A novel dual-band balanced power amplifier (DBPA) using a pair of branch-line couplers with four arbitrary terminated resistances is designed in this paper. The DBPA operating at 2.02 GHz and 2.6 GHz consists of two identical single-stage class-AB PAs connected in parallel and two branch-line couplers for power division and combination. Due to the usage of branch-line couplers with four arbitrary terminated resistances, the load/source-pull impedance obtained by ADS (Advanced Design System) can be matched to an arbitrary real impedance which decreases the complexity of dual-band matching network of the DBPA. To demonstrate the proposed design, a prototype based on CREE's GaN HEMT CGH40010F is fabricated and measured. The simulated results exhibit 67.9% and 73.6% power-added efficiency (PAE) values with output power of 44.1 and 43.4 dBm at 2.02 GHz and 2.6 GHz, respectively.

Energy selective surface (ESS) proposed in recent years is one of the most effective means for defending high intensity electromagnetic wave attacking. This paper presents an improved ESS structure and its systematic design method. An ESS prototype is designed and fabricated based on a given requirement. Its insertion loss is measured in an anechoic chamber, and its shielding effectiveness is tested under HPM and UWB irradiation. Measured results show that the ESS sample meets the given requirement.

A dual-band multiple-input-multiple-output (MIMO) antenna system for LTE 700/2300/2500, UMTS2100, GSM 1800/1900 mobile phone applications is presented. The whole system consists of four identical 3-D IFAs (inverted F antenna) loaded with lumped inductors and folded on FR4 cuboids. Without any special designed decoupling structures, the measured isolation among antenna elements is higher than 13 dB. Return loss characteristics, correlation coefficient, gain and radiation performance are also presented.

In this communication, a systematic approach for design of planar monopole ultra-wideband (UWB; 3.1~10.6 GHz) antenna for wireless USB dongle has been proposed. The simple planar monopole antenna consists of a rectangular metallic radiating patch whose modal analysis is carried out first by means of the Theory of Characteristic Modes (TCM), in order to identify the different radiating modes and get the physical insights of these radiating modes of the antenna. Further, based on the physical evidences obtained from the radiating modes of the similar planar monopole antenna, a bevel transition feed with rectangular slot has been used to enhance the bandwidth and obtain the desired radiation characteristics of the proposed antenna. The modal analysis is carried out using characteristic modes (CM) analysis tool in CADFEKO 7.0 simulation software. The proposed antenna exhibits a very compact dimensions of 12 mm × 16 mm × 5 mm and yields a good insights in simulated and measured impedance bandwidth of 3.1~12 GHz with VSWR < 2. Furthermore, the proposed antenna exhibits symmetrical radiation patterns, stable-high gain and efficiency and ultra-wide bandwidth making it suitable candidate for practical UWB-USB applications.

An ultra-wide band 45° phase shifter based on a new planar artificial transmission line which can be used for UWB communication systems is presented. The planar artificial transmission line is composed of host line, grounded interdigital capacitors and meandered-line inductors. The phase shifter was measured to have a bandwidth about 114.7% (2.9 GHz to 10.7 GHz) for a maximum phase deviation of 2.9°, a maximum insertion loss of 1.2 dB, a minimum return loss of 13 dB and a compact size of 16.35 mm × 5.2 mm.

The parabolic equation(PE) method is widely used in radiowave propagation predictions. It has the advantages of high efficiency and stability, but it will lead to greater predicting errors in some situations, because the effects of transverse terrain gradients are not modeled. This problem can be solved by extending the 2D PE to the three-dimensional (3D) PE. However, the computing efficiency will degrade because of large scale matrix operations. In this paper, a new method is presented, in which the 3D PE is decomposed into two 2D PEs. It increases the computational efficiency and accuracy effectively. To verify the capability of the proposed method in radiowave propagation prediction, an experiment platform was set up. The computational results using this new method are compared with the experimental and Method of Moment(MoM) numerical computational results. Good agreements are achieved in the comparison.

We present a critical account of intense pulsed-laser field induced refractive index changes caused by flow, crystalline axis reorientation and distortion and other high order photonic processes in transparent liquid crystals. In particular, the optical nonlinearity associated with Maxwell Stress induced flow-reorientation in nematic liquid crystals is explicitly calculated, and their possibility for all-optical switching application is experimentally demonstrated. Similar flows processes have also been observed in Blue-Phase liquid crystals with nanosecond and picosecond pulsed-lasers.

A tunable planar bandpass filter based on a technique that utilizes a half mode substrate integrated waveguide (HMSIW) and novel inter-resonator coupling is presented. The tunable HMSIW based bandpass filter is implemented using two half triangle shaped cavities coupled together through inter-resonator coupling forming half mode bowtie-shaped structure. The bowtie-shaped filter exhibits similar performance as found in rectangle- and circle-shaped SIW based bandpass filters. This concept reduces the circuit foot print, and miniaturization high quality factor is maintained by the structure. The tunable filter utilizes packaged RF MEMS switches; switching between different configurations of switches achieves four distinctive frequency states between 4.8-5.3 GHz. The filter maintains a constant absolute 1 dB bandwidth of 100±10 MHz for all frequency states.

In this work, a low-profile metamaterial backed planar antenna structure designed to work in the UHF/VHF range is presented. The antenna has right-hand circular polarization. It is ideal for satellite-based communications and radar systems. An artificial magnetic conductor was designed using a metamaterial composed of a split ring resonators to reduce the size of the planar antenna and ground plane system. The proposed artificial magnetic conductor has more confined surface waves at the reflecting plane than previous designs and is suitable for circular polarization. Through numerical simulations, performance characteristics including return-loss, and realized gain of the antenna systems are calculated and analyzed in the VHF range. The proposed antenna system is narrowband and is linearly scalable in the range of 100 MHz-1 GHz.

The waveguide re-entrant or inverted re-entrant turnstile circulator relies for its operation on either a quarter wave long cylindrical or prism resonator mounted on either a circular or an equilateral platform with its open face separated from the top waveguide wall by a suitable gap. The adjustment of the prism geometry, the main endeavour of this paper, is characterized by two degrees of freedom. One degree of freedom is the orientation of the prism inside the junction with respect to a typical waveguide feed. The others are the aspect ratio of the gyromagnetic resonator and the choice of platform or piston. The agreement between some calculations based on a Finite Element (FE) engine and experiment is excellent. The work undertaken here indicates that the preferred geometry is that for which the platform has the crosshairs section of the resonator.

In this paper, a novel algorithm based on an equivalent current source is proposed to reconstruct objects buried in a multilayered medium. First, a radiating current source, one part of the equivalent current source, is obtained directly in closed-form from scattering data via the signal-subspace method. Secondly, a nonradiating current source, the other part of the equivalent current source, is represented with the linear superposition of vectors in the noise-subspace. Finally, the objects and equivalent current source are reconstructed efficiently by solving an optimization problem in a lower dimensional linear space with the conjugate gradient (CG) method. To test the new method, the effects of the frequency of incident wave, array aperture size, and SNR are studied in detail. Numerical results show that the proposed method has a high capacity to reconstruct objects buried in a multilayered medium.

A new mutual coupling compensation method for wideband adaptive arrays is proposed. The new method is developed by combining the element pattern reconstruction method and the cubic Hermit interpolation method to achieve wideband mutual coupling compensation. For the employment of this method, mutual coupling matrices at some frequencies obtained by element pattern reconstruction method are needed and stored. By employing the cubic Hermit interpolation method, all entries of mutual coupling matrix for any frequency within the entire frequency band can be obtained accurately and efficiently. A uniform circular array with eight wideband dipole antennas is designed to verify the validity and effectiveness of the proposed wideband compensation method by numerical examples.

The plasmonic behavior of nanostructured materials has ignited intense research for the fundamental physics of plasmonic structures and their cutting edge applications concerning the fields of nanoscience and biosensing. The optical response of plasmonic metals is generally well-described by classical Maxwell's Equations (ME). Thus, the understanding of plasmons and the design of plasmonic nanostructures can therefore directly benefit from lastest advances achieved in classic research areas such as computational electromagnetics. In this context, this paper is devoted to review the most recent advances in nanoplasmonic modeling, related with the latest breakthroughs in surface integral equation (SIE) formulations derived from ME. These works have extended the scope of application of Maxwell's Equations, from microwave/milimeter waves to infrared and optical frequency bands, in the emerging fields of nanoscience and medical biosensing.

We prove the existence of complex eigenfrequencies of open waveguide resonators in the form of parallel-plate waveguides and waveguides of rectangular crosssection containing layered dielectric inclusions. It is shown that complex eigenfrequencies are finite-multiplicity poles of the analytical continuation of the operator of the initial diffraction problem and its Green's function to a multi-sheet Riemann surface, and also of the transmission coefficient extended to the complex plane of some of the problem parameters. The eigenfrequencies are associated with resonant states (RSs) and eigenvalues of distinct families of Sturm-Liouville problems on the line; they form countable sets of points in the complex plane with the only accumulation point at infinity and depend continuously on the problem parameters. The set of complex eigenfrequencies is similar in its structure to the set of eigenvalues of a Laplacian in a rectangle. The presence of a resonance domain in the form of a parallel-plane layered dielectric insert removes the continuous frequency spectrum and gives rise to a discrete set of points shifted to (upper half of) the complex plane.

A low-profile planar monolayer antenna for ultra-wideband (UWB) operation is presented. To achieve a UWB performance along with a compact size, a hybrid square-circular radiator and a rectangular open slotted ground plane with two symmetrical I-shaped tuning stubs are proposed. The antenna is fed by a coplanar waveguide line and has a small size of 44 × 32 × 1.6 mm³. The prototype of the proposed antenna was fabricated and tested in an anechoic chamber. The simulated and measured results show good agreement over the entire ultra-wide bandwidth. The measured results indicate that the proposed antenna can provide a wide impedance bandwidth of more than 154% from 1.7 to 13.3 GHz with -10-dB reflection coefficient. In addition, it is demonstrated that by introducing several antenna designs, the impedance bandwidth can be improved from 43% to 154%. Besides several mechanical advantages, such as compact in size, easy fabrication, and monolayer configuration without any back ground plane, the proposed antenna also shows a good performance in its radiation characteristics and time-domain behaviors. The measured results in both frequency and time domains prove that the proposed antenna can be used in a wide range of UWB applications.

A single layer, single feed microstrip antenna with multifrequency operation in compact size is proposed. A modified inverted π-shaped slot is introduced at the left side radiating edge of the patch to reduce the size of the antenna by reducing the resonant frequency. Multiple resonant frequencies with increased frequency ratio are also obtained by cutting the modified inverted π-shaped slot. The measured result shows that the proposed antenna resonates at 3.3, 4.55, 5.56 and 6.08 GHz in microwave S and C band. The size of the proposed patch is only 0.176λ_L×0.132λ_L at its lower operating frequency. The proposed patch antenna has achieved 68% size reduction as compared with the conventional rectangular microstrip antenna with same patch area. An extensive analysis of the reflection coefficient, voltage standing wave ratio, gain, radiation efficiency and radiation pattern of the proposed antenna is presented in this paper. The proposed antenna is suitable for WiMax and HiPERLAN wireless systems.

A MMW/IR compound Cassegrain antenna system for mono-pulse radar applications is presented in this paper. By comparing different modeling methods of conformal frequency selective surface (CFSS), a sub-reflector, with a good performance of reflection at 93 GHz and transparency at the wavelength of 1.06 μm, is achieved according to sputtering technique. At the wavelength of 1.06 μm, transmittance of the sub-reflector is 67%. Compared to a Cassegrain antenna system consisting of a metallic sub-reflector with identical size, the gain of the compound antenna system has a negligible loss (less than 0.4 dB) at 93 GHz. Compared with the patent in [13], the design can improve the limited size of receiving system and the utilization of aperture of the compound detection system at IR region, and can also enhance the heat dissipation.

In this paper, a high-gain amplifier module has been presented for millimeter wave applications. In order to suppress oscillation of the high-gain amplification block, a rectangular waveguide (WG) is fully integrated into the metal case, on which a cascaded two-stage amplifier is mounted. Due to the integrated WG, additional WG-to-microstrip line (MSL) transitions are required. Therefore, a low-loss and wide-band WG-to-MSL transition is designed and fabricated on a 5 mil thick RT5880 substrate. Two sets of WG-to-MSL transitions in back-to-back structure are assembled in the metal case for the high-gain amplifier module and are characterized. The measured transition loss and operational returnloss (S₁₁) bandwidth less than -10 dB are less than -0.44 dB/a transition and 15.9 GHz from 34.1 to 50 GHz, respectively. The fabricated high-gain amplifier module shows a high gain over 39.7 dB from 38 to 41 GHz. At 38.7 GHz, its maximum gain of 44.25 dB is achieved.

Simulating steady state performance of high quality factor (Q) resonant RF structures is computationally difficult for structures with sizes on the order of more than a few wavelengths because of the long times (on the order of ~ 0.1 ms) required to achieve steady state in comparison with maximum time step that can be used in the simulation (typically, on the order of ~ 1 ps). This paper presents analytical and computational approaches that can be used to accelerate the simulation of the steady state performance of such structures. The basis of the proposed approach is the utilization of a larger amplitude signal at the beginning to achieve steady state earlier relative to the nominal input signal. The methodology for finding the necessary input signal is then discussed in detail, and the validity of the approach is evaluated.

A plasma sheath can significantly alter the electromagnetic properties of an object, which leads to many practical applications. In this article, the electromagnetic scattering properties of a DB metamaterial cylinder coated with unmagnetized plasma are studied. The effects of layer thickness, non-uniform cladding (eccentric coating), electron number density, electron-neutral collision frequency and the frequency of incident wave on radar cross-section (RCS) of the object are discussed. It is found that the RCS of the DB metamaterial objects can be reduced or enhanced by appropriate values of plasma parameters, thickness or eccentricity. The anomalous behavior of backscattering crosssection of plasma coated DB cylinder has been observed at frequencies near plasma frequency. The results may serve as a noteworthy reference for experimentalists working in plasma stealth technology for metamaterials.