In this paper we developed the method of broadband Green's function with low wavenumber extraction (BBGFL) for arbitrary shaped waveguide. The case of Neumann boundary condition is treated. The BBGFL has the advantage that when using it to solve boundary value problems in a waveguide, the boundary conditions have been satisfied already. The broadband Green's function is expressed in modal expansion of modes that are frequency independent. To accelerate the convergence of the Green's function, a low wavenumber extraction is performed. The singularity of the Green's function is also extracted by such low wavenumber extraction. Numerical results show that BBGLF and direct MoM are in good agreement. We next illustrate the application of BBGFL for broadband simulations of vias in printed circuit boards (PCB) by combining with the method of Foldy-Lax multiple scattering equation. The results show that BBGFL are in good agreement with MoM and HFSS. It is also shown that BBGFL is many times faster than direct MoM and HFSS. The computational efficiency in broadband simulations makes this technique useful for fast computer-aided design (CAD).

In this paper, a pattern diversity antenna, capable of radiating broad side as well as conical radiation patterns using quarter mode substrate integrated waveguide sub-array, has been presented. The pattern diversity is achieved by in-phase and out-of-phase excitation of the sub-array using a rat-race coupler feed network. The overall profile height of the proposed antenna is 3.17 mm. The measured performance of the antenna, in terms of return loss, isolation, gain and diversity performance in the -10 dB impedance bandwidth, is in agreement with the simulated results. The proposed sub-array occupies 25% less area than the conventional microstrip antenna.

In this paper, a novel dual-band antenna with coupled line and different impedance extension lines is presented and analyzed. This simple antenna is composed of three antenna radiations with symmetric coupled lines, and it occupies a compact space of 80 × 30 × 1 mm³. The achieved 10-dB bandwidths of the dual-band operation in free-space condition are 200 MHz and 100 MHz, respectively, which support the 1.8/2.6 GHz Long Term Evolution (LTE) operating bands. Furthermore, various parameters are investigated to examine the effects of the antenna parameters on return loss as well as the gain of the proposed antenna.

A new balanced bandpass filter (BPF) with tunable bandwidth using tri-mode stub-loaded resonators is proposed. To tune the differential-mode bandwidth, the two even-mode resonance frequencies and two transmission zeros (TZs) are tuned while the odd-mode resonance frequency keeps unchanged. To realize high selectivity for differential mode, another two TZs are created by the source-load coupling and coupling sections. Furthermore, wideband common-mode (CM) suppression is achieved. The fabricated filter has 3-dB fractional bandwidth ranging from 20.0% to 26.0% centered at 1.71 GHz and wideband suppression (17 dB from 2 to 4.4 GHz) for the differential mode, as well as common-mode suppression better than 20 dB from 0 to 4.5 GHz.

A compact 4-port asymmetric coplanar strip (ACS)-fed MIMO antenna working in the ultra-wideband (UWB) frequency band with two shared radiators is presented in this paper. The proposed antenna is composed of two radiators, and each radiator is shared by two antenna elements in order to achieve a very compact size of 36×36 mm². By etching two I-shaped slots in the radiators and attaching a rectangular patch on the back, the operating band width is broadened, and the isolation between any two antenna elements is enhanced. The stub of the ground also has great effect on the return loss and isolation. The working frequency band of the MIMO antenna covers 3.1-10.6 GHz with isolation over 15 dB between any two antenna elements. Furthermore, the proposed antenna with a simple feeding structure and compact size makes it possible to be used in portable devices.

A tri-band multiple-input-multiple-output (MIMO) antenna that covers all frequency bands required for WLAN and WiMAX applications is presented. Three resonant bands are achieved by a folded monopole with a compact size of 11.5×15.6 mm². The MIMO system consists of two symmetrically placed monopoles. A stepped slot ended with an ellipse on the ground plane is etched to reduce the mutual coupling between the two monopoles. The overall dimension of this MIMO system is 50×50 mm². The prototype of the antenna is fabricated and measured. Measured results show that the antenna's impedance bandwidth is 450 (18%), 350 (10%), 1200 (21.8%) MHz at the three resonant frequency points (2.5 GHz, 3.5 GHz, 5.5 GHz) with mutual coupling between the antenna elements less than -18 dB in whole frequency band, making this antenna a good candidate for portable application.

In this paper, we propose an enhancement of the Equivalent Circuit Method (ECM) for analysis of frequency selective surface (FSS) with square loop geometry of the unit cell. For this, genetic algorithms and rational algebraic models are used to obtain a more accurate value of the effective electrical permittivity (ε_eff). We use simulated data obtained with a commercial software to adjust some parameters. So, genetic algorithm is used to obtain a better value of an exponent that calculates ε_eff minimizing the rational algebraic models. In this paper, this is done for the square loop geometry, but the methodology can be extended to any geometry. Finally, prototypes are built and the technique is validated.

This paper introduces a new volumetric conical notch-band antenna. Structure of this antenna is in contrast with planar and printed band rejection antennas currently existing in almost all of the literatures. The radiation pattern of the proposed antenna is symmetrical and stable against frequency variation, while planar and printed antenna types suffer from high variation of their radiation pattern with frequency, and consequently asymmetric and unstable omnidirectional behavior. The frequency band of the antenna is notched with two slots implemented on the antenna structure. Uniform various frequency band rejections are achieved by changing the slots dimensions and position. Both measured and simulation results of manufactured antenna show the frequency bandwidth of the antenna is from 3 to 4.9 GHz and from 6.2 to 11 GHz with reflection coefficient less than -10 dB. Moreover, the antenna notches the frequency band from 4.9 to 6.2 GHz with nearly uniform reflection coefficient level of approximately -3 dB. Stable radiation pattern and proper range of frequency band rejection make the designed antenna an appropriate candidate for the use in UWB and indoor communication systems.

A novel polarization independent RFID tag employing multiple resonators is proposed. The prototype of the tag is fabricated on a low-cost substrate of dielectric constant 4.4 and loss tangent 0.02. Designing a reader for chipless RFID is a hard task since both the polarization and operating frequency agility have to be implemented. The new tag design proposed in this paper is polarization independent, making the design of the reader easier. A prototype of a 3 bit data encoded tag is demonstrated using single structure which can be extended to any order by cascading. This new design is experimentally validated in the frequency domain using monostatic measurement with magnitude response to decode the information.

A three-step molding softlithographic process has been developed for the construction of a sharp Y-junction structure formation in a 1x2 Y-branch plastic optical fiber (POF) coupler design. The 1x2 Y-branch POF coupler is based on a Y-junction splitter which requires that the splitting part is constructed with sharp infinitesimal junction. The softlithographic process enables a PDMS mold to be constructed which then allows mass replication of the polymer-based POF coupler. A standard master mold based on PMMA material is fabricated using CNC milling. A secondary or auxiliary-mold process step is then introduced in order to produce a sharp Y-junction structure which is then transferred to the final PDMS stamp prior to device replication. This step utilizes a free flowing, low viscosity casting-based resin, which after curing and hardening provide the auxiliary mold for PDMS mold fabrication. The result shows that a very fine and sharp Y-junction structure can be produced easily which cannot be produced via standard two step molding softlithographic process. Models for the Y-branch POF coupler produced with and without an auxiliary mold process are constructed which show that a 16% increased in optical performance with the device replicated with the auxiliary mold process.

A planar ultra-wideband (UWB) antenna with triple-notched bands using triple-mode stepped impedance resonator (SIR) is presented in this paper. By coupling the novel triple-mode SIR beside the microstrip feedline, band-rejected filtering properties around the C-band satellite communication band, the 5.8 GHz WLAN band, and the X-band satellite communication band are generated. The notched frequencies can be adjusted according to specification by altering the triple-mode SIR. The results indicate that the proposed planar antenna not only retains an ultra wide bandwidth but also owns triple band-rejections capability. The UWB antenna demonstrates omnidirectional radiation patterns across nearly whole operating bandwidth, which is suitable for UWB communications.

Numerical solution is presented for light scattering from two kinds of free-standing periodic arrays, that is, disks made of noble-metal and circular apertures perforated in a thin noble-metal sheet. The shapes of them are complementary to each other, and the circular areas are allocated along two orthogonal coordinates with the same periodicity. Using the generalized boundary conditions of the surface impedance type, we formulate the boundary value problem into a set of integral equations for unknown electric and magnetic current densities defined over the circular area. Employment of the method of moments allows us to solve the integral equations and give the expansion coefficients of the current densities, from which we can find reflected, transmitted, and absorbed powers. Dependence of the powers on the array parameters and wavelength is discussed in detail from the viewpoint of grating resonance. Special attention is paid to the extraordinary transmission which occurs in the arrays of apertures of sub-wavelength size by analytical derivation of the quasi-static solutions.

This paper proposes a fast Minimum-Variance-Distortionless-Response (MVDR) beamforming algorithm for an antenna array for cancellation of multiple interference signals. The proposed algorithm uses Sample-Average Estimate (SAE) of the data covariance matrix and reduces its computational effort by applying the Matrix-Inversion-Lemma (MIL) to its covariance Matrix Inversion (MI) operation. The proposed algorithm is compared to two SAE-based algorithms: the Sample Matrix Inversion (SMI) algorithm that requires an MI operation and the Auxiliary Vector (AV) algorithm that does not need an MI operation. A non-SAE based algorithm using the Least Mean Square (LMS) method is also included for comparison. Simulation results show that the proposed algorithm converges slower than the SMI scheme but outperforms the AV and LMS schemes during the transient phase. Once convergence is achieved, the proposed algorithm converges to a better Mean Square Error than the rest of the algorithms evaluated.

In this paper, a cylindrical permanent magnet linear motor (PMLM), which has a high performance, was designed and developed, because the motor has a zero normal force and a higher thrust density. The structure of the motor plays a vital role at the stage of design. During the design stage, several models of the PMLM that had different structural parameters were simulated using FEM software, and the model that produced the high-performance was identified. The structural parameters involved include the radius and height of the permanent magnet, r_pm, and h_pm, the height of coil, h_c, and the shaft radius, r_s, within a fixed total radius, r_total. Each model of the PMLM was simulated using FEM software and the model that produced the highest thrust was identified. To prove its high-performance characteristics, the performance of the PMLM was then compared to the commercialized PMLM using four performance indexes which are thrust F, thrust constant k_f, motor constant k_m and motor constant square density G. About 200 commercialized PMLMs with three different types have been chosen which are the slot type PMLM, slotless type PMLM and shaft motor. Based on the comparisons, the designed PMLM had a better performance than the commercialized PMLM. In order to validate the simulation result, the PMLM was manufactured. The simulation and measurement static thrust characteristics were then compared, and it was found that the simulated thrust had a good agreement with the measured one.

In this paper, three omnidirectional microstrip array antennas are optimized, fabricated and measured. The proposed planar antennas are composed from series of microstrip line sections with inverted top and bottom conductors at each section. The antenna design parameters are optimized to design three different antennas: wide bandwidth, high-gain and dual-band antennas. In the wideband antenna, a good impedance matching is obtained for relative bandwidth of 31% that covers the frequency range of WLAN. The dualband omnidirectional antenna operates at 2.45 GHz and 5.25 GHz with gain of 6.69 dBi and 7.71 dBi, respectively. Also, the optimized high-gain antenna achieves 9.3 dBi gain. The three optimized antennas are fabricated and tested. The measurement results show a very good agreement with the simulation ones. The optimization results verify the ability and capability of the antenna to achieve the desired specifications.

This paper presents two dual-band bandpass filters with controllable passband frequencies and bandwidths. The filters are realized utilizing a novel quad-mode stub-loaded ring resonator. All the four mode equivalent circuits of the resonator are quarter-wavelength resonators, and their fundamental resonance frequencies are used to form the passbands. So the designed filters have a compact circuit size and relatively wide upper stopband. For validation, two experimental filters operating at 1.5/2.4 GHz and 1.5/3.5 GHz are designed. In the design of the second filter, hook-shape feed-lines and source-load coupling are applied to generate more transmission zeros, which greatly improve the selectivity of the filter. Finally, the filters are fabricated, and measured. The measured results have good agreement with the simulated ones.

In this paper, we present the design of a low-profile antenna consisting of two orthogonal parasitic meandered monopoles excited by the near-filed coupling with a feeding bow-tie. The two parasitic radiators and the driven element are placed on two different faces of the same dielectric substrate and a coaxial probe excites the bow-tie through a metallic ground plane. In this way, the antenna has compact dimensions of 21×10.5×1.6 mm³(λ₀/6×λ₀/12×λ₀/75, excluding the ground plane) and exhibits a good impedance matching in the 2.4-2.485 GHz Wi-Fi band with an overall efficiency around 50%.

Underground mines are challenging environments for off-body wireless communication, since the signal propagation is majorly affected by small scale and large scale fading. The use of multiple antennas at the transmitter and the receiver sides is a known technique to combat fading and enhance capacity. In this paper, the channel parameters of a 2×2 Multiple-Input Multiple-Output (MIMO) off-body system are investigated in an underground gold mine and compared to the Single-Input Single-Output (SISO) system parameters. Measurement campaigns were conducted using monopole antennas at a center frequency of 2.45 GHz for both Line Of Sight (LOS) and None Line of Sight (NLOS) scenarios. The measured frequency responses are converted into impulse responses through an Inverse Fourier Transform (IFT). The results show that for a constant transmitted power, the path loss exponents at NLOS are smaller than their counterpart values at LOS. The channel capacity values decrease as the propagation distance increases and when the link is obstructed at NLOS. The RMS delay spread is generally increasing with distance for both LOS and NLOS situations. When a fixed Signal-to-Noise Ratio (SNR) is assumed, MIMO topologies improved the SISO capacity by roughly 8 bps/Hz. The channel characterization results demonstrate that the MIMO configurations provided a remarkable improvement in terms of capacity, coherence bandwidth, and time delay spread compared to the SISO topologies.

Sparse representation is the fundamental technology of compressive sensing, sparse three-dimensional (3-D) imaging, and dictionary-based parameter estimation. Typical sparse representation models of radar signal work in the frequency domain, which may encounter high dimension and large data amount of dictionary. This paper presents a time-domain (TD) representation model for multi-aspect SAR data. We generate the multi-aspect two-dimensional (2-D) TD responses of the 3-D scattering center model. Then we cut off the low-energy area of the 2-D TD response and use cutoff responses to construct the dictionary of sparse representation. Such a TD dictionary is a sparse matrix. Moreover, we build and solve the sparse representation model based on the TD dictionary. Compared with the frequency-domain (FD) sparse representation model, the data size of our TD dictionary is remarkably lower, and the solving of TD sparse representation problem is in higher efficiency. We utilize the TD sparse representation to reconstruct 3-D images from multi-aspect SAR data. Experimental results demonstrate the effectiveness and efficiency of the TD sparse representation model.

Evanescent mode substrate integrated waveguide (SIW) is one of the promising technologies for design of light-weight low-cost microwave components. Traditional realization methods used in the standard evanescent waveguide technology are often not directly applicable to SIW due to dielectric filling and small height of the waveguide. In this work, one of the realization methods of evanescent mode waveguides using a single layer substrate is considered. The method is based on the use of coaxial stubs as capacitive susceptances externally connected to a SIW. A microwave filter based on these principles is designed, fabricated, and tested. The filter exhibits a transmission zero due to the implemented stubs. The problem of evanescent mode filter analysis is formulated in terms of conventional network concepts. This formulation is then used for modelling of the filters. Strategies to further miniaturization of the microwave filter are discussed. The approach is useful in applications where a sharp roll-off at the upper stop-band is required.