This paper reports material selection methodology for radio frequency - micro electro mechanical systems (RF-MEMS) switches used for reconfigurable antennas. As there are variety of materials available to design engineer, a proper technique to select the best possible material is needed. Three primary performance indices, pull-in voltage, RF-loss, and thermal residual stress, are used to obtain the desired performance. The selection chart shows that aluminum is the most suitable material for being used as bridge material in RF-MEMS switches to provide the best performance in reconfigurable antenna.

Geosynchronous Circular Synthetic Aperture Radar (GeoCSAR) has the Circular SAR configuration and undergoes a near-ellipse geosynchronous track rather a ``8''-like track of conventional GeoSAR. It could produce three dimensional (3-D) images of extended Earth scenes. GeoCSAR raw data simulator is of vital for predicting system performance, developing suitable data processing algorithms, etc.. It should include degrading conditions such as motion instability, angular deviations and orbit perturbations in order to approach the real situation. The common generation algorithm of raw data in time domain is precise but time-consuming for extended 3-D scene. In this paper, a novel raw data simulation algorithm based on inverse Improved Polar Format Algorithm (IPFA) for GeoCSAR was proposed, which possessed both the advantages of precision of time domain simulator and efficiency of frequency domain simulator. Implementation details were presented, and several simulation results were provided and analyzed to validate the algorithm.

Split ring resonator (SRR) can potentially be used as a design to be incorporated onto the truncated pyramidal microwave absorber. This study considers three different patterns of edge couple split ring resonator (EC-SRR) designs. Each EC-SRR design is then placed onto the truncated pyramidal microwave absorber. Outer split gap dimension widths of the EC-SRR are varied, and the various S₂₁ performances are compared. This EC-SRR truncated pyramidal microwave absorber is simulated using CST Microwave Studio simulation software. The study and simulation are performed in low frequency range (0.01 GHz to 1 GHz) as well as in microwave frequencies range (1 GHz to 20 GHz). Simulation results of this EC SRR show improvement of reflection loss and S₁₁ performance in the high frequency range of the pyramidal truncated microwave absorber.

A mesh generation algorithm for the Method of Moments (MoM) is described. The algorithm, named CGSM, can mesh arbitrary planar shapes described with line segments and circular arcs into mixed triangular and rectangular cells. CGSM creates contours of the meshed shape and uses them to provide edge mesh (denser mesh near edges), creates an adaptive grid and uses it to insert axis-aligned rectangles in the interior, and finally, triangulates the remaining area (the Delaunay condition is imposed on the triangulation). CGSM is compared to two commercial applications (Designer® and IE3D™) on the example of a 2-GHz hybrid ring coupler. The same simulation results are obtained. However, with CGSM, simulation time is significantly reduced.

In this paper, the electromagnetic field distribution inside a jet engine is studied through full wave analysis. Results are statistically analyzed by comparisons to the models used for the reverberation chamber with a mechanical mode stirrer. The jet engine is simulated as an open cylinder containing one set of rotating blades by using 'Ansys R HFSS'. A simple Hertzian dipole illuminates the interior structure as an incident wave excitation representing a transmitting antenna radiating continuous wave fields. The field distribution inside the engine, which results from a distinct set of rotating positions of the blades, is primarily studied through the simulation program. In our case, the mechanical stirrer is represented by the rotating set of blades. The field values are extracted at different planes along the cylindrical engine, and the average field is statistically analyzed. We show that the squared magnitude of the field component along the engine's main axis has an exponential distribution compared to the theoretical exponential distribution proved in a reverberation chamber. This approach promises to act as a novel effective method to analyze the engine system without dealing with the complex details inside the engine cavity.

Thinning of large arrays in order to produce low side lobes is a difficult task. Conventional gradient methods often stuck in local minima and hence are not capable of obtaining optimum solutions. As a result, global optimization methods are required to thin large antenna arrays. In this paper, a global evolutionary method, Biogeography based optimization (BBO) is introduced as a new tool for thinning large linear and planar antenna arrays of uniformly excited isotropic antennas. The aim is to synthesize linear arrays so as to yield the maximum relative sidelobe level (SLL) equal to or below a desired level while also keeping the percentage of thinning equal to or above the desired level. The results obtained by BBO are compared with the previous published results of Genetic Algorithm (GA), Ant Colony Optimization (ACO), Immunity Genetic Algorithm (IGA) and Binary Particle Swarm Optimization (BPSO).

The design of wireless technology which involves radio frequency identification (RFID) and Bluetooth technology for tagging and transmission of data that will be applied to point of sale (POS) is presented. A complete POS circuitry system has been designed to allow certain item to be a tag easily identified and localized. This is implemented by using RFID technology which will communicate with personal computer (PC) either through Ethernet or Wifi connection. An Impinj RFID reader and Bluetooth mobile phone are selected in the proposed POS system. Matlab simulation has been performed for RFID transceiver part and Bluetooth data transmission. A prototype software is developed to interface the Impinj RFID reader through the Ethernet connection. Additionally, a data encryption from Bluetooth is paired with PC to achieve a secure and simple pairing feature when customer transaction is performed. It involves hardware and software implementation. Moreover, in simulation result, a double side band modulation is used to design the RFID reader for better item tagging. The results show the feasibility of using this design for POS and achieving very good read ranges. Finally, Bluetooth system enables fast transaction and makes purchase securely by using the proposed asymmetric algorithm.

We previously reported on the complex permittivity and dc conductivity of waste-activated sludge. The measurements, spanning a frequency range of 3 MHz to 40 GHz, were made using an open-ended coaxial transmission line. Although this technique is well established in the literature, we found that it was necessary to combine methods from several papers to use the open-ended coaxial probe to reliably characterize biological samples having a high dc conductivity. Here, we provide a set of detailed and practical guidelines that can be used to determine the permittivity and conductivity of biological samples over a broad frequency range. Due to the electrode polarization effect, low frequency measurements of conducting samples require corrections to extract the intrinsic electrical properties. We describe one practical correction scheme and verify its reliability using a control sample.

Power efficiency is a key issue in wireless sensor networks due to limited power supply. Buffer management is also crucially important in the scenario where the incoming traffic is higher than the output link capacity of the network since a buffer overflow causes power waste and information loss if a packet is dropped. There are many available buffer management schemes for traditional wireless networks. However, due to limited memory and power supply of sensor nodes, the existing schemes cannot be directly applied in wireless sensor networks (WSNs). In this work, we propose a multi-layer WSN with power efficient buffer management policy which simultaneously reduces the loss of relevant packets. Unlike the conventional WSNs which consider the whole network as single layer, we divide sensor network topology logically into multiple layers and give a three-layer model as an example. In our proposed scheme, the layers are differentiated by the sensors' information. The buffer can then judge the packets from different layers and then make a decision on which packet to be dropped in case of overflow. We show that our proposed multi-layer WSN can reduce the relevant packet loss and power waste for retransmission of lost packets.

In this paper, antenna ultra wideband enhancement by non-uniform matching is proposed. The antenna consisted of a rectangular shaped radiator with two convex circled corners. Simulated results using CST Microwave Studio and measured results of a fabricated antenna concord well to prove that it can operate from about 3.5 GHz to 4.6 GHz and from 7.4 GHz to 12.7 GHz for S₁₁ (dB) < -10 dB. In addition, a good impedance matching is noted in the IEEE radar engineering X band range since the return loss coefficient remains below -50 dB value at 9.5 GHz and can reach -45 dB at 11 GHz. A current density comparison at 11 GHz, supporting our argument, between a stepper corner and convex corner demonstrates that the current density can reach 52 A/m with a convex corner whereas it does not exceed 33 A/m for the antenna with a stepper corners. Radiation patterns at various frequencies and peak gains show clearly interesting features of such antennas.

Star-junction multiplexers are used when the number of channels is relatively small since the resonating junction has to be connected to many filters' outputs. In this paper, novel topologies of star-junction multiplexers with resonating junctions are proposed. The advantage of the proposed topologies is that the number of connections to the resonating junction is reduced and thus allowing multiplexers with more channels to be implemented. An optimization technique is used to synthesize the coupling matrix of the proposed multiplexers, and numerical examples are illustrated in this paper.

In this paper, a new circuit configuration composed of two main and reference paths is proposed for the modified multi-section Schiffman phase shifter, which improves its bandwidth. The method of least squares (MLS) is developed for its design, based on a circuit model including dispersion relations and dissipation effects. The differential phase shift and reflection coefficients from the input ports are obtained by conversions among the impedance, admittance, ABCD and scattering matrices of the circuit model. Then, an error function is constructed, whose minimization is performed by the combination of genetic algorithm and conjugate gradient method, which gives the optimum values of the physical dimensions of the metallic strips. The impedance matching function of the proposed phase shifter circuit makes it a dual action device, leading to some circuit miniaturization. Three phase shifter circuits with single, double and quadruple sections are designed and one prototype model is fabricated and measured. The MLS, full-wave simulation softwares and measurement results agree very well, which validate the proposed circuit configuration and MLS design procedure. The multi-section phase shifters have actually increased the frequency bandwidth.

We present a pin-Traveling wave Photodetector (TWPD) on semi-insulating (SI) InP substrate at 1.55 μm wavelength window with an electrical bandwidth of more than 120 GHz, a line characteristic impedance of about 50 W, and microwave index matched to the optical group index. The internal quantum efficiency more than 99% for a 200μm long device is determined. The layer stack of the TWPD has previously utilized in a semiconductor optical amplifier (SOA). The TWPD can be monolithically integrated with passive and active components such as arrayed waveguide grating (AWG), Mach-Zehnder Interferometer (MZI), laser and modulator.

High-accuracy pulse repetition interval (PRI) estimation is meaningful for passive sensors to identify radar emitters. This paper considers the problem of estimating the PRIs of motionless radars in moving passive sensor systems. A modified method which based on observation calibration is proposed. This method can efficiently compensate the estimation bias induced by model mismatch, through calibrating the pulse time of arrival (TOA) measurements with emitter geolocation information. Performance analysis and simulation results show that our method can improve the PRI estimation accuracy significantly.

Fractal-shaped microwave passive circuits offer a great deal of promise for achieving good performance in small circuits. In this paper, isosceles right-angled triangular patch resonator with fractal hole is analyzed, and new single band and dual-band RF filters by using isosceles right-angled triangular patch resonators with fractal pattern are proposed. It is shown that with the assistance of a fractal, the right-angled triangular resonator can be miniaturized and filter performance is greatly improved, simultaneously, resonance of the resonator higher order mode is enhanced, which is helpful for a dual-band filter implementation. Two proposed fractal bandpass filters are fabricated, and their performance is verified by measurement. The proposed filters demonstrate the applications of right-angled triangular patch resonator and exhibit advantages of a simple structural topology and compactness, which are essential in RF circuit design.

Previous works on maximum ratio combining (MRC) diversity have derived a closed-form cumulative distribution function (CDF), referred to as Lee's formula, for spatially correlated Rayleigh fading channels. It is usually believed that (due to its singularity) Lee's formula will result in large numerical error when two eigenvalues of a diversity antenna's covariance matrix are close to each other. This letter shows that the limit of Lee's formula converges to the true CDF as eigenvalues converge to each other, which implies that Lee's formula is robust in determining diversity gains of arbitrary antennas based on stochastic measurements.

In this paper, a new linear method for optimizing compact low noise oscillators for RF/MW applications will be presented. The first part of this paper makes an overview of Leeson's model. It is pointed out, and it is demonstrates that the phase noise is always the same inside the oscillator loop. It is presented a general phase noise optimization method for reference plane oscillators. The new method uses Transpose Return Relations (RRT ) as true loop gain functions for obtaining the optimum values of the elements of the oscillator, whatever scheme it has. With this method, oscillator topologies that have been designed and optimized using negative resistance, negative conductance or reflection coefficient methods, until now, can be studied like a loop gain method. Subsequently, the main disadvantage of Leeson's model is overcome, and now it is not only valid for loop gain methods, but it is valid for any oscillator topology. The last section of this paper lists the steps to be performed to use this method for proper phase noise optimization during the linear design process and before the final non-linear optimization. The power of the proposed RRT method is shown with its use for optimizing a common oscillator, which is later simulated using Harmonic Balance (HB) and manufactured. Then, the comparison of the linear, HB and measurements of the phase noise are compared.

An efficient model order reduction method for three-dimensional Finite Element Method (FEM) analysis of waveguide structures is proposed. The method is based on the Efficient Nodal Order Reduction (ENOR) algorithm for creating macro-elements in cascaded subdomains. The resulting macro-elements are represented by very compact submatrices, leading to significant reduction of the overall number of unknowns. The efficiency of the model order reduction is enhanced by projecting fields at the boundaries of macro-elements onto a subspace spanned by a few low-order waveguide modes. The combination of these two techniques results in considerable saving in overall computational time and memory requirement. An additional advantage of the presented method is that the reduced-order system matrix remains frequency-independent, which allows for very fast frequency sweeping and efficient calculation of resonant frequencies. Several numerical examples for driven and eigenvalue problems demonstrate the performance of the proposed methodology in terms of accuracy, memory usage and simulation time.

High speed analog-to-digital (A/D) sampling and a large amount of echo storage are two basic challenges of high resolution synthetic aperture radar (SAR) imaging. In this paper, a novel SAR imaging algorithm which named CS-MTMAB is proposed based on compressed sensing (CS) and multiple transmitters multiple azimuth beams (MTMAB). In particular, this new algorithm, which respectively reconstructs the targets in range and azimuth directions via CS technique, simultaneously provides a high resolution and wideswath two-dimensional map of the spatial distribution of targets with a significant reduction in the number of data samples beyond the Nyquist theorem and with an implication in simplification of radar architecture. The simulation results and analysis show that this new imaging scheme allows the aperture to be compressed and presents many important applications and advantages among which include reduced on-board storage constraints, higher resolution, lower peak side-lobe ratio (PSLR) and integrated side-lobe ratio (ISLR), less sampled data than the traditional SAR imaging algorithm, and also indicate that it has high robustness and strong immunity in the presence of serious noise. Finally, the real raw airborne SAR data experiment is performed to validate the proposed processing procedure.

In this work, we use the numerical steepest descent path (numerical SDP) method in complex analysis theory to calculate the highly oscillatory physical optics (PO) integral with quadratic phase and amplitude variations on the triangular patch. The Stokes' phenomenon will occur due to various asymptotic behaviors on different domains. The stationary phase point contributions are carefully studied by the numerical SDP method and complex analysis using contour deformation. Its result agrees very well with the leading terms of the traditional asymptotic expansion. Furthermore, the resonance points and vertex points contributions from the PO integral are also extracted. Compared with traditional approximate asymptotic expansion approach, our method has significantly improved the PO integral accuracy by one to two digits (10^-1 to 10^-2) for evaluating the PO integral. Moreover, the computation effort for the highly oscillatory integral is frequency independent. Numerical results for PO integral on the triangular patch are given to verify the proposed numerical SDP theory.