This paper presents a novel compact microstrip hybrid four-mode bandpass filter (BPF) with good selectivity and multi-transmission zeros. By adding an external resonator to a triple-mode stub-loaded uniform impedance resonator, four modes are generated in the desired passband and a hybrid four-mode BPF is implemented. Even- and odd-mode theory is introduced to investigate the mode characteristics of triple-mode resonator in detail. Circuit model and coupling matrix are built to further explain the proposed methodology. A microstrip BPF with central frequency of 3.4 GHz for wireless communication was designed and fabricated. Three transmission zeros are obtained at 3.2 GHz, 3.55 GHz and 3.73 GHz, which improve selectivity and out-of-band rejection of the filter. The measured results of the fabricated filter represent good in-band and sharp sideband characteristic, which match well with simulated results.

The adaptive linearly constrained minimum power (LCMP) beamformer can improve the robustness of the Capon beamformer. And quadratic constraints on the weighting vector of the LCMP beamformer can improve the robustness to pointing errors and to random perturbations in sensor parameters. But how to solve it and how to select the constraint parameters are its key problems. In this paper, the Lagrange multiplier method is proposed to solve the LCMP beamformer under quadratic inequality constraint (QIC). The problem of finding the optimal weight vector is solved, and the choice of the quadratic constraint parameter is analyzed and the selected bound is also given. Since the quadratic equality constraint (QEC) is stronger than the quadratic inequality constraint (QIC), the performance of the QECLCMP beamformer is more robust than that of the QICLCMP beamformer. Therefore, the QECLCMP beamformer is proposed and is solved effectively. Numerical examples attest the correctness and the efficiency of the proposed algorithms. And the results show that the QECLCMP beamformer has the advantage of overcoming the steering vector mismatch, namely the optimal negative loading has the preferable robustness.

For analyzing the electromagnetic problems with the fine structures in one or two directions, a novel weakly conditionally stable finite-difference time-domain (WCS-FDTD) algorithm is proposed. By dividing the 3-D Maxwell's equations into two parts, and applying the Crank-Nicolson (CN) scheme to each part, a four sub-step implicit procedures can be obtained. Then by adjusting the operational order of four sub-steps, a novel 3-D WCS-FDTD algorithm is derived. The proposed method only needs to solve four implicit equations, and the Courant-Friedrich-Levy (CFL) stability condition of the proposed algorithm is more relaxed and only determined by one space discretisation. In addition, numerical dispersion analysis demonstrates the numerical phase velocity error of the weakly conditionally stable scheme is less than that of the 3-D ADI-FDTD scheme.

In this work, we show how to manipulate the electromagnetic wave at will by using an indefinite medium with extremely strong anisotropy. The negative element in the indefinite permittivity tensor goes to the negative infinity while the positive element is equal to 1, which stretches the hyperbolic equifrequency contour into a straight line type. The direction of the Poynting vector and the wave vector is aligned by the straight line type equifrequency contour along the orientation of the extremely negative permittivity, thus control the wave propagation. The other permittivity of 1 makes the indefinite medium matched with the air. Moreover, because of the hyperbolic equifrequency contour, evanescent wave can also transmit in the indefinite medium under the propagation mode, implying the possibility of controlling an evanescent wave by this special indefinite medium. Simulations are performed to demonstrate the controlling performance and a potential design to realize such a medium by metamaterial with multilayered metal/dielectric structure. This work may supply a shortcut for those former devices based on the Transformation optics.

This paper studies the characteristics of a constant-K lens when considered as a possible substitute for a Luneburg lens in a reflector. The competitiveness of the substitute lens is investigated in its 2D analogue, by comparing the backscattering radar cross section for the range of D/λ ∈ (0, 200). The performance of cylindrical reflectors with either a constant-K lens or a cylindrical Luneburg lens (approximated by a finite number of stepped-index dielectric layers) when illuminated by an electromagnetic plane wave is studied using the semi-analytic Method of Regularization. Because of similar underlying physical principles, these studies provide insight into the 3-D analogue. The radar cross section calculations of the two reflectors for incidence angles varying from normal to grazing incidence show that the cheaper-to-manufacture constant-K lens reflector is able to provide a more powerful and stable backscattering performance than the cylindrical Luneburg lens reflector, for electrical sizes in the range considered.

A convenient method for canceling the parasitic winding capacitance of integrated electromagnetic interference (EMI) filter is proposed. Based on the concept of split ground structure, mutual inductances and structural capacitances can be appropriately utilized to expand the effective frequency range in common mode (CM) noise suppression. Compared with the former approaches, it requires no additional conductor layers or components since the split winding can simultaneously serve for CM capacitance. To demonstrate the parasitic capacitance cancellation mechanism, a simplified equivalent circuit is derived and investigated. Besides, the design procedure with considered structural constraints is presented to obtain the best parasitic capacitance cancellation effect. Prototype of an integrated CM filter with split ground layers is designed and constructed. Experimental results show the split winding can effectively shift the resonance frequency of filter inductor, and hence better filtering characteristics can be achieved.

This paper presents differential-fed patch antennas with excellent cross-polarization. This paper provides a detailed graphic illustration of factors that lead to deteriorated H-plane cross-polarization by the conventional single-ended feeding probes. A novel differential rat-race feeding structure was constructed to allow easy impedance matching. An experimental antenna was realized on low-temperature co-fired ceramic (LTCC) at 8 GHz. An excellent cross-polarization of less than -22.5 dB was achieved. When the operation frequency is high, the parasitic inductance caused by feeding probes may degrade the performance of antennas. This paper further proposes the use of differential aperture-coupled structures at high frequencies. An aperture-coupled antenna, realized at 40 GHz with low cross-polarization <-15 dB has been achieved.

In this paper, a chiral metamaterial (CMM) with complementary U-shaped structure assembly is proposed. The microwave experimental and simulated results of the proposed complementary structure exhibit giant optical activity. The experimental results are in good agreement with the numerical ones. The retrieval results reveal that negative refractive indices for right-handed and left-handed circularly polarized waves could be easily realized due to strong chirality. The mechanism of the chiral behaviors of resonance frequencies will be illustrated by simulated current distributions. Further, the complementary U-shaped structure assembly also exhibits stronger circular dichroism, giant optical activity, and negative index at near-infrared region by simulations.

The electromagnetic susceptibility model of discontinuous microstrip circuits with the presence of a uniform plane incident wave is established. First, the analytical expressions are modeled as equivalent voltage and current sources for discussing the global effect of the incident plane wave on the associated interconnects. Then, these field-induced equivalent source expressions are incorporated into ADS circuit solver, and a fast model is established for analyzing the output responses of discontinuous microstrip circuits, such as the cross bend, the band-rejection filter and the single-stage amplifier. The corresponding simulation results from the proposed model are validated by comparing the results from both simulation and measurement. The results also show that the incident plane wave may influence the output terminal responses significantly, and the proposed approach would be an efficient method to solve the electromagnetic susceptibility problems associated with the discontinuous microstrip circuits.

Radar imaging experiment of ground moving target --- a light rail-way train by Ku-band radar with two receiving channel is introduced. Both coherent and incoherent imaging as well as co-pol and cross-pol interferometric imaging were conducted with SAR amplitude images as well as interferometric --- phase images obtained. In the obtained SAR images, there are 24 stronger scattering centers which correspond to 24 bigger doors of the train. Along-track interferometric --- phase images indicate that the train travels at an increasing speed in one direction and at a decreasing speed in the opposite direction. Short Time Fourier Transform (STFT) is applied to the azimuthal signals to get the instant Doppler frequencies (IDFs), from which one can judge acceleration or deceleration status of the moving train. Electromagnetic scattering characteristics of the train are analyzed according to the SAR images. The estimated speed and length of the train are very well agreed with real situation.

In this paper, an inverse procedure algorithm is proposed in the time domain to evaluate lightning return stroke currents along a lightning channel using measured magnetic flux density at an observation point while the current velocity along a lightning channel is assumed to be a height dependent variable. The proposed method considers all field components and it can evaluate the full shape of currents and the current velocity at different heights along a lightning channel. Moreover, a sample of measured magnetic flux density from a triggered lightning experiment is applied to the proposed algorithm and the evaluated currents and current velocities are validated using a measured channel base current and magnetic flux density at another observation point.

In this paper, a new ultra-wideband (UWB) disc antenna compatible with cognitive radio is presented. The proposed antenna is developed to operate from 0.77 to 11.23 GHz. It consists of a circular disc radiator with a rectangular slot on the patch and the implementation of the bevel technique on the ground plane. A prototype of the antenna has been constructed and shows adequate impedance matching, radiation pattern and gain for cognitive radio applications.

In the field of automatic target recognition and tracking, traditional image metrics focus on single images, ignoring the sequence information of multiple images. We show that measures extracted from image sequences are highly relevant concerning the performances of automatic target tracking algorithms. To compensate the current lack of image sequence characterization systems from the perspective of the target tracking difficulties, this paper proposes three new metrics for measuring image sequences: inter-frame change degree of texture, inter-frame change degree of target size and inter-frame change degree of target location. All are based on the fact that inter-frame change is the main cause interfering with target tracking in an image sequence. As image sequences are an important type of data in the field of automatic target recognition and tracking, it can be concluded that the work in this paper is a necessary supplement for the existing image measurement systems. Experimental results reported show that the proposed metrics are valid and useful.

Localized surface plasmon resonance (LSPR) biosensors are employed to detect target biomolecules which have particular resonance wavelengths. Accordingly, tunability of the LSPR wavelength is essential in designing LSPR devices. LSPR devices employing silver nano-particles present better efficiencies than those using other noble metals such as gold; however, silver nano-particles are easily oxidized when they come in contact with liquids, which is inevitable in biosensing applications. To attain both durability and tunabilty in a LSPR biosensor, this paper proposes alumina (AL2O3) capped silver nano-disks. It is shown that through controlling the thickness of the cap, the LSPR resonance frequency can be finely tuned over a wide range; and moreover, the cap protects silver nano-particles from oxidation and high temperature.

Traditional detection approaches for the dim moving target are addressed under the background of homogeneous sea clutter. However, the realistic clutter commonly appears inhomogeneous, resulting in the low detectability. A heterogeneous multiple-scan detection framework is described in this paper, which combines the inhomogeneous coherent integration in the dwell of single scan and the non-coherent integration of the results from single-scan process across the multiple scans. In the inhomogeneous coherent integration, the Heterogeneous Single-scan Coherent Detector (HSCD) is derived, resorting to the two-step Generalized Likelihood Ratio Test (GLRT) criterion and a hybrid covariance matrix estimation scheme, where the nonhomogeneous Kelly detector and the inhomogeneous Adaptive Matched Filter (AMF) are also considered. Additionally, the Viterbi-Like (VL) algorithm is employed as the noncoherent integration strategy. Finally, the numerical simulations with Monte Carlo method analyze the performance of the nonhomogeneous multiplescan detectors under amplitude and distribution clutter heterogeneity.

A low-profile microstrip planar monopole antenna with triple-band operation for WiMAX and WLAN applications is proposed. The antenna has a simple structure which consists of a rectangular radiation patch with an L-shaped slot and an inverted L-shaped stub extending from the ground plane. By etching an L-shaped slot on the rectangular radiation patch, the antenna can excite two resonant modes. The third resonant mode is introduced by extending an inverted L-shaped stub from the ground plane. The designed antenna has a small overall size of 17*30 mm². A prototype is designed, fabricated, and then measured. The experimental and simulation results show good impedance bandwidth, radiation pattern and stable 9gain across the operating bands.

From the point of view of mixed-mode scattering parameters, S_mm, a two-port device can be excited using different driving conditions. Each condition leads to a particular set of input reflection and input impedance coefficient definitions that should be carefully applied depending on the type of excitation and symmetry of the two-port device. Therefore, the aim of this paper is to explain the general analytic procedure for the evaluation of such reflection and impedance coefficients in terms of mixed-mode scattering parameters. Moreover, the driving of a two-port device as a one-port device is explained as a particular case of a two-port mixed-mode excitation using a given set of mixed-mode loads. The theory is applied to the evaluation of the quality factor, Q, of symmetrical and non-symmetrical inductors.

A novel design of an electromagnetic bandgap (EBG) structure based on the uniplanar compact EBG (UCEBG) concept is proposed in this paper. The structure is realized by inserting split-ring slots inside two reversely connected rectangular patches, which is known as a split-ring slotted electromagnetic bandgap (SRS-EBG) structure. The bandgap properties of the EBG structure are examined by the suspended microstrip line and finite element methods (FEM). The achieved bandgaps have widths of 4.3 (59.31%) and 5.16 GHz (38.88%), which are centered at 7 and 13 GHz, respectively. The SRS-EBG is applied to enhance the performance of a single-element microstrip patch antenna (at 7 GHz) and a two-element array (at 13 GHz) configuration. A wider bandwidth is obtained with a better reflection coefficient level for the single element antenna; a reduction in mutual coupling of more than 20.57 dB is obtained for the array design. In both cases, the gain and radiation characteristics are improved. The results are verified by measuring the fabricated lab prototype, and a comparison with the computed results showed good agreement.

A multi-monopole-antenna system capable of generating two wide operating bands with good input matching by a voltage standing wave ratio (VSWR) of 1.5 to cover the 2.4 GHz (2400-2484 MHz), 5.2 GHz (5150-5350 MHz), and 5.8 GHz (5725-5825 MHz) bands for wireless local area network (WLAN) applications is introduced. The design mainly comprised three, metal-plate, monopole antennas symmetrically located on a main, hexagonal, ground plane and backed by vertical, step-shaped grounds protruding thereon. The step-shaped grounds not only facilitated the attaining of wide impedance bandwidth but also good port isolation. In addition, directional antenna radiation was also produced. Further, a triangular-cylinder shielding wall was placed in the center of the main ground plane for integration of the wireless, surveillance-camera module into the proposed antenna system. Details of the design prototype are described and discussed in the article.

Automated and accurate classification of MR brain images is extremely important for medical analysis and interpretation. Over the last decade numerous methods have already been proposed. In this paper, we presented a novel method to classify a given MR brain image as normal or abnormal. The proposed method first employed wavelet transform to extract features from images, followed by applying principle component analysis (PCA) to reduce the dimensions of features. The reduced features were submitted to a kernel support vector machine (KSVM). The strategy of K-fold stratified cross validation was used to enhance generalization of KSVM. We chose seven common brain diseases (glioma, meningioma, Alzheimer's disease, Alzheimer's disease plus visual agnosia, Pick's disease, sarcoma, and Huntington's disease) as abnormal brains, and collected 160 MR brain images (20 normal and 140 abnormal) from Harvard Medical School website. We performed our proposed methods with four different kernels, and found that the GRB kernel achieves the highest classification accuracy as 99.38%. The LIN, HPOL, and IPOL kernel achieves 95%, 96.88%, and 98.12%, respectively. We also compared our method to those from literatures in the last decade, and the results showed our DWT+PCA+KSVM with GRB kernel still achieved the best accurate classification results. The averaged processing time for a 256x256 size image on a laptop of P4 IBM with 3 GHz processor and 2 GB RAM is 0.0448 s. From the experimental data, our method was effective and rapid. It could be applied to the field of MR brain image classification and can assist the doctors to diagnose a patient normal or abnormal in some degree.