This work presents the results of numerical simulations and parametric studies of dielectric loaded wire monopole antenna, of which the main advantage is bandwidth enhancement. Introducing dielectric loading makes it possible to tune antenna to operate over a frequency range not covered with unloaded antenna, while maintaining an omnidirectional radiation pattern. The simulations are performed when loading is done with lossy as well as lossless dielectric and the results are compared. The observational frequency range is extended up to 40 GHz. In addition, the simulated results are compared with the measured S₁₁ of four fabricated antennas loaded with lossy dielectric and a good agreement is obtained.

This paper presents new semi-analytical expressions to calculate the selfinductance and the electromagnetic force for a ferromagnetic cylinder of finite length placed inside a circular coil of rectangular cross section. The proposed analytical model is based on boundary value problems with Fourier analysis. Laplace's and Poisson's equations are solved in each region by using the separation of variables method. The boundary and continuity conditions between the different regions yield to the global solution. Moreover, the iron cylinder is assumed to be infinitely permeable. Magnetic field distribution, self-inductance and electromagnetic force obtained with the proposed analytical model are compared with those obtained from finite-element.

In this letter, a novel compact dual-mode tri-band microstrip bandpass filter (BPF) is proposed using three sets of dual-mode resonators, i.e., the quarter-wavelength resonator (QWR) which is designed for the first passband, and two sets of stub loaded resonators (SLR) for the second and third passband, respectively. The center frequencies and bandwidths of three passbands can be flexibly tuned and designed. Multiple transmission zeros can be generated to improve the selectivity. Meanwhile, the BPF can obtain more compact size by adopting the folded resonators and extended feed lines. Finally, a tri-band microstrip BPF prototype with fractional bandwidths 18.3% at 1.8 GHz, 5.5% at 3.6 GHz and 12.2% at 5.25 GHz is designed. The measured results are in good agreement with the full-wave simulation results.

A fully integrated CMOS wideband distributed variable delay line for time array beam-formers is presented. The delay line works over a full differential mode, and the delay cell function is based on differential amplifiers with active inductive peaking loads. A delay resolution of 15 ps is obtained with a maximum delay capability of 150 ps . The designed active delay line provides 3 scanning angles with 8.6^o degrees of spatial resolution. This delay line is applicable for a 4 channel beam-former with an operational bandwidth of 500 MHz centered at 5 GHz. Our active delay line consumes up to 352 mW of power from 2.5 V supply. The circuit is simulated in standard 0.25 μm BiCMOS process and occupies 252 μm × 123 μm of silicon area.

A novel approach for the design of image encryption system based on one stage of 3D photonic bandgap structure is proposed. Using the Finite Integration Time Domain (FITD) method, the performance of the proposed design is optimized through the utilization of the reflection properties from 3D photonic bandgap structure while maintaining constant phase encoding. To demonstrate the robustness of the suggested encryption system, root mean square error is calculated between the original and decrypted images revealing the high accuracy in retrieving the images. In addition, as the proposed system renders itself as easy to fabricate, it has an excellent potential for being very useful in both microwaves and photonics imaging system applications.

Transmission characteristics of 1-D photonic crystal (PC) structure with a defect have been studied. We consider a Si/ZnS multilayer system. We also consider the refractive index of both layers to be dependent on temperature and wavelength simultaneously. The refractive indices of Si and ZnS layers are functions of temperature as well in the wavelength of incident light. This property can be used while tuning defect modes at desired wavelength. As defect modes are function of temperature, one can tune the defect modes to desired wavelength. It is found that the average change in central wavelength of each defect mode is 0.07 nm/K. This property can be exploited in the design of a tunable wavelength demultiplexer for DWDM application in optical communication.

Basic equations of quasi-isotropic approximation (QIA) of geometrical optics method are presented, which describe electromagnetic waves propagation in weakly inhomogeneous and weakly anisotropic media. It is shown that in submillimiter range of electromagnetic spectrum plasma in all modern thermonuclear reactors, both acting and under construction, manifest properties of weakly inhomogeneous and weakly anisotropic medium, even for extreme electron density N_e ~ 10¹⁴ cm^-3 and magnetic field B₀ ~ 5 T accepted for project ITER. In these conditions QIA serves as natural theoretical basis for plasma polarimetry in tokamaks and stallarators. It is pointed out that Stokes vector formalism (SVF), widely used in polarimetry, can be derived from QIA in a generalized form, admitting the rays to be curvilinear and torsiened. Other important result of QIA is development of angular variables technique (AVT), which deals directly with angular parameters of polarization ellipse and operates with the system of two differential equations against three equations in form of SVF.

In this paper, transient electromagnetic scattering by general Chiral objects is investigated using time-domain integral equations with the Poggio, Miller, Chang, Harrington, Wu, and Tsai (PMCHWT) formulations. By introducing a pair of equivalent electric and magnetic currents, electromagnetic fields inside a homogeneous Chiral region can be represented by these sources over its boundary. The uncoupled equations are solved numerically by the Galerkin's method that involves separate spatial and temporal testing procedures. The scaled Laguerre functions are used as the temporal basis and testing functions. The use of the Laguerre functions completely removes the time variable from computation, and the results are stable even at late times. Numerical results are presented and compared with analytical results, and good agreements are observed.

A general multiobjective optimization and design procedure of a Luneberg lens antenna (LLA) with a compact multiband multi-polarized feed-system for a broadband satellite communication terminal is presented. The LLA utilizes a compact multiband feed horn, consisting of an inner dielectric loaded circular horn for the K/Ka-band (dual-circular polarization) and a coaxial waveguide with axially corrugated flange for the Ku-band (dual-linear polarization). Measurements show good agreement with simulations. Moreover, an efficient multiobjective evolutionary algorithm based on decomposition (MOEA/D) with differential evolution operator and objective normalization technique is firstly coupled with the vector spherical wave function expansions (VSWE) for the optimal design of a 7-layer 650 mm diameter LLA, which provides higher aperture efficiency at Ku/K/Ka-band simultaneously. The frequency dependence of the LLA is also investigated. Finally, the gain and sidelobe level of a 5-layer design are jointly evaluated and compared with previous works. The proposed design procedure provides much better radiation performances and greater design freedom to the designers, as a group of Pareto-optimal LLA solutions can be obtained with just one simulation.

This paper addresses the problem of detecting multiple point-like targets in the presence of steering vector mismatches and Gaussian disturbance with unknown covariance matrix. To this end, we first model the actual useful signal as a vector belonging to a proper cone whose axis coincides with the whitened direction of the nominal array response. Then we develop two robust adaptive detectors resorting to the two-step GLRT-based design procedure without assignment of a distinct set of secondary data. The performance assessment has been conducted by Monte Carlo simulation, also in comparison to previously proposed detectors, and confirms the effectiveness of the newly proposed ones. In the last part of the work, in order to restore the detection performance of the newly proposed detectors in the presence of a large number of range cells contaminated by useful signals, we consider two adaptive detectors which resort to the structure information of the disturbance covariance matrix, and show that the a-priori information on the covariance structure can lead to a noticeable performance improvement.

In this paper, a new simple equivalent circuit model for analysis of dispersion and interaction impedance characteristics of ridge-loaded folded-waveguide slow-wave structure is presented. In order to make the computational results more accurately, the effects of the presence of the beam-hole and discontinuity due to the waveguide bend and the narrow side dimension change of this kind of structure were considered. The dispersion characteristics and the interaction impedance are numerical calculated and discussed. The analytical results agree very well with those obtained by the 3-D electromagnetic high-frequency simulation software. It is indicated that the equivalent circuit methods are reliable and high efficiency.

In this paper, we focus on the adaptive prior detection threshold setting problem to optimize the overall performance of the joint detection-tracking system for maneuvering target tracking in clutter. It is shown that our problem can be reduced to the information reduction factor (IRF) maximization by Gaussian fitting of maneuvering target Markovian switching dynamics via moment matching, even for the case with the nonlinear measurement equation. Our proposed adaptive threshold setting method outperforms the conventional threshold setting approaches greatly and also exhibits a mildly improvement in comparison with the earlier method for this problem in terms of tracking performance, especially in track loss percentage (TLP). However the computational burden of our method is reduced significantly because in our method generally only one IRF corresponding to the common validation region, not the every IRF corresponding to the individual model-conditioned validation region, is needed for threshold optimization at each time step and an approximate closed-form solution can also be obtained for the special case of the Neyman-Pearson (NP) detector.

In this paper, we present a new type of a double-negative metamaterial (MTM) absorber based with resonant-magnetic structures, with a periodic array composed of a split-ring resonator (SRR) and two open complementary split-ring resonators (OCSRRs). In contrast to common absorber configurations, the absorber proposed in this paper does not use a metallic back plate or a resistive sheet. In order to eliminate the need for this metallic back plate, a planar array of SRRs is placed parallel to the incident wave propagation direction. An appropriately designed combination structure of two OCSRRs and a SRR exhibits negative permittivity and negative permeability in the same frequency band. Each unit cell is printed on both sides of an FR-4 substrate. A prototype absorber was fabricated with a planar array of 75 × 42 unit cells. Both simulations and experiments verify the effectiveness of the proposed backplane-less MTM absorber. The proposed backplane-less absorber can be used for microwave applications.

Time reversal focusing of electromagnetic waves is investigated in case of source motion. We extract analytical formulation of uniformly moving source in presence of ideal time reversal cavity (TRC) and a more realistic model, time reversal mirror (TRM). Similar to the acoustic case, it has been observed that in case of moving point source spatial focusing is still achievable. Furthermore, we also investigate super resolution effects on time reversal (TR) focusing of moving source in continuous random media. Results shows that an increase in (multipath) leads to better focusing resolution of the time-reversed signals.

A 2-way symmetrical Doherty power amplifier (PA) with high efficiency is presented. This amplifier delivers 49.2 dBm (83 W) of saturated output power and 63% drain efficiency with 38.2 dB of power gain at 460MHz. The drain efficiency at 6 dB backed-off power level shows about 62%. After digital pre-distortion (DPD) system corrected, about 48% power-added efficiency (PAE) at 42.2 dBm (16.6 W) average output power has been demonstrated, while achieving -52 dBc (-28 dBc before linearization) Adjacent Channel Leakage Ratio (ACLR) at 20 MHz offset using a LTE-Advanced input signal with 6.5 dB peak to average ratio (PAR) to meet the IMT-Advanced system requirements. We also used a π type structure network based on lumped elements to replace the traditional Doherty amplifier 1/4λ transmission line, and compared the performance.

A compact multimode bandpass filter with low insertion loss, high stopband rejection and wide stopband bandwidth is introduced by using cascaded multimode resonators and compact loading cells in combination. The measured minimum insertion loss is of 1.7dB including the connector loss in the input and output ports in the passband of 5.7~8 GHz. Through the use of cascaded multimode resonators, steep skirt selectivity and wide stopband up to 18 GHz can be achieved. When incorporated with the lowpass loading cells, which have elliptical low-pass response by using the source-load coupling, the stopband of the proposed filter can be further extended up to 40 GHz, with only negligible influence on the passband performance.

Tapered resistive strip realized by patterning the constant resistive strip is used to suppress edge scattering of a finite wedge. The suppression effect is simulated and evaluated by the reduction in mono-static RCS (Radar Cross Section). This reduction is compared with the one which loaded by the ideal tapered resistive strip. The result indicating that patterning a constant resistive strip to create a gradient in sheet resistance is feasible. To verify this method of fabricating tapered resistive strip, patterned resistive strip with a proper gradient in sheet resistance is conducted and loaded on the wedge target for test. The gradient in sheet resistance used for test is obtained from the optimization. Resistive strip with this sheet resistance gradient renders a promising effect of edge scattering suppression. The test result shows a reduction of 20dB for the geometric mean of mono-static RCS in the angular range of 45º. This value is close to the one of 23dB in simulation.

The internal electric-field distribution from single layers of dielectric spheres with high refractive index (n=2.65) has been analyzed for a number of different compactness cases by FDTD (Finite-Difference Time-Domain) method. The field distributions from the transmission spectra were compared with the internal electric-field distribution of the Mie modes of an isolated sphere. In general, the agreement is very good in almost all cases studied. The results show that TE and TM Mie modes are the origin of the resonances in the transmission spectra of the single layers. The resonances of the monolayer attributed to TE₁₁ and TM₁₁ Mie modes are only excited for compactness values lower than 0.38, suggesting a dependence of periodical arrangement effects for these modes. Moreover, the field distribution corresponding to some of the dips in the spectrum cannot be directly attributed to Mie modes (TE₂₁). The result indicates these are formed by degenerated or weakly coupled Mie modes induced by the periodic structure.

A generalized two-way coupled-line power divider with extended ports for dual band is proposed in this paper. The power divider is composed of two section coupled-lines, one conventional transmission line, and an isolation resistor, and employs extension of a transmission line or coupled-line at each port. The design equations are obtained based on even- and odd-mode analysis, and analytical ideal closed-form scattering parameter expressions derived. Because the traditional ring structure is a special case of coupled line, four cases of this generalized power divider are discussed and compared. In addition, the six power dividers simulated results of three special cases are shown. Finally, three fabricated power dividers measurements are used to certify this proposed structure and corresponding design parameters.

Medical applications of microwaves (i.e. a possibility to use microwave energy and/or microwave technique and technology for therapeutical purposes) are a quite new and very rapidly developing field. Microwave thermotherapy is being used in medicine for cancer treatment and treatment of some other diseases since early eighties. This paper is a contribution to a theory of phase array applicators to be used for a microwave thermotherapy (microwave hyperthermia) in a cancer treatment. It deals with a study and theoretical evaluation of homogeneity of SAR distribution in cylindrical agar phantom for several different values of its radius. Discussed SAR distribution is in our case created by simulations of EM field exposure done by aid of four microwave stripline type TEM mode applicators of the same type.