In this paper, a novel and compact dual-band filter with enhanced upper stop characteristics has been presented. Dual band pass filter characteristics are achieved by introducing transmission zero (TZ) in pass band of band pass filter (BPF). The wide band pass filter (BPF) is implemented by combining low pass filter characteristics (i.e. stepped impedance resonator) and high pass filter characteristics (i.e. short stubs). Closed rectangular ring resonator (CRRR) and open loop rectangular ring (OLRR) combination is used to produce two transmission zeros (TZs). One TZ is placed on the pass band of BPF such that resultant filter characteristic consists of two pass bands. However, the second TZ is placed at edge of the pass band in BPF to improve skirt selectivity. The two pass bands are designed to cover two popular wireless bands namely WiMAX (center frequency f₁ (3.5 GHz) and WLAN (center frequency f₂ (5.7 GHz)) bands i.e. 3.35-3.65 GHz and 5.5-5.85 GHz respectively. Equi-ripple low pass stepped impedance resonator (SIR) filter response is responsible for improved and spurious free upper stop band (>20 GHz i.e. >6f₁) and also provides sharp skirt attenuation at upper stop band. The proposed filter is implemented on an RT/Duroid 5880 (ε_r=2.2) substrate with thickness of 0.785 mm and surface area of 19 × 12 sq. mm. Good agreement between simulated and measured results ensures that the proposed filter is a suitable candidate for modern dual band communications.

A compact multiple-input-multiple-output (MIMO) antenna that covers the WLAN (2.4 GHz) and UWB (3.1-10.6 GHz) bands for wireless device applications is presented. The proposed antenna consists of two open L-shaped slot (LS) antenna elements and a narrow slot on the ground plane. The antenna elements are placed perpendicularly to each other to obtain a high isolation, and the narrow slot is added to reduce the mutual coupling between antenna elements at the WLAN band (2.4 GHz). The presented MIMO antenna has a small size of 40×40mm², and the prototypes of antenna is fabricated and measured. The measured results show that the antenna has an impedance bandwidth of larger than 2.4-10.6 GHz with the mutual coupling less than 20 dB in WLAN band and 18dB in 3.1-10.6GHz, making the antenna a good candidate for portable applications.

Based on the Minimum Variance Distortionless Response-Sample Matrix Inversion (MVDR-SMI) method, we propose a novel Adaptive Covariance Estimator (MVDR-ACE) beamformer for adaptation to multiple interference environments. The MVDR-ACE beamformer iteratively determines a minimum number of data samples required while maintaining its average signal-to-interference-noise to be within 3dB from the performance of a theoretical optimum MVDR beamformer and meeting an instantaneous interference cancellation requirement. Finally, based on numerical simulations, we analyze and validate the performance of the MVDR-ACE beamformer. We also compare its performance to the conventional MVDR-SMI beamformer that uses a fixed data sample in its covariance estimator.

An efficient wide-band analysis that combines modified integral equation-physical optics (IE-PO) hybrid formulation with the best uniform approximation is proposed for antennas around an electrically large platform in this paper. The modified single-level Fast Fourier Transform (FFT) algorithm which is based on the subdomain FFT acceleration is employed by interpolating the Green's function and introducing the concept of the empty groups. Furthermore, the correction of the near-interaction is avoided. On the other hand, the best uniform approximation technique is applied to analyze wide-band properties of antennas. Due to the above modifications, the hybrid method needs fewer unknowns and memory requirements than the conventional one.

Mixed near-field and far-field sources localization problem has received significant attention recently in some practical applications, such as speaker localization using microphone arrays and guidance systems, etc. This paper presents a novel space-time matrix method to localize mixed near-field and far-field sources. Using the proposed method, both the direction-of-arrival (DOA) and range of a source can be estimated by the same eigen-pair of a defined spacetime matrix. Therefore, the pairing of the estimated angles and ranges is automatically determined. Compared with the previous work, the presented method offers a number of advantages over other recently proposed algorithms. For example, it can avoid not only parameters matching problem but also aperture loss problem. It has lower computational complexity since the proposed method does not require the high-order statistics or any parameter search. Simulation results show the performance of the proposed algorithm.

In this paper, we investigate electromagnetic problems for nanoscale antennas by using a boundary integral equation method with fast inverse Laplace transform. The antennas are designed for realizing ultrafast and high-density magnetic recording. Characteristics of nanoscale antennas are discussed in terms of eigenmodes and time domain responses of electric fields. Our computational method is highly efficient and the computational cost can be reduced by selecting coarse time step size and performing parallel computation.

A tunable electromagnetic-bangap (EBG) structure based on a double layer slotline using plasma is proposed. The plasma permittivity can be tuned by the electron density. The idea of integrating periodical plasma elements inside the slot to tune the stopband is investigated. An electron density and an electron collision frequency equal to 1.75 10¹³ cm^-3 and 10¹⁰ s^-1 respectively, are the plasma parameters selected in this study. The simulations reveal a shift rate of the second stopband equal to 6%. A new configuration of the structure is also proposed to adapt it better to the experimental requirements. Based on the simulation results, adding the plasma elements to the modified configuration shifts the stopband 4% and reduces its bandwidth by 43% (at -20 dB).

Bistatic forward-looking SAR (BF.SAR) has many potential applications, such as self-landing in bad weather and military detection. Therefore, BFSAR receives considerable attention recently. The imaging algorithms for BFSAR are the difficulties of the study. The original Loffeld's Bistatic Formula (LBF) can handle most general bistatic SAR configurations well. But in some complex bistatic geometries, such as high squint or forward-looking cases, the performance of LBF is degenerated. Some extended LBF (ELBF) methods have been developed, which improve the performance of LBF in some special geometries, but still not the forward-looking configuration. In this paper, we modify the LBF method and try to solve the instantaneous azimuth frequencies of transmitter and receiver directly. Then, we can obtain a bistatic point target reference spectrum (BPTRS), which is accurate enough for forward-looking configuration. A range Doppler algorithm (RDA) based on this BPTRS is derived. Finally, simulations validate the accuracy of the modified Loffeld's Bistatic Formula (MLBF) and effectiveness of imaging algorithm.

This paper presents a new approach for localizing mobile phone users using the promising technique of stratospheric platform (SP) flying at altitudes 17-22 km high and a suitable Direction-of-Arrival technique (DOA). The proposed technique provides information about accurate locations for mobile stations - through high resolution DOA technique - which is very important for traffic control and rescue operations at emergency situations. The DOA estimation in this technique defines the user location using MUSIC algorithm which provides good accuracy comparable to the Global Positioning System (GPS) techniques but without the need for GPS receivers. Several scenarios for users' locations determination are tested and examined to define the robustness of the proposed technique.

In this paper, a novel near zero refractive index metamaterial is designed and used as a superstrate of a microstrip antenna. In order to decrease the return loss, particle swarm optimization (PSO) is used to optimize the metamaterial structure. One of the important factors in the antenna designing, which influences the radiation efficiency, is to determine the accurate position of the feed, and PSO is used to find a precise location of the feed with minimum return loss. The simulation and fabrication of the microstrip antenna using the optimized metamaterial structure is also presented. The performance of the antenna is improved, and the gain is increased up to 4.5 dB. The directivity and radiation efficiency are significantly enhanced. Moreover, a very good agreement is observed between simulation and measurement results.

A volume-surface integral equation (VSIE) formulation is developed for determining the electromagnetic TM scattering by a two-dimensional conducting cylinder coated with an inhomogeneous dielectric/magnetic material. The electric field integral equations (EFIEs) are utilized to derive the VSIE. The surface EFIE is applied to the conducting surface, while the volume EFIE is applied to the coating region. By employing the surface and equivalence principles, the problem is reduced into a set of coupled integral equations in terms of equivalent electric and magnetic currents radiating into unbounded space. The moment method is used to solve the integral equations. Numerical results for the bistatic radar cross section for different structures are presented. The well-known exact series-solution for a conducting circular cylinder coated with multilayers of homogeneous materials is used along with the available published data to validate the results. The influence of using coatings with double-positive (DPS) and/or double-negative (DNG) materials on the radar cross section is investigated.

A dual-beam microstrip array antenna based on conical beam elements is proposed in this paper. Circular patch operating at the TM₀₁ mode is used to achieve conical beam pattern. Grating lobes of the array is used to obtain dual-beam patterns with large elevation angle and high gain. Detailed analysis and design have been presented. A 4x4 antenna prototype has been fabricated and measured. Experimental results show that the antenna array has the return loss better than 10 dB over 12.26 GHz-12.88 GHz and exhibits two symmetric radiation beams, directed at ±49.4° with 16.6 dBi gain at 12.5 GHz. Good agreement between the simulated and measured results is observed. Compared with the previous scheme, the alternative proposal possesses the advantages of being easy to form a planar array with low cross-polarization and having relatively high aperture efficiency simultaneously.

The Radar Cross Section(RCS) of moving targets varies dramatically with aspect or time. The accuracy of simulated dynamic RCS is very important for radar system simulation. A novel simulation approach of aircraft's dynamic RCS is proposed in this paper. Firstly, the electromagnetic (EM) model of aircraft is built and the all-space mono-static RCS database calculated. Secondly, the aspect angles (azimuth and elevation) in target coordinate system are calculated from flight path by coordinate transformation. Then dynamic RCS is obtained based on database and aspect angles by linear interpolation method. Account for the influence results from aircraft vibration in target motion, we use a white Gaussian distributed random series to modify the simulated results. The statistical characteristics of three kinds of dynamic RCS values are investigated, and the desirable agreement of results between modification and measurement shows the applicability of this simulation approach.

In this paper, an analytical model of permanent magnet electrodynamic suspension systems (PEDSs) is proposed. Horizontal and vertical magnetic fields of a permanent magnet (PM) are affectively approximated by sinusoidal functions. By this means, closed form solutions are obtained for lift and drag forces of PEDS for the first time. The suspension system is modelled by finite element method (FEM). The analytical values of lift and drag forces are compared with the FEM results. Also, the analytical results are evaluated by experimental results. As so, the accuracy of the analytical model is validated by FEM and experimental measurements.

We provide a critical account of the dynamics of laser induced refractive index changing mechanisms in nematic liquid crystals which may be useful for all-optical switching and modulation applications in the visible as well as the Terahertz and long-wavelength regime. In particular, the magnitude and response times of optical Kerr effects associated with director axis reorientation, thermal and order parameter changes, coupled flow-reorientation effects and individual molecular electronic responses are thoroughly investigated and documented, along with exemplary experimental demonstrations. Emphases are placed on identifying parameter sets that will enable all-optical switching with much faster response times compared to their conventional electro-optics counterparts.

The generic foundry approach will lead to a revolution in micro and nanophotonics, just as it did in microelectronics thirty years ago. Generic integration leads to a drastic reduction in the entry costs for developing Photonic Integrated Circuits. Integrated circuits using generic integration open up a whole new range of applications including data communications, fiber-to-the-home, fiber sensors, gas sensing, medical diagnostics, metrology and consumer photonics. Present status and prospects of InP-based photonic foundry technology are reviewed.

The idea of transformation inside a null-space region is introduced for the first time, and used to design a novel DC magnetic compressor that concentrates DC magnetic flux greatly and behaves as a DC magnetic funnel. The proposed device can be used as a passive DC magnetic lens to achieve an enhanced DC magnetic field (e.g. 7.9 times or more depending on the size and other parameters of the compressor) with a large gradient (e.g. 400T/m or more) in free space. After some theoretical approximation, the proposed device can be easily constructed by using a combination of superconductors and ferromagnetic materials. Numerical simulations are given to verify the performance of our device. The proposed method (use a null-space region as the reference space) can be extended to reduce the material requirement when designing other devices with transformation optics.

We present a broadband microwave metamaterial (MM) absorber, the unit cell of which consists of a lumped-resistor-loaded electric-inductive-capacitive (ELC) resonator and a cut-wire on the same side of a flexible polyimide substrate. In contrast to the common MM absorber, the metallic pattern layer of the proposed structure is placed parallel to the direction of propagation of the incident wave in order to reduce the radar cross-section (RCS) at frequencies other than the targeted frequency bands. Our experiments show that the proposed absorber exhibits a peak absorption rate of 92% and 93% at 8.6 GHz and 13.4 GHz, respectively, and 88% of the full-width at half-maximum (FWHM) bandwidth is achieved.

This paper presents a low-cost strip-to-bilateral-slotline transition with operating bandwidth from 0.53 to 6 GHz. The low-cost design concept is realized by utilizing conventional cheap FR-4 substrate and wide slotline with large slot width. By virtue of the low price of FR-4, less strict fabrication tolerance of wide slotline and the avoidance of metallic vias, the fabrication cost is reduced significantly compared to schemes using expensive Rogers RT laminates, extremely narrow slotline with strict fabrication tolerance and metallic vias. The broadband impedance matching difficulty caused by the high characteristic impedance of wide slotline is solved by three means. Firstly, bilateral structure is used to lower the characteristic impedance of the slotline. Then an elliptic slotline stub and an innovative half-elliptic strip stub are proposed to provide good impedance matching. Finally, multi-section stepped impedance transformers are used to match the transition from high impedance to standard 50 Ohm. The validity of the design methods is verified through experiments.

A compact millimeter-wave (MMW) wideband high-gain antenna is proposed and implemented. The development is based on the design principle of wideband Fabry-Perot resonator antennas (FPRAs). The antenna consists of three dielectric slabs and a PEC ground, and it is fed by a rectangular waveguide. All slabs are used to form the superstrate that exhibits the increasing reflection phase at the designed frequency band. Size reduction of the superstrate is carried out to enhance the bandwidth of the antenna. The effect of ground size and resonant frequency shift due to size reduction of the superstrate were studied. A wide bandwidth of over 30% was finally obtained, and measurements of the fabricated prototype validate the theory and simulation results.