This paper focuses on the fluctuating target detection in low-grazing angle using Multiple-input Multiple-output (MIMO) radar systems with widely separated antennas, where the multipath effects are very abundant. The performance of detection can be improved via utilizing the multipath echoes, which is equivalent to improve the signal-to-noise ratio (SNR) by using multipath echoes. First, the reflection coefficient considering the curved earth effect is derived. Then, the general signal model for MIMO radar is introduced for fluctuating target in low-grazing angle. Using the Neyman-Pearson sense, the detectors of fluctuating targets, i.e., Swerling 1-4, with multipath are analyzed. Finally, the simulation results show that the performance can be enhanced markedly when the multipath effects are considered.

During the last decade, selective photonic crystal filters have received much research interest in the fields of nanotechnology and optical interconnection network. The main focus of this paper consists of an analysis and a synthesis of one-dimensional photonic crystal selective filters. The optimization is performed by employing the simulated annealing algorithm. The filters synthesis is obtained by acting on the Bragg grating layer widths. Simulated annealing is applied to solve the PhC-1D filters synthesis problem in order to reduce the quadratic error and to obtain a desired transmission according to a Gaussian function defined in advance by the user. Starting from the Maxwell's equations for dielectric nonmagnetic structure, we show the derivation of the Helmholtz equation and find its solution for 1D layered structure. In addition, the boundary conditions and equation transformation to set of linear equations which are solved using Cramer‟s method are described thoroughly. This mathematical technique is then applied for computation of the transmission spectra of 1D perfectly periodic structure and structures with different defects. These results can be easily applied for design of selective filters.

A highly efficient asymmetrical GaN Doherty power amplifier using traditionalλ/4 transmission line and an asymmetrical GaN Doherty power amplifier(DPA) using composite right/left-handed transmission lines(CRLH-TL) for linearity improvement are presented in this paper.The CRLH-TL is designed to suppress the second harmonic of the output of the carrier amplifier. This DPA using CRLH-TL is designed for 3.5 GHz LTE-Advanced Application with 100 MHz bandwidth and 37 dBm average output power, the carrier and peaking amplifiers are fabricated with the same 30 W GaN HEMT and unevenly driven in purpose of maintaining high efficiency at back-off power (BOP) region. At 9-dB and 6-dB BOP, the DE achieves 30% and 40.1%, respectively, and the adjacent channel power ratio(ACPR) are less than-37.1 dBc for 40 MHz 16 QAM signal at 37 dBm. In addition, the further linearization of the DPA is realized by using digital pre-distortion(DPD), the ACPRs are improved to-49.6 dBc for 40 MHz 16 QAM signal.The measured results show linearity improvement compared with the traditional DPA.

A novel quarter-mode substrate integrated waveguide (QMSIW) resonator with back-to-back triangular complementary split-ring resonators (CSRRs) etched on the waveguide surface is proposed in this paper. The proposed CSRR structures allow the implementation of a forward-wave passband propagating with high selectivity below the characteristic cutoff frequency of the conventional QMSIW. Utilizing the property of flexible open structure on QMSIWs' two sides, a cascaded quadruplet (CQ) bandpass filter (BPF) using the proposed QMSIW resonator and proximity coupling structure is presented. Compared with some other reported BPFs with SIW technique, the presented BPF using the novel QMSIW resonator has great improvements on size reduction and selectivity, simultaneously, with simple geometry. At the center frequency of 3.7 GHz, the designed BPF filter achieves a wideband with a fractional bandwidth up to 24.3% and a high selectivity with a shape factor of 1.23. The compact dimension of this filter is as small as 0.36λ_g×0.36λ_g, where λ_g is the guide wavelength at the center frequency. The proposed filter is simulated, fabricated and tested. The measured results are in good agreement with the simulation.

We present a new composite material containing calcium alginate microspheres incorporated into an epoxy matrix. The new material is mechanically stable and does not degrade over time. Its di-electric properties are extracted by model calculations and compared to the properties of some selected human tissues. Good agreement is observed, which identies the proposed composite material as a good candidate for the use as a phantom material. The presented material is a two component composite and it is shown how its effective properties can be predicted by using appropriate mixing formulas.

A technique for magnetic resonance brain image classification using perceptual texture features, fuzzy weighting and support vector machines is proposed. In contrast to existing literature which generally classify the magnetic resonance brain images into normal and abnormal classes, classification with in abnormal brain which is relatively hard and challenging problem is addressed here. Texture features along with invariant moments are extracted and the weights are assigned to each feature to increase classification accuracy. Multi-class support vector machine is used for classification purpose. Results demonstrate that the classification accuracy of the proposed scheme is better than the state of the art existing techniques.

In this paper, a 3-D unconditionally stable meshless method is introduced to simulate time-domain electromagnetic problems. It combines the conventional radial point interpolation method (RPIM) and weighted decaying Laguerre polynomials together to discrete Maxwell's differential equations. The new method called Laguerre-RPIM retains the advantages of both the node-based meshless method and the unconditionally stable scheme of weighted Laguerre polynomials. The accuracy and efficiency of the proposed method are verified through two numeral examples. It can be seen from the computational results that the proposed method has a high accuracy and still remains stable when time step is 10 times of the Courant stability condition. Computational cost can be saved by more than 70% compared with the conventional RPIM method.

A new wideband magneto-electric dipole antenna using coplanar waveguide (CPW) structure is proposed in this paper. The proposed antenna consists of a pair of horizontal triangular patches and two vertically oriented L-shaped strips. By introducing triangular patches working as an electric dipole, the antenna can operate in a wide band. With the use of L-shaped strips equivalent to a magnetic dipole, the antenna is low in profile. A microstrip feed line is located between the two L-shaped strips to form a coplanar waveguide structure and excite the antenna. By carefully adjusting the gap between the feed line and the strips, the impedance bandwidth can be improved largely. A parametric study is performed to provide information for designing and optimizing such an antenna. A prototype is fabricated and measured. The simulated and measured results show that the impedance bandwidth for SWR less than 2 of the proposed antenna is 58.7% (1.95-3.57 GHz). Due to the complementary nature of the antenna, the proposed antenna has a unidirectional radiation pattern with low-polarization and low back-lobe radiation over the whole operating band. Furthermore, the gain of the antenna is stable across the entire bandwidth.

In this paper, without using external power and active components, a design of pin coupled functional antenna tuner is presented. The tuner consists of two parts, a coupling pin and a tuning circuit. It is used to tune the bandwidth and antenna gain of the proposed slot patch antenna. The prototype, including a slot patch antenna and the tuner, was constructed and excited through a T-shape microstrip feed circuit resonated at 2.6 GHz. The impedance bandwidth BW (-10 dB return loss) of the slot patch antenna without coupling to the tuner was 3% referred to the operation frequency at 2.6 GHz. When the tuner was matched with the impedance 75 Ω through the coupling pin to the proposed antenna, the BW of the antenna was increased to 11% operated at 2.6 GHz. However, if the tuner was matched with the impedance 25 Ω to the proposed slot patch antenna, the impedance bandwidth of the antenna was increased 21% at operation frequency. Relatively uniform antenna gain was obtained when the matching impedance was decreased from 75 Ω to 20 Ω. In the meantime, the lower matching impedance corresponds to more reducing cross-polarization of the proposed slot patch antenna can be observed in the measured field patterns.

Wireless implantable body area network (WiBAN) is useful for monitoring vital human parameters in medical diagnosis such as breast cancer, heart attack and high blood pressure. The main objective of this paper is to design a small printed monopole antenna for WiBAN applications at 6.0 GHz. The small implantable antenna was tested in a lossy environment by being submerged into canola oil that mimics the dielectric properties of human breast fat tissue. The antenna performances were measured by using vector network analyzer (VNA) in order to evaluate the return loss and operating bandwidth of the antenna. The other parameters such as efficiency, radiation pattern and gain are evaluated by simulation of CST Studio 2012 software. When compared, there is good agreement between the simulation and measurement results. The simulated antenna gain and efficiency are 5.8 dBi and 97%, respectively, when submerged into canola oil. The antenna radiation pattern is directional, and it has 6 lobes implying its coverage in more directions which is of good benefit due to body movement. The antenna's polarization was tested by placing a wideband antenna at several degrees around the proposed antenna. The value of S₂₁ was also analyzed to investigate the path gain of the selected links.

This paper considers the radar scenes which contain numerous rapidly changing terrains, i.e., there are more than one clutter-edge in the environment. This kind of radar scenes incurs sharply degradation in the performance of the present adaptive constant false alarm rate (CFAR) detectors as the statistical characteristic of reference cells is highly heterogeneous. To solve this problem, we propose a homogenous reference cells selector to improve the performance of CFAR detector in highly heterogeneous environment. The selector is comprised of an M-N clutter-edge detector cascading a terrain classifier. The M-N clutter-edge detector is used to obtain multiple clutter-edges in heterogeneous environment. With the detected clutter-edges, the terrain classifier is derived to obtain identical distributed range cells. Based on the selector, a modified Log-t-CFAR detector is suggested. Finally, the performance of the proposed selector and CFAR detector is evaluated by measured data and computer simulation.

In this paper, a novel monolayer multi-octave bandwidth log-periodic microstrip antenna (LPMA) is presented. This antenna consists of a 50 Ω microstrip feed-line and fourteen rectangular patch elements. Twelve rectangular patch elements are fed by edge-coupling from the microstrip feed-line and two other patch elements are directly connected with the microstrip feed-line. A mixed microstrip line feed is applied to expand the bandwidth. Our measured results closely agree with the simulated results. These results show that the proposed antenna lends itself well to operation in the impedance bandwidth from 2 GHz to 8 GHz with a voltage standing-wave ratio (VSWR) less than 2.

In this study, a three-dimensional (3-D) structural model of an adult male body, including 12 kinds of tissues and organs, was analyzed using a 3-D model design application (i.e., 3ds Max). The standard model of Asians was used as reference. The electrical parameters of brain tissues at different electromagnetic frequencies were introduced to obtain the electromagnetic model. Computational electromagnetic software based on the finite-difference time-domain was used to calculate the model absorption of electromagnetic waves under ultra-wide band electromagnetic irradiation. The specific absorption rates (SARs) of the ensemble average and the model human tissue were also obtained. This study aims to provide a parameter for the development of electromagnetic radiation protection standards, and to discuss related research.

A novel circular arc fractus named Arched Bow-shaped Fractal Curve (ABFC) is originally proposed. Four ABFCs are connected end-to-end, forming so called Arched Bow-shaped Fractal Loop (ABFL). The loop antenna peculiarly presents multiband multimode characteristics with resonance compression. The normal mode, which is pertinent to the loop area and circumference, is found improved with the iterative procedure. Thus, an eight-turned wire helix of small pitch angle (α=3 °) with a circular disc ground called Arched Bow-shaped Fractal Helix (ABFH) antenna is shaped from K₂ ABFLs. It can unprecedentedly operate in multiband of axial and off-axial modes with dual-sensed circular polarizations and high gain. Four matched bands (|S₁₁|≤-10 dB) are obtained within 2 GHz-8 GHz, of which f₁=2.34 GHz (400 MHz, 17.09%; G=10.63 dBi; RHCP), f₂=4.24 GHz (770 MHz, 18.16%; G=12.43 dBi; LHCP), f₃=5.48 GHz (300 MHz, 5.47%; G=8.13 dBi; RHCP), and f₄=6.98 GHz (960 MHz, 13.75%; G=15.89 dBi; RHCP). The unique multiband multimode property has been theoretically analyzed with illustrations and can be attributed to existence of the fractal boundary, which particularly encloses multiple equivalent loops with considerable areas. These peculiarities make K₂ ABFH antenna a very attractive candidate for multiband circularly polarized antennas, especially for space applications, such as spacecrafts communication, remote sensing, and telemetry, where reduction of quantity, height and weight of antennas are urgently wanted. It can also be configured into large array for higher gain service like radars and radio astronomy.

In this paper, a compact tri-band impedance transformer by utilizing stubbed coupling line for matching a load at three arbitrary frequencies is proposed. The transformer is composed of two parts, and each part is constructed from parallel-coupled transmission lines. Two structures with different configurations of the proposed transformer have been given and analyzed. Then, the close-form equations for the transformer parameters are derived analytically, and the corresponding analytical design approach is verified by numerical examples. To certify the validity of design formulas, an impedance transformer is fabricated and measured at 0.9/1.8/3.2 GHz. Good experimental performances at each frequency are obtained, which are in good agreement with the simulated results.

Cooperative wide-band spectrum sensing has been considered to enable cognitive radio operation of wireless regional area networks (WRAN) in the UHF and VHF TV broadcasting bands. In this paper, cooperative compressed spectrum sensing is considered to enable fast sensing of the wide-band spectrum. The speed and accuracy of spectrum sensing are improved by further optimization of the compressed sensing receiver, which is done blindly without any prior knowledge of the sensed signal. Enhanced compressed spectrum sensing algorithms are proposed for the cases of individual spectrum sensing and cooperative spectrum sensing (CSS). The cooperative signal reconstruction process is modified to optimally combine the received measurements at the fusion center. A low complexity authentication mechanism, which is inherent to cooperative compressed spectrum sensing, is proposed to make the cognitive radio system immune to adversary attacks.

This article describes a time-domain transmission line model based on distributed parameters for transient analysis. This model is based directly on the differential equations for the basic transmission line without any previous simplification. The solution presented here for these differential equations results in a more detailed time-domain model than others models currently in use, and with certain structural similarities with the distributed parameter frequency-domain model for long transmission lines. The deduction of a general time-domain transmission line model for fundamental frequencies parameters and single-phase line are presented in this article, but the model can also be extended to cases with multiconductor and frequency-depended parameters. In order to validate the model, a comparative test is presented to facilitate the analysis about the main similarities and differences between this and other models.

The synthetic aperture radar (SAR) is a widely used instrument for high-resolution imaging from aircraft or satellite platforms. In the paper, the problem of the defocusing of multi-look SAR images by uncompensated phase errors presented in the received data is analyzed. It is shown that the phase errors on a multi-look processing interval can be effectively described in terms of local quadratic and local linear phase errors. Approximate analytical expressions are derived to describe the azimuth resolution degradation. Criteria for acceptable phase errors are given. The obtained results are verified by numerical simulations. The approach is illustrated by two typical motion errors: slow deflections of a SAR platform trajectory from a reference flight line and periodic trajectory deviations.

This paper deals with the modeling the radiation of the power electronics component: the MOSFET. First, the magnetic near field measurements are made to characterize the radiation of the component. The MOSFET under test is referenced by IRF640 used in DC-DC converter. Second, we have applied the electromagnetic inverse method based on the measured field at 20 MHz to create a model of radiation sources of the MOSFET. The obtained results show a good agreement between the magnetic near field cartography obtained by the developed model and those measured. Finally, the developed model was used to predict the magnetic field in another distance and it wasvalidated with measured cartography.

In this paper, we provide a new theoretical model describing mechanism of electromagnetic radiation (and scattering) by passive single- and double-stranded (bifilar) helices. The proposed model is derived from basic physical principles till the end formulas which were computer processed for predicting a polarization type of the wave scattered by a helix. Comparison of the two types of helical oscillators revealed radical differences in their scattering performance (intensity and polarization). Optimal parameters of the bifilar helix for transformation of the polarization state from linear to circular were found for a non-axial direction of the incident and scattered field. Key features of the proposed model were confirmed by computer simulations.