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.

A compact planar ultra-wideband (UWB) antenna with triple band notch characteristics is proposed in this paper. The antenna consists of a rectangular radiating patch and a modified partial ground plane, and has an overall dimension of 24 mm × 22 mm. Three resonant elements are placed above the ground plane to generate three notch frequency bands separately in the WiMAX, the lower WLAN and the upper WLAN frequency bands. The proposed antenna successfully simulate, prototyped and measured. Effects of the key deign parameters on band notch characteristics are also investigated. The realized antenna achieved an operating bandwidth (VSWR ≤ 2) ranges from 2.9 to more than 11 GHz with triple notched bands of 3.26-3.71 (12.9%), 5.15-5.37 (8.5%), and 5.78-5.95 (2.9%) GHz. Measured flat transfer function and constant group delay within the operating band except at notched bands makes the proposed antenna suitable for being used in practical UWB applications.

With the development of China's Compass Navigation Satellite System (CNSS), the demand for terminal antennas is quite urgent. In CNSS system, dual-band antennas are more attractive, because they can provide both the navigation and communication functions. In addition, since the `BEIDOU' antennas operate at low frequencies, they are not easy to be installed due to their usually large volumes, limiting their practical application. In this paper, we present a dual-band miniaturized CNSS microstrip antenna based on high-permittivity ceramic substrate. This antenna works at S Band (2492 MHz±5 MHz, right-handed circular polarization, RHCP) and L Band (1616±5 MHz, left-handed circular polarization, LHCP). Numerical results show that the impedance bandwidth (S₁₁<-10 dB), 3 dB axial ratio bandwidth and antenna gain at L Band are about 26 MHz, 6.5 MHz and 3.22 dB, respectively. While the impedance bandwidth (S₁₁<-10 dB), 3 dB axial ratio bandwidth and antenna gain at S Band are about 127 MHz, 28 MHz and 4.72 dB, respectively. An experiment was carried out to verify our design and the measured results agree well with the simulation ones. In addition, by using high-permittivity ceramic (ε_r=16) as the substrate, the antenna keeps its performances with a reduced size by 80% comparing with the conventional ones using low-permittivity substrates. This makes it suitable for practical applications.

A compact quad-band rectangular wide-slot antenna is developed for GPS L1 band, 2.5/3.5/5.5 GHz WiMAX and 2.4/5.2/5.8 GHz WLAN applications. The planar antenna consists of an L-shaped microstrip feed line and three stubs extending from the wide-slot on the ground plane. The performance of the antenna is enhanced by etching meander line on the top of the wide-slot. The proposed antenna has a size of 36*42*1 mm³ which is more compact than the previously reported antennas for the same application. The antenna has been simulated, fabricated and measured successfully. The measured results show that the antenna has the impedance bandwidths of 160 MHz (1.54-1.7 GHz), 380 MHz (2.38-2.76 GHz), 570 MHz (3.2-3.77 GHz) and 1130 MHz (5.12-6.25 GHz) for S₁₁ ≤ -10 dB. In addition, good radiation characteristics and stable antenna gains over the operating bands are obtained.

In this paper, dielectric characteristics of female breast tissues were measured. Breast Tissues were mainly composed of fat, fibro-glandular and tumor. Measured tissues were directly extracted from mice and a rat just before the measurements to maintain the tissues as fresh as living ones before degeneration. This makes the measured results more accurate. Because the extracted tissues were very thin, they were measured by two methods using HP probe and a newly designed two-port sample holder. Numerical results for the two-port sample holder were obtained for both the forward and inverse problems. Dielectric properties of breast tissues were measured in the frequency range between 50 MHz and 5 GHz. We calculated the electrical constant with the measured data from the two-port sample holder. As a result of the measurement, the dispersion characteristics of the female breast tissues were fitted into the first Cole-Cole model.

In bistatic synthetic aperture radar (SAR) with one stationary station, two-dimensional spatial variance is a major problem which should be handled. In this paper, an Inverse Scaled Fourier Transform (ISFT) imaging algorithm to deal with this problem is proposed. The approach linearizes the two-dimensional spatiallyvariant point target reference spectrum to derive the reflectivity pattern's spectrum. Based on this spectrum, an ISFT along range direction and a frequency shift along azimuth direction are used to achieve the two-dimensional spatial variance correction. This method is efficient as it only uses phase multiplication and FFTs. Numerical simulations verified the effectiveness of the method.

In this paper, we have investigated the marginal moment generating function (MMGF) for the correlated Nakagami-m fading channel by using maximal-ratio combining (MRC) diversity scheme at receiver for the computation of the channel capacity for various adaptive transmission schemes such as: 1) optimal simultaneous power and rate adaptation, 2) optimal rate adaptation with constant transmit power, 3) channel inversion with fixed rate, and 4) truncated channel inversion with fixed rate. The effects of diversity receiver as well as correlation coefficients on all these transmission schemes are discussed and the channel capacity obtained by this proposed approach for all schemes is compared with reported literature.

An analysis for circularly-polarized (CP) ring slot antennas fed by a coupling strip with resistive loading is presented. By treating the antenna as a two-port circuit, the amplitudes and phases of two orthogonal modes excited from the slot antenna can be found and expressed in terms of the S parameters of the circuit. The axial ratio calculated through the S parameters has a good agreement with that obtained from the pattern simulation of IE3D. The effects of varying key parameters of the coupling strip on the amplitudes and phases of the dual orthogonal modes are investigated in detail.