K′ valleys. More importantly, we find that there is a terahertz absorption peak in the radiation frequency range 2–10 THz. The intensity and width of this absorption peak depend sensitively on temperature and the position of the peak can be tuned via changing the electron density. This study shows thatn-type monolayer MoS2can be applied as frequency tunable THz optical and optoelectrical devices. [ABSTRACT FROM AUTHOR]

In this paper, an efficient link bandwidth design method for the Network-on-Chip (NoC) is proposed to satisfy NoC performance requirements with less bandwidth cost. First, the relationship between link bandwidth and the data delay is constructed. Then, a bandwidth allocation method is proposed to assign proper bandwidth to each link in NoC. Finally, the effectiveness of our method is validated through simulation. The simulation results show that the NoC can satisfy the system performance requirements after using our bandwidth allocation method. Moreover, compared with the NoC with uniform link bandwidth, our method can reduce the cost of link bandwidth. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for networking of high-bandwidth services in existing homes has resulted in several options for implementing an in-home network. Among the options are power-line communication techniques, twisted-pair copper wires, wireless links, and plastic or glass optical fibers. Whereas it is easy to install high-bandwidth optical fibers during the construction of new living units, retrofitting of existing homes with networking capabilities requires some technology innovations. This article addresses some trade-offs that need to be made on what transmission media can be retrofitted most effectively in existing homes. [ABSTRACT FROM PUBLISHER]

A small broadband and low cost switched-beam smart antenna suitable for mobile WiMAX applications (band class 5-3.5 GHz) is presented in this paper. Present mobile terminal antennas are expected to show increased bandwidth as well as low-loss impedance matching while maintaining low-profile geometry. The proposed structure consists of four planar inverted-F antennas (PIFA) connected forming a cross, sharing the same ground plane, in a configuration designed for symmetrical coverage of the horizontal plane (Cross-PIFA). A custom genetic algorithm (GA) is used in order to optimize the proposed antenna parameters regarding resonant frequency and radiation pattern orientation angle and beamwidth. The optimized antenna exhibits small size (dimensions cm), satisfactory directivity for mobile terminal applications of 3.38 dB over an operation bandwidth of 120 MHz around the central frequency of 3.5 GHz. Simulation and measurement results and parameters range are exposed below followed by the according radiation pattern and variation of the VSWR indicating consistency between design and implementation. [ABSTRACT FROM AUTHOR]

This paper presents a novel dual-band bandpass filter with two sets of stub-loaded open-loop resonator, using stepped-impedance, which results in a reduction in size. Two sets of resonators are synthesized using a doublet coupling scheme for 60/77 GHz resonance. The two passbands are flexible due to implement with two parallel transmission paths and tuning each bandwidth independently by changing even-mode resonant frequency. The fractional 3-dB bandwidths at 60 and 77 GHz are 11.4 and 8.3%, respectively. The values at 60 and 77 GHz are -2.26 and -2.63 dB and the values at 60 and 77 GHz are -24.8 and -18.5 dB, respectively. Between the two passbands, the transmission zero at 67 GHz gives nearly 22.6 dB isolation. Good performance makes this system attractive for wireless communications. [ABSTRACT FROM AUTHOR]

Compact coplanar waveguide (CPW)-fed zeroth-order resonant (ZOR) antennas with broad bandwidth are presented in this paper. The ZOR characteristic is introduced by the composite right/left-handed (CRLH) unit cell on the CPW single layer substrate. The modified structure with a gradual change of the feeding part enables this impedance-matching property. Three prototypes of the designed antennas are fabricated to verify the predictions and the measured -10 dB bandwidths are all more than 30%. The features of easy fabrication and extended bandwidth have made the antennas valuable in wireless communications. [ABSTRACT FROM AUTHOR]

Modern wireless communication systems need antennas with further bandwidth and smaller size. Fractals have unique properties such as self-similarity and space-filling. The concepts of fractals can be applied to the design of low-profile and multi-band antennas. In this article, a super wideband antenna by applying a new fractal geometry to a wire monopole antenna is presented. The modelling and simulation are performed using SuperNEC electromagnetic simulator. The results show that the proposed antenna can be used for frequency range 10–40 GHz, i.e. it is a super wideband antenna with 30 GHz bandwidth. Radiation patterns and gain are also studied and show a good agreement over the bandwidth. [ABSTRACT FROM PUBLISHER]

Free-space optic links are degraded by such weather conditions as rain, fog, and atmospheric scintillation. The inherent advantages of free-space optic communication—providing higher data rates, security, and easy redeployment ability—motivate the avoidance of switching over free-space optic links to low bandwidth radio frequency links. This article establishes viable alternatives over free-space optics/radio frequency hybrid links to achieve higher capacity operation exploiting on–off keying and multiple pulse position modulation schemes with variable data rates to overcome the effect of fading due to adverse weather conditions. Results of an experimental free-space optical link at 1,550 nm are presented. [ABSTRACT FROM AUTHOR]

The next generation wireless systems are supposed to handle high data rate as well as large coverage area. It should consume less power and utilize bandwidth efficiently. At the same time, the mobile terminals must be simple, cheap, and smaller in size. In wireless environment, the quality of received signal level degraded due to path-loss and shadowing from various obstacles in propagation path. In addition to this, signal quality suffers from fading due to constructive and destructive interference of multi-path components which makes it difficult for the receiver to extract the message correctly. Effect of fading can be suppressed by diversity technique in which replicas of signal is provided to the receiver. Receiver can make a decision on behalf of these replicas; hence, reliability of reception can be improved. Diversity can be achieved with the help of multi-antenna system where multiple antennas are installed at transmitter/receiver. However, implementing multiple antennas at wireless terminal is not practical due to size, cost, and weight constraints. Recently, cooperation among nodes has been the subject of great interest among the research community because it creates spatial diversity in wireless network, even if individual nodes do not use antenna arrays for transmission and reception. Here, achieved diversity gains can be translated into robustness against fading for same transmit power or substantially reduced transmitted power for same level of performance. In this paper, we discussed the state of art of cooperative communication. [ABSTRACT FROM AUTHOR]

Short-slot couplers are a particular type of waveguide directional coupler commonly used due to their compact size in comparison with other waveguide configurations. The common short-slot Riblet coupler is used as a 3 dB hybrid (equal power division to the coupled and the through ports) in microwave networks supporting high power and providing good performance over a moderate bandwidth. In this article, the general case of short-slot couplers with arbitrary power division is presented, in E- or H-plane configuration. Moreover, it is shown that the port closer to the input can handle either more or less power than the further port, depending on the design parameters and the length of the main guide of the coupler. Several designs in E- and H-plane are shown to introduce the concept. In addition, two experimental prototypes, with either rectangular waveguide interfaces or coaxial input/output, are manufactured and tested showing good agreement with the expected results. [ABSTRACT FROM AUTHOR]

A classic phase lock loop (PLL) consists of a voltage controlled oscillator (VCO), a phase detector (PD) or phase comparator and a loop filter. The characteristics of a PLL are well established. A modification is introduced in the VCO in the name of phase modulation input along with its original frequency modulation input. This paper analyzes the characteristics such as damping factor, relative stability, noise bandwidth, transient behavior in this modified version of 2nd order PLL and compares them with the classic PLL. [ABSTRACT FROM AUTHOR]

This paper presents the design of electromagnetic band gap (EBG) structure using fractals geometry and its effect on antenna performance. The EBG structure has been designed on substrate ∈r=4.3 and thickness h=1.53 mm. The 1st iterative EBG structure offers the surface wave suppression around 20 dB down from 2.94 to 4.58 GHz corresponds to 43.62% bandwidth. The experimental results of 2nd iterative EBG structure revealed the surface wave suppression in two bands from 2.45 to 3.36 GHz and from 8.52 to 11.02 GHz. The surface wave suppression bandwidth for both the bands is 31.325 and 25.59%, respectively. The antenna designed with the proposed EBG in same plane exhibits improvement in the bandwidth by 20.5%, gain by 2.44 dB and reduction in back lobe in comparison to antenna without EBG. [ABSTRACT FROM AUTHOR]

A cavity-backed bow-tie dipole antenna is presented as base station antenna for wide band American and European cellular communication systems (1.7–2.17 GHz). A beam widening of the horizontal plane is achieved by the cavity aperture reduction and the inclusion of a metallic support between the cavity floor and the antenna reflector plane. The structure design procedure is exposed, and a reasonable agreement between simulations and measurements is obtained. Single antenna and medium gain array prototypes have been manufactured and tested. A 35% reflection bandwidth and an 85° to 95° sector coverage is achieved in the desired operation band. [ABSTRACT FROM AUTHOR]

In many diagnostics and imaging applications intensity only measurements of the diffracted field are available. Hence, it is of interest to develop procedures able to solve the underlying inverse scattering problem under these conditions. In this paper, we introduce an approach in which the geometrical and electromagnetic properties of unknown complex targets are reconstructed from the squared amplitudes of the diffracted fields. The approach relies on some preliminary considerations on the spatial bandwidth of the diffracted intensities which allow one to fix rules to effectively measure the data and on an alternative formulation of the electromagnetic scattering that lowers the 'degree of non-linearity' of the relationship among the electric features of the targets and the fields. The proposed procedure is tested against benchmark experimental data in the microwave frequency range and the obtained results confirm the possibility of achieving faithful quantitative images of unknown targets from phaseless data without making approximations in the inverse scattering problem. [ABSTRACT FROM AUTHOR]

The digital divide is conventionally measured in terms of information and communication technology (ICT) equipment diffusion, which comes down to counting the number of computers or phones, among other devices. This article fine-tunes these approximations by estimating the amount of digital information that is stored, communicated, and computed by these devices. The installed stock of ICT equipment in the consumer segment is multiplied with its corresponding technological performance, resulting in the “installed technological capacity” for storage (in bits), bandwidth (in bits per second), and computational power (in computations per second). This leads to new insights. Despite the rapidly decreasing digital equipment divide, there is an increasing gap in terms of information-processing capacity. It is shown that in 1996 the average inhabitant of the industrialized countries of the Organization for Economic Cooperation and Development (OECD) had a capacity of 49 kibps more than its counterpart from Latin America and the Caribbean. Ten years later, this gap widened to 577 kibps per inhabitant. This innovative approach toward the quantification of the digital divide leads to numerous new challenges for the research agenda. [ABSTRACT FROM AUTHOR]

In a novel application a slab of S-shaped ring resonators is used to fill a rectangular waveguide for the construction of a band-rejection waveguide filter with adjustable bandwidth and cutoff frequency. Results obtained from theoretical analysis, simulation and measurement of a specific structure are presented. Then, by using finite element simulation, we show that the cutoff frequency and stopband bandwidth of the filter can be controlled by changing the slab substrate properties (permittivity and thickness) and its position inside the waveguide. Results also show that varying the real part of relative permittivity of the slab substrate from 1 to 6, while keeping its physical thickness fixed (0.508 mm), the cutoff frequency drops from 10.6 to 6.9 GHz. On the other hand, when the physical thickness of slab substrate changes from 0.508 mm to 4 mm while keeping its permittivity fixed (εr = 2.2), the filter cutoff frequency decreases from 8.8 to 5.9 GHz. We show that the width of rejection band of the filter can be decreased from about 4.7 GHz to about a few MHz by increasing the distance of the slab from the central plane of the waveguide. [ABSTRACT FROM AUTHOR]

A novel broadband E-plane omni-directional planar antenna is designed and fabricated, which consists of four curved printed dipole radiators with eight parasitical strips. The impedance bandwidth is expanded by properly adding two parasitical strips along the boresight of each dipole radiator. A good omni-directionality is achieved at horizontal plane, and the measured variations of far field-patterns in the E-plane are less than ±1.5 dB, cross polarization levels of all directions in the E-plane better than -10 dB over the operating frequency range 5.1 ∼ 6.8 GHz with the reflection coefficients less than -10 dB. It is demonstrated experimentally that the proposed antenna is suitable for WLAN operation in the 5 GHz band, such as the 5.2 GHz (5.15 ∼ 5.35 GHz) and 5.8 GHz (5.725 ∼ 5.875 GHz) bands. [ABSTRACT FROM AUTHOR]

CPW-fed planar inverted-F antennas (PIFAs) with small ground plane for dual-band performance are proposed. The lower band and upper band can be selected independently: PIFA is for the lower band, and capacitively coupling slot is for the upper band. Moreover, the frequency ratio of upper band to lower band can be obtained from 1 to 3.1. The proposed antenna with wider frequency ratio will enable antenna engineer to design dual-band antenna easily. The radiation patterns for the lower band are decided by the PIFA with the quarter-wavelength electric L-shaped monopole patterns, and those for the upper band are dominant over the coupling slot with the half-wavelength magnetic dipole patterns. Hence, both patterns in the dual-band are near omni-directional. An antenna example is given for WLAN dual-band applications. Simulated data are consistent with the measured ones. Measured impedance bandwidth for 2.4 GHz band is 1090 MHz (47.9%), and that for 5 GHz band is 1180 MHz (20.6%). Additionally, through a suitable adjustment in antenna parameters, a wider bandwidth of 1970 MHz (51.2%) can be obtained with center frequency at 3.845 GHz. The radiation patterns and gains are also studied and analyzed. [ABSTRACT FROM AUTHOR]

A new dual-polarized microstrip patch antenna fed by probe feed and aperture coupled feed is presented. The hybrid feed, a T-shaped microstrip feedline, is adopted to improve the isolation between two ports, and the “hour-glass” shaped slot is used to improve the input impedance of the proposed antenna. The measured center frequency is 2.37 GHz, the return loss for port 1 is -16.08 dB and -21.92 dB for port 2, and the isolation between the two ports is -24.24 dB. Finally, four slots are embedded along the centerline of the ground plane so that the bandwidth of antenna is greatly improved. Good agreement between the measured and simulated results has been achieved. [ABSTRACT FROM AUTHOR]

We analysed stability and predictive capabilities of known nitrogen absorption features between plant material prepared for NIRS (dried) and RS (fresh) studies. Grass spectra were taken of the plant canopy, and again after the grass sample was dried and ground. Models were derived using stepwise multiple linear regression (sMLR). Regression values (adj.r2) produced using the dried material were greater than those produced using canopy material. For dried material only wavebands from the SWIR region were selected. Wavebands selected by sMLR on canopy material were located in both the VNIR and SWIR regions. Using wavebands selected for dried material models produced low adj.r2 values when applied to canopy plant material; differences in adj.r2 values are smaller when wavebands selected in canopy material models are applied to dried material. Widening of nitrogen features produced higher adj.r2 values for both dried and canopy material. This work shows that obtaining models with high predictive capabilities for nitrogen concentration is possible, but waveband selection should not be limited to features identified by NIRS studies. To accommodate for variability in absorption features, and instrument errors, absorption features should be widened. [ABSTRACT FROM AUTHOR]

A broadband circularly polarized (CP) irregular slot antenna with a parasitic slot is proposed. Irregular slot formed by triangles, rectangles and a circle is adopted to achieve both broadband and circularly polarized characteristics. Meanwhile, an accessional slot is cut at proper position to help broadening the bandwidth. A simple 50Ω microstrip line is used to excite this irregular slot. The proposed antenna has a small size of only 25×30×0.8 mm3 and covers a frequency band from 2.35 GHz to 5.95 GHz for S11 less than -10 dB. The 3 dB axial ratio bandwidth is 1.25 GHz (2.65–3.9 GHz) and 0.25 GHz (5.15–5.4 GHz), which are 35.5% and 4.7% respectively. The peak gain of the antenna is 3.19 dB, which appears at 4 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a new configuration of the wide-band amplified spontaneous emission (ASE) source is proposed using dual-stage scheme with a broadband fiber Bragg grating. The ASE source utilizes a Bismuth-based erbium-doped fiber (Bi-EDF) as a gain medium with either forward or backward pumping scheme. A wide-band and flat ASE output is achieved using a forward pumping scheme with the power ripples of less than 4.9 dB and 3 dB bandwidth of 90.5 nm. The ASE spectrum obtained covers the whole C-, L- and extended L-band regions from 1520 to 1620 nm. However, the backward pumping scheme provides a better pumping efficiency as compared to the forward pumping. The total ASE power reaches up to 26.6 mW at maximum pump power of 320 mW with a pumping efficiency of 8%. [ABSTRACT FROM AUTHOR]

A microstrip printed monopole antenna with defect ground plane is proposed. It provides wideband performance with radiation pattern similar to ideal monopole antenna. It is compact and has low profile. It is demonstrated that the antenna provides an impedance bandwidth ranging from 2.37 GHz to 6.12 GHz (for VSWR < 2) and supports a monopole type pattern. Extensive simulations are employed through varying its geometric parameters and discussed in the paper. [ABSTRACT FROM AUTHOR]

Resonator antennas made from simple radiating devices placed between a woodpile and a ground plane are studied. A woodpile is a dielectric three-dimensional electromagnetic bandgap material that presents large stop-bands. A woodpile superstrate and a metallic plane, placed at an appropriate distance from each other, are equivalent to a woodpile cavity, the transmission response of which presents peaks inside the bandgaps. This property can be exploited to obtain highly directive radiators from low-directivity antennas. The cavity is fed by a double-slot antenna. The role of the permittivity of the constituent material of the rods is investigated. An evaluation of the bandwidth is performed for the directivity enhancement of the studied antennas, and the role of the woodpile covering area is pointed out. [ABSTRACT FROM AUTHOR]

In the field of design and engineering education, the fast and expansive evolution of information and communication technologies is steadily converting traditional learning approaches into more advanced ones. Facilitated by Broadband (high bandwidth) personal computers, distance learning has developed into web-hosted electronic learning. The emergence of portable communication devices, wireless, and ad hoc networks has enabled electronic learning to develop into mobile and ubiquitous learning. In the literature there is a fuzziness in terms of the concepts and goals of these advanced learning solutions, mainly because the technological platforms and methodological approaches are not clearly distinguished. This paper attempts to demarcate them based on the level of flexibility in processing courseware and the extent of blending technological heterogeneity. These descriptors allowed us to highlight their differences, not only in terms of the types of interaction devices and communication platforms, but also in terms of the development and manner of using advanced learning solutions. What this paper goes on to illuminate is that by the process of the demarcation based upon the level of flexibility in processing courseware and the extent of blending technological heterogeneity, a more rational, useful and common understanding can be developed. [ABSTRACT FROM AUTHOR]

Investigations of a wideband balanced antenna for mobile handsets covering three bands—GSM1800, GSM1900, and UMTS—are presented. Balanced antennas have advantages in handset applications as they are less affected by juxtaposition with human tissue than unbalanced types. The antenna is a slotted planar dipole with its arms folded and not connected at their ends. The antenna is fed by a balanced voltage source. The antenna impedance was investigated using two different methods, including an S-parameter method and a mirror image method. For the purpose of antenna stability evaluation and power gain measurement, a wide bandwidth planar balun was adopted and modified to feed the antenna from an unbalanced source. For validation, prototypes of the antenna were fabricated and tested. The calculated and measured results in terms of return loss show good agreement and the results also show good wideband characteristics. [ABSTRACT FROM AUTHOR]

A miniature printed sleeve meander antenna used in tire pressure monitoring system (TPMS) is proposed in this paper. By using the meander structures including the radiation patch and ground plane, the antenna provides a degree of 78% miniaturization. Meanwhile, a L-shaped stub is loaded on the meander ground to improve the impedance bandwidth, thus a wide bandwidth of 24.2% (VSWR < 3.0) and 13.8% (VSWR < 2.0) for TPMS application is obtained. The antenna has good radiation pattern characteristic, and its performance is relatively stable. Design details of the proposed antenna and results of both simulations and experiments are presented and discussed. [ABSTRACT FROM AUTHOR]

Low-frequency radio astronomy has become a fascinating research area in the field of astronomy, including on its instrumentation development. In this paper, a multiband VHF antenna for low-frequency transient radio telescope is developed. The multiband has been achieved by combining V-shape half-wavelength dipole, traps, and parasitic elements. Measurement result shows that the antenna can work properly in three different frequencies designated by International Telecommunication Union (ITU) for radio astronomical purposes. [ABSTRACT FROM AUTHOR]

This paper presents a new design of wideband filter for X-band application using hybrid hairpin resonator and half wave coupled line resonator in multilayer microstrip configuration. Different resonator shapes were put on two substrates with different dielectric constants. In this work R/T Duroid 6010 and R/T Duroid 5880 with dielectric constant 10.2 and 2.2 respectively were used as the substrates, producing a very small filter size, only at 10 × 10 cm2. This configuration is not only producing compact size filter, but also high bandwidth since the overlapping gap between two resonators produces a tight coupling which is needed for wideband filter. The filter can cover whole X-band frequencies by producing 44% bandwidth at 10.2 GHz center frequency with excellent responses, where the measured passband return loss for this filter is better than –12.5 dB and the insertion loss is better than 2.3 dB. [ABSTRACT FROM AUTHOR]

A via stitching (VS)-electromagnetic bandgap (EBG) is analyzed with the compact circuit modeling method. From this analysis, a compact EBG structure is proposed to mitigate wideband simultaneous switching noise (SSN) in mobile phones. This EBG structure is compact enough to be used in mobile phones. Simulations and measurements show that the proposed EBG structure meets the requirements of stopband characteristics, having a stopband range from 750 MHz to 3.25 GHz with –60 dB suppression. [ABSTRACT FROM AUTHOR]

Recently, various uncommon materials such as metamaterials have been the subject of intensive research. In this paper, we introduce a new class of materials called double zero materials (DZR) having the real parts of both its epsilon and mu equal to zero and investigate the electromagnetic wave propagation in them, particularly the propagation constant k and intrinsic impedance η. We investigate the reflection and transmission coefficients from multilayer structures made of DZR material located in various media. It is shown that the DZR constants namely k and η and also the reflection and transmission coefficients from the multilayer structures are all real quantities. Several numerical examples are provided for both dispersive and nondispersive DZR materials. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel type of annular ring Printed Monopole Antenna (PMA) for ultra wideband (UWB) applications. The proposed antenna consists of a truncated ground plane and radiating patch with dual annular structure, which provides a wide usable bandwidth with high radiation pattern stability. Moreover, the effects of a double-fed structure inserted in the radiating patch, on the impedance matching and radiation behavior is investigated. Its impedance bandwidth, defined by measured voltage standing wave ratio (VSWR) less than 2, is from 3.1 to 16 GHz with a ratio of about 5.15 : 1. This novel monopole antenna has ultrawide impedance bandwidth, compact size (18 mm × 14 mm), low fabrication lost, and omni-directional H-plane radiation patterns, which are suitable for various broadband applications. [ABSTRACT FROM AUTHOR]

A compact single-layer planar antenna is proposed for dualband operation. The antenna is a coplanar waveguide-fed patch with dual embedded inverted-L shaped slots. The effects of the proposed antenna with/without the embedded slots in the patch on impedance matching condition have been examined theoretically. Prototype of the proposed antenna has been fabricated and measured for the electromagnetic performance including the impedance bandwidth, radiation pattern, and antenna gain. The designed antenna, which, including the ground, is only 18 × 22.5 mm2, leads to good dual bandwidths covering 2.4/5 GHz WLAN operation. Also, a stable radiation pattern and high average gains of about 3.6 and 4.3 dBi, respectively, over the two operating bands have been obtained. [ABSTRACT FROM AUTHOR]

In this paper, a novel method is proposed to design wideband bandpass filters with compact size. Combining half mode substrate integrated waveguide (HMSIW) and periodic dumbbell-shaped defected ground structure (DGS), two compact wideband bandpass filters with different HMSIW-microstrip transitions are fabricated and measured. The filters are found to possess wide passband bandwidth and compact size. Good agreement between the measured and simulated results demonstrates the validity of this technique. [ABSTRACT FROM AUTHOR]

In this paper, a wideband compact planar balun with impedance-transforming ratio of 2 : 1 is developed for push pull applications. The proposed balun is composed of broadside coupled strip lines and lumped capacitors. In this design, by utilizing broadside coupled strip lines with large enough spacing between strip and ground plane, even mode impedance of the transmission line and bandwidth is increased. Size reduction is effectively obtained by the use of discrete capacitors. As an example, one balun on a double-sided PCB is designed, simulated, fabricated and measured. Measured results show that the return loss is better than 15 dB over the frequency band from 470 MHz to 860 MHz, or around 59% bandwidth. The amplitude and phase imbalance between the two balanced output ports at worth case are 0.7 dB and 6 degree, respectively, over the operating frequency band. [ABSTRACT FROM AUTHOR]

A broadband planar antenna fed by coplanar waveguide (CPW) with gradually changed central feeder line is proposed. Central feeder line of the CPW and the ground plane are designed to be graded structure, which endow the proposed antenna with better impedance matching characteristic and broader bandwidth than microstrip line (MSL) fed antenna. Compared with antennas in previous researches, this proposed antenna has smaller size but covers wider bandwidth, which can operate from 0.7 GHz to 5.9 GHz for return loss less than –10 dB, and shows omni-directivity in azimuth plane. [ABSTRACT FROM AUTHOR]

We analyze the spatial-frequency dependence of the gain of phase-insensitive and phase-sensitive optical parametric amplifiers with plane-wave pumping. We discuss the dependence of their spatial bandwidths on pump power and crystal length, L, and observe that the well-known (ks/L)1/2 approximation of spatial bandwidth is not very accurate (here ks is the signal beam's wavevector magnitude). We derive an alternative approximation that is highly accurate at large gains and moderately accurate at low gains. The differences between the phase-insensitive and phase-sensitive amplifier bandwidths are shown to be insignificant for gains above several dB. Maximum phase-sensitive gain and bandwidth are realized by imposing an optimum phase profile onto the input signal's spatial spectrum, which has nearly parabolic shape with added series of π/2 phase discontinuities at spatial frequencies outside the main bandwidth of the amplifier. We show that, apart from the discontinuities, such a profile can be closely approximated by placing the image plane into the middle of the nonlinear crystal (converging input beam). The phase discontinuities contribute an additional narrow component to the point-spread function of the phase-sensitive amplifier. [ABSTRACT FROM AUTHOR]

The paper presents the design of a compact ultra wideband antenna composed of two circular coplanar strips which enclose slot aperture of the similar shape. The antenna is fed with three coplanar strip-lines of 50 Ω. The effect of the outer strip edge on the antenna bandwidth is investigated. This antenna configuration has been modeled and experimentally tested, showing good performance in 1.7–15.5 GHz frequency range where return losses |S11| < –10 dB are achieved. Stable radiation patterns across the whole band is also observed. [ABSTRACT FROM AUTHOR]

This article presents comprehensive methods for the design of a wideband CMOS transmit/receive (T/R) switch. Techniques such as RF floated body to extend the bandwidth and decrease the insertion loss (IL), and stacking architecture with high substrate isolation to enhance the power-handling capability, are used for the design of a T/R switch on a standard 0.18-μm triple-well process. The measured performance of the T/R switch demonstrates the effectiveness of the methods presented in this article such that IL less than 1.28 dB, isolation higher than 24 dB, and input 1 dB compression point of 27 dBm can be achieved from 2 to 5.8 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a novel compact modified pentagonal shaped planar ultra-wideband (UWB) monopole antenna with small size of 19.5 × 21 × 1 mm3 is presented. The band rejection operation achieve at the WLAN band (5.15–5.85 GHz) band by adding two symmetric pentagonal shape parasitic patches. The antenna is fabricated on FR4 substrate with a relative dielectric constant of 4.4 and thickness of 1 mm which fed by a 50Ω line. The calculated and measured impedance bandwidth of the proposed antenna ranges from 3 GHz to 12 GHz for a VSWR less than 2. Also, it has a relatively stable radiation patterns over its whole frequency band of interest. [ABSTRACT FROM AUTHOR]

A novel design of planar Artificial Magnetic Conductor (AMC) based on a Frequency Selective Surface (FSS) for frequencies in the SHF RFID band is presented. A discussion about design parameters and the influence of dielectric substrate thickness on the operating band and on the bandwidth is analyzed. The designed AMC shows polarization angle independency. Its angular margin when operating under oblique incidence is also tested. The discussion is supported by a FEM simulation and measurements in anechoic chamber of the manufactured prototype, with a good agreement between simulations and measurements. [ABSTRACT FROM AUTHOR]

This paper proposes a novel planar Wilkinson power divider operated in 2.4 GHz/UWB with a notch characteristic in the 5.2 GHz WLAN band (4.7–5.7 GHz) by using a simple defected ground structure (DGS). Over the whole operating band except the notched frequency band, the measured results explore broadband operation with return loss of higher than 10 dB, a low insertion loss of less than 0.8 dB and good isolation of higher than 10 dB. It shows good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

A disk-loaded monopole antenna array has been demonstrated, which uses a coplanar waveguide (CPW) feeding technique and has a capability of beam switching. The antenna is designed for 2.45 GHz ISM band for on-body communications or WLAN base station applications. It has a gain of 6.7 dBi, and the input return loss bandwidth is about 10%. The simulation and measurement results show a very good agreement. [ABSTRACT FROM AUTHOR]

In this paper, a printed quasi-rhomboid slot antenna with an end-loaded microstrip feed line is presented. With the use of the quasi-rhomboid slot and the end-loaded microstrip feed line, bandwidth enhancement for wideband operation can be obtained. The final design is fabricated and measured. Measured results indicate that the proposed quasi-rhomboid slot antenna can operate from 4.54 GHz to 15.67 GHz with a 10 dB return loss. Details of the proposed quasirhomboid slot antenna are described. [ABSTRACT FROM AUTHOR]

This paper proposes a new monopole antenna for ultrawideband (UWB) applications. The frequency band is considered 3.1–10.6 GHz, which has been approved by the Federal Communications Commission (FCC) as a commercial UWB band. The proposed antenna has a small size of 33 × 33 mm2 fed by a microstrip line and provides an impedance bandwidth as high as 120% (3 GHz–12 GHz) at a center frequency of 7.5 GHz for S11 < -10 dB. The impedance bandwidth of the antenna is improved by creating two circular slots in patch of monopole antenna. Various mobile communication services such as WLAN (5 GHz), WIMAX (3.4 GHz), and UWB can be easily covered by the proposed antenna simultaneously. [ABSTRACT FROM AUTHOR]

A shorted rectangular-loop antenna is presented for circular polarization applications. The proposed antenna is connected to feeding pin in one end of rectangular-loop metal and shorted to ground in the other end of rectangular-loop metal. It can own wide impedance bandwidth, wide AR bandwidth, and high gain performances in the low profile configuration, especially, without a balanced feeding structure. It is well-known situation of open-loop antenna with circular polarization. The proposed antenna in this paper is interesting for shorted-end of loop antenna, and then, it still has the similar antenna performances as open-loop antenna. An example of WLAN 2.4 GHz application is given. The antenna height is adjusted to fit the required AR bandwidth. The measured impedance's center frequency and bandwidth are 2.56 GHz and 17.5%, respectively. Also, the AR's center frequency and bandwidth are 2.44 GHz and 4.1%, respectively. Both impedance and AR bandwidths satisfy the specification of WLAN 2.4 GHz applications. Besides, radiation patterns are broadside radiation and antenna gain in the operating band is about 8 dBic. The proposed shorted rectangular-loop antenna can be applied to high gain antenna or become the elements of higher gain antenna by its good performances and simple feeding structure in a low profile configuration. [ABSTRACT FROM AUTHOR]