Nowadays, there is expanding interest in planar compact microstrip filters applied in microwave wireless system nowadays. The compact microstrip resonant cell (CMRC) and spiral compact microstrip resonant cell (SCMRC) are more and more popular in filter design due to their slow-wave and band-stop effects. In this paper, a novel double-folded SCMRC (DSCMRC) is proposed, analyzed and measured, which turns out to have more compact dimensions and distinctly broader stopband than CMRC and SCMRC. Furthermore, an improved DSCMRC circuit with two parallel open-ended stubs that are added into the DSCMRC structure is presented, which could introduce more transmission zeros in the stopband for better out-of-band rejection than the original DSCMRC. The measured results show the excellent performance of the improved DSCMRC circuit structure. Finally, a novel low-pass filter incorporating two improved DSCMRC in series is simulated and measured, which proves to have an excellent performance of out-of-band rejection up to 25 GHz with a really compact circuit size.

A simple and nonlinear LDMOS transistor model with multi-bias consideration has been proposed. Elements of the model are optimizes using particle swarm optimization (PSO) algorithm to fit the measured RF specifications of a typical transistor. The developed model is used then to design a high efficiency power amplifier with 55% power added efficiency (PAE) at 33 dBm output power with 12 dB power gain. This amplifier has a novel topology with optimized BALUN and microstrip matching network which makes it unconditionally stable and extensively linear over UHF frequency range of 100 MHz to 1 GHz with 163% fractional bandwidth. This power amplifier is fabricated and realized with 12-V supply voltage. A good agreement between simulated and measured values observed, indicating high accuracy of either the model and the amplifier design approach.

The beneficial effects of chronic/repeated magnetic stimulation on humans have been examined in previous studies. Although pain relief effects have been reported several weeks after magnetic treatment, no report is available regarding the prompt effect of magnetic stimulations. In this study, a novel apparatus was developed to generate time-varying magnetic fields with rotating magnets. Adult, conscious rats were exposed to the rotating magnets in a posture in which their spines were parallel to the induced electric current. The magnetic field suppressed the paw withdrawal reflex in the anesthetized rats, and the suppression effect disappeared 5 minutes after magnets stopped rotating. The tail flick (TF) latency and mechanic withdrawal thresholds (MWT) of the rats were significantly increased by the rotating magnets; the increases positively correlated with the velocity and period of the magnet rotating. These analgesia effects recovered to the baseline level 30 minutes after magnets stopped rotating. A biophysics model was proposed to qualitatively understand the mechanism of pain inhibition by the rotating field. The prompt analgesia effect of the rotating magnets and its rapid recovery encourage the application of this technique as a promising new analgesia and anesthesia method.

Synthetic Aperture Radar is well known for producing a radar image of the ground, so it can be used for detecting on-the-ground object which is interesting for some applications. A possible application can be Foreign Object Detection (FOD), which is an important issue in aviation safety. A ground-based Circular Bistatic Synthetic Aperture Radar (Circular-BiSAR) is introduced in this paper. The circular movement makes it more practical while the bistatic configuration offers some advantages. Wideband Linear Frequency Modulated (LFM) chirp pulses are employed here, for transmission and reception of reflection pulses to and from the under test object. A simulated model is developed for the system which analyzes the transmitting, receiving, Doppler and LFM signals by considering the distances and movement of antennas. A prototype system is launched, and some experiments are done to detect and localize various objects based on their reflection properties of microwaves. A processing algorithm is proposed in this paper to confirm the detection. The results show that the proposed system can detect and localize on-the ground objects with as small a dimension as 2 cm height and 2 cm diameter located several metres away.

In this paper, two slots which connect with waveguides and a microwave network are studied by using multi-modes technique. A TE incident plane wave is assumed. The moment method is employed to solve the problem. And the mode and triangular functions are used as basic and test functions. A different HM-pattern is obtained. It is found that the microwave network greatly affects the HM-pattern.

This paper presents comparison of two measurement techniques for ultra wideband (UWB) off-body radio channel characterization. A measurement campaign was performed in indoor environment using UWB wireless active tags and reader installed with the tag antenna and same set of measurement was repeated in the frequency domain using Vector Network Analyser (VNA) and cable connecting two standalone tag antennas for comparison/with a view to finding out the cable effects. Nine different off-body radio channels were experimentally investigated. Comparison of path loss parameters and path loss model for nine different off-body radio channels for the propagation in indoor environment both measurement cases are shown and analyzed. Results show that measurement taken by VNA connecting two standalone antennas through cables experiences lower path loss value for all nine different off-body channels. Least square fit technique is obtained to extract the path loss exponent. Increase of 12.96% path loss exponent is noticed when measurements are made using UWB tags and reader, i.e., without cable measurement scenario.

In this paper, a polarization-independent wide-angle planar metamaterial absorber exhibiting dual directional absorption is proposed. Measurement results indicate that the planar metamaterial absorber achieves absorptivities of 86.87% and 91.48% to the normally incident electromagnetic waves propagating in forward (+z) and backward (-z) directions, respectively. Due to geometry's fourfold rotational symmetry, the absorber is polarization-independent. Additionally, the absorber works well for a wide range of incident angles for both transverse electric and transverse magnetic polarizations. Besides its impressing performance, this planar metamaterial absorber is also extremely thin that it's thickness is approximately 1/32 of the working wavelength.

We present the design, fabrication and measurment of a dual-resonant broadband terahertz (THz) matamterial based on a modified split-ring resonator (MSRR) structure. The proposed MSRR is constructed by connecting the inner split ring with the outer split ring of adjacent cell. Transmission and reflection characteristics of the proposed structure are simulated using Ansoft HFSS, and the permittivities show negative values in 0.492-0.693 THz and 0.727-0.811 THz bands. The designed sample is fabricated on a gallium arsenide layer, and experiments are performed in Terahertz Time-Domain Spectroscopy. Measured transmission characteristics agree well with the simulations.

In this paper, the Raindrop Size Distribution (DSD) modeling and analysis are presented. Drop sizes are classified into different rain types, namely: drizzle, widespread, shower and thunderstorm. The gamma and Lognormal distribution models are employed using the method of moments estimator, considering the third, fourth and sixth order moments. The results are compared with the existing raindrop size distribution models such as the three parameter lognormal distribution proposed by Ajayi and his colleagues and Singapore's modified gamma and Lognormal models. This is then followed by the implementation of the proposed raindrop size distribution models on the computation of the specific rain attenuation. Finally, the paper suggests a suitable raindrop size distribution model for the region with its expressions. The proposed models are very useful for the determination of rain attenuation for terrestrial and satellite systems.

|In this paper, a careful study is made of the magnetostatic potential and eld of a magnetic dipole embedded in, and with dipole moment parallel to, the interface between two magnetic regions. Unlike the case of a magnetic dipole perpendicular to the interface, the detailed position of the current of the dipole relative to the location of the interface has a profound effect on the value of the field produced away from the dipole. As a consequence, the question of dening and determining the magnetic polarizability of a superconducting object partially embedded in a magnetic interface is examined. The results of this paper are important for the proper modeling of arrays of scatterers embedded in an interface, such as frequency-selective surfaces (FSSs) and metalms.

A class E power amplifier including coupling coils is proposed for application in a wireless power transfer system using magnetic coupling. The proposed amplifier is directly connected to the coils with no discrete components for harmonic filtering and dc feeding, which could cause efficiency degradation of the amplifier. The system with the differential amplifier shows 6.95 W of transmitted power and 44.6% transmission efficiency at 6.8 MHz with 14-cm distant coils. The power-added efficiency of the amplifier is 92.1% with a 14 V supply voltage, excluding the coupling efficiency of the wireless power transfer network.

In this paper, we will present a quasi-elliptic bandstop filter using asynchronously tuned resonators. To demonstrate this technique, a novel broadband microstrip bandstop filter is also proposed using distributed resonators. To achieve wide bandwidth using distributed resonators, strong couplings are required. This is achieved using tap coupled to avoid very narrow gaps which are costly to manufacture. The filter exhibits a factional bandwidth of approximately 35%. A simple practical transformation technique for transforming Chebyshev bandstop filter to asynchronously tuned quasi-elliptic bandstop filter will be presented.

Design of a composite dipole antenna array with direct feed is presented. In the form of printed-circuit antennas, the structure of the design consists of a doublet antenna and an elliptic loaded monopole antenna with a skirted dipole. As the load of the antenna array, this elliptic monopole provides wider bandwidth. Therefore, with the load possessing a radiation characteristic, it contributes to enhancing efficiency of the antenna array and hence the omni-directional radiation gain. A good agreement between simulated results by CST Microwave Studio^® and tested results suggests that the reflection coefficient for the frequency range between 4.35 GHz to 5.0 GHz is lower than -10 dB. The out-of-roundness on H-plane is lower than 2dB and the maximum gain is higher than 6dB for the frequency range from 4.6 to 5.0 GHz. What's more, the gain per wavelength is about 4 dB, showing the antenna's excellence in miniaturization.

Two fusion strategies for target recognition using multi-aspect synthetic aperture radar (SAR) images are presented for recognizing ground vehicles in MSTAR database. Due to radar cross-section variability, the ability to discriminate between targets varies greatly with target aspect. Multi-aspect images of a given target are used to support recognition. In this paper, two fusion strategies for target recognition using multi-aspect SAR images are proposed, which are data fusion strategy and decision fusion strategy. The recognition performance sensitivity to the number of images and the aspect separations is analyzed for those two target recognition strategies. The two strategies are also compared with each other in probability of correct classification and operating efficiency. The experimental results indicate that if we have a small number of multi-aspect images of a target and the aspect separations between those images are proper, the probability of correct classification obtained by the two proposed strategies can be advanced significantly compared with that obtained by the method using single image.

The time-harmonic electromagnetic scattering problem from a random inhomogeneous dielectric medium (here a turbulent plasma wake created by the atmospheric reentry of a vehicle) is considered. The electronic density of the plasma, that gives rise to its dielectric permittivity, has a fluctuating part ε_f (r), the variance and correlation function of which are known a priori. Because the electrical dimensions of the wake can be very large, the numerical solution of Maxwell's equations via a full-wave calculation performed with a boundary element and finite element method is prohibitive when statistical quantities such as the mean Radar Cross Section (RCS) and its variance are required, that necessitate a large number of random realizations. To remedy this difficulty, two approximations are considered and illustrated for a 2D scattering problem. First, a Mie series approach is adopted where the medium is discretized with small disks, thus reducing considerably the number of unknowns for a given random realization of ε_f (r), and a domain decomposition method is proposed to further reduce the complexity of the numerical solution of the corresponding system. Second, the statistical mean and the variance of the RCS are derived in closed-form from the Born approximation and yield accurate results when, as expected, the statistical mean of the relative dielectric permittivity is close to unity and |ε_f (r)| is small. Conversely, it is shown how these expressions can be used to validate the results obtained with the Mie series approximation. Numerical examples are presented that illustrate the potentialities of these techniques.

The arrays of compound-slots (inclined and displaced from waveguide centre) are not so common in the literature and the existing systematic method of design does not take into account the presence of surrounding elements. For this kind of slots, the reasons why the Elliott's procedure cannot be applied are physically explained. A new method based on circuit theory and scattering matrices connection to include the effects of the external mutual coupling in compound slots arrays is presented in this paper. To certify the validity of the complete technique, the performance of various designed arrays are compared to the results given by full-wave commercial solvers.

Liao's absorbing boundary condition (ABC) is a classic ABC algorithm. It has the advantages of better absorption effect, easy programming and needless to split field. However its numerical stability is poor, especially for the higher-order ones, which greatly limits the scope of its application. To solve this problem, a weighting method for improving the stability of Liao's higher-order ABC is presented in this paper. This method is simple and effective, and it can be implemented easily compared with other improvement methods before. It improves the stability of Liao's higher-order ABC remarkably, and extends its application range.

This paper addresses the application of measurement on goodness-of-fit (GoF) for amplitudes of radar clutter sample data against reference/theoretic parameterized probability density function (PDF). In general, various existing methods for this problem highly depend on empirical PDF parameters. This makes GoF assessments with these methods less perceivable and their accuracies are hard to control. A new method based on chi-squared type of measurement is proposed to overcome these difficulties. This method evaluates GoF by estimating the distance between the true PDF of the clutter data amplitude and the reference PDF. Hence the distance is statistically approximately independent with empirical PDF parameters. The new method has higher accuracy and symmetric property. It is especially useful for GoF comparison over multiple radar clutter data sets.

Conventional Far-field decomposition of the scattered electromagnetic (EM) field in the [EH] plane in terms of the horizontal and vertical components (i.e., h, v), introduces ambiguity for multi-static, multi-platform and/or scene-centric polarimetric synthetic aperture radar (SAR) image exploitation. This is due to the fact that a 2-dimensional (2D) vector field can not constitute a complete space capable of modeling 3-dimensional (3D) field transformations. To address this, extension of the Stokes vector, target scattering vectors and coherency parameters' analytic descriptions to 3D is explored and presented. The results are also applicable to compact polarimetry (CP) where mathematically consistent 3D Stokes parameters can be defined.

A dual-band dual-element multiple-input-multiple-output (MIMO) antenna system with enhanced isolation is proposed. The MIMO antenna system is based on printed 4-shaped antenna elements. Dual band isolation is achieved by using an array of printed capacitively loaded loops (CLLs) on the top side of the board for high band isolation improvement and a complementary CLL structure on the GND plane of the antenna for lower band isolation improvement. The lower band of operation covers 827-853 MHz and the higher band covers 2.3-2.98 GHz. Two prototypes were investigated to access the effect of the isolation mechanism. Measured isolation improvement of 10 dBs was observed in the lower operating band while the improvement in the higher band was approximately 2.5 dBs. The isolation improvement was at the expense of 5% reduction in efficiency. The measured gain patterns as well MIMO figures of merits such as the correlation factor, TARC and MEG were investigated as well.