This paper aims to provide an effective solution to the problem of detecting a large number of densely stacked DVDs. The number is in the range of 2000. In order to achieve that goal, firstly the structure and the properties of materials comprising a DVD disc and a DVD case are investigated. The effect of the metal layer in the disc on the interrogating wave is evaluated via theoretical analysis and simulation. Based on that analysis and simulation, and on numerous experiments on either a single labeled DVD in free space or multiple labeled DVD in a DVD stack, two solutions are proposed whereby over 95% DVDs in a great portion of a 2000 DVD stack could be detected. Eliminating the tags which have weak performance, the percentage can be 100%. This paper not only expands the range of categories detectable by UHF RFID systems but also provides a process and method for item-level tagging in which the number of the items is in the range of thousands.

We propose a switchable and wavelength spacing tunable multi-wavelength fiber optical parametric oscillator (MW-FOPO) with two cascaded fiber Bragg gratings (FBGs). The MW-FOPO can operate at two multi-wavelength lasing modes with different wavelength spacings, which can be switched by adjusting some polarization controllers (PCs). Stable multi-wavelength lasing at those two different operation modes at room temperature is achieved due to the four wave mixing (FWM) effect and the broadband gain of the fiber optical parametric amplifier (FOPA) based on a highly nonlinear fiber. The wavelength spacing of the proposed MW-FOPO can be tuned by adjusting the wavelength of the pump light or the central wavelength of the FBG at the two multi-wavelength lasing modes.

With the increasing threat of terrorism in recent years, the detection of concealed weapons, plastic bombs and other contraband at secure locations attracts more and more countries' attention all over the world. Three-dimensional (3D) microwave imaging surveillance systems, allowing for acquisition of full 3D microwave images of volumetric scatters of human body, have been developed for security applications. In this paper, we firstly propose a 3D imaging algorithm which not only accounts for the free space propagation losses and wavefront curvature but also avoids 3D interpolation in the 3D wavenumber domain without suffering from any approximations and truncation errors. Then, the sampling constraints and the resolution issues associated with proper and alias-free implementation of the 3D reconstruction are analyzed. Finally, the focusing capabilities of our proposed imaging algorithm are investigated and verified by means of numerical simulations as well as theoretical analysis, and an approach for better displaying projected images is examined.

The modeling of the reverberation chamber with the use of deterministic techniques, one of which is the Ray Launching (RL) method, requires a careful tuning with measurements. A few factors that most severely influence the simulation results are: the minimum number of stirrer rotations to produce representative outcomes, the number of reflections of each traced ray and, finally, the size of the receive probe and the wall reflection loss. In the course of investigations it was demonstrated that these factors have a different, and in some instances --- even opposite, impact on the simulated results in the electromagnetic (EM) power domain and in the time domain (the time delay spread). A simple procedure consisting of a few steps has been proposed for tuning deterministic RL models to the measured data.

In this paper, a tunable coplanar waveguide (CPW) line using the bismuth zinc niobate (BZN) thin film has been proposed and demonstrated for low-voltage phase shifter applications. In order to reduce the operation bias voltage the air gaps between the signal strip and ground plane are filled with the tunable thin films. At low E-fields of 1.3 kV/cm, the fabricated CPW line shows the phase difference of 10 degree at 10 GHz.

A miniaturized ultra-wideband (UWB) bandpass filter (BPF) with U-slot etched around the metallic via in the ground is proposed based on a simplified composite right/left-handed transmission line (SCRLH TL) structure. The U-slot etched in the ground makes it feasible to reduce the overall size. A demonstration of FCC standard UWB bandpass filter (BPF) is designed, fabricated and measured. Very good agreement is shown between measurement and simulation.

An effective procedure is developed in this paper to compensate the probe positioning errors when using a near-field to far-field transformation technique with helicoidal scanning for long antennas. It is based on a prolate ellipsoidal modelling of the antenna under test and makes use of an iterative scheme to retrieve the uniformly distributed helicoidal near-field data from the irregularly spaced acquired ones. Once these data have been recovered, those required to perform a standard near-field--far-field transformation with cylindrical scanning are efficiently determined via an optimal sampling interpolation algorithm. Some numerical tests are reported to assess the accuracy of the approach and its robustness with respect to random errors affecting the data. At last, the validity of the developed technique is further confirmed by the experimental tests performed at the Antenna Characterization Lab of the University of Salerno.

In this paper, we propose an optimization method based on Gravitational Search Algorithm (GSA) for design of reconfigurable dual-beam concentric ring array of isotropic elements with phase only control of five-bit digital phase shifters. The problem is to find a common radial amplitude distribution using four-bit digital attenuator that will generate three different types of broadsided beam pair in vertical plane: a pencil/pencil beam pair, a pencil/flat-top beam pair and a flat-top/flat-top beam pair sector pattern) with desired value of side lobe level, first null beam width and ripple. The two patterns differ only in radial discrete phase distribution while sharing a common discrete radial amplitude distribution. The optimum sets of four-bit discrete radial amplitude distribution generated by four-bit digital attenuators and five-bit discrete radial phase distribution generated by five-bit digital phase shifters for obtaining dual radiation patterns are computed by Gravitational Search Algorithm.

In this paper we propose a computational method for constructing variable surface impedance, based on combining Rytov's perturbation method and level set technique. It is well-known that the choice of the most appropriate order of Rytov's expansion is important both for accuracy and implementation. By using level set method, we constructed a piecewise distribution of low- and high-order surface impedance boundary conditions on the surface of an arbitrarily shaped conductor. It is found that the proposed method is able to give good results both in terms of accuracy and implementation cost.

A novel procedure for estimating the Fresnel reflection coefficient of a transversally homogeneous half-space medium is introduced. GPR multistatic measurements are exploited as data whereas the Fresnel coefficient (as a function of the incidence angle) is retrieved by inverting a linear integral equation. Having estimated the reflection coefficient it can be exploited to determine the medium electromagnetic parameters. Numerical examples are used to show procedure effectiveness for different types of homogeneous half-space media within a two-dimensional scalar geometry. The case of a layered half-space is also discussed.

In this paper, novel uniplanar tunable and switchable bandpass filters are designed by using the centrally-loaded slot-line resonator. From the voltage-wave distribution along the resonator, the appropriate location for the loading element is determined to be the center of the slot-line resonator, where the voltages of the fundamental signal and second harmonic are maximum and zero, respectively. As a result, the fundamental frequency can be tuned while the second harmonic remains almost unchanged. For the first time, the properties of the centrally-loaded slot-line resonator are analyzed by using the even- and odd-mode method, and their respective resonant frequencies are derived. The demonstrated tunable bandpass filter can give a 30.9% frequency tuning range with acceptable insertion loss when a varactor is used as the loading element. By replacing the loading varactors with PIN diodes, a switchable bandpass filter is realized in which the attenuation in the fundamental passband can be controlled. In experiments, the switchable bandpass filter exhibits a 2.13 dB insertion loss in the fundamental passband when the PIN diodes are off and more than 49 dB isolation across the passband when the PIN diodes are on.

Using a building block approach which combines a transverse resonance method with a mode-matching technique, a rigorous analysis of a lossless bi-isotropic H-guide is presented. First, the modal equation of a parallel-plate waveguide containing the inner medium of the H-guide is obtained. Then, a mode matching technique is used to develop a full-wave analysis of the H-guide. The influence of nonreciprocity on the guidance properties of the structure is discussed.

A non-resonant microwave method has been proposed for complex permittivity determination of low-loss materials with no prior information of sample thickness. The method uses two measurement data of maximum/minimum value of the magnitude of transmission properties of the sample. An explicit expression for sample thickness and two expressions for inversion of the complex permittivity of the sample are derived. The method has been validated by transmission measurements at X-band (8.2--12.4 GHz) of a low-loss sample located into a waveguide sample holder.

In this paper propagation losses of body implanted antennas are studied at the ISM bands of 433 MHz, 915 MHz, 2450 MHz and 5800 MHz. Two body models are used, one based on a single equivalent layer and the other based on a three layer structure, showing the advantages and limitations of each one. Firstly, the antenna pair gain at different implanted antenna depths is analyzed. Next, we show the effects of the thickness of the different body tissue layers. Finally, we discuss the consequences of using a coating layer to isolate the antenna from the harsh environment of the human body.

This paper presents a new unequally spaced and excited resonant slotted-waveguide antenna array. It is realized by employing an improved resonant-slot coupled cavity chain composite right/left-handed (CRLH) waveguide. As the CRLH waveguide works at the infinite wavelength frequency, all the slot elements along the waveguide wall are excited in-phase. Thus both the element spacings and excitation amplitudes are introduced into the synthesis to realize a resonant slotted-waveguide antenna array. A seven-element unequally spaced and excited antenna array which generates pencil beam is synthesized, simulated and fabricated. The results show, with comparison to the equally spaced but unequally excited resonant slotted-waveguide antenna array, the proposed unequally spaced and excited array produces a lower peak sidelobe level (PSLL).

A canonical problem is used to investigate the effects of various radar parameters on the performance of both steppedfrequency and short-pulse through-barrier radar imaging systems. For simplicity, a two-dimensional problem is considered, consisting of a perfectly conducting strip located behind a lossy dielectric slab of infinite extent illuminated by line sources. To assess the impact of the parameters on system performance, images of the target are created using the reflected field computed at several positions in front of the barrier and adjacent to the sources. Specific parameters considered include sample rate, A/D bit length, pulse width, and SNR for a time-domain system. For a stepped-frequency system, A/D bit length, bandwidth, and SNR are considered.

Charges and fields in a rotating non-magnetic conducting sphere under stationary conditions are investigated by using Minkowski's electrodynamics of moving media and the Lorentz force equation, taking into account the electric permittivity of the sphere. Starting from the assumption that the magnetic field inside the sphere is constant, exact solutions of the corresponding field equations are obtained in a first-order theory. However, it is found that there is a range of values of the sphere's net charge for which the physical interpretation of the results is difficult within a continuum model. Outside that range, our solution to the classic electromagnetostatic problem appears plausible.

A novel class of electromagnetic media called that of SQ-media is defined in terms of compact four-dimensional differential-form formalism. The medium class lies between two known classes, that of Q-media and SD-media (also called self-dual media). Eigenfields for the defined medium dyadic are derived and shown to be uncoupled in a homogeneous medium. However, energy transport requires their interaction. The medium shares the nonbirefringence property of the Q-media (not shared by the SD media) and the eigenfield decomposition property of the SD media (not shared by the Q-media). Comparison of the three medium classes is made in terms of their three-dimensional medium dyadics.

In recent years, through the wall imaging has become a topic of intense research due to its promising applications in police, fire and rescue or emergency relief operations. In this paper, we propose to use the DORT method (French acronym for Decomposition of the Time Reversal Operator) to detect and localize a moving target behind a wall. One of the DORT method major strengths is that detection remains possible through a distorting medium. In this paper, the DORT method is successfully applied to detect and track moving human beings behind a thick concrete wall. The smallest detectable displacement is also investigated.

Evaluation of electric and magnetic fields due to lightning discharge is important in determination of lightning induced voltage and power system protection especially to the distribution system. In this paper, by using dipole method, Maxwell equations and second order finite-difference time domain (later referred as a 2nd FDTD method) on two realistic return stroke currents, an algorithm for evaluation of electric fields is proposed, which is based on numerical methods in the time domain. Besides proving greater accuracy, it also allows the evaluation of electric and magnetic fields away from lightning channel. In addition, the comparison between simulation results and measured fields' wave shape showed that the proposed algorithm is in good agreement for evaluation of electric and magnetic fields due to lightning channel.