Wideband code division multiple access (WCDMA) is an interference-limited system. When the system operates at nearly full capacity, admitting another user may affect the stability of the system. Therefore, proper Call Admission Control (CAC) is crucial and should balance between Quality of Service (QoS) requirements for the new user and also for the existing users and at the same time keep the accepted traffic as high as possible. In this paper, we investigate this tradeoff in the uplink direction using power-based Multi-Cell Admission Control (MC-AC) algorithm. Multimedia services are considered with different QoS requirements. Different traffic scenarios are considered. Simulation results reveal that MC-AC algorithms have many advantages over single cell admission control in terms of overall stability of the system and total system throughput.

MEMS phase shifter has been developed using inductors. The design consists of a CPW line capacitively and inductively loaded by the periodic set of inductors and electrostatic force actuated MEMS switches as capacitors. By applying a single bias voltage on the line, the characteristic impedance can be changed, which in turn changes the phase velocity of the line and creates a true time delay phase shift. The governing equations for the impedance and loss are derived. The ABCD matrix is defined for a unit cell and multi-cell DMTL phase shifter to extract scattering parameters equations. The MEMS switch is actuated by a 39 voltage waveform using a high resistance bias line. Estimated spring constant and switching time is 22 N/m and 3 μs, respectively. The structure is designed for Ka-band frequency range. The acceptable frequency range for the design containing 21 cells is between 26 GHz and 27 GHz and optimum condition occurs at 26.3 GHz. For the whole structure and optimum condition the un actuated position results in a return loss -16 dB and insertion loss of -1.65 dB. The actuated position results in a return loss -12.5 dB and insertion loss of -1.6 dB. The phase shift for the whole structure is 190 degree. The optimum condition can be easily changed by modifying the design parameters. The spacing in the proposed structures is S = 250 μm. The structure is also low loss. The length and the loss per bit with the phase shift of 270^◦ are decreased by 37.5 percent and 21 percent respectively.

This paper presents an accurate and robust time-domain electromagnetic model for microwave components of integrated circuits. The time-domain model has been validated on different structures such as metallic waveguides, planer lines and the transition of waveguide-microstrip line under harmonic oscillation excitation. The results obtained from simulation were compared to the experimental test results. The simulation results demonstrated that the approach is suitable to model microwave components of integrated circuits.

Dual-polarized antenna is widely used in communication systems such as ECM and DF systems. In this paper a novel doubleridged horn antenna with dual polarizations is introduced for frequency range of 8-18 GHz. Common double ridged horn antennas have single polarization over the operating frequency. We have used five layers polarizer to provide dual polarizations performance of the double-ridged horn antenna. In order to achieve dual polarizations the strips width, strips spacing and layers distances are optimized. It is worth mentioning that the corresponding VSWR of the antenna during the optimization process should be maintain below a certain value (VSWR<2). Simulation results show that the proposed antenna yields dual polarizations performance and low VSWR over the operating frequency. We have used CST software for antenna simulation which is based on the finite integral technique.

In this paper, we report, for the first time to the best of our knowledge, the detailed modeling and performance of Raman amplification and superluminal propagation of weak ultrafast femtosecond optical pulses in nonlinear loop single mode silicon-oninsulator anomalously dispersive optical waveguides. Using the device, theoretical results for 100-fs signal optical pulse show that when the launch peak power of signal pulse is fixed at −10 dBm, the gain value up to 30 dB can be achieved, and the delay time of superluminal propagation can also be adjusted by changing the system parameters, including initial chirp and peak power of pump pulse, initial delay time between pump and signal pulses, and waveguide length, etc.

The ground conductivity is the most important factor in the transmitter's coverage area in ground wave propagation. Regarding the day-to-day increase in digital broadcasting, a lower sensitivity of this kind of broadcasting and ability to create single frequency networks, it seems necessary to increase the accuracy of ground conductivity to minimize fading zones. The higher the abovementioned conductivity, the lower the ground wave attenuation. Also in this case, the transmitted wave will tilt less towards the ground to satisfy the boundary conditions in electric conductivity and so-called will enter the earth. In most of the presented papers to determine the field strength, conductivity is considered as known, but it's dependent upon the soil genus, the annual/monsoon precipitation and the heat average. Here it is intended to provide a new method based on Mie algorithm to determine the conductivity based on the difference of Horizontal Electric Dipole near the ground. The previous conductivity measurements included determining it in a point by point manner in a low frequency and determining the conductivity based on the coverage area intensity. The new method holds the two methods advantages together.

Analysis of a frequency agile broadband E-shaped patch antenna (ESPA) symmetrically loaded with tunnel diodes is presented in this paper. The notch parameters such as notch-length, notch-width and position are optimized to achieve the optimum broadband operation of ESPA. Under the optimum conditions of ESPA (bandwidth 32.35%), the performance of the antenna is also analyzed as a function of bias voltage of tunnel diode. It may be mentioned that the proposed antenna can be operated in tunable band that varies from 1055 MHz (bandwidth 42.54%) to 1324 MHz (bandwidth 49.77%) with the bias voltage. Further, the radiated power of the proposed antenna is enhanced by 5.67 dB as compared to the E-shaped patch antenna.

The adaptive beamformers often suffer severe performance degradation when there exist uncertainties in the steering vector of interest. In this paper, we develop a new approach to robust adaptive beamforming in the presence of an unknown signal steering vector. Based on the observed data, we try to estimate an equivalent directionof- arrival (DOA) for each sensor, in which all factors causing the steering vector uncertainties are ascribed to the DOA uncertainty only. The equivalent DOA of each sensor can be estimated one by one with the assumption that the elements of the steering vector are uncorrelated with each other. Using a Bayesian approach, the equivalent DOA estimator of each sensor is a weighted sum of a set of candidate DOA's, which are combined according to the value of the a posteriori probability for each pointing direction. In this way, the signal steering vector and the diagonal loading sample matrix inversion (DL-SMI) version adaptive beamformer can be obtained. Numerical simulations illustrate the robustness of the proposed beamforming algorithm.

A rectangular patch antenna with two circular apertures, a defected ground structure (DGS), and a shorting post is proposed in this paper. The novel structure can reduce the radar cross section (RCS) of the antenna at its operating frequency. At the same time, the return loss of the proposed antenna is maintained, and the RCSs of the patch antenna at the frequencies outside the operating band are also reduced. The proposed antenna is simulated by using high frequency electromagnetic simulation software. The peak of RCSs is reduced about 7 dB and the broadband RCSs are below −30 dB from 2 to 8 GHz. This result is useful for low-RCS antenna application.

Monopole antennas are usually used for measurement of the shielding effectiveness of metallic enclosures. This paper presents an accurate numerical modeling for monopole antennas attached in shielded enclosures with apertures. The electric field integral equation (EFIE) is formulated for the induced currents on both the monopoles and enclosure. The precorrected-FFT accelerated method of moments (pFFT-MoM) is used to solve the integral equation and the incomplete LU (ILU) preconditioner is applied to speed up the convergence of the equation. Compared with existing methods, the model presented in this paper considers the mutual coupling between the monopoles and shielded enclosure. Therefore, it is a better approximation to the actual measurement geometry.

Detection andestimation of depth of shallow buried landmines using microwave remote sensing is a complex and computationally intensive task. Despite a lot of research to correctly locate and identify the buried landmines, and to estimate its depth using microwave remote sensing data which is essential for demining with minimal risk, a lot of uncertainties still exist. Therefore in this paper, an extensive study using a groundbasedX-bandscatterometer for detection of shallow buried landmine and estimation of its depth has been carriedout. An experimental setup consisting of a ground basedscatterometer operating in microwave X-band(10 GHz, 3 cm) has been usedto generate backscatter data in a gridof 24×24 and a series of experiments under laboratory conditions conducted using dummy landmines (without explosives) buried to different depths up to 10 cm in dry smooth sand. It is difficult to detect the buried landmine by visual inspection of the raw data; therefore a novel approach by fusion of image processing techniques with electromagnetic (EM) analysis has been evolvedfor detection andestimation of depth of the landmine. The raw data generated through the experiments was processedthrough a series of image processing steps and a region of interest segmentedusing Otsu andmaxim um entropy based thresholding methods for further processing. A detection figure test has been proposedat this stage to reduce false alarms. Genetic algorithm (GA) with an electromagnetic (EM) model fusion has been proposedto estimate the depth after segmenting a suspectedregion containing the mine. The main advantage of the proposed model is that it does not have any requirement of separate training and test data set to train the optimizer and validate the results. Analyses of the results indicate that it is possible to segment suspected region of interest containing the landmines in data obtained in microwave Xband using either of the two thresholding methods. The depth of buriedland mines estimatedusing the proposed GA optimized EM model was also foundto be in goodagreemen t with the actual depth. The proposedanalysis is expectedto be extremely useful in future in detection and estimation of the depth of landmines using satellite data in microwave X-band.

Recently, hyperthermia has been investigated as an alternate therapy for the treatment of tumors. This paper explored the feasibility of preferential hyperthermia as a method of treating deep seated tumors. The overall goal of this research was to determine theoretically if preferential heating could be used to attain the desired thermal dose (DTD) for a two cm diameter tumor. The simulations in this work show that, when using a single rod insert, the model cannot provide enough energy for an entire 2 cm diameter tumor to receive the DTD. However, when using an enhanced design model with multiple (4) rods inserts, the DTD could be attained in a tumor up to 3.5 cm in diameter. This study involved using the model a spherical 2 cm tumor, assuming the tumor is located in deep tissue with a constant perfusion rate and no major blood vessels nearby. This tumor was placed in the center of a cube of healthy tissue. To achieve the preferential heating of the tumor, a rod insert was placed in the center of the tumor and microwave energy was applied to the insert (in the form of volumetric heating). The thermal modeling of this system was based on the Pennes Bioheat equation with a maximum temperature limitation of 80^◦C. Additional enhanced design models were also examined. These models include 2 cm and 4 cm tumors with four rod inserts symmetrically placed about the tumor and a 4 cm tumor model using a single rod insert with antennae attached to insert to increase energy distribution to the tumor. The simulations show that only the enhanced design cases with four rods inserts can achieve the DTD for an entire 2 cm tumor. The main purpose of this research was to determine if a minimally invasive treatment system using one or more rod inserts could be used to preferentially heat (and attain the DTD) a 2 cm diameter (or larger) tumor. Achieving the DTD for a 2 cm or larger tumor was important because currently the maximum diameter tumor that can be treated via hyperthermia is approximately 2 cm. In the remainder of this paper. I present the following: First, a background of prior research performed on various subject matters related to basic hyperthermia treatments, combination hyperthermia treatments, and computer modeling. After that, the development and verification of simplified thermal computer models of human tissue is described. Discussed next is the method of calculating the resulting thermal dose, the process of analyzing the results of the simulations of the thermal computer models. Once these introductory topics have been considered, the results of the computer modeling (using the primary thermal model) are presented. First, the effects of varying the perfusion rates in the computer model are explained. Then, a comparison of the overall treatment times, where the optimal treatment time was chosen, is discussed. Presented next is the results of varying the heat input rate. Rates examined include a constant heat generation rate, a constant insert temperature, a pulsed heat generation rate, various ramp heat generation rates, as well as exponential decay heat generation rates.

Extraction of vegetation water content and soil moisture from microwave observations requires development of a high fidelity scattering model. A number of factors associated with the vegetation canopy and with the underlying bare soil should be taken into account. In this paper,w e propose an electromagnetic scattering model for a soybean canopy which includes the coherent effect due to the soybean structure and takes advantage of recently advanced scattering models for rough surface. We also take care of some other issues, such as including curvature effect in studying the ground bounce scattering mechanisms,and using array theory with perturbation for characterizing the inter-plant structure to account for the prevailing agriculture practice of soybean. Good agreements are obtained between the model results and measurement data.

In this paper, a set of formulas to analyze the scattering from open-ended rectangular cavity is presented on the basis of Shooting and Bouncing Ray (SBR) method. By analyzing the ray paths inside the cavity, the Physical-Optics (PO) integration on the aperture is carried out in a close form. Using closed-form solution, the Radar Cross Section (RCS) of cavity in high frequency can be studied sententiously and accurately. All the peaks and nulls in the RCS plot of cavity are predicted successfully with the formulas deduced in the paper, and a 3-D scattering pattern of rectangular cavity is simulated by the proposed method.

In this paper an approach for stability analysis of microwave oscillators is proposed. Using the perturbation theory and averaging method, a theorem which relates the oscillation stability to the stability of the periodic average of the circuit's Jacobian is mentioned. Using this theorem, a criterion for oscillation stability is devised. The proposed criterion is applied to the stability analysis of a negative resistance diode oscillators and a Colpitts oscillator. This method is readily applicable to microwave CAD routines.

In this paper we describe an effective and inherently parallel approximate inverse preconditioner based on Frobenius-norm minimization that can be easily combined with the fast multipole method. We show the numerical and parallel scalability of the preconditioner for solving large-scale dense linear systems of equations arising from the discretization of boundary integral equations in electromagnetism. We introduce simple deflating strategies based on low-rank matrix updates that can enhance the robustness of the approximate inverse on tough problems. Finally, we illustrate how to improve the locality of the preconditioner by using nested iterative schemes with different levels of accuracy for the matrix-vector products. Experiments on a set of model problems representative of realistic scattering simulations in industry illustrate the potential of the proposed techniques for solving large-scale applications in electromagnetism.

In this paper a novel numerical optimization technique for antenna configurations is introduced. This algorithm is inspired from colonizing weeds, which is shown to be very robust and adaptive to changes in the environment. Thus, capturing their properties would lead to a powerful optimization algorithm. The feasibility, efficiency and effectiveness of the proposed algorithm for optimization of antenna problems are examined by a set of antenna configurations. The obtained results are compared with a particle swarm optimization technique which is widely used in antenna optimization. Numerical results show that there is a good agreement between the corresponding results.

In this paper, analytical relation for pulse width evolution and broadening in fiber systems using the Volterra series transfer function (VSTF) in linear and nonlinear cases are derived. This evaluation is done for traditional and optimum dispersion compensated fibers. Effects of group velocity dispersion (GVD) and self-phase modulation (SPM) are taken into account. It is shown that the analytical formulation can be applied to design and analysis the long hauls practical systems, and is helpful in understanding the pulse distortion caused by the interaction between SPM and GVD. The proposed relations are extracted analytically and for the first time pulse broadening factor in general case is derived.

Computation of coherent electromagnetic wave propagation through rain medium with a realistic raindrop shape is the subject of this work. T-Matrix approach towards the computation of forward scattering amplitude of raindrops is considered numerically exact. The results of Total Cross Section and forward scattering amplitude due to raindrops with MPP model shape are calculated by T-Matrix method. Both horizontal and vertical polarization of incident wave are considered where specific attenuation, phase shift and cross polarization discrimination (XPD) for terrestrial coherent electromagnetic wave propagation in the frequency range of 3-300 GHz are presented. Furthermore the effect of temperature on specific attenuation vs. frequency is investigated.

This paper presents a new quasi-metallic-wall technique for improving the gain of CB-CPW single antenna and arrays. This technique allows reducing the surface wave losses of the CB-CPW antennas, which decreases the antenna radiation efficiency. It consists on including pins as quasi-metallic wall between the upper and lower ground planes in the CB-CPW antenna structure. To validate the proposed approach, a CB-CPW-slot antenna fed through an inductive coupled CPW-line operating at 5.8 GHz is considered. This approach allows to increase the antenna efficiency from 70% to 95% around the operating frequency. The antenna gain achieves then an improvement of 2 dBi. Also, an antenna array is designed and the pins technique is also applied to prove its applicability for the array case. An efficiency increase from 64% to 95% was achieved. Both single antenna and antenna array withpins were fabricated and measured. A good agreement between numerical and experimental results was obtained.