A new method is presented for analysis of transient electromagnetic fields in regular structures with abrupt discontinuities. The method is based on mode expansion of the fields in the Time Domain. The modes propagate independently in the regular parts of the structure and are coupled at the discontinuity. The main idea consists in solving 1D FDTD equations for each independent mode channel in the regular waveguides and using mode-matching at the junction cross-section in order to relate the mode amplitudes in all the channels at the same time instant via imposing boundary conditions. As examples the problems of pulse signal diffraction at a step discontinuity in a parallel-plate waveguide, diffraction at a junction of circular and coaxial waveguides, and pulse radiation of a bi-conical antenna are considered. The latter problem is treated as a junction of two conical lines (one of which is the free space) that are regular in spherical coordinates.

In this paper, a large number of studies of the effect of the foliage on single or lines of trees on modern wireless communication systems are reviewed. The paper is focused on the experimental works mainly done for commercial applications such as cellular communication and high speed point-to-point fixed link at the microwave and millimeter wave frequencies. For this review study, the development of the foliage loss prediction methods and the factors influencing the tree-induced shadowing effect are highlighted. In view of current research work in this area, some possible future works are proposed to improve the performance of modern wireless communication systems with the effect of foliage.

Adaptive Neuro-fuzzy systems constitute an intelligent systems hybrid technique that combines fuzzy logic with neural networks in order to have better results. A study is presented to forecast the relative magnetic permeability using ANFIS. The global electromagnetic parameter, namely, the magnetic induction has been used as input to estimate the relative magnetic permeability. In this exceptional research, finite element simulations are carried out to build up a database which will be used to train ANFIS network. The ANFIS approach learns the rules and membership functions from training data. The hybrid system is tested by the use of the validation data. Performance of the trained ANFIS network was compared with the multilayer feed forward network model and experimental results. The results show the effectiveness of the proposed approach in solving inverse electromagnetic problem.

In this paper a multifunctional microstrip antenna is designed, fabricated and experimentally verified for operation in AWS, GSM, WiMAX and WLAN bands. This microstrip patch antenna has two U-shaped slots to achieve the dual wideband operation required to meet these specifications. The dimensions and locations of the U-slots are designed appropriately. The thick substrate used here helps in integrating the antenna with the existing aircraft panel material while achieving wide bandwidths. Experimental results of this single feed antenna indicate that it meets all current requirements for in-cabin wireless communication needs.

A capacitive method for measuring hand grip position on a mobile phone equipped with a dual-band planar inverted-F antenna (PIFA) and a monopole antenna was studied using different electrode arrangements. A capacitive sensor with a dual-electrode configuration and an antenna-integrated capacitive sensor for hand grip recognition were developed. The sensitivities of the sensors were measured along the front, side and back of the phone. The dual-electrode sensor configuration exhibited its best sensitivity of 29 fF at the bottom end of the phone. The PIFA antenna-integrated sensor proved to have sensitivity of 420 fF and the monopole antenna-integrated sensor had sensitivity of 115 fF, making them both reasonable solutions for hand grip sensors in mobile applications.

Shielding prevents coupling of undesired radiated electro-magnetic energy into equipment otherwise susceptible to it. In view of this, some studies on shielding effectiveness of different shields against angle of incidence with conductors and conductive polymers using plane-wave theory are carried out in this paper. The plane wave shield- ing effectiveness of new combination of these materials is evaluated as a function of angle of incidence for Single, Double and Laminated Shields. Conductivity of the polymers, measured in previous investigations by the cavity perturbation technique, is used to compute the overall reflection and transmission coefficients of single and multiple layers of the polymers. With recent advancements in synthesizing stable highly conductive polymers, these light-weight mechanically strong materials appear to be viable alternatives to metals for EM1 shielding. The analysis is done at a particular frequency for all three types of shields.

A LOD-like method that characterizes the analytical solution is proposed to study the one-dimensional (1-D) chiral media. Through theoretical analysis and numerical simulation, it is found that the proposed scheme is unconditionally stable. This scheme employs the new mesh-dividing method for bi-isotropic media, in which the two sections on the right side of the rearranged curl equations are regarded as two directions and the LOD-like algorithm is used to deal with the equivalent two-dimensional (2-D) problem. In the first substep, the conventional LOD method is used in computation, while for the second substep, the analytical solution is employed instead. By simulating the polarization rotation of a mono-frequency linear polarized wave both in a 1-D homogeneous chiral media and through a chiral slab, the scheme is testified to be unconditionally stable.

The formation process of antenna mode scattering is analyzed, and a new prediction method to calculate the antenna mode scattering is proposed. Since the antenna mode scattering is essentially the reradiation of reflected energy, this reflected energy comes from the incident wave received by the antenna and reflects on the mismatched point of the feed network. Thus the calculation of the antenna mode scattering can be divided into three steps: 1. calculation of the antenna received energy; 2. calculation of the reflected energy from the feed network; 3. reradiation of this reflected energy. The numerical results of antenna mode scattering from a patch antenna and a dipole array are proposed to verify this approach.

A novel CPW-fed triple-band monopole antenna designed by embedding an S-shaped meander strip into a C-shaped strip is proposed for WLAN and WiMAX applications. The antenna with a very simple and compact structure is easy to be fabricated, and the prototype of the proposed antenna has been constructed and measured. The triple operating bands with 10-dB return-loss bandwidths of about 110 MHz centered at 2.45 GHz, 310 MHz centered at 3.55 GHz, and 39% ranging from 4.1 to 6.2 GHz, covering the required bandwidths of 2.4/5.2/5.8 GHz WLAN and 3.5/5.5 GHz WiMAX standards, are obtained. In addition, good radiation performance and antenna gain across the three frequency ranges have been obtained.

In this paper, a modified square monopole antenna with multi-resonance performance, for UWB applications is proposed. The proposed antenna consists of a square radiating patch with a pair of T-shaped slots and a ground plane with a pair of rectangular sleeve and a T-shaped resonator which provides a wide usable fractional bandwidth of more than 125% (3.05-13.57 GHz). By optimizing dimension of rectangular sleeves, T-shaped slots and resonator, the total bandwidth of the antenna is greatly improved. The designed antenna has a small size of 14×22 mm². Good return loss and radiation pattern characteristics are obtained in the frequency band of interest. Simulated and experimental results are presented to demonstrate the performance of a suggested antenna.

Shift-Operator Finite difference Time Domain (SO-FDTD) method is introduced as a new efficient technique for simulating electromagnetic wave interaction with chiral medium. The dispersive properties of this medium are presented as polynomials of jω. These polynomials are converted to time domain by replacing jω by the time derivative operator. Then this time derivative operator is converted to the corresponding time shift operator which is used directly to obtain the corresponding update equations of electric and magnetic field components. The resulting update equations do not require time convolution or additional vector components. The present analysis does not require also any transformation. Significant improvement is obtained in memory requirements by using this method while the computational time is nearly the same compared with other similar techniques like Z-transformation FDTD.

In the field of maritime surveillance, HF surface wave radars seem to be considered as an optimum and low cost solution. Nevertheless, the commonly used radiating elements of those radars are not yet able to only launch surface waves. We aim to design a specific radiating element optimized for exciting such waves. The first step of such an issue is to set thoroughly the problem. In this paper, surface waves on the boundary between two dielectric media are considered. Kistovich decomposition is applied in order to discuss the influence of the Zenneck wave on the field excited at the sea surface. It is shown that Zenneck approach and Norton's one are not contradictory. Above all, we point out that, using Kistovich decomposition to design radiating elements, we can expect a significant improvement of the surface wave intensity.

We extend our previously-derived generalized closed-form representation for spectral dispersing performance of the Virtually-Imaged-Phased-Array (VIPA) based on a 3D vectorial Gaussian beam formulation to demultiplexing application. To analyze VIPA in the demultiplexer scheme, a spherical lens is added after the VIPA, so that the device plane is superimposed on the focal plane of the lens. The calculated output profile at previous step is reformulated in a matrix form in this step. Finally, the derived closed-form is simulated, and the numerical outcomes are compared with the previous results. The 3D output radiation of VIPA demultiplexer pattern is also depicted and found to be very intuitive and promising for some applications especially WDM demultiplexer and optical Code Division Multiple Access (CDMA).

Ultra Wideband (UWB) radar has been extensively investigated as a means of detecting early-stage breast cancer. The basis for this imaging modality is the dielectric contrast between normal and cancerous breast tissue at microwave frequencies. However, based on the dielectric similarities between a malignant and a benign tumour within the breast, differentiating between these types of tissues in microwave images may be problematic. Therefore, it is important to investigate alternative methods to analyse and classify dielectric scatterers within the breast, taking into account other tumour characteristics such as shape and surface texture of tumours. Benign tumours tend to have smooth surfaces and oval shapes whereas malignant tumours tend to have rough and complex surfaces with spicules or microlobules. Consequently, one classification approach is to classify scatterers based on their Radar Target Signature (RTS), which carries important information about scatterer size and shape. In this paper, Gaussian Random Spheres (GRS) are used to model the shape and size of benign and malignant tumours. Principal Components Analysis (PCA) is used to extract information from the RTS of the tumours, while eight different combinations of tumour classifiers are analysed in terms of performance and are compared in terms of two possible approaches: Linear Discriminant Analysis (LDA) and Quadratic Discriminant Analysis (QDA).

In this paper, a novel band-notched wide slot antenna for UWB applications has been proposed. The antenna consists of a circularly slotted square ground, two wide-slots separated by a conductive ring, and an equiangular spiral feed line, which excites the antenna through traveling-wave. Experimental prototypes are fabricated and tested. The obtained results indicate that the proposed antenna has a small size and offers a broad bandwidth from 3.1 to 12 GHz, with a band notch from 3.4 to 3.9 GHz. The radiation patterns display nearly omnidirectional performance and the measured group delays are within ±1 nanosecond except for the notch band.

Although the discontinuity structures in the microstrip transmission lines such as a gap and bend have been largely studied, the three-dimensional edge effects, skin effects and metal losses have hardly been analyzed. In this paper, modeling of transmission line with bend and gap discontinuity with equation based process technology independent method are developed. The effect of the signal layer thickness is fully included in the model. Gap model is verified with EM simulation and implemented in BiCMOS technology on Silicon substrate. The bend is modeled with transmission line with effective length for the discontinuity area, and the equations have been generated. The bend model is compared with EM simulations, existing bend model generated with curve-fitted method and measured results. Gap and bend are enabled as library device in a 0.13 μm SiGe BiCMOS process design kit. Both bend and gap device have a scalable layout pattern and a schematic symbol, which allows users to choose them with different dimensions and metal stacks. In addition, the models can be migrated into other process technologies with different metal options. Very good match have been achieved among model, EM simulation and measurements for different process technologies and metal stacks.

Design of a compact planar phase shifter is described that possesses ultra-wideband (UWB) performance. The proposed device is composed of 50Ω input/output microstrip-lines which are connected to a low-impedance rectangular microstrip patch, and located at close proximity to each other. The common ground-plane incorporates a slot-line terminated with two rectangular slots, which are located under the rectangular patches in order to provide effective electromagnetic coupling between the microstrip-line and slot-line. Thus a phase shifter is realized with ultra-wideband characteristics on a single substrate. The length of the slot-line and width of patch determines the desired phase shift required between the input and output ports. It is demonstrated that the design can provide phase shift anywhere between 4°- 27° across the entire UWB frequency band from 3.1 to 10.6 GHz. The simulated results show fixed phase shift 5.625°± 0.865°, 11.25°± 1.93°and 22.5°± 2.5°with insertion-loss less than 0.5 dB and return loss better than 12 dB across the ultra-wideband frequency span. The phase shifter is relatively compact in size with a dimension of 15×25 mm². The phase shifter was fabricated and its performance measured to validate the simulation results.

A novel microstrip array antenna based on the meta-material zeroth-order resonator (ZOR) is presented in this paper. Considering both zeroth-order resonance and the array theory, a resonant array antenna has been designed and fabricated which has small dimensions both in length and width as well as an acceptable gain. Since the resonant frequency of the zeroth-order resonator is independent of the physical length of the resonator and determined only by LC values loaded in the resonator, therefore, antenna size can be reduced arbitrarily with no changes in the operation frequency and due to the array structure antenna gain can be enhanced. Additional benefit of the ZOR antennas is lower ohmic losses as compared to the other small antennas and hence the efficiency of the antenna is higher. The discrepancy between simulation and measurement determined by fabricating some of the simulated design and comparison between the results, has been taken into account for designing the final array. A small-sized two-elements ZOR array antenna with 50% reduction in size as compared to the conventional array with a acceptable gain and broad radiation pattern is tested at 4.25 GHz. The proposed antenna has application in radio altimeters. The commercial softwares such as CST and HFSS were utilized for design and analysis of the structure.

In this paper, two compact patch antenna designs for a new application --- outdoor RF energy harvesting in powering a wireless soil sensor network --- are presented. The first design is a low-profile folded shorted patch antenna (FSPA), with a small ground plane and wide impedance bandwidth. The second design is a novel FSPA structure with four pairs of slot embedded into its ground plane. Performance of both antennas was first simulated using CST Microwave Studio. Antenna prototypes were then fabricated and tested in the anechoic chamber and in their actual operating environment --- an outdoor field. It was found that the FSPA with slotted ground plane achieved a comparable impedance bandwidth to the first design, with an overall size reduction of 29%. Simulations were also carried out to investigate the effects of different design parameters on the performance of the proposed slotted ground plane FSPA.

We will demonstrate an alternative topology to greatly increase the operating bandwidth of an analog RF feedback power amplifier. A limited operating bandwidth due to the group delay mismatch of a feedback loop discouraged the use of an RF feedback technique in spite of its powerful linearization performance and great tolerance capability. By introducing a negative group delay circuit (NGDC) in the feedback loop, group delay match condition could be satisfied. With the fabricated 2-stage distributed element negative group delay circuit with a 30MHz of bandwidth and a -9 ns of group delay for a wideband code division multiple access (WCDMA) downlink band, the proposed feedback amplifier with the proposed topology experimentally achieved an adjacent channel leakage ratio of -53.2 dBc with a cancellation bandwidth of over 50 MHz.