For the inverse synthetic aperture radar (ISAR) imaging of a target at a long range, range alignment using the existing polynomial method brings about poor results because the flight trajectory changes depending on the initial position, and the motion parameters, meaning the polynomial cannot fit the trajectory. This paper proposes an improved range alignment method that models the trajectory using a combination of a polynomial and Gaussian basis functions. Initial parameters of the polynomial and Gaussian basis functions are determined by fitting the proposed model to the center of mass curve of the range profile history using the least square curve-fitting algorithm, and the optimum value is found using particle swarm optimization. This method is computationally more efficient and preserves the image quality.

We have proposed a simple waveguide method for complex permittivity determination of dielectric materials which are not completely filling the entire sample holder. The method reconstructs the permittivity from measured reflection-only scattering parameters by a one-port vector network analyzer of two configurations of the sample holder. It not only eliminates the necessity of any knowledge of the location of the shifted sample inside its holder but also decreases measurement errors occurring with the presence of undesired air gaps, which seriously affect the measurement accuracy of transmission-only measurements, present between the sample and holder walls. Furthermore, the reconstruction of permittivity can be realized by any one-port vector network analyzer, which is less expensive than their two-port counterparts. Therefore, the proposed method is cost-effective. We have analyzed the accuracy of the proposed method and noted a good compromise between the reference data and measured values of permittivities of low-loss polyvinyl-chloride and polytetrafluoro−ethylene samples (less than 8 percent for dielectric constant and less than 15 percent for loss tangent values).

This paper presents a basic analysis about the results of experiments using planar coils inner to ring coils, when planar coil is applied to a square wave voltage. In this study an uncommon phenomenon occurs in the ring coil, which is analyzed.

In this paper, we present an innovative method of cross-polarisation suppression by forming the antennas in a so called Clover Array (CA). Such structure enables usage of polarisation diversity even for UWB systems. The simplified theoretical model of operation is presented as well as exemplary results of crosspolarisation patterns. The theory was verified for CA of planar Volcano-Smoke antennas. For fabricated array the cross-polarisation in main beam is below -14 dBi in the whole FCC-UWB frequency range (3.1 GHz - 10.6 GHz).

Miter bend mirror has been designed for microwave transmission between two corrugated waveguides of the same size by iterative phase correction method. Geometrical Optics (GO) approximation has been used in our design at a frequency of 110 GHz. The equivalence principle is also adopted to forward-propagate and backward-propagate the beam onto the miter-bend mirror. The designed miter bend mirror shows a coupling coefficient up to 99.619%, much better than that of a flat mirror. The convergence rate shows that the design is very efficient with only a few iterations required.

An internal shorted patch antenna integrated with a RF/battery shielding metal case for application in a UMTS mobile phone is presented. The shorted patch antenna is mounted at the dented portion of the shielding metal case, with the top patch flushed with the top surface of the shielding metal case. This configuration shows no protruded portions, which makes the antenna very suitable to be integrated in a UMTS mobile phone as an internal antenna. With the integrated design, which provides a coupling-free region for the nearby electronic components or conducting elements in the mobile phone, possible coupling between the antenna and associated components can be avoided. Details of the proposed design showing a wide bandwidth for UMTS (Universal Mobile Telecommunication System, 1920 ~ 2170 MHz) operation are demonstrated, and effects of the dimensions of the RF/battery shielding metal case are presented and discussed.

A Sub Harmonically Pumped (SHP) mixer suitable for direct conversion receiver in 3G mobile frequency band is presented. This mixer is realized with N anti-parallel diode pairs (APDPs) and designed in self-biased structure to obtain minimum noise figure and conversion loss. In this paper, a simultaneous signal and noise analysis CAD routine to analyze a circuit consists of Arbitrary Number of anti-parallel diode pairs in self-biased structure is proposed. Then the results of this CAD routine are confirmed with other method. The mixer is optimized to obtain a maximally flat conversion gain and minimum Noise Figure over various LO powers. The proposed CAD is used to obtain the optimum number of APDPs. Also the optimum self-biased resistance and output load are calculated.

A novel circuit structure of dual-band bandstop filters is proposed in this paper. This structure comprises two shunt-connected tri-section stepped impedance resonators with a transmission line in between. Theoretical analysis and design procedures are described. The derived synthesis equations have two degrees of freedom which provide more design flexibility in filter synthesis. Notably, three advantages of the proposed filter structure lie in the fact of its increased nonuniform impedances, resulting in a compact size, wide range of realizable frequency ratio, and more realizable impedances. Three experimental dual-band bandstop filters with various frequency ratios were fabricated to demonstrate the feasibility of the new filter structure.

Based on swept frequency RCS measurements system, foam column and proper data processing procedure, the resonance curves of conducting spheres with RCS below -32.95 dBsm are achieved in a single reflector Compact Antenna Test Range (CATR), with measurement errors within 1.0 dB over most of the measurement frequencies. Nine spheres down to -49.01 dBsm are clearly imaged with Range-Doppler (R-D) method and pointwise vector background subtraction technique.

The resonant characteristic of frequency selective surfaces (FSSs) on in-plane biased ferrite substrates for the TE polarization is described. An approximate formula for evaluating the resonant frequency is presented. The tunable property of the resonant frequency of a dipole FSS is firstly demonstrated by the results obtained from the moment method (MM) and the waveguide simulator measurement. Then the approximate formula is validated by the MM as well as measured results already published in a previous paper. It is interesting to note that two separate resonances occur at any magnetic bias field, and both increase as the magnetic bias field increases. The fractional tuning range is investigated based on the approximate formula. The results show that it increases as the saturation magnetization increases and decreases as the center frequency increases.

Phase unwrapping is a key problem to generate digital elevation maps (DEMs) by synthetic aperture radar (SAR) interferometry. A lot of phase unwrapping algorithms have been proposed to solve this problem. However, in noisy region, many unwrapping algorithms are inoperative because of the denseness of residues. In this paper, we propose a path following phase unwrapping method, namely Residue-Pairing (RP) algorithm. The algorithm starts from residues, based on the aggregate of coordinates of each positive residues (or negative residues), to search the nearest opposite polar residue and connect them. Compared to the Goldstein's algorithm, the brunch cuts produced by this algorithm can effectively decrease their total length and contract the isolated region especially in noisy region. With raw data simulation, the results confirm the validity of RP algorithm in dense-residues region.

A dual-band multifunction hybrid antenna for carborne satellite communication relay system is presented in this paper. As a consequence of the radiation requirements, the proposed antenna consists of a left-hand circularly polarized (LHCP) microstrip patch and an omnidirectional biconical antenna with a conductor tube holding and radome. The LHCP microstrip antenna is used for satellite signal reception, and bionical antenna is used for relay communication transmission. A novel overmoded coaxial waveguide feed structure eliminates the interference between two feed ports. The proposed antenna has the advantages of robustness, low cost, and easy fabrication with conventional materials and printed circuit technology. An antenna prototype is fabricated to validate the design. Both the simulated and measured results are obtained with reasonable agreement.

In this paper, jerk function for a transient process of RL circuit is investigated. Some new concepts such as time rate of change of induced emf, time rate of change of displacement current, and Appell function have been introduced for the first time in electromagnetic jerky dynamics. The problems on Appell function of several simple models in electromagnetic jerky dynamics are discussed. In the last conclusions and remarks are also presented.

This paper presents some improved analytical expressions of the magnetic field produced by arc-shaped permanent magnets whose polarization is radial with the amperian current model. First, we show that the radial component of the magnetic field produced by a ring permanent magnet whose polarization is radial can be expressed in terms of elliptic integrals. Such an expression is useful for optimization purposes. We also present a semi-analytical expression of the axial component produced by the same configuration. For this component, we discuss the terms that are difficult to integrate analytically and compare our expression with the one established by Furlani [1]. In the second part of this paper, we use the amperian current model for calculating the magnetic field produced by a tile permanent magnet radially magnetized. This method was in fact still employed by Furlani for calculating the magnetic field produced by radially polarized cylinders. We show that it is possible to obtain a fully analytical expression of the radial component based on elliptic integrals. In addition, we show that the amperian current model allows us to obtain a fully analytical expression of the azimuthal component. All the expressions determined in this paper are compared with the ones established by Furlani or in previous works carried out by the authors.

An all-dielectric composite route is proposed for the construction of a left-handed material at THz frequency. It is shown that the interaction between the crystal lattice vibration of the polaritonic dielectric and the electromagnetic wave could induce a negative permittivity. By combining the electric inclusion of polaritonic dielectric with the magnetic inclusion based on Mie resonance, the dielectric composite exhibits simultaneously negative permittivity and negative permeability, hence a negative refractive index. Additionally, the simulation results of the electromagnetic coupling between the electric and magnetic inclusions indicate that the behavior of the negative refractive index is closely related to the distance between the two inclusions.

A compact dual-band annular-ring slot antenna (ARSA) is proposed for use in 2.4/5 GHz wireless local-area networks (WLANs). With a meandered grounded strip embedded in the ring slot, three resonant modes were excited. With a pair of notches properly etched in the inner circular patch, the third resonant band was sufficiently lowered so that the second and third resonant bands are combined to form a wider upper operating band. If scaled to the same lower operating-band center frequency, the proposed ARSA measures only 53.6% the area of a conventional microstrip-line-fed ARSA. Measured and simulated results were found to agree reasonably well with each other.

Based on the use of micro electro-mechanical system (MEMS) switches this paper presents a composite right/left-handed (CRLH) transmission line (TL) with a reconfigurable behaviour. The design strategy here adopted consists on the use of metal-insulator-metal (MIM) capacitors and short-circuited stubs resulting in a very compact and monolithic CRLH unit cell well suited for phase shifter applications.

A novel circularly polarised (CP), single-fed widebeam microstrip antenna is presented. The antenna consists of a corner-truncated square patch and a three dimensional circular ground structure. Simulated and measured results show that, owing to the ground structure, the 3 dB beamwidth of the CP radiation can reach more than 165^o, which is about 85^o, greater than that of a corresponding regular microstrip antenna. It is also shown that experimental results were in good agreement with the simulated performance. Details of the proposed 3-D circular ground structure are described, and the effects of various dimensions of the proposed ground structure on the beamwidth enhancement of CP radiation are studied.

This paper addresses the sensor selection problem which is a very important issue where many sensors are available to track a target. In this problem, we need to select an appropriate group of sensors at each time to perform tracking in a wireless sensor network (WSN). As the theoretical tracking performance is bounded by posterior Cramer-Rao lower bound (PCRLB), it is used as a criterion to select sensors. Based on the PCRLB, sensor selection algorithms with and without sensing range constraint are developed. Without sensing range limit, exhaustive enumeration is first adopted to search all possible combinations for sensor selection. To reduce complexity of enumeration, second, we restrict the selected sensors to be within a fixed area in the WSN. With sensing range constraint, a circle will be drawn with the help of communication range for sensor selection. In a similar manner, two approaches, namely, selecting all sensors inside the circle or using enumeration to select sensors within the circle are presented. The effectiveness of the proposed methods is validated by computer simulation results in target tracking for WSNs.

Modern electronic products are increasingly based on high-speed, high-density circuitry operating at lower voltages. With such designs, the signal integrity (SI) in a poor printed circuit board layout is affected by noise and may become unstable. Crosstalk is a major source of noise that interferes with SI. Generally, crosstalk can be reduced by adding a guard trace between the victim and aggressor areas of the circuit. In addition, grounded vias can be added to the guard trace to help reduce crosstalk. Since a large number of grounded vias degrade the SI and reduce the flexibility of the circuit routing, we propose a method to calculate the optimal distance between grounded vias in the guard trace and determine the smallest number of vias required to achieve optimal performance in reducing crosstalk. We show by time-domain simulation that our method reduces the near-end crosstalk by 27.65% and the far-end crosstalk by more than 31.63% compared to the three-width rule. This is backed up by experimental results that show not only reductions of 34.49% and 37.55% for the near- and far-end crosstalk over time-domain, respectively, but also reductions of 2.1 dB and 3.3 dB for the near- and far-end crosstalk over the frequency-domain, respectively. Our results indicate that our method of optimal grounded vias has better performance than other methods.