This paper presents an approach of a shaped reflector antenna synthesis using a steepest decent method (SDM). It first discretizes the reflector surface into small patches and then uses grid nodes as variables in the synthesis procedure. Even though the number of variables can be very large for a large reflector antenna, the advantage of providing closed-form solutions for the derivatives of a cost function potentially makes this approach very efficient. The large number of variables also assists this procedure to reach a more global optimum as usually met in ordinary SDM. Numerical examples are presented to validate this approach.

The aim of this paper is to present a method to carry out the synthesis of large phased arrays when they are affected by complex environments which can influence the radiation pattern. The synthesis is performed with the help of the Multilevel Characteristic Basis Function Method to calculate a matrix relating input voltages and the far field pattern samples. The method is illustrated with the synthesis of a Secondary Surveillance Radar antenna on a turret containing multiple obstacles.

This paper proposes a methodology for numerically synthesizing element values of coupled resonator filters. These element values are compatible in retrieving coupling matrix of a cross-coupled quadruplet structure (also known as the folded structure). Differed from direct synthesis by matrix rotation, numerical solution has been adopted here to its equivalent coupling model. For varied specified return loss, numerical solutions of these element values have been derived and their accuracy is verified with their analytical counterparts to be extended for stringent design requirement. In addition, multiple sets of data are tabulated and categorized for efficient filter synthesis design under different specified pass-band return loss. In the end, an example quadruplet filter is designed, fabricated and measured for validation of the presented synthesis design methodology.

The properties of composite electromagnetic scattering from a square conducting plate target above a one-dimensional sea surface are discussed with the diffraction of plate edge taken into account. The characteristics of electromagnetic scattering from the sea surface are investigated based on the Kirchhoff Approximation (KA). The backscattering field of a plate target is calculated with the method of higher equivalent edge currents. Besides, the method of equivalent edge currents (MEC), Physical Optics (PO) approximation and the reciprocity theorem method are combined to calculate the composite scattering field from the conducting plate target above a sea surface. The effect of the plate size, inclination, edge diffraction and the frequency of incident wave on the composite scattering field is analyzed.

A method of acquiring clear three-dimensional image of human tooth in vitro, which is based on optical coherence tomography, is described. The background noise of the cross-section image is eliminated by image preprocessing algorithms, then the three-dimensional image is reconstructed by ray-casting algorithm, and gives the whole view of dental crown which contains dentin and enamel. A plane can be used to cut the tooth interactively to observe the inner tissue. This image is convenient for doctors to locate lesions and has a great potential for the clinical diagnosis of early dental caries.

In this paper, the protection of a sensitive car-size system using a hemispherical shielding cover is discussed. The shield cover spreads on the soil, inserting some vertical (metal) rods into the ground, and adding a gridded wire carpet under the cover structure. The shielding performance of the cover structure was considered by a numerical simulation and experiments. The proposed cover structure shows the shielding effectiveness (SE) of -40 dB in worst case in the frequency range of 10 to 200 MHz.

This paper presents a method to construct composite right/left-handed transmission line using coupled lines. A general procedure to design a composite right/left-handed unit cell is presented. The procedure was used on a specific coupled line configuration, which is the coupled microstrip lines with slotted ground. It is shown that by proper design of the slotted ground, the coupling between the two microstrip lines can be increased dramatically keeping practical dimensions for the coupled line width and spacing. Moreover, with accurate slotted ground design, equal even and odd electrical lengths can be achieved. The performance of this composite right/left-handed line, which is characterized by backward waves with phase advance, is demonstrated by both simulated and measured results and they show good agreement. The realized composite right/left-handed transmission line has a broad bandwidth and small size.

A novel time-domain integral equation (TDIE) solver for transient analysis of conducting wires is proposed. It is formulated using the induced electric dipoles as unknown functions. The triangular and B-spline functions are employed as the spatial and temporal basis functions, respectively. By using these basis functions, the matrix elements are found obtainable via exact closed-form formulae, which furnish a robust scheme in terms of stability and accuracy. In addition, to accelerate the matrix filling, a recursive algorithm is introduced. Numerical validations are provided by a dipole antenna, a V-shape antenna and a helical antenna.

While a geostationary weather radar would enable unprecedented monitoring of hurricanes and other severe weather, surface clutter could seriously limit its performance. The large incidence angles necessary for wide-area coverage, combined with the footprint size could cause surface clutter to obscure atmospheric return up to several km above the surface. The authors describe a Doppler filtering approach to clutter suppression and show simulation results. They find that Doppler filtering can significantly reduce the surface return, bringing surface clutter to acceptable levels. The authors then consider this approach when a staggered pulse repetition frequency is used to improve the maximum unambiguous velocity. They find that a method previously developed for ground-based weather radars can be successfully applied.

A compact three-layer shared-aperture dual-band dual-polarised sub-array operating in L/C-band is designed for application in synthetic aperture radar (SAR). Square, aperture-coupled patches in the C-band and a square, perforated L-band patch are combined on the top layer. They are fed from behind the ground plane by a combined feed system. Combined layers of patches and feed layers results in a highly compact antenna suitable for low weight applications such as space borne synthetic aperture radars (SAR).

A new method for analyzing the RCS of array antennas is presented in this paper. In the proposed method, the total RCS of the array can be simply decomposed to array RCS factor and element RCS factor. By this decomposition, the effects of the array distribution and antenna elements on scattering can be clearly exhibited. Thus, the analyzing of scattering characteristic of array antennas becomes easier. Moreover, proposed method has good compatibility for calculating the RCS of the array antennas with the same array distribution for different element.

In this paper, the inter-digital capacitance loaded loop resonators (IDCLLRs) are proposed to design microstrip band-reject filters. The analyzed structures are based on the coupling of IDCLLRs to a conventional 50 Ω microstrip transmission line. We have firstly studied the frequency response of one-stage IDCLLR-loaded microstrip transmission line. The main fratures of the IDCLLRs are small dimensions (much smaller than the wavelength at resonance) and more structural parameters (provide flexibility in design); Then a 6-stage IDCLLR-based microstip band-reject filter was designed and fabricated, it performs relative rejection bandwidth of 8.1% and rejection level of 23 dB. This stop-band is resulted from presence of the artificial medium with negative effective permeability (μ_eff<0). In addition, it is easy to control the rejection bandwidth by only employing different length of inter-digital fingers (for multiple tuning). A 9-stage band-reject filter with multiple tuned IDCLLRs has been fabricated and tested, its relative rejection bandwidth is extended to 11.5%. Simulated and measured results are presented.

The pump power and thulium-doped fiber (TDF) length for both single-pass and double-pass Thulium-Doped Fiber Amplifiers (TDFA) are theoretically optimized by solving differential equations. The 1050 nm pump is used to provide both ground-state and excitedstate absorptions for amplification in the S-band region. The TDFA is saturated at a shorter length with a higher gain value as the operating pump power increases. The double-pass TDFA allows double propagation of the test signal in the gain medium, which increases the effective TDF length and thus improves the gain of the TDFA compared to the single-pass configuration. Therefore, a small signal gain improvement of approximately 15 dB is obtained in the 1465 nm region. However, a noise figure penalty of approximately 1 dB is also obtained in this wavelength region. The theoretical result is in agreement with the experimental result.

A lowpass filter with a very sharp transition band using defected ground structures (DGS) is described. The lowpass filter was designed by using three dumbbell slots at the ground plane. Two of those dumbbell slots are the reshaped rectangular and the third dumbbell slot is an inverted triangle. The lowpass filter esigned at cutoff frequency of 3.0 GHz, which is suitable for GSM900, GSM1800 and UMTS applications of the mobile communications. The equivalent circuits for the proposed lowpass filter and its corresponding LC parameters are given. The proposed lowpass filter provides a size of 33x30 mm², and have good transition band with good performance in the passband and have wide rejection up to 9.25 GHz plus harmonic suppression in the stopband. Measurements results show good agreements with the simulated results.

Thresholded Landweber Iteration (TLI) is an attractive algorithm since it has the advantage of simplicity for the problem of sparse reconstruction. However, this algorithm depends heavily on the coherence property of the redundant ictionary, and its convergence rate is slow. In this paper, we develop a modified version of TLI by using a sensing dictionary. The proposed algorithm significantly improves the reconstruction performance and the convergence roperties when compared to the classical TLI. We provide a sufficient condition for which the modified TLI algorithm an be guaranteed to exactly identify the correct atoms and also discuss the convergence properties for this agorithm. Finally, simulation results are presented to demonstrate the superior performance of the proposed lgorithm.

The specific features of TE-wave propagation in a structure fabricated by periodic alternating ferrite and semiconductor layers are investigated. Dispersion characteristics of eigenwaves are calculated. The transmission spectra of an electromagnetic wave oblique incident from the uniform medium onto the multilayer periodic ferrite-semiconductor structure is considered. The features of transmission spectra of the structure with periodicity breakdown are studied.

A resistive sensor (RS) devoted for high power microwave pulse measurement in cylindrical waveguide is considered. The modeling results of the interaction of the TE01 (H01) wave with a semiconductor plate with contacts on sidewalls of the plate placed on a wall of the circular waveguide are presented. A finite-difference time-domain (FDTD) method was employed for the calculation of the electromagnetic field components, reflection coefficient from the semiconductor obstacle, and the average electric field in it. The features of the resonances have been used to engineer the frequency response of the RS. It has been found that such electrophysical parameters of the plate can serve as the prototype of the sensing element (SE) for the circular waveguide RS with flat frequency response.

More accurate hybrid PO-MOM process combining physical optics (PO) with method of moment (MOM) is employed to analyze an electrically large antenna-radome structure. The mutual interactions among the antenna, the inner and outer surfaces of the radome are considered through a group of associated integral equations. In the analysis, the antenna surface and the sharp tip part on the radome surface are modeled accurately by using MOM while the rest smooth parts on the radome surfaces are approximated by using PO. Numerical results indicate that the hybrid process presented in this paper is much more accurate than the conventional PO-MOM ones.

The complex permittivity and permeability of barium hexaferrite in the 8-12 GHz range was determined by using perturbation of electromagnetically coupled Ag thick film patch antenna due to overlay. In this technique even minor change in the overlay material properties changes the antenna response. The power gain of the EMC patch antenna was enhanced by 50% due to barium hexaferrite overlay. Barium hexaferrite was synthesized by co precipitation method and their fritless thick films were fabricated by screen printing technique. The properties were found to depend on the synthesis conditions such as Fe/Ba molar ratio, pH of the solution.

Design aspects of high efficiency profiled circular horns feed with smooth wall for the high-power microwave (HPM) system are presented in this paper. The modal content at the circular aperture of horn necessary to closely approximate a linear polarized Gaussian distribution is established. Slope discontinuities along the axis of the horn are then used to generate the necessary waveguide modes with the appropriate amplitudes and phases at the aperture. The performance of the horn is calculated using the mode matching technique. Significant improvement in the performance of radiation over a straight conical horn can be achieved on the premise of high power capacity. The excellent correspondence between the predictions and simulated result by CSTMWS (CST microwave studio) supports this conclusion.