The primary requirement for maximum power transfer and minimum power loss is matched impedance in a transmission system. However, static design variations in system such as parasitics and dynamic variations such as changes in transmission frequency will result in reflections. A redesign or reconfiguration of complex systems is neither easy nor cost effective. A noble technique for compensating reflections in a communication system is presented here. The proposed methodology adapts the system to change without any modification to the system physical configuration. In this methodology compensation signals are added by I/O drivers with programmable phase delay and drive strength adjustments to cancel reflections. The concept application is demonstrated for a narrow bandwidth antenna system. An operating frequency off the antenna frequency results in a degraded received message eye. Using the proposed technique, without modifying the antenna, reflections were compensated and a significantly improved data eye was produced, as measured by the enhancement of critical performance parameters. The architecture of an expanded driver to implement the concept is outlined here. An algorithm and flow chart to dynamically identify and compensate for reflections are also presented.
The resonance frequency of Split-Ring Resonators (SRRs) loading a microstrip transmission line was tuned by means of a Ba0.5Sr0.5TiO3 (BST) ferroelectric thin film. For a bias of 30 Volts, we obtained a band-stop response with a shift around 7% of the resonance to higher frequencies in Ku band. The originality of the device under test is (i) the utilisation of single C-shaped SRRs, (ii) the localisation via chemical etching of the BST film to voltage controlled interdigitated capacitances and (iii) the enhancement of the operating frequency (around 17 GHz).
In this paper, we present a new dual band planar antenna. The proposed antenna consists of a microstrip patch with a U-shaped slot that is fed by a broadband electromagnetic coupling probe, known as L-probe. Radiation characteristics of the antenna and different methods for control of the resonant frequencies are investigated.
This paper presents microstrip array antenna integrated with novel shapes of 2D-electromagnetic band-gap structure (2D-EBG). Three different shapes of 2D EBG are used for harmonic suppression, optimizing the current distribution on the patches and decreasing the mutual coupling between array elements. As a result, the performance of the antenna array is improved. The three novel shapes of 2D-EBG presented are star, H shaped and I shaped slots. Simulated and measured results verify the improved performance of the array antenna compared to the antenna without EBG as well as antenna array with conventional EBG shapes. The harmonic suppression and reflection coefficients are improved by about 18 dB. Minimum mutual coupling is less than -20 dB, and the antenna size is reduced by 15% compared to the original size.
Two novel designs for compact reconfigurable antennas are introduced for wireless communication devices. These designs solve the steering frequency problem by tracking the desired resonance frequency or by generating various operating frequency bands to be selected electronically. In the first design, the length of the rectangular defected ground structure (RDGS) is electrically adjusted to change the resonant frequency of the MPA. While in the second design different turns of spiral AMC ground plane generate frequency bands, or modes, that are selected/optimized to serve different communication systems simultaneously. These systems may include various combinations of bluetooth, S-band and wireless local-area network (WLAN). These designs have several advantages as the total antenna volume can be reused, and therefore the overall antenna will be compact, although, the radiation of the MPA is kept fixed without any degradation. The designs are verified through both numerical simulations and measurement of a fabricated prototype. The results confirm good performance of the single and multiband reconfigurable antenna designs.
A novel approach is proposed for automated dimension estimation in memory polynomial based power amplifiers/transmitters behavioral models. This method consists of successively identifying the static nonlinearity order and memory depth of the model in accordance with a predefined performance criterion. The proposed method is validated using a 3G Doherty power amplifier driven by various WCDMA signals. Experimental results demonstrate the robustness of the proposed successive sweep approach compared to the conventional blind simultaneous sweep approach. The proposed dimension estimation method is an enabling tool for efficient design optimization of power amplifiers circuits to enhance their linearizability.
A novel planar dipole for Ultra-High-Frequency (UHF) Radio Frequency Identification (RFID) systems is presented here. Referring to a realization based on the use of a chip produced by Texas Instruments, the proposed design approach has been numerically and experimentally investigated. Reported results demonstrate that the proposed antenna exhibits good radiation properties and matching (|S11|<-10 dB) over the entire UHF RFID bandwidth (860-960 MHz).
This paper suggests the design of a novel miniaturized dual-band bandpass filter based on the composite right/left-handed (CRLH) metamaterial structure. In detail, subwavelength resonators are realized through the zeroth order resonance (ZOR), and inverter structures are proposed to control the coupling between neighboring ZOR resonators. The proposed technique is validated by the EM predictions, the proof of metamaterial properties with the ZOR field distributions and extracted constitutive parameters, and measurements. It is found that the suggested method enables the remarkable size reduction from the conventional filters such as the parallel coupled type which is designed on the basis of the half-wavelength resonance.
In this paper a novel method for crosstalk reduction is proposed. This is achieved through using the step shaped transmission line, which basically attempts to create steps along the transmission lines to decrease the crosstalk, while having negligible variation in return loss. To this end, various simulations are carried out to get an intuition regarding the underlying processes conducted to the far-end crosstalk, thereby enabling to optimize the far-end crosstalk, and simultaneously to yield a small variation in the return loss. Accordingly, a conventional coupled transmission line is employed as a benchmark, enabling to have an idea regarding the impact of the proposed method in terms of the ability to decrease the far-end cross talk. Furthermore, the proposed transmission line and the benchmark structure are fabricated and then evaluated to verify the experimental results to that of the simulation. In addition, comprehensive parametric studies have been carried out to get insight on the effect of various adjustable parameters over the crosstalk. The obtained results show that the crosstalk is decreased more than 4 dB over the entire operating bandwidth. Some advantages such as ease of design and fabrication have made the proposed technique an advisable method when dealing with low crosstalk.
A new reciprocal heuristic diffraction coefficient for lossy dielectric wedge is presented which is applicable to arbitrary positions of transmitter and receiver in a complex channel environment. The prediction obtained using proposed coefficient is compared with those obtained using rigorous Maliuzhinets'solution. The comparison shows significant improvement over available heuristic coefficients. The coefficient is valid for both parallel and perpendicular polarizations. Further, the measurement of the electric field in the vicinity of edge of the building is carried out, and the measurement result, thus obtained, is compared with predictions using the proposed coefficient.
In this paper, a novel band-notched circular slot (BNCS) antenna for ultra-wideband (UWB) communication is proposed. This antenna is comprised of a circular stub that excite similar-shaped slot aperture. The proposed antenna is designed on the RO4350B substrate with thickness of 500 μm and relative permittivity (εr) of 3.4 to operate in UWB band released by the US's Federal Communications Commission (FCC) in 2002 (i.e., 3.1-10.6 GHz). To reject the frequency band of 5.15-5.825 GHz, which is limited by IEEE 802.11a and HIPERLAN/2, an inverted-cup strip is parasitically attached to the feed layer. The size of our proposed antenna is 50×50 mm2, and this antenna has good radiation characteristics. Effects of varying the parameters of parasitic inverted-cup strip on performance of the proposed antenna have been studied. The antenna with optimal parameters obtained from parametric study is fabricated and measured. It is observed that the simulated and experimental results have good agreement with each other.
This paper presents a CPW-fed planar inverted cone antenna (PICA) for ultra-wideband (UWB) communication applications. The proposed PICA provides a conventional monopole type omnidirectional radiation pattern, and it utilizes the advantages of the coplanar-waveguide (CPW) to simplify the structure of the antenna into a single metallic level. To improve radiation characteristics, a tapered and corrugated ground plane is used. In addition, the PICA's radiating element with three self-similarity holes is attempted to enhance performance of the antenna. The simulated and measured results demonstrate that the proposed PICA achieves a broad impedance bandwidth from 1.3 GHz to 11GHz within the magnitude of S11 (dB) less than -10 dB and maintains nearly omnidirectional radiation characteristics.
This paper presents the design of a novel dual-band unequal Wilkinson power divider. The proposed power divider can operate at arbitrary two frequencies without reactive components. The design and analysis of power divider are presented. The structure of the power divider and the formulas used to determine the design parameters have been given. Closed-form design equations are derived based on network theory. For verification, a microwave power divider operating at 1 and 2 GHz is fabricated, the experimental results show that the designed unequal power divider fulfills all the features of a conventional Wilkinson power divider.
A proposal for the new modified W type optical fiber structure with ultra high effective area and small dispersion as well as dispersion slope is presented. For the proposed structure, all these features are achieved due to placing extra depressed cladding layers, which is the key to achieve higher effective area and flat dispersion curve compared with the conventional W structures. Meanwhile, the suggested design method is based on the Genetic Algorithm optimization technique to choose optimal value for the structural parameters. Also, our calculation for extracting optical properties of the proposed structure is evaluated analytically. The designed dispersion flattened single mode fiber has dispersion and its slope respectively within [0.1741-0.9282] ps/km/nm and [(-0.011)-(0.0035)] ps/km/nm2 in the spectral range of [1.46-1.625] μm (S+C+L bands) which are noticeably smaller than the reported value for ultra-low dispersion slope fibers . The designed fiber has ultrahigh effective area from 103.56 to 232.26 μm2 in the above wavelength interval. Meanwhile, we show that there is a breakthrough in the quality factor of the ultra-low, ultra-flattened chromatic dispersion single mode optical fiber.
In this paper, we propose a circularly polarized (CP) stacked annular-ring microstrip antenna (SARMSA) with an integrated feeding network in the UHF RFID band. A circular parasitic patch is suspended above the annular ring to improve the impedance matching and bandwidth. Through the parametric studies on SARMSA, the CP characters of the entire antenna are well understood，and an optimized CP character is obtained. Prototypes are fabricated to confirm the theoretical results. The experimental results indicate the impedance bandwidth for S11<-10 dB is 870-967 MHz (10.6% at 915 MHz)，and the 3 dB AR bandwidth is 893-948 MHz (6%). Meanwhile, the measured CP gain reaches 8.9 dBic at 915 MHz.
Holography is a technique employed to make three dimensional images using electromagnetic waves. Holographic interferometry is one of the most important applications of holography. It is concerned with the formation and interpretation of fringe patterns, which appears when a wave generated at some earlier time and stored in a hologram is later reconstructed by interfering with comparison wave. We report a technique, which uses double exposure holographic interferometry together with simple mathematical interpretation, which allows immediate finding of stress, mass, fringe width and thickness of thin film. We tested different normalities of solutions. It is observed that increase in deposition time increases thickness and mass of thin film but decreases stress to substrate. The thin films are prepared using electrodeposition technique. The structural, optical and surface wettability properties of the deposited films have been studied using X-ray diffraction (XRD), optical absorption and contact angle measurement, respectively.
This paper presents the simulation study of a wideband modified fractal rectangular curve iteration-1 (FRC-1) dielectric resonator antenna (DRA) along with conventional FRC DRAs of different iteration levels for WiMAX application. The simulation study has been carried out using CST Microwave Studio software. The design procedure and radiation performance characteristics of modified and conventional FRC DRAs are described and the simulation results for modified FRC-1 DRA are compared with those of a conventional FRC-1 DRA of identical outer dimensions. The simulation results for the material dielectric constant dependent radiation characteristics of both the FRC-1 DRAs are also presented. The results presented here may be useful in designing portable personnel communication device antennas and in analyzing the performance of these antennas for wireless communication.
We have investigated elliptical annular ring microstrip antennas having a sine wave periphery both theoretically and experimentally. The proposed antenna gives a good circular polarization at the center frequency of 1.296 GHz, with measured 3 dB axial ratio bandwidth of about 0.73% (9.5 MHz) and impedance bandwidth of about 1.7% (22.0 MHz). Input and radiation characteristics are also examined for different sine wave amplitudes applied to the periphery of elliptical ring patch antenna.
With deregulation of telecom sector (law 24/96) in our country (Morocco), many operators of cellular network appear. Among the operators technology that operate, we find GSM9800 and CDMA900 that are used by two different operators. It turns out from the measurements of indicator of quality of service that the performance of GSM900 is degraded, and the major cause is the interference created by CDM800 which cannot be neglected. In this paper, we adopt a new approach in order to make GSM900 and CDMA800 operate in harmony. This method is based on a physical optimization of antenna systems and could be understood as a physical symmetry rotation in the space of parameters such that tilt and Azmit control the system. It independently reduces the interference effects on the distance between the base stations. Moreover, it allows us to improve client service without using hard installations and inexpensive technologies.
In this paper, a dual-loop gate antenna is designed to generate the magnetic field distribution in various directions. It is applied to Radio Frequency Identification (RFID) systems for animal identification operating at the low frequency (LF) band of 125 kHz and 134.2 kHz. The percentage of volume of magnetic field intensity is introduced and used as a figure of merit in the design. The optimum antenna parameters are also designed by the genetic algorithm (GA) in conjunction with the Numerical Electromagnetic Code (NEC). The prototype antenna was fabricated and tested to confirm the antenna performance in the LF-RFID system for animal identification. It is found that the dual-loop gate antenna can be efficiently used in the LF-RFID system.