The performance assessment of maritime microwave communications and radar systems requires accounting simultaneously for the non-homogeneous propagation medium over the sea and the rough sea surface scattering. The tropospheric ducting, specific for over water propagation, is one of the most difficult to treat propagation mechanisms. The proposed work combines a recently published in the literature phase correction, responsible for the shadowing effects, to the Ament rough surface reflection coefficient and the Parabolic Equation method (as implemented in the Advanced Propagation Model) to simulate the microwave propagation over the sea under evaporation duct conditions. Propagation factor and path loss results calculated for phase-corrected Ament, non-phase-corrected Ament and the other widely used, Miller-Brown, rough surface reflection coefficient are compared and discussed. The main effects from the accounting of the shadowing result in the shift of the interference minima and maxima of the propagation factor, changes in the path loss pattern and destruction of the trapping property of the duct.

In this paper, the characteristics of three different types of high impedance surfaces (HIS) to be used as ground planes for low profile wire antennas are investigated and compared: a mushroom-like surface, which is the classical example of HIS with connecting vias, and two surfaces with no vias, one of which is anisotropic. Both the simulation results and the measurements verify that the high impedance behaviour is successfully accomplished around the resonant frequency. In order to complete the study, return loss and radiation pattern of a horizontal dipole placed above the surfaces are analyzed.

Image preprocessing is commonly used in infrared (IR) small target detection to suppress background clutter and enhance target signature. To evaluate the performance of preprocessing algorithms, two performance metrics, namely PFTN (potential false targets number) decline ratio and BRI (background relative intensity) decline ratio are developed in this paper. The proposed metrics evaluate the performance of given preprocessing algorithm by comparing the qualities of input and output images. The new performance metrics are based on the theories of PFTN and BRI, which describe the quality of IR small target image, by representing the difficulty degree of target detection. Theoretical analysis and experimental results show that the proposed performance metrics can accurately reflect the effect of the image preprocessing stage on reducing false alarms and target shielding. Compared to the traditional metrics, such as signal-to-noise ratio gain and background suppression factor, the new ones are more intuitive and valid.

A novel ultra-wideband (UWB) pulse synthesizer is proposed, which uses a distributed amplifier to combine Gaussian pulses of different polarities, amplitudes and delays. The center frequency and bandwidth of the synthesized pulse can be adjusted by varying the number of the Gaussian pulses and the delays between them. Compared to other UWB pulse generators, the present synthesizer is capable of higher voltages and higher efficiencies. Using 0.25-μm pHEMTs, a prototype synthesizer has been designed and fabricated with a center frequency of 4.0 GHz and a bandwidth of 1.9 GHz. Under a Gaussian input pulse of 1.5 V and 100 ps, the synthesizer outputs into 50 Ω a pulse of 4.5 V and 1 ns. At a pulse-repetition frequency of 10 MHz, the synthesizer consumes 1 mA at 3 V with 17% efficiency. Approaches to maintain high efficiency by scaling the supply voltage for different input amplitudes and pulse-repetition frequencies have also been verified experimentally.

A novel resonate-type composite right/left handed transmission line (CRLH TL) is presented based on a high-low impedance section and a capacitive gap on the conductor strip, and a Minkowski-loop-shaped complementary split ring resonators (ML-CSRRs) etched on the ground plane. Influence of different iteration orders on the performance of novel CRLH TL and miniaturization mechanism are investigated in depth by electrical simulation (an analysis of circuit model) together with planar electromagnetic (EM) simulation. The close-form results of negative refractive index and complex propagation constant are provided by constitutive parameters retrieval method. For application, a compact branch-line coupler (BLC) centered at 0.88GHz (GSM band) is designed, fabricated and measured. The upper signal line of CRLH impedance transformer is constructed as Koch curves of first order to facilitate further integration of the BLC. Exact design method for fractal implementation is involved. Measurement results indicate that the proposed coupler achieves a comparable 81% size reduction and good in-band performance with regard to already covered ones. The concept, validated by consistent measurement data, is of practical value for other components design.

The kinematic properties of an array of transmitting antennas that are transiently excited by a sequence of modulated pulses, with high repetition rate, are explored. The array's parameterization is carried out via the energy radiation pattern. It is shown that the energy radiation pattern can be decomposed into a set of different types of beam contributions, defined over a beamskeleton, which is determined by the array's physical and excitation parameters. The different types of beams are main beams, gratinglobe beams and cross-pulsed lobe beams, each corresponding to a different pulsed interference mechanism. While grating lobes are timeharmonic phenomena, cross-pulsed lobes are unique for excitation with a pulsed sequence. The different beam types set limits for array sparsity in terms of the array's physical and excitation parameters. The array's directivity is introduced as a figure of merit of its performance and to demonstrate the resulting effect of the time-domain excitation characteristics. The array's parameterization can be used with any type of excitation --- from extreme narrow band (time-harmonic) to extreme ultra-wideband (transient/short pulsed) excitation. For timeharmonic excitation, the resulting characterization matches that of the classical frequency domain antenna theory.

This paper demonstrates the exhibition of pulse compression from an electronic circuit with negative group delay (NGD). This circuit consists of a field effect transistor (FET) cascaded with shunt RLC network. Theoretic and experimental investigations have proved that, at its resonance frequency, the group delay of this circuit is always negative. The present study shows that around this resonance, it presents a gain form enabling to generate pulse compression. To validate this concept, as proof-of-principle, devices with one- and two-stages FET were implemented and tested. Measurements of the one-stage test device evidenced an NGD of about -2.5 ns and simultaneously with 2 dB amplification operating at 622 MHz resonance frequency. In the frequency domain, in the case of a Gaussian input pulse with 40\,MHz frequency standard deviation, this resulted in 125% expansion of pulse width compared to the input one. In time domain, simulations showed that the compression was about 80% in the case of an input Gaussian pulse with 4 ns standard deviation. With the other prototype comprised of two-stage NGD cell, the use of a sine carrier of about 1.03 GHz allowed to achieve 87% pulse width compression.

The renormalization group theory (RGT) is used in this paper to develop an extension of the multi-scale approach (MS-GEC), previously developed by the authors, in order to enable the study of fractal structures at infinite iterations. In this work, we focused on active fractal structures with incorporated PIN diodes but the developed concept can be applied to a wide variety of fractals. The MS-GEC method deals with fractal-shaped objects as a set of scale levels. The processing is done gradually, one scale at each step, from the lowest scale till the highest one. To compute the input impedance of fractal-shaped structures using the MS-GEC method, we demonstrated that the input impedance of any scale level is generated from the input impedance of the previous scale level. When the iteration of fractal tends toward infinity, the structure contains an unknown number of levels. Since the atomic level cannot be defined, a critical point is reached limiting then the scope of the MS-GEC and of the existing classical methods. Based on RGT concepts, if the relation between the input impedances of two consecutive levels can be rewritten independently of the critical parameter (which is in our case the scale level), a transformation called "renormalization group" is generated. Consequently, the input impedance of the infinite active fractal structure approaches the fixed point of the defined transformation independently of the system details at the atomic level. The MS-GEC method combined to the RGT is a very powerful technique since it profits from the advantages (rapidity and reduced memory requirements) of the MS-GEC method and from the ability of the RGT to solve problems at their critical point.

Present study examines biological effects of 2.45 GHz microwave radiation in Parkes strain mice. Forty-day-old mice were exposed to CW (continuous wave) microwave radiation (2 h/day for 30 days). Locomotor activity was recorded on running wheel for 12 days prior to microwave exposure (pre-exposure), 7 days during the first week of exposure (short-term exposure) and another 7-day spell during the last week of the 30-day exposure period (long-term exposure). Morris water maze test was performed from 17th to 22nd day of exposure. At the termination of the exposure, blood was processed for hematological parameters, brain for comet assay, epididymis for sperm count and motility and serum for SGOT (serum glutamate oxaloacetate transaminase) and SGPT (serum glutamate pyruvate transaminase). The results show that long-term radiation-exposed group exhibited a positive y (phase angle difference) for the onset of activity with reference to lights-off timing and most of the activity occurred within the light fraction of the LD (light: dark) cycle. Microwave radiation caused an increase in erythrocyte and leukocyte counts, a significant DNA single strand break in brain cells and the loss of spatial memory in mice. This report for the first time provides experimental evidence that continuous exposure to low intensity microwave radiation may have an adverse effect on the brain function by altering circadian system and rate of DNA damage.

This paper presents an effective analysis method for EBG reducing patch antenna coupling. A couple of coaxial probes are used to analyze the mutual coupling reduction range of patch antenna arrays loaded with EBG in this method. Conventional FDTD/PBC algorithm for EBG structures is appropriate only in infinite ground plane and substrate. The gained frequency band-gap by using the algorithm can not be directly used in finite ground plane because of the edge effects. While the proposed coaxial probe method is valid not only in infinite ground plane and substrate, but also for finite ground plane. The method is more suitable for real environments. In order to validate the described method, a two-element microstrip patch antenna array is fabricated and measured. The experimental results are in good agreement with the theoretical data obtained by using the proposed method.

In the field of High Frequency Surface Wave Radar (HFSWR), this paper deals with a study which determines the electric permittivity and conductivity values that a medium must hold to propagate a sole surface wave at its interface with air. Firstly, we demonstrate clearly the reason why the Zenneck Wave cannot be excited on sea surface. Kistovich decomposition is used for this purpose. Secondly, the reasoning is extended to identify electric permittivity and conductivity values that permit to excite a surface wave on an homogeneous medium. Finally, numerical validation is obtained by comparison with the analytic formulation of the field radiated by a vertical Hertzian dipole as it has been established by Norton.

An eye-shaped segmented (ESS) antenna is presented for ultra-high frequency (UHF) near-field radio frequency identification (RFID) applications. The proposed antenna shows in-phase current even though the perimeter of the eye-shaped loop is comparable to the operating wavelength. The ESS antenna is fabricated on a FR4 printed circuit board (PCB) and embedded in a metal cavity with an overall size of 250×180×50 mm³. The measured bandwidth is around 11MHz (860-871 MHz) under the condition of VSWR less than 2.0, which covers the Europe standard (865MHz-868MHz) and agrees well with the simulated results. Finally, as a reader antenna in the RFID system, the measured read distance and read width can achieve 16.1 cm and 8 cm, respectively. The ESS antenna is desirable for UHF near-field RFID reader applications.

This paper presents a novel pyramidal (EH) horn antenna based on Electromagnetic Band Gap structures (EBGs). The reported pyramidal woodpile-based horn antenna possesses a symmetrical radiation pattern and a wide operating frequency range. Such antennas can substitute metallic horns in certain circumstances, which is especially valuable for millimetre and THz devices. The principle of creating EH-horn antennas in the woodpile structure is explained in detail. In particular, this paper presents the design of a symmetrical woodpile EH-horn antenna operating at frequencies around 110 GHz. The reported antenna exhibits a wide operating bandwidth (more than 10%), while possessing high directivity and radiation efficiency equal to 16.35dBi and -0.55dB (88%) respectively.

This paper is devoted to a laser --- based diagnostic technique described as a method for solving an applied inverse problem in turbulent media using laser beam propagation. This problem consists of extracting local information about temperature fluctuations inside a hot turbulent jet of air, from the luminous photodiode trace produced by a laser beam, after having traversed the jet. A genetic algorithm is implemented in order to calculate the optimized laser beam directions corresponding to the whole luminous trace. An approximated ray equation which is proved from the geometrical optics is solved numerically by using those directions and enables to determine the variance of temperature fluctuations along the whole path of the laser beam. A good agreement coming from the comparison between the results obtained and the published experimental data proves the validity of the method.

In this paper, we investigate surface plasmon-polariton propagation at the interface of metal and magnetooptic dielectric semiinfinite layers where both layers are magnetized. Using magnetic group theory, we calculate scattering matrices for the waveguide sections with three orientations of dc magnetic field. Solving analytically the wave equation for the Voigt configuration, we obtain exact dispersion relation for this waveguide. Numerical examples show that the nonreciprocal phase shift between forward and backward waves can be increased significantly as compared with the case where only the magnetooptic dielectric layer is magnetized.

In this paper, a novel high selectivity dual-wideband microstrip bandpass filter (BPF) is proposed using two stub-loaded triple-mode stepped-impedance resonators (SIR) which are the same type but with different sizes. The SIR is formed by attaching one T-type open stub at the center plane and two identical short-circuited stubs symmetrically to stepped-impedance open microstrip line. And it can generate one odd mode approximatively determined by the stepped-impedance microstrip line and two even modes flexibly controlled by the loaded stubs. Either of the SIRs in this filter can not only separately generate one passband but also control the passband performance. Due to the intrinsic characteristics of the SIR, four transmission zeros can be created to improve the selectivity. A dual-wideband filter with the fractional bandwidth 14.9% for the first band from 3.09 GHz to 3.58 GHz and 10.2% for the second band from 4.99 GHz to 5.53 GHz is designed and fabricated. The filter is evaluated by experiment and simulation with good agreement.

The time domain modeling and simulation of electromagnetic (EM) waves interaction with nanodevices, at high spatial and time resolution, requires high computational power. For the first time, in this paper we present an effective implementation of the Hertzian Potential Formulation (HPF) on the Graphics Processing Units (GPUs), through the NVIDIA's CUDA (Compute Unified Device Architecture) programming model. It accelerates the nanodevice EM simulations at nanometer scale harnessing the massive parallelism of the GPU based systems. This study is useful for similar electromagnetic codes including the Finite Difference approaches. The results demonstrate that this GPU tool outperforms the CPU based HPF implementation, reaching a speedup from 30× to 70×.

A correlation spectroscopy (COSPEC) based on a multi-wavelength fiber laser is first proposed for the detection of gas concentration. The lasing wavelengths are selected to match several characteristic absorption peaks of the gas under test, and the gas concentration is easily measured by correlating it with the reference gas. The present method is immune from the instability of the light source and the influence of other gases. The concentration measurement of C₂H₂ is demonstrated in the experiment in its near-infrared dominant absorption region. The technique has prospects for simultaneous detection of multiple gases, and the measurement of mixed gases of C₂H₂ and CO₂ is also analyzed.

In this paper, design and fabrication of a quad-band microstrip bandpass filter (BPF) using multi-layered stepped impedance resonators (SIRs) structure is proposed. One pair of SIR on the top layer is designed to operate at the 1st and 3rd passbands (1.56/3.57 GHz), and the other pair is at 2nd and 4th passbands (2.42/5.23 GHz) by tuning the impedance and length ratios of the SIRs. In order to find the desired coupling location between the SIRs located on different layers and the input/output (I/O) lines, the voltage, current and power wave on the I/O lines are analyzed. It is verified that the proposed quad-band filter has good passband performances with an excellent isolation between adjacent bands for GPS, WLAN, and WiMAX applications.

This work deals with an exact solution of cylindrical wave equation for electromagnetic field in fractional dimensional space. The obtained fractional solution is a generalization of the cylindrical wave equation from integer dimensional space to a fractional dimensional space. The resulting theoretical framework can be used to study the phenomenon of electromagnetic wave propagation in any fractal media because fractal media can be described as an ordinary media in a fractional dimensional space. The classical results are recovered from fractional solution when integer dimensional space is considered.