We show that the optical modes of a periodic nanostructure with frequency dependent dielectric constant (i.e., a dispersive optical nanostructure), in general can be written as an ordinary eigenvalue problem of a "dielectric function operator", for each distinct symmetry representation of the periodic nanostructure. For a frequency dependence in the form of polynomial rational function, the problem translates to a polynomial eigenvalue equation in the frequency of the mode. The resulting problem can be solved using the basis functions of a dielectric backbone structure, which has a frequency independent dielectric constant. Rapid convergence is achieved when the basis functions are selected to be the modes of a dielectric backbone structure that minimizes the frequency perturbation of the dielectric function of the optical nanostructure. In particular, using a two dimensional photonic crystal constructed with a polar crystal as an example, we demonstrate that, remarkable simple cubic equations are sufficient to obtain accurate descriptions of eigenfrequencies.

A compact interdigital capacitor coupled dual-behavior resonator (DBR) filter with high spurious responses suppression is proposed in this paper. The technique is based on two equivalent topologies of J-inverter and dual-line equivalent circuit of open-circuited stubs. The first compact equivalent topology capacitive inverter is a high pass structure, and consequently, the spurious responses can be suppressed effectively at low frequencies. The second equivalent topology π-network is employed in realizing a compact size and adding new transmission zeros dedicated to the spurious responses suppression at high frequencies. Further compactness is achieved with a dual-line equivalent circuit of open-circuited stubs. The relevant equations are given in the paper. Finally, a 3rd-order compact DBR filter is designed and measured. This structure has a high degree of miniaturization(83%) in comparison to the classical one. Measurement results show good agreement with the simulated ones.

Random antenna array (RAA) that uses the conventional beamforming method produces a poor beam pattern with high sidelobe level. This greatly reduces the performance and the efficiency of the antenna. The use of Genetic Algorithm (GA) to find the best positions for the antenna elements in RAA to lower the sidelobes has been widely researched. However, there has been no solution proposed for the reduction of sidelobes when the user has no autonomy over the position of the radiating elements, for instance in cases such as emergency communications. This paper proposes a novel Pareto Elite Selection Genetic Algorithm (PESGA) optimization method to reduce the sidelobes in an RAA that has fixed elements' position. The proposed method uses a single fitness function (peak sidelobe level) for parent selection while an additional function (number of sidelobes above a threshold level) is introduced to select the elitist in every generation via Pareto Front (PF) selection. Results indicate that the proposed PESGA method is best used for scenarios where the array size is small. In such cases, the proposed method provides much reduced sidelobe compared to the conventional RAA beamforming method and up to 200% improvements in terms of mainlobe to peak sidelobe ratio compared to GA weight optimized beamforming method.

In this paper we present a methodology to guarantee the convergence of the electromagnetic inverse method. This method is applied to electromagnetic compatibility (EMC) in order to overcome the difficulties of measuring the radiated electromagnetic field and to reduce the cost of the EMC analysis. It consists in using Genetic Algorithms (GA) to identify a model that will be used to estimate the electric and magnetic field radiated by the device under test. This method is based on the recognition of the equivalent radiation sources using the Near Field (NF) cartography radiated by the device. Our contribution in this field is to improve the ability and the convergence of the electromagnetic inverse method by using the Pseudo Zernike Moment Invariant (PZMI) descriptor and the Artificial Neural Network (ANN). The validation of the proposed method is performed using the NF emitted by known electric and magnetic dipoles. Our results have proved that the proposed method guarantees the convergence of the electromagnetic inverse method and that the convergence speeds up while retaining all the other performances.

A low-profile microstrip planar monopole antenna with triple-band operation for WiMAX and WLAN applications is proposed in this paper. The antenna has a simple structure which consists of a rectangular ring patch, two inverted L-shaped strips extending from the rectangular ring patch, and a microstrip feed line. By adding two L-shaped strips on the rectangular ring patch, three resonant modes can be excited independently. The antenna has a simple structure and a compact size of 21 × 33 × 1.6 mm³. The measured -10 dB impedance bandwidth of the proposed antenna covers 2.39-2.51 GHz, 3.26-4.15 GHz, and 5.0-6.43 GHz, which can fully cover the 2.4/5.2/5.8 GHz WLAN bands and 3.5/5.5 GHz WiMAX bands. A prototype is fabricated, and then measured. The experimental and simulation results show good impedance bandwidth, radiation pattern and stable gain across the operating bands.

A compact multiband Inverted-F Antenna (IFA) for the use in a mobile phone is presented. By adopting a novel folded 3-D structure, a quarter-wave resonator and a parasitic strip, the proposed antenna covers eight bands and exhibits reduced electrical size and low profile. S₁₁ less than -6 dB is obtained in the GSM900, GSM1800, DCS, Bluetooth, Wi-Fi, WLAN5.2, WLAN5.8 and the WiMAX bands. The dimensions of the proposed antenna with the 3-D structure are only 39.6×4.3×3.4 mm³, which are very small in respect with other antennas in mobile terminal devices. A prototype of the proposed antenna is fabricated and measured. Measured and simulated results exhibit good bandwidth, radiation patterns and efficiency across all eight bands.

In this paper, a bandstop to allpass reconfigurable filter technique is proposed in Single Pole Double Throw (SPDT) switch design. Proof of concept of the bandstop to allpass reconfigurable filter is presented. It is physically realized using transmission line and radial stub in 3.5 GHz band (3.4 to 3.6 GHz). The isolation, insertion loss and return loss of the SPDT switches are analyzed and to validate this technique the prototypes are fabricated using FR4 substrate with a thickness of 16 mm. A very good agreement is shown between the simulated and measured results. Using this technique, it is able to produce more than 30 dB isolation with minimum number of PIN diodes, thus reducing 42.7% of the total circuit size compared with conventional design. Besides, additional 22.9% of isolation bandwidth can be obtained with the use of radial stub compared with transmission line stub. The potential application of this SPDT switch is Time Division Duplex (TDD) switching for WiMAX and LTE communication system in the 3.5 GHz band.

A stereo-synthetic aperture radar (stereo-SAR) technique is proposed to estimate the terrain height of a target area. A reference point with known altitude is located within the target area to calibrate the height estimation. The estimated height error can be reduced to one meter. This method requires the processing techniques of conventional SAR, while achieving a fairly fine resolution in height estimation for practical applications.

This paper presents a tri-band bandpass filter (BPF) using a novel stub-loaded resonator. Different from other stub-loaded resonator, this resonator utilized a short-ended main transmission line and a centerly-loaded open stub. The resonator is theoretically analyzed. The first three resonant frequencies can be individually adjusted and this enables the convenient designs of tri-band BPFs. For demonstration, a tri-band BPF is implemented. Transmission zeros are created close to each passband edge, resulting in high skirt selectivity. Comparisons of the measured and simulated results are presented to verify the theoretical predications.

This paper deals with a novel miniaturized FSS with wide stop band characteristics for UWB applications. The proposed FSS consists of garland like design printed on either side of the dielectric substrate. The design provides a bandwidth equal to 3.5 GHz at -20 dB reference level of insertion loss which lies within the UWB range. The design delivers stable response for various angular incidences. In addition to this, the symmetrical nature of the FSS holds identical response for both TE and TM Mode of polarization. The proposed geometry is fabricated and its simulated results are validated with measurements. A comprehensive analysis is made by adjusting various parameters associated with the proposed design.

The paper deals with the propagation of electromagnetic waves through twisted clad dielectric optical fibers. The structure of these fibers is analogous to travelling wave tubes used in microwave devices, and the usefulness would be in the areas of optical sensing. This is because the twists in fiber would be affected due to the imposed stress and/or strain, leaving thereby the possibility to alter the propagation characteristics. A rigorous analytical investigation has been carried out with the emphasis on the energy flux density patterns due to the different propagating modes in the fiber. The dispersion relations of the system are deduced and the energy flux densities are evaluated under different pitch angles of twist. The effect due to conducting helix pitch on the electromagnetic wave propagation is emphasized.

A compact multilayer substrate integrated waveguide (SIW) dual-mode filter with multiple transmission zeros for high-selectivity application is presented. By introducing mixed coupling between source and load, the proposed filter could have four transmission zeros which can be controlled flexibly. Owing to the multilayer structure, the proposed filter occupies similar area in comparison with conventional dual-cavity dual mode SIW filters, but exhibits better frequency selectivity. An experimental filter with a center frequency of 10 GHz is designed using low temperature co-fired ceramic (LTCC) technology to validate the proposed structure, and measured results agree well with simulated ones.

The Polar Format Algorithm (PFA) is suitable for spotlight synthetic aperture radar (SAR) image focusing either in monostatic or bistatic cases. The classic linear-trajectory PFA complete data correction in wavenumber domain, converting data from the polar format to the rectangular format. However, the two-dimension processing (either using interpolation or chirp-z transform) introduces heavy computational load, which limits its real-time applications. This study presents a conical-trajectory PFA for bistatic SAR, in which the transmitter and receiver are designed to fly on conical surfaces, to simplify image formation procedures via eliminating the necessity of range processing. Moreover, the conical-trajectory PFA provides a space-invariant range resolution to simplify the SAR image comprehension. A spotlight forward-looking bistatic missile guidance application was simulated for the algorithm validation and performance analysis.

A satellite-borne frequency selective surface (FSS) for atmospheric sensing application is presented. This brand new type of band-pass filter has an operating frequency at 183 GHz, which is a typical frequency on H₂O absorption line. Comprising an ultra-thin gilding layer and a SiO₂ substrate layer, this complex periodic component exhibits an extremely low insertion loss (< 0.22 dB) and high isolation (> 20 dB) between closely spaced frequency channels of 45° incident wave. Periodic Method of Moment (PMM) approach is applied to determine the initial geo-metrical parameters of FSS unit cell, and the optimization approach based on the Genetic Algorithm (GA) enables us to obtain the requisite spectral response and transmission characteristics for both TE and TM polarization. The experimental results show that the proposed PMM-GA technique is effective for analyzing space-borne FSS at millimeter wave range.

A novel triple-frequency fork-shaped antenna for WLAN/WiMAX applications is proposed and investigated in this paper. The presented antenna is simply composed of three radiating elements viz. Stub1, Stub2, Stub3. By adjusting the lengths of the three stubs, three desired resonant frequencies can be achieved and adjusted independently. Experimental results show that the antenna impedance bandwidths for S₁₁ ≤ -10 dB are 2.4-2.65 GHz, 3. 3.3-4.05 GHz, and 5-5.98 GHz, covering the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. Furthermore, nearly omni-directional radiation patterns over the operating bands have been obtained.

A one-step leapfrog alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method for lossy media is presented. Different from the method provided by others, the proposed method is originated from the conventional ADI-FDTD method instead of considering the leapfrog ADI-FDTD method as a perturbation of the conventional explicit FDTD method. Its unconditional stability is analytically proven through a method that combines the von Neumann method with the Jury criterion. In addition, its unconditional stability and computational efficiency are verified through numerical experiments.

This paper proposes a novel corner-fed Circular Polarization (CP) reader antenna for handheld Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) application. The CP mechanism is accomplished by a multi-bending feeding strip located at corner of a high dielectric constant (K = 60) ceramic substrate. By using the high dielectric substrate, the dimension of the proposed antenna can be effectively reduced to 27 × 27 × 4 mm³, which consists of a top radiating patch, an antenna ground plane, a coupling multi-bending feeding strip, and a SMA connector for RF input. The top radiating patch is printed on the top surface of the ceramic substrate and the antenna ground plane is formed on the opposite side. The central frequency of resonant band can be easily controlled by adjusting the size of the top radiating patch. By optimizing the coupling feeding mechanism, not only impedance matching can be achieved for bandwidth operation in Taiwan's UHF RFID band, but also two orthogonal field components with 90° phase difference for circular polarization are obtained. In addition, the proposed antenna is placed on an 80 × 80 × 0.8 mm³ FR4 system ground plane for reducing hand holding effect.

This paper illustrates an explicit multiresolution time-domain (MRTD) scheme based on Daubechies' scaling functions with a spherical grid for time-domain Maxwell's equations. The stability and dispersion property of the scheme are investigated and it is shown that larger cells decrease the numerical phase error, which makes it significantly lower than FDTD for low and medium discretizations. Moreover, this technique is applied to the modeling of an air-filled spherical resonator, and numerical results demonstrate the effectiveness of the proposed algorithm.

In this paper, a new Frequency-Reconfigurable Stacked Patch Microstrip Antenna (FRSPMA) with a new coupling method applied in an aperture-coupled technique controlled by the switching circuit is presented. This antenna uses a combination of aperture-coupled technique and stacked patch in order for the radiating elements to increase the bandwidth. Two shapes (Ishape and H-shape) and sizes of aperture slots are etched onto the ground with a purpose to couple the energy between feedline and stacked patch. One PIN diode switch is integrated in the feed network to control the length of the feedline. A variation of the feedline length controls the selected aperture slots to be active. The waves from the selected activated aperture slots will radiate to particular radiating patch (top or bottom patch) and achieve the frequency reconfigurability. When the switch is in ON mode, the antenna has a capability to configure its operating frequency at 2.6 GHz and at 3.5 GHz during the OFF mode. Besides that, the air gap is used to improve and avoid any coupling problem between the aperture slots and both of the two patches. Improper alignment between the aperture slots and patches will interfere waves radiating from aperture slots to the particular patch. In addition, the proposed antenna produces a high gain of more than 5 dB during ON or OFF modes respectively. The simulated results are compared with measured results.

A hybrid tuning method for microwave filters is presented in this paper. This novel tuning technique is based on the combination of the Cauchy method and aggressive space mapping (ASM) technique. Cauchy method is applied to determine the characteristic polynomials of the filter's response, then the parameters (coupling matrix) of the low-pass prototype is extracted from the characteristic polynomials. The aggressive space mapping is used to optimized the fine model to guarantee that each step of a tuning is always in the right direction. The validity is verified by two examples. One deals with the four-resonator cross-coupled filter and the other one is an direct coupled six-resonator filter.