This paper presents a novel bulk acoustic wave stacked crystal filter (SCF) configuration that improves the inherent narrow bandwidth of this kind of devices and increases their selectivity by means of the allocating of transmission zeros. A set of parallel connected SCFs with their resonant frequencies split along the passband achieves the bandwidth improvement. The SCF detuning is carried out by the thickness of its middle metallic electrode. The filter response covers the 60 MHz bandwidth of a W-CDMA RF application working at 2.14 GHz. The use of SCFs considerably simplifies the layer stack configuration in contrast to other acoustically coupled structures as coupled resonator filters.

In this paper, we propose a method to reduce the length of the narrowband microstrip Uniform Coupled Transmission Lines (UCTLs), which has a general application to compact microstrip circuits. In this method, we use Nonuniform Coupled Transmission Lines (NCTLs) instead of UCTLs. To synthesize the desired NCTLs, their normalized width and gap are expanded as two truncated Fourier series. Then, the optimal values of the coefficients of the series are obtained through an optimization approach. The usefulness of the proposed method is verified using some examples. Also, an edged-coupled bandpass filter is compacted using the proposed method and then is fabricated and measured.

In this paper, a fast and efficient method has been proposed to analyze the electromagnetic shielding rooms with electrical large sizes and arbitrary shapes. The ray-tracing method is used to predict the Shielding Effectiveness (SE) of the electromagnetic shielding rooms. The proposed method is based on speeding up the ray tracing algorithm. The performance of the proposed method is verified by a comprehensive example. The effect of additional metal cabinet in the shielding effectiveness of shielding room has been investigated. Also the position of it has been found optimally to produce a ``best" performance for the shielding room.

Novel and computationally e±cient method for optimization of microwave structures is presented. The technique is based on the adjustments of the design specifications and exploits the coarse model --- computationally cheap representation of the structure being optimized, e.g., equivalent circuit. It is demonstrated that the proposed approach allows rapid design improvement while being simple to implement. Limitations and modifications of the technique are also discussed.

In this work we consider the problem of obtaining a capacitive image by scanning a "one-dimensional" surface of a closed conductor of arbitrary geometry. To solve our problem we propose a novel integral numerical method. The method is applied to different geometries by considering deterministic surfaces as complex as those with a fractal structure and random rough surfaces with Gaussian statistics. We find that the images obtained by simulating a prototype of a capacitive microscope, strongly depend on the interaction between the object and the probe. Despite this interaction, important information can be obtained regarding the statistical properties of the random roughness of the object surface.

A novel compact planar antenna with a frequency band-filter characteristic for UWB applications is proposed and investigated. Having a dual-Y-shaped slot on the patch, a frequency-notched characteristic at 5.2 GHz is obtained. The band-notched mechanism of the designed antenna is implemented and experimentally studied.The designed antenna satisfies the voltage standing wave ratio (VSWR) requirement of less than 2.0 in the frequency band between 2.8 and 18.6 GHz while showing the band rejection performance in the frequency band from 5.0 to 5.6 GHz. This technique is suitable for creating ultra-wideband (UWB) antenna with narrow frequency-notched characteristics.

Aiming at the bandwidth enhancement for patch antennas, a new impedance matching scheme is presented. In this design, open-ended microstrip-lines are used as the matching resonators; the gaps between the lines are used as the J inverters. Numerical and experimental studies are executed to demonstrate this new structure. The measured and predicted results are in good agreement. The measured data show that the bandwidth of a sample antenna is increased by a factor of 3.3 after adding two matching resonators. The proposed matching structure is good in performance, and smaller in size than traditional matching structures.

Partial dischagre is the precursor of insulators breakdown. In this work the propagation of electromagnetic radiation emitted from partial discharge in high voltage insulating materials is investigated. Three common dielectric materials used in power industry: polymer, epoxy resin and ceramics are studied. The results obtained are envisaged to support the development of appropriate sensors for partial discharge detection. The radiation pattern is dependent on a multitude of parameters. Among these, the intensity distribution of the source as well as the dielectric material and its geometry are the main parameters. Significant differences in the radiation spectra are obtained for insulators made of ceramic material compare to non-ceramic insulators.

A microstrip dual-mode dual-band bandpass filter using stepped impedance resonators (SIRs) is designed for dual-band wireless local area network (WLAN) applications at 2.4 and 5.2 GHz. By appropriately selecting the impedance ratio (R_z) and length ratio (α) of the SIRs, the harmonic frequencies can be tuned for generating the dual-bandpass response. Based on SIRs, a dual-mode dual-band bandpass filter is designed with one transmission zero. To improve the selectivity, another three transmission zeros in stopbands be created by introducing two stubs in input/output (I/O) lines. Two experimental filters are fabricated. Both simulated resulted and measured resulted are presented.

Agriculture waste has potential to be used as an alternative material for the microwave absorber used in the anechoic chamber. Compared to the current materials used, such as polystyrene and polyurethane, agricultural waste has low cost and is environmental friendly. In this paper, rice husks from paddy are used as the material in the pyramidal microwave absorber design, to operate effectively in the frequency range from 1 GHz to 20 GHz. Urea Formaldehyde (UF) and Phenol Formaldehyde (PF) are the resins investigated, and are used to make the rice husk particle board. There are four main stages in designing the rice husk pyramidal microwave absorber. They are fabricating the rice husk particle board, deriving the dielectric constant value of the resin-rice husk mixture particle board, simulating the rice husk pyramidal microwave absorber using CST Microwave Studio software, and analyzing the performance of the rice husk pyramidal microwave absorber. Various parameters that affect the performance of the pyramidal microwave absorber are investigated, such as the dielectric constant of the material used, mixed resin percentages, source-port distance and angles between the signal source and the surface of the pyramidal microwave absorber. The excellent reflection loss results show that the rice husks can be potentially used as the material in a microwave pyramidal absorber.

Hadamard speckle contrast reduction (SCR) is considered to be an effective approach to deal with speckle problems in coherent imaging systems. A Hadamard SCR system is divided into two sub-systems, which implement phase patterns projection and reflected waves imaging respectively. The performances of both sub-systems are discussed with numerical simulations and linked to certain parameters so as to give more insights of this approach. For generality, both optical and millimeter wave imaging systems are discussed. To distinguish from former literature based on Fourier optics, the simulation is implemented via wave optics, which is more physical and more accurate. Moreover, considering the fact that the Hadamard method originates from statistics, the effectiveness of Hadamard SCR is in the first place linked to the texture of the object's surface. Statistical optics is also adopted during qualitative analysis of the results. It is shown that the ratio between the dimension of a resolution cell and the granular size of the object's randomly rough surface is closely linked to the performance of Hadamard SCR. Differences in the roughness model in imaging cases of optical and millimeter waves are discussed, which would help to evaluate the validity of the Hadamard SCR approach in practice. The purpose of this paper is to clarify the misunderstandings of Hadamard SCR in previous literature and to give a guideline to apply this approach.

Millimeter wave High Impedance Surfaces (HIS) based antennas are designed, fabricated, and characterized for high data rate communications at frequencies around 40 GHz. HIS with different finite surface area sizes are used as a ground plane for the microstrip patch antennas to suppress the surface waves. The antenna measurements and full wave electromagnetic simulations demonstrate a wide bandwidth of 12-15% in the frequency range of 38-44 GHz with a high gain of ~6 dB and a very low cross polar contribution better than -20 dB.

A new type of microwave transmission line structure is proposed in order to reduce the crosstalk between transmission line circuits. In this structure, the edge of the metal strip line is periodically corrugated with subwavelength grooves of appropriate geometric parameters, and thus the transmission lines can support highly localized spoof surface plasmon polaritons (SPPs) at microwave frequencies. The theoretical simulation shows that the crosstalk between such a transmission line and a conventional strip line is very low at microwave frequencies, and this is further verified experimentally. This type of transmission line structures has great potential applications in high speed circuit systems.

This paper presents a six-section multi-layer asymmetric 10 dB directional coupler based on offset broadside coupled striplines, using Low Temperature Co-fired Ceramic (LTCC) technology, which operates over a decade bandwidth from 1.8 to 18 GHz. It features high performance transitions between the external signal layer and the buried signal layers, as well as a novel mixed first section to solve the limitations of the coupler access bends. A prototype was manufactured that exhibits a return loss of better than 15 dB, isolation of better than 23 dB and a high coupling accuracy of 10.3±0.6 dB over the 1.8-18 GHz band. This design outperforms previously reported results in terms of bandwidth and shows excellent potential for microwave measurement applications.

The goal of this paper is to use polymer-based materials (instead of hard ceramics) in fabrication of dielectric resonator antennas at millimeter-wave frequencies. The soft nature of polymers facilitates machining of antennas, while the low permittivity of polymers naturally enhances the bandwidth. More importantly, advantageous properties (e.g., flexibility and photosensitivity) of some polymers introduce special capabilities which can not be achieved by ceramics. A photosensitive polymer is utilized in this paper to fabricate polymer-based resonator antennas. As a result, deep X-ray lithography is enabled to produce high quality antenna structures. The proposed dielectric resonator antennas which inherently have very low relative permittivity (usually in a range from 3 to 5) are excited effectively using a slotcoupled feeding method and analyzed in both the frequency and time domains. Impedance and radiation properties are compared with higher permittivity ceramic antennas. Impedance bandwidths up to 32 percent are measured and stable radiation patterns with low cross polarization levels over the entire bandwidth are achieved for the prototype antenna. This method enables lithography-based batch fabrication of structures with fine features and complex geometries.

A novel hybrid adaptive iterative physical optics-method of moments (AIPO-MoM) technique is presented for the electromagnetic analysis of jet engine structures that are both electrically large and complex in both stationary and dynamic cases. In this technique, the AIPO method is used to analyze the smooth inlet region, and the MoM method is used to analyze the electrically complex compressor region, including blades and a hub. It is efficient and accurate by virtue of combining the respective merits of both methods. In the dynamic case, a concept for modified impedance equation is proposed to reduce computational load. Numerical results are presented and verified through comparison with Mode-FDTD and measured and commercial simulation packages results.

According to the derived transfer function using different orders of approximation, stability and signal transmission analysis of a driven metallic single-walled carbon nanotube (SWCNT) bundle interconnect are performed. It is shown that as the length of SWCNT bundle interconnect increases, the poles will be closer to the imaginary axis, which causes the transmitted signal response tends to be more damping. Using the fourth-order approximation of the transfer function, the transmitted pulse waveform along the SWCNT bundle interconnect is captured accurately, with signal overshoot and time delay examined. Further, a complete physical model for the transient response of carbon nanotube bundle interconnect is derived, which can also accurately predict the transient response of carbon nanotube bundle interconnect including time delay and crosstalk.

Medical implants in the form of linear conductive structures partially insulated along their length are especially prone to induced heating when subjected to the radiofrequency field used during magnetic resonance imaging (MRI). Leads or similar structures are often implanted near the skin and we have analyzed such implants when the implantation depth is varied in steps from 3 mm to 9 mm or more. Current, electric field, and induced temperature rise distributions in tissue have been obtained. The results have been validated by laboratory measurements.

A Modular Toroidal Coil (MTC) is composed of several solenoidal coils (SCs), which are connected in a series and distributed in the toroidal and symmetrical form. This paper presents analytical equations of mutual inductance and electromagnetic torque of the MTC applicable to Tokomak reactors. These equations are based on those formulated by Neumann. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. The results obtained from the numerical simulation agree with the empirical results, the experimental results, and the virtual work theorem, which indicates the reliability of the presented equations. The behavior of the mutual inductance of the coil shows that the maximum stored energy is obtained when the electromagnetic torque is zero, and vise versa.

This paper presents a fast and effective electromagnetic reconstruction algorithm with phaseless data under weak scattering conditions. The proposed algorithm is based on the phaseless data multiplicative regularized contrast sources inversion method (PD-MRCSI). We recast the weak scattering problem as an optimization problem in terms of the undetermined contrast and contrast sources. Using the conjugate gradient iterative method, the problem is solved by alternately updating the contrast sources and the contrast. Additionally, this method can combine with the PD-MRCSI method. Taking advantage of the properties of fast convergence of this algorithm and stable convergence of PD-MRCSI method, the combined technique makes image reconstructions more fast and effective. Although the method is derived from weak scattering situation, it is also useful for the case which weak scattering approximation is not satisfied. The synthetic numerical reconstruction results, as well as experimental reconstruction results, presented that the proposed method is a very fast and effective reconstruction algorithm.