Search

The folding antennas are anticipated to become mandatory because of integration necessity according to communication object shapes. The effect of folded antennas on electromagnetic (EM) radiation is an open question for RF and microwave wireless engineers. An innovative approach to explore the flexible patch antenna (FPA) parameters through V-folding analysis is addressed for this problem. This paper is focused on the methodological approach of the FPA study by considering an innovative V-folding behavior compared to the classical flat condition. As a proof-of-concept, FPA prototypes are designed on a Kapton substrate, simulated, fabricated, and tested. A non-shifting operating frequency is achieved at 3.4 GHz for all percentage-wise folding with a flat (unfold) bandwidth about 360.8 MHz with good acceptable performance. The FPA performance prediction as reflection coefficient, efficiency, gain, and directivity versus forward and back V-folding percentage and angle are examined. The obtained result can be exploited to predict the V-folding effect on the communication performances of transceiver systems like radar, satellite, and multimedia applications. [ABSTRACT FROM AUTHOR]

An original application of stopband (SB) type negative group delay (NGD) electronic function is introduced. The unfamiliar SB-NGD circuit is designed with RLC-network lumped passive topology. The SB-NGD circuit is exploited to operate as a true-time delay (TTD) device for smart dual-beam phased array design. The two-port passive topology for designing an SB-NGD circuit constituted by an RLC-network is described. The theory and design method of the employed SB-NGD passive circuit are detailed. The microwave theory of the SB-NGD topology is elaborated from S-matrix modelling. The SB-NGD canonical form is innovatively introduced in function of the expected specifications. The synthesis design equations allowing to determine the R, L, and C component values in function of the NGD specifications are formulated. The SB-NGD behavior is verified by comparison of calculated and simulated S-parameters from two different proofs-of-concept (POC). Illustrative results with a very good agreement showing SB-NGD behavior are observed around the arbitrarily chosen central frequencies f1 = 0:7 GHz and f2 = 1 GHz over a bandwidth of 50 MHz. The design principle of TTD-based smart dual-beam is described. The dual-band SB-NGD circuit is designed to operate as a dual-band TTD device with fixed delays at t1 (f1) = 357 ps and t2 (f2) = 875 ps, respectively. A radiation pattern showing the smart dual-beam steering operating system at f1 and f2 frequencies is discussed. [ABSTRACT FROM AUTHOR]

In this paper, the extended $\eta$ - ${\mathcal F}$ composite fading distribution is proposed. This new distribution is simple, characterized in terms of physical parameters, able to model environments where the multipath fading coexists with shadowing and takes into account the clustering imbalance between the in-phase and quadrature components. For the aforementioned distribution, new expressions are derived for the probability density function (PDF); cumulative distribution function, higher-order moments and moment generating function of the instantaneous signal-to-noise ratio; joint envelope-phase PDF and amount of fading. Subsequently, expressions are deduced for the outage probability, average symbol error probability and average channel capacity. An asymptotic analysis is also provided. Several curves are presented and the theoretical results are corroborated by Monte-Carlo simulations. Furthermore, an empirical validation is demonstrated in an underwater acoustic scenario, in which a better fit between the theoretical PDF and the empirical data is perceived for the extended $\eta$ - ${\mathcal F}$ model, when compared to the extended $\eta$ - $\mu$ and $\kappa$ - $\mu$ shadowed distributions. [ABSTRACT FROM AUTHOR]

In this article, a new expression for the joint moment generating function (MGF) of the signal-to-noise ratio (SNR) considering correlated $\eta$ - $\mu$ fading is determined. Based on this result, a new closed-form expression is presented for the bit error probability (BEP) of the rectangular quadrature amplitude modulation ($R$ -QAM) scheme, considering frequency non-selective channel subject to cascaded double correlated $\eta$ - $\mu$ fading and a receiver with dual branch maximum ratio combining (MRC). The signal is received from two links with correlated cascaded double fading in the second link. In addition, a new expression for the outage probability (OP) is derived. All expressions determined in this paper are new and corroborated by simulations performed with Monte Carlo method. [ABSTRACT FROM AUTHOR]

The degradation level of high voltage equipment insulation systems can be estimated from the monitoring of partial discharge (PD) activity. The radiometric method stands out as one of the most promising methods for monitoring these discharges, however, in substations, the PD signals may be susceptible to external interference and, in some cases, hide by background noise. This work presents the application of the stationary discrete wavelet transform (SDWT) over PD signals measured by bio-inspired printed monopole antennas (PMA) operating at the UHF frequency range (300-3000 MHz). In addition to the filtering from the SDWT, the use of the SDWT scaling coefficients energy is evaluated as a support tool for the location of PD. The PD signals are investigated under low signal-to-noise ratio (SNR) and; high SNR with a high pulse repetition rate. These signals are obtained from a laboratory setup composed by a discharge generating oil cell, and acquired through a bio-inspired PMA. After the application of the SDWT over the evaluated signals, together with the energy calculation using different mother wavelets, it is verified that the proposed methodology provides an efficient filtering result, being appropriate for PD detection. From the energy of SDWT scaling coefficients, it is possible to highlight the constant delays between the detection of consecutive pulses, minimally interfering over the time differences of arrival and providing better location results. [ABSTRACT FROM AUTHOR]

A new, exact and closed-form expression is presented for the Beaulieu-Xie (BX) phase-envelope joint distribution. In addition, bivariate statistics are also determined for the BX distribution: the bivariate probability density function (PDF) of the envelope, the bivariate PDF of the instantaneous signal to noise ratio (SNR) and the generalized joint moment of the envelope, with and without correlation between the in-phase and quadrature components. Theoretical curves are plotted for different parameter values that characterize the fading. [ABSTRACT FROM AUTHOR]

In this letter, a mathematical characterization for the cascaded double Beaulieu-Xie (BX) fading model is presented. Exact and new expressions are determined for the probability density function (PDF) and for the cumulative distribution function (CDF) of the random variable that models the envelope of the cascaded double BX fading, and for the PDF and the CDF of the instantaneous signal-to-noise ratio received. Expressions are obtained for the moment generating function, higher order moments, average channel capacity, outage capacity, outage probability, amount of fading, channel quality estimation index and symbol error probability, for different modulation schemes, of the channel model considered. Several curves, corroborated by simulations performed with Monte Carlo method, are presented for different parameters that characterize the fading model. [ABSTRACT FROM AUTHOR]

In this paper, an upper bound on the symbol error probability (SEP) of the M-ary θ -quadrature amplitude modulation scheme, in a channel subject to additive white Gaussian noise (AWGN) and η - μ fading, is calculated by means of the union bound. In addition, an exact and closed-form expression for the pairwise error probability (PEP) of the system is derived. The PEP expression obtained is written in terms of the Beta function and the Lauricella hypergeometric function. Another expression for the PEP, written in terms of the Beta function and the Appell hypergeometric function, and two bounds for the PEP, one lower and one upper, are also presented. An exact expression for the optimum rotation angle for quadrature phase shift keying constellation, considering this channel model, is also determined. In addition, an analysis, in terms of PEP, of the modulation diversity system combined with a maximum ratio combining receiver in channels subject to η - μ fading and AWGN noise, is performed. PEP and SEP curves, as a function of signal-to-noise ratio, are plotted and corroborated by simulations performed with the Monte Carlo method under different parameters that characterize the channel mathematically. All the expressions determined in this article are closed and new. [ABSTRACT FROM AUTHOR]

This article presents new exact expressions, written in terms of elementary transcendental functions, for calculating the bit error probability of M-ary Quadrature Amplitude Modulation (M-QAM) scheme considering the wireless communication channel modeled by a Markov chain with N states. For the numerical evaluation of the expressions obtained, a particular case of a Markov chain with two states is considered, with each state representing distinct scenarios. In the first scenario it is considered the presence of Gated Additive White Gaussian Noise (GAWGN) and fading η-μ or κ-μ, while the second scenario considers the presence of the Double Gated Additive White Gaussian Noise (G²AWGN) and fading η-μ or κ-μ. Bit error probability curves as a function of the signal-to-permanent-noise ratio for different values of the signal-to-impulsive-noise ratio, fading parameters and modulation order M are also presented. [ABSTRACT FROM AUTHOR]

In this paper, new exact expressions for evaluating the bit error probability (BEP) of the M-ary quadrature amplitude modulation scheme (M-QAM) for a channel model characterized by double gated additive white Gaussian noise (G2AWGN) and Nakagami fading are presented. The derivation of the BEP is performed considering a method in which the multiplicative fading is transformed in an additive noise R obtained by dividing the received signal by the estimated fading envelope. In addition, the probability density function (PDF) and cumulative density function (CDF) of the random variable R that represents the aforementioned noise are obtained for the G2AWGN. The BEP curves as a function of the signal to permanent noise ratio for several values of the signal to impulsive noise ratio, modulation order, and fading parameters are also presented. [ABSTRACT FROM AUTHOR]

This letter presents a new technique for determining the polarization of the electromagnetic waves by using a passive circuit. The necessary mathematical operations required to retrieve the polarization are achieved using a passive circuit built with the cascaded Wilkinson power dividers. This technique is robust and simple, and enables the detection of all necessary characteristics for determining the incident-wave polarization. It requires two orthogonal linearly polarized antennas for amplitude measurements only. Measurement results with two circularly polarized patch antennas are shown in order to validate the proposed technique. A comparison with a classic method is also provided, which confirms the accuracy and simplicity of the technique. [ABSTRACT FROM AUTHOR]

This paper presents new and exact expressions for the bit error probability (BEP) of the square M‐ary quadrature amplitude modulation scheme subject to η‐μ, κ‐μ or α‐μ fading and multilevel double gated additive white Gaussian noise, which is composed by the sum of a white Gaussian component of variance σg2 and a white Gaussian noise component of variance σi2 gated by a discrete random process defined in continuous time, which takes values into a finite discrete set. BEP curves, with and without imperfect channel estimation, corroborated by simulations using the Monte Carlo method, are presented for different values of parameters that characterize mathematically the channel. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a new and exact expression for the bit error probability (BEP) of the square M‐ary quadrature amplitude modulation (M‐QAM) scheme, with the channel under double gated additive white Gaussian noise (G2AWGN) and η‐μ fading in a communication system using the spatial diversity technique. The expression for the BEP is written in terms of the Appell function. The BEP curves are presented under different values of the number of branches of the maximum ratio combining (MRC) receiver, order of the constellation M, and parameters that characterize mathematically the channel, corroborated by simulations performed with Monte Carlo method. [ABSTRACT FROM AUTHOR]