This paper presents a novel quad-band power divider with equal power division ratio. The proposed power divider is realized using two cascaded sections of dual-band transformers based on coupled microstrip lines. Limitations of using dual-band quarter-wavelength transformers based on coupled lines are studied through parametric analysis to obtain useful design guidelines related to available fabrication facilities. General closed-form expressions are used to calculate design parameters. To verify analysis and design methodologies, a prototype of quad-band equal power divider is proposed. Compared to conventional quad-band power dividers using sections of transmission line transformers the proposed power divider records a size reduction of about 20% and reduced parasitic effects at higher frequencies according to the usage of only two resistors instead of four with much smaller ohmic values. In addition, a quad-band power divider is proposed, fabricated and measured for 3G and 4G applications at 2.1, 2.5, 3.5, and 3.8 GHz frequencies. Measured and simulated data are in very good match which validates the novel design.

The effect of temperature on the photonic band gap has been investigated. One dimensional photonic crystal in the form of Si/air multilayer system has been studied in this communication. The refractive index of silicon layers is taken as a function of temperature and wavelength both. Therefore, this study may be considered to be physically more realistic. It may be useful for computing the optical properties for wider range of wavelength as well as temperature. We can use the proposed structure as temperature sensing device, narrow band optical filter and in many optical systems.

In this paper, a bandwidth enhancement technique of asymmetrical slot antennas with two different excitation methods is presented. One method of excitation is the microstrip line feed, and the other is the coplanar waveguide feed. The rectangular slot excited by microstrip line feed gives an impedance bandwidth of 14.76% (|S₁₁| < −10 dB). When the rectangular slot is excited by a coplanar waveguide (CPW), it gives an impedance bandwidth of 26.61%. Both impedance and radiation characteristics of these antennas are studied.

A TM mode analysis in a metamaterial based dielectric waveguide is proposed and introduced. Rigorously derived from Maxwell's equations, the dispersion properties are focussed on the fundamental properties of bound, surface and leaky modes of metamaterial based dielectric waveguide. Comparing with the conventional right handed material based waveguide, typical backward wave characteristic of volume and surface wave modes are found from the distribution of Poynting power to the transverse direction of waveguide.

Handset antennas strongly interact with the human body. When a user holds a handset during a phone call, the proximity of the human head considerably affects the antenna performance and eventually the quality of the wireless connection. Consequently, the assessment of the antenna parameters regarding free-space conditions is not enough to fully characterize the performance of handset antennas and a further analysis taking into account human head interaction is required. In this sense, this paper presents a study that deals with the human head interaction concerning two aspects: functional and biological. The first one analyzes the effect of the human head over the main antenna parameters (reflection coefficient, efficiency, and radiation pattern) whereas the second one evaluates the impact of the antenna over the human head in terms of Specific Absorption Rate (SAR). Four representative prototypes of radiating structures are measured in both conditions in order to compare their performance: a dual-band Planar Inverted F Antenna (PIFA), a hexa-band PIFA with a slotted ground plane, a set of coupled monopoles, and a new architecture referred as compact radiating system based on the excitation of the ground plane through a set of non-resonant ground plane boosters. A figure of merit that relates the antenna efficiency with the SAR values is proposed for comparison purposes. The results demonstrate that losses caused by the human head power absorption can be minimized if the antennas are placed in the edge located at a higher distance from the human cheek. Furthermore, the study reveals the robustness of the compact radiating system taking into account the human presence. This fact reinforces its position as an alternative solution to current handset antennas, capable of providing penta-band operation (GSM850/900, DCS, PCS, and UMTS) through ground plane boosters featured by their reduced volume of only 250 mm³.

A novel broadband horizontally polarized (HP) omnidirectional planar antenna is developed for mobile communications. The proposed antenna consists of four printed arc dipoles that form a circular loop for HP omnidirectional radiation. A broadband feeding network which includes four broadband baluns and an impedance matching circuit is designed to excite the four arc dipoles. An eight-element linear antenna array is developed for 2G/3G base stations. A broadband power divider is used to feed the antenna array. Experimental results show that the HP omnidirectional antenna element has a bandwidth of 31% (1.66-2.27 GHz) while its array has a bandwidth of 34% (1.67-2.35 GHz) and an omnidirectional antenna gain of ~8 dBi. Both of the antenna element and its array have good omnidirectivity over the 10-dB return loss bandwidth. Simulated and measured results for the antenna element and its array are presented.

An active ring slot resonator loaded by switchable radial stubs is investigated. It is shown that this element can be used as the unit cell of a switchable reconfigurable frequency selective surface (RFSS). Equivalent circuit and full-wave mathematical models are obtained to evaluate the reflection characteristics of the RFSS based on this element. The possibility to obtain different resonant transmission frequencies is discussed. The mathematical model developed is used to design an X band RFSS capable of obtaining resonant frequencies at 9.65, 10.28, 10.83 and 12.05 GHz. Commercially available RF MEMS switches are used to evaluate the effect of the off-state capacitances over the response of the periodic structure. To validate the numerical simulation results, different active and passive diaphragms were designed, fabricated, and tested using the waveguide simulator. A good agreement between numerical and measured results was found.

The aim of this work is to asses the performance of a nodal-based finite element formulation when applied to the computation of specific absorption rate (SAR) problems. This formulation solves numerically the regularized Maxwell equations using nodal elements and, in principle, it offers several advantages: It provides spurious-free solutions and well-conditioned matrices without the need of Lagrange multipliers or scalar potentials. Its integral representation is well-suited for hybridization with integral numerical techniques because of a low-order singular kernel. Also, the nodal approximation of the electromagnetic problem is easier to couple to a thermal finite element problem which usually also employs nodal elements. But, on the other hand, we need to take special care of the points of the domain where the field is singular to obtain accurate solutions. In this paper, we show the impact of the singularities on the performance of the proposed finite element formulation and how its good features are affected when solving real-life SAR problems.₁

A wideband circular polarized planar monopole antenna array (PMAA) that employs dual band-notched characteristics is presented in this paper. The proposed antenna array is formed by four pinwheel-shaped folded planar monopole antennas (PMAs) in order to improve the performance of circular polarization and high directivity. Also, it achieves low-profile, smallsized structure. The attractive characteristics of the proposed PMAA are a wide impedance bandwidth of 87.3% (1 GHz to 2.55 GHz), the 3 dB axialratio (AR) bandwidth of 92.3% (1.05 GHz to 2.85 GHz) excluding dual notch bands, the total bandwidth of 35% (1.8 GHz to 2.55 GHz), and the maximum gain of 8.24 dBic within the total bandwidh. Moreover, in order to generate dual band-notched characteristics in a circular polarized antenna, a folded PMAA with multiple U radiators and inverted W slots is proposed.

We applied a useful uncertainty model, ignored in most metamaterials retrieval studies, to monitor the accuracy of retrieved electromagnetic properties of bianisotropic metamaterial (MM) slabs composed of split-ring resonators and cut wires. Two different MM slab structures are considered to make the analysis complete. As uncertaintymaking factors, we took into consideration of uncertainties in scattering (S-) parameters of bianisotropic MM slabs as well as the length of these slabs. The applied uncertainty model is based upon considering the effect of minute change (differential) in uncertainty factors on the retrieved electromagnetic properties of bianisotropic MM slabs. The significant results concluded from the analysis are: 1) any abrupt changes in the phase of S-parameters of bianisotropic MM slabs remarkably influence the retrieved electromagnetic properties; 2) any small-scale loss (i.e., the loss of the substrate) in the bianisotropic MM slabs improves the accuracy of the retrieved electromagnetic properties of these slabs; and 3) precise knowledge of bianisotropic MM slab lengths are required for correct analysis of exotic properties of these slabs. The presented uncertainty analysis can be utilized as a metric tool for evaluating various retrieval methods of MM slabs in the literature.

The proposed theoretical path-loss prediction procedure and measured results of radio wave propagation in an orchard environment are presented. The wireless sensor network (WSN) in a Durian orchard is primarily chosen to be an example of this study. The three-dimensional (3-D) modified uniform geometrical theory of diffraction (UTD) for curved impedance surface is employed for theoretical path-loss prediction in this paper. The orchard scenario is modeled by using canonical geometries such as a dielectric flat surface and cylindrical structures with an impedance surface to respectively represent ground and trees. Moreover, since the wireless sensor node is attached to the outside peel of a hanging durian fruit, the fruit partially acts as a wireless sensor node. Therefore, to obtain greater accuracy in the source radiation pattern, the Gaussian beam (GB) expansion via the CSP technique is used for source modeling. The path loss prediction from the proposed numerical procedure and the measured results are in good agreement. The proposed numerical procedure to calculate the path loss from actual scenario of the orchard is useful for network planning such as the pre-harvesting WSN system and other orchard scenarios.

A Gunn mounted active microstrip slot-ring antenna (ASRA) has been investigated for the reception of FM microwave signal. Current well/valley phenomenon has been successfully utilized to demodulate the modulation information. The monolithic behaviour of an active slot-ring antenna as a lock-in amplifier, FM (Frequency Modulation) to AM (Amplitude Modulation) converter and square law detector has been demonstrated in this paper. Theoretical analysis coupled with experimental results has been presented. The proposed receiving scheme is unique in the sense that it does not require IF electronics for the purpose of demodulation. It also works well in a multi-channel environment due to the excellent noise-squelching property of an Injection Locked Gunn Oscillator.

A novel circular slot antenna with two pairs of T-shaped slots is proposed for satisfying WLAN and WiMAX applications simultaneously. The proposed antenna consists of a 50 Ω microstrip feed line with a tuning stub on the top and a circular slot ground plane with an embedded straight strip and two pairs of etched T-shaped slots on the bottom side. By carefully adjusting the length of the straight strip, the proposed antenna can operate in two separate bands. With the use of two pairs of T-shaped slots, a new resonant frequency has been excited, and the impedance bandwidth can be widened. The measured results show that the 10 dB return loss bandwidths of the proposed antenna are 760 MHz (3.18-3.94 GHz) and 1002 MHz (5.05-6.07 GHz), which can cover both 5.2/5.8 GHz WLAN bands and 3.5/5.5 GHz WiMAX bands. The design evolution and parametric study of the proposed antenna are presented to provide information for designing and optimizing such an antenna. Furthermore, good omnidirectional radiation patterns with appreciable antenna gain are obtained over the operating bands.

This paper presents an experimental study of the performance of a wireless resonant energy link for implantable biomedical devices. More specifically, the proposed system consists of two planar resonators: a primary resonator that is connected to a power source and operates outside the body, and a secondary resonator that is connected to the implanted device and operates inside the body. Each resonator is a planar spiral resonator; the wireless power transmission is obtained by exploiting the magnetic coupling between the two resonators when they are operating at small distances. A prototype working in the ISM band centered at 434 MHz has been developed and analyzed. Reported results confirm that the proposed system is a viable solution for wirelessly providing implantable devices with the power necessary for operation.

In this paper, a novel suspended stripline IF block is proposed for the design of millimeter-wave finline balanced mixer which covers the full U-band. In high IF frequency applications, IF block of a finline mixer is needed to act as open terminal for IF signal, and is required to have minimum attenuation for LO signal. For the purpose of reducing the insertion loss of the IF block in the LO path, a novel compact low loss IF block is developed for the first time. Then the IF block, two Schottky diodes, a LPF, a finline to waveguide transition and a suspended stripline to waveguide transition are integrated together to compose the mixer. The RF port matching is designed by using impedance substitution method to achieve better RF return loss. The measured results show that a conversion loss of 4.1 to 9.6 dB over a 20 GHz instantaneous IF bandwidth has been achieved when sweeping RF from 40 to 60 GHz under fixed LO condition. The P_-1dB at RF port is higher than 5 dBm, and the return loss of RF port is between -18 to -4 dB.

Overhead-line power conductors do not run parallel to the ground; they actually sag between adjacent towers, defining catenary curves. However, in the analysis of inductive coupling phenomena between power lines and neighboring circuits, the standard approach to deal with the sag effect is to assign a constant average height to power line conductors. The purpose of this research is to assess the accuracy of such an ordinary procedure. To do that, two different approaches are developed in order to more accurately account for the sag effect: a pure segmentation method, and a corrected segmentation method which takes into consideration the real curvature of the sagged conductors. The latter, and novel, approach is compared with the other options. Calculations presented in this work utilize magnetic vector potential as an analysis tool.

In this paper, a second-order Chebyshev active bandpass filter (BPF) with three finite transmission zeros is presented. The filter utilizes a tapped-inductor feedback technique to compensate resistive losses of on-chip inductors, and a shunt-feedback inductor between input and output ports to achieve the transmission zeros. Moreover, one transmission zero is in the lower stopband, and two transmission zeros are in the upper stopband, thus improving the selectivity of the filter significantly. The filter is designed and fabricated in a standard 0.18-μm CMOS technology with a chip area of 0.57 mm×0.65 mm including all testing pads. The circuit draws 6 mA from a 0.7-V supply voltage. Additionally, the filter achieves a 1.65-dB insertion loss and 13.2-dB return loss with a 17% 3-dB bandwidth at 23.5 GHz. The measured NF and input P_{1 dB} is 6.7 dB and -3.5 dBm. The rejection levels at the transmission zeros are greater than 15.2 dB. Finally, the large-signal characterizations are also investigated by the 1-dB compression point (P_{1 dB}) of the filter.

This paper proposes a planar printed wideband antenna for eight-band LTE/GSM/UMTS WWAN wireless USB dongle applications. An inductive shorted strip with a chip capacitor loaded is employed in order to improve the characteristics of small-size terminal antennas which usually have a narrow band over the LTE700/GSM850/900 (698-960 MHz) operation. While the desired upper band is mainly realized by the rectangular radiating patch, covering DCS1800/PCS1900/UMTS2100/LTE2300/2500 (1710-2690 MHz) band. Easily printed on a 0.8-mm thick FR4 dielectric substrate of size 20×70 mm², the proposed antenna structure occupies a compact size of 20×19 mm². Then the proposed design can be attached to laptop computer by the USB interface. Good radiation efficiency and antenna gain for frequencies over the desired operating bands is obtained. Detailed design considerations of the proposed antenna are described, and both experimental and simulation results are also presented and discussed.

We present an adaptive clutter suppression method for airborne random pulse repetition interval radar by using prior knowledge of clutter boundary in Doppler spectrum. In this method, by exploiting the intrinsic sparsity, compressed sensing based on iterative grid optimization (CS-IGO) is applied to directly recover the clutter spectrum with only the test range cell instead of nonhomogeneous training data from adjacent range cells. Since the sensing matrix and clutter spectrum obtained by CS-IGO are well adapted to the data, the prewhitening filter can be effectively obtained to cancel the mainlobe clutter. Further, the clutter residue can be suppressed by the iterative reweighted l1 minimization to enhance the target response. Simulation results show that the approach is capable of effective suppression of clutter and precise recovery of targets' unambiguous spectrum, offering a high performance of output signal to clutter and noise ratio.

The Antarctic continent is an extremely suitable environment for the application of remote sensing technology as it is one of the harshest places on earth. Satellite images of the terrain can be properly interpreted with thorough understanding of the microwave scattering process. The proper model development for backscattering can be used to test the assumptions on the dominating scattering mechanisms. In this paper, the formulation and analysis of a multilayer model used for sea ice terrain is presented. The multilayer model is extended from the previous single layer model developed based on the Radiative Transfer theory. The Radiative Transfer theory is chosen because of its simplicity and ability to incorporate multiple scattering effects into the calculations. The propagation of energy in the medium is characterized by the extinction and phase matrices. The model also incorporates the Dense Medium Phase and Amplitude Correction Theory (DM-PACT) where it takes into account the close spacing effect among scatterers. The air-snow interface, snowsea ice interface and sea ice-ocean interface are modelled using the Integral Equation Method (IEM). The simulated backscattering coefficients for co- and crosspolarization using the developed model for 1 GHz and 10 GHz are presented. In addition, the simulated backscattering coefficients from the multilayer model were compared with the measurement results obtained from Coordinated Eastern Artic Experiment (CEAREX) (Grenfell, 1992) and with the results obtained from the model developed by Saibun Tjuatja (based on the Matrix Doubling method) in 1992.