A multiband microstrip antenna is designed for wireless communication application with fractal and defected ground structures. Antenna prototype is fabricated using Rogers RT Duroid 5880 dielectric material on a double layer PCB with dielectric constant 2.2 and thickness 0.8 mm. Through implementing the concept of elliptical shape fractal geometry to microstrip patch antenna, more miniaturization is achieved. Further with defected ground structures, wide impedance bandwidth and gain are achieved. A compact microstrip feedline is used to couple electromagnetic energy to radiator through lumped port. Proposed antenna shows multiband characteristics. Antenna resonates at 2.6 GHz, 6 GHz and 8.2 GHz frequency bands with impedance bandwidth of 410 MHz, 1070 MHz and 4840 MHz. Experimental validation is done to validate simulation results. Antenna operates on different wireless standards like Wi-Fi (2.4 GHz), WLAN (2.4/5.2/5.8 GHz), Wireless Body Area Network (2.3/2.4 GHz), which falls under ISM (Industrial Scientific and Medical) band applications. It also covers communication bands, X-band (8-12 GHz) and S-band (2.3-2.4 GHz).
The paper is focused on reliable analysis of the phenomena associated with the resonant and anomalous transformation of the field of a plane, density modulated electron beam, flying over the periodically rough boundary of a natural or artificial medium, in the field of bulk outgoing waves. The physical results presented here have been obtained as the result of numerical implementation of the rigorous mathematical models described in the two first papers of this series. The corresponding analytical constructions have been associated with the correct formulation of model problems and their algorithmization, with the provision of the possibility of a correct physical interpretation of the results of their numerical solution.
This paper introduces a method for efficiently eliminating false detections in coherent radar systems due to sea spikes. The proposed method employs scan-to-scan processing over a predefined number of successive antenna scans. Processing consists of matching estimated range-azimuth-velocity centroid associated with each radar plot extracted from a set of data detected within the current scan (initial plot) with centroids of radar plots generated in the previous scans. For each initial plot, the proposed method matches radar plots using a sequence of correlation windows generated in turn for each of the predefined previous scans. Each correlation window defines a range-azimuth region, with center and extent in range and azimuth adjusted from scan-to-scan. A group of matched plots is selected from all plots falling into a correlation window; these plots meet the velocity matching condition. Only the one radar plot, which minimizes the predefined overall matching criterion, is selected from the given group of matched plots for inclusion in the set of correlated plots associated with the initial plot. For each identified set of correlated plots, an overall correlation value is computed. If the correlation value exceeds a predefined threshold, the initial plot associated with that set of correlated plots is stored in memory for further processing and visualization. Otherwise, the initial plot is retained for plot rematching with modified velocity centroids. The modified velocities provide the detection of those targets of interest that may have been missed due to ambiguous radial velocity measurements. In contrast to known methods, the proposed method minimizes the correlation window area at a given probability of falling into the window for radar plots associated with a target corresponding to an initial plot. The proposed method efficiently eliminates the false detections while maintaining reliable detection performance for targets of interest; the detection performance is essentially improved compared to known methods. Additionally, the proposed method ensures reliable target detection when radial velocity measurements are ambiguous, a situation where known methods collapse.
In this paper, a design of dual band 10 × 10 antenna array for 5G Massive Multi-Input Multi-Output (MIMO) applications in the mobile phone is presented. The designed array is proposed to cover the sub-6 GHz bands (LTE bands 42/43 and LTE band 46). To realize MIMO operation in these three LTE bands, ten ring loop antenna elements are integrated into a limited space cell phone circuit board. Due to the implementation of spatial diversity techniques on the antenna elements, better isolation can be achieved. The proposed array was simulated, fabricated and measured. It achieved good MIMO performances, such as ergodic channel capacities higher than 27.1 bps/Hz and 57.6 bps/Hz for LTE bands 42/43 and LTE band 46 respectively. Also, the achieved Envelope Correlation Coefficient (ECC) is lower than 0.006. Moreover, it exhibited good isolation below -26 dB. The effects of user's hand phantom on the proposed array performance are also studied in two scenarios: Single Hand Mode (SHM) and Dual Hands Mode (DHM). The simulated results indicate that the proposed MIMO array can still achieve good MIMO performances in the presence of DHM and SHM. The Specific Absorption Rate (SAR) are also presented.
We here present a bivariate Chebyshev series method for the approximation of the experimental frequency and temperature dependent dielectric functions of materials. Within the framework of this method, the dielectric properties are modeled as a low-degree polynomial of the temperature variable (T), the coefficients of which have a frequency (variable f) dependency. This model is then rephrased in terms of the temperature coefficients which are given here as the rational functions of frequency. The principal merits of this method are that it produces a near-best polynomial approximation to the target function, rapidly improves with the order of approximation, and is easy to compute. The favorable features of our approach are demonstrated by considering the experimental wideband Cole-Cole models of animal tissues with the temperature-dependent parameters. The numerical results show the inferiority of the commonly used power-of-f representation of the polynomials concerned due to large rounding errors when the frequency range is large. This problem is ameliorated by expressing the appertaining coefficients as polynomials in the transformed frequency variable x(f) in the Chebyshev basis. Areas of application of the results of this article include the modeling of human exposure to radiofrequency fields, development of treatment and diagnostic procedures, and food processing technologies.
Reflective interference caused by impedance discontinuities in the interconnect is a serious impediment to high speed serial link designs. The reflections can be addressed either through expensive equalization circuits or through interconnect redesign. Here a new technique for determining the most significant places to make changes in an interconnect design is presented. Through linearizing the S-parameter cascading process three unique reflection budgets are created based on 1) frequency domain insertion loss deviation, 2) time domain peak distortion analysis and 3) time domain reflectometry. Example analysis of a 25.8 Gb/s NRZ system identifies the connectors as the primary contributors to reflective interference and estimates that the interactions with the rest of the interconnect with the connector impedance discontinuities reduces the system eye height by 84 mV.
Uncertainty quantification and variability analysis are two domains of interest when looking at the efficiency of HPEM sources. Vircator is known to be a low efficiency high power microwave source subject to several generally volatile phenomena such as plasma expansion and shot-to-shot variability. In this study, a computationally low cost framework combining the Extreme Value Theory (EVT) and the Generalised Design of Experiments is proposed in order to study the peak power distribution of a Vircator obtained with a surrogate model. Following the pre-screening of random variables, the optimised parameters are introduced in 2.5D and 3D simulation tools, namely XOOPIC and CST-PS. It has been confirmed that the peak power output can reach a 40% increase. This shows that the EVT proves to be successful in classifying and quantifying random variables to influence the distribution tails.
A compact six elements MIMO antenna is presented for UWB applications. The proposed MIMO array consists of non-identical monopole antennas with distinctive ground planes so as to nullify mutual coupling amid side-by-side elements. Also, by properly placing the antenna elements exploiting cross polarization diversity, a good isolation throughout the operating bandwidth is achieved. Moreover, two parasitic inverted L stubs in combination with small rectangular stubs are employed near the middle-placed radiators and corner placed radiators, respectively, in order to extend the frequency band and enhance the impedance matching. Results show a good reflection coefficient about -10 dB, a high isolation >20 dB, an envelope correlation coefficients <0.15, a high diversity gain equal to 9.3, and finally, a maximum value of efficiency for both used antenna elements which is about 78% and 60% with 6 and 5 dBi of gain, respectively. They validate the proposed MIMO antenna efficiency for UWB diversity applications.
This paper is the continuation and development of the discussion started in our previous work with the same title. For the first time, eigen waves of the plane boundary separating vacuum and an artificial plasma-like medium are considered in reasonably substantiated way and in a sufficiently extensive and profound volume. The possibility of extending the results obtained for a plane boundary to the case of a weakly profiled periodically uneven boundary is shown. This paper demonstrates the potential and urge to use the analytical results in the studies of the resonant transformation of the field of a plane, density modulated electron beam flying over a periodically uneven boundary of a natural or artificial medium in the field of bulk outgoing waves.
The paper is focused on reliable modeling of the effects associated with the resonant transformation of the field of a plane, density modulated electron beam, flying over the periodically uneven boundary of a natural or artificial medium, in the field of volume outgoing waves. Here, the general information (analytical basis) is presented on the peculiarities and principal characteristics of electromagnetic fields arising in the situations under consideration, on the procedures for regularization of model boundary value problems describing these situations, and on possible eigenmodes of periodic structures. Without relying on this information, it is impossible to advance considerably effectively in solving numerous urgent physical problems(establishing the conditions providing anomalously high levels of Vavilov-Cherenkov and/or Smith-Purcell radiation; diagnostics of beams of charged particles, artificial materials and media) and in practical implementation of new knowledge aboutthe effects of diffraction radiation and their wave analogues in new devices and instruments of optoelectronics, high-power electronics, antenna, and accelerator technology.
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