In this paper, the ICA (independent component analysis) technique is applied to PCA (principal component analysis) based radar target recognition. The goal is to identify the similarity between the unknown and known targets. The RCS (radar cross section) signals are collected and then processed to serve as the features for target recognition. Initially, the RCS data from targets are collected by angular-diversity technique, i.e., are observed in directions of different elevation and azimuth angles. These RCS data are first processed by the PCA technique to reduce noise, and then further processed by the ICA technique for reliable discrimination. Finally, the identification of targets will be performed by comparing features in the ICA space. The noise effects are also taken into consideration in this study. Simulation results show that the recognition scheme with ICA processing has better ability to discriminate features and to tolerate noises than those without ICA processing. The ICA technique is inherently an approach of high-order statistics and can extract much important information about radar target recognition. This property will make the proposed recognition scheme accurate and reliable. This study will be helpful to many applications of radar target recognition.

In order to enhance the accuracy of the complex permittivity data employed in Ground Penetrating Radar (GPR) techniques, an adaptive cavity setup is presented. The use of moveable walls permits to relax the mechanical constraints on the sample dimensions so that it can be employed also in complicate measurement condition as, for example, in the case of wet samples. Moreover, exploiting the cavity resonance phenomenon, low loss materials, such as some type of marbles, can be accurately evaluated. The numerical characterization, the parametric analyses and the L-band measurement results show the validity and the reliability of this configuration.

In this paper, synthesis of superconducting circular antennas mounted on circular array is designed by the combination of a method based on particle swarm and full-wave method. Full-wave method is used for computing the resonant frequency, the bandwidth, radiation pattern and efficiency of a perfectly superconducting, or an imperfectly conducting circular microstrip, which is printed on isotropic or uniaxial anisotropic substrate. Particle Swarm Optimization (PSO) has been used to obtain the minimum side lobe level (SLL) of circular array, by varying element excitations and/or positions. Numerical results concerning the effect of the parameters of substrate and superconducting patch on the antenna performance are presented and discussed. It is found that superconducting circular antenna could give high efficiency. Also, results show the efficiency of PSO in producing desired radiation characteristics and are in good agreement with previously published data.

Radio astronomy has a wide electromagnetic spectrum. It is based on antennas, electronics, software etc., and thus highly technical. The radio data obtained from distant objects like stars, galaxies, pulsars etc. are useful for studying the Universe. Many of the radio emissions, especially from the Sun have been studied over decades for understanding the ionosphere and its effects on radio communication. Untill now, this subject of radio astronomy has found its existence among those who are associated with astronomy and possessing at least some knowledge of RF engineering. A requirement of a review literature on this subject with technical details is felt by many working engineers and scientists. It is thus proposed to write a series of articles covering the subject from both engineering and scientific angles. This paper is the first of this series. It focusses on the foundation of this subject and briefly describes the supersynthesis technique. Overview of various concepts like cosmic radio signals, continuum, synchrotron emission etc., general instrumentation for radio astronomy, imaging techniques and radio interference have have been presented.

Solidification of pure aluminum without and with a magnetic field has been investigated by differential thermal analysis (DTA). DTA curves showed that the nucleation temperature of pure aluminum was decreased as a magnetic field strength increased although its melting process was almost not influenced. The nucleation suppression could be attributed to the increase of the solid-liquid interfacial energy which might originate from more orderly arrangement of atoms on the solid-liquid interface upon applying a magnetic field.

In this paper, we present a novel method to design a microstrip bandpass filter (BPF) with high selectivity and upper rejection band. The proposed coupling structure mainly composes of half-wavelength input/output (I/O) microstript lines and open-loop ring resonators. By properly selecting the coupling position between the I/O lines and resonators, the spurious response of the BPF can be well suppressed. A filter example centered at 2.4 GHz achieves a high band selectivity and a wide upper-stopband rejection greater than 20 dB from 2.7 to 6 GHz. Experimental results show a good agreement with the simulated ones.

An efficient approach called general sparse matrix canonical grid (G-SMCG) method is proposed to analyze the electromagnetic scattering from 2-D dielectric rough surface with a conducting object partially buried. In this paper, the scattering of 3-D arbitrarily shaped object is computed by using the traditional method of moments (MoM)with RWG basis function, and the scattering of rough surface is analyzed by using the SMCG method. The coupling interactions between an object and rough surface are calculated by iterative method. Combing the ocean rough surface with Pierson Moskowitz (PM) spectrum, the bistatic scattering coefficients of typical objects buried in the ocean surface have been computed by using the proposed method. Then the accuracy and efficiency of this method are discussed. Finally, the bistatic scattering coefficients of a ship located on ocean surface are calculated, and the influence of sea state and wind direction on the scattering coefficients is indicated.

Here we present the rigorous electrodynamical solution of diffraction problem about the microwave scattering by a multilayered cylinder. The number and thickness of layers is not limited. We offer the solution when the central core of multilayered cylinder can be made of different isotropic materials as a metamaterial, a ceramic matter or a semiconductor as well as of a perfect metal. The isotropic coated layers can be of strongly lossy materials. The signs of the complex permittivity and the complex permeability can be negative or positive in different combinations. Here we present dependencies of the scattered power of the incident perpendicularly and parallel polarized microwaves by the metamaterial-glass cylinder on signs of metamaterial permittivity as well as permeability. Here are also presented the glass layer absorbed power and the metamaterial core absorbed power dependent on the hypothetic metamaterial permittivity and permeability signs at the wide range frequencies 1-120 GHz. The metamaterial core of cylinder has a radius equal to 0.0018 m and the thickness of the coated acrylic-glass layer is 0.0002 m. We have found some conditions when the scattered-power has minimal values and the absorbed power by the coated acrylic glass layer is constant in a very wide frequency range. We have discovered that the glass layer absorbed power decreases with increasing of the frequency at the range 1-120 GHz for both microwave polarizations.

Utilization of wearable textile materials for the development of microstrip antenna segment has been rapid due to the recent miniaturization of wireless devices. A wearable antenna is meant to be a part of the clothing used for communication purposes, which includes tracking and navigation, mobile computing and public safety. This paper describes design and development of four rectangular patch antennas employing different varieties of cotton and polyester clothing for on-body wireless communications in the 2.45 GHz WLAN band. The impedance and radiation characteristics are determined experimentally when the antennas are kept in flat position. The performance deterioration of a wearable antenna is analyzed under bent conditions too to check compatibility with wearable applications. Results demonstrate the suitability of these patch antennas for on-body wireless communications.

This paper presents a coplanar composite right-left handed zeroth-order resonator (CRLH CPW ZOR) and a coplanar composite right-left handed transmission line (CRLH CPW TL). These devices are realized using an elementary cell designed in a coplanar waveguide configuration on alumina substrate. Additional lumped elements are carried out with an interdigital series capacitor and a short-circuited stub inductor as a shunt. The CRLH CPW ZOR is fabricated and analyzed using equivalent circuit modeling and three dimensional finite element method. The proposed devices are fabricated and measured. The resonator has a measured insertion loss of 2.7 dB and a return loss better than 13dB. The length of the proposed device is only 5.2 mm; this very small size compared with a traditional half wave resonator shows the interest of this kind of approach.

A new circularly-polarized (CP) sleeve antenna fed by a CPW for DTV signal reception applications is presented in this paper. The CPW-fed sleeve monopole antenna consists of square loop sleeve, CPW-fed and complementary SIR radiators. The lower and upper resonance frequencies of the desired band are controlled by the complementary SIR arms, making designs of the wide-band antenna very easy. To demonstrate the idea, the proposed antenna was designed at the band with 470-863 GHz (BW=393 MHz, 58.9%) for DTV UHF-bands. The antenna gains are varied about 2.2 to 4.0 dBi. An omnidirectional radiation property is also shown. The CP operation for the proposed design can be achieved by properly adjusting the asymmetrical radiators. The reflection coefficient, axial ratio, radiation pattern and gain of the proposed antenna were studied, and reasonable agreement between the simulated and measured results was obtained.

In this paper, direction of arrival (DOA) algorithms for Frequency Modulated (FM) point source have been implemented over a real time system. The source was a commercial FM radio station broadcasting at 89 MHz. Experiments were carried out in order to determine the location of a FM transmitter using spectral and sub-space algorithms. The complete Radio Frequency (RF) front end and Uniform Linear Array (ULA) of dipole antennas were designed at 98 MHz having bandwidth of 20 MHz covering the complete FM band. The estimated DOAs are in close agreement to each other.

In this paper, a simple method and structure to design a dual-band bandpass filter (BPF) by using a dual feeding structure and embedded uniform impedance resonator (UIR) is presented. In this structure, two passbands can be designed individually and several transmission zeros can be created to improve the band selectivity and stopband performance. The first passband is determined by the dual feeding structure and the second passband is determined by the UIR. Moreover, by using the inter coupling in the UIR, the performance of the second passband can be easily tuned without degrading the first passband. In order to verify the design concept, two filter examples, including 0.9/1.575 GHz for multi-services communication and 2.4/5.7 GHz for wireless local area network (WLAN), are designed in this study. Experimental results of the fabricated samples show a good agreement with the simulated results.

This paper discusses for the first time the combined optoelectronic-electromagnetic modelling of a new technology that represents a paradigm shift in the way millimetre-wave and terahertz electronics can be implemented using the REconfigurable Terahertz INtegrated Architecture (RETINA) concept. Instead of having traditional metal-pipe rectangular waveguide structures with metal sidewalls, RETINA structures have photo-induced virtual sidewalls within a high resistivity silicon substrate. This new class of substrate integrated waveguide (SIW) technology allows individual components to be made tuneable and subsystems to be reconfigurable, by changing light source patterns. Detailed optoelectronic modelling strategies for the generation of virtual sidewalls and their electromagnetic interactions are presented in detail for the first time. It is found with double-sided illuminated RETINA structures that an insertion loss of 1.3 dB/ λ_g at 300 GHz is predicted for the dominant TE₁₀ mode and for a cavity resonator a Q-factor of 4 at 173 GHz is predicted for the TE₁₀₁ mode. While predicted losses are currently greater than other non-tuneable/reconfigurable SIW technologies, there is a wide range of techniques that can improve their performance, while still allowing completely arbitrary topologies to be defined in the x-z plane. For this reason, it is believed that this technology could have a profound impact on the future of millimetre-wave and terahertz electronics. As a result, this paper could be of interest to research groups that have the specialised experimental resources to implement practical demonstrator exemplars.

The purpose of this paper is to provide some further observations on the use of reverberation chambers to imitate real wireless channels. It is shown, that when RMS delay spread is calculated appropriate threshold has to be chosen. Based on the threshold value the required dynamics of measurements performed for realistic wireless channels can be estimated. It is also shown, that the reverberation chamber loading method allows only for representing outdoor channels.

We numerically compare the mode birefringence and confinement loss with four patterns of index-guiding photonic crystal fibers (PCF) using the finite element method. These PCFs are composed of a solid silica core surrounded by different sizes of elliptical air holes and a cladding which consist of the same elliptical air holes in fiber cladding with tetragonal lattice. The maximal modal birefringence and lowest confinement loss of our proposed case A structure at the excitation wavelength of λ=1550 nm can be achieved at a magnitude of 5.3×10^-2 (which is the highest value to our knowledge) and less than 0.051 dB/km (an acceptable value less than 0.1 dB/km) with only four rings of air holes in fiber cladding, respectively. The merit of our designed PCFs is that the birefringence and confinement loss can be easily controlled by turning the pitch (hole to hole spacing) of elliptical air holes in PCF cladding.

A new type of miniaturized stepped impedance resonator (SIR) for bandpass filter applications is proposed in this paper. The new resonator incorporates a ground plane window with a floating conductor in the backside of the substrate. The ground plane window increase the characteristic impedance of the lines used to implement the inductive region of the quasi-lumped resonator, thus allowing some size reduction. Moreover, the presence of a floating conducting patch printed below the capacitive region of the resonator pushes up the first spurious band of the filter. A meaningful improvement of its out-of-band rejection level is then achieved. The coupling between adjacent resonators is also enhanced thus leading to wider achievable bandwidths. Some filter designs using the new resonator and other standard resonators are included for comparison purposes.

This paper proposes a metamaterial reflective surface (MRS) as a superstrate for a single-feed circularly polarized microstrip patch antenna (SFCP-MPA). It illustrates a simultaneous enhancement on antenna gain, impedance bandwidth (ZBW) and axial-ratio bandwidth (ARBW) by adding the MRS atop the SFCP-MPA. The MRS can enhance the ZBW and ARBW by 3.5 and 9.9 times, respectively, compared to the circularly polarized patch source. Moreover, the gain of the CP-MPA with the MRS is 7 dB higher than that of the conventional CP-MPA. The small spacing between the MRS and patch source is another merit in the present design, which is as low as λ_o/16 as it results in a low-profile antenna design that well suits modern wireless communications.

In this paper, a new simple design procedure of multi-frequency unequal split Wilkinson power dividers (WPDs) is presented. The procedure is based on using N-sections of transmission line transformers, instead of the conventional quarter-wave WPD branches, to realize a WPD that operates at N frequencies. Good isolation is achieved by using lumped resistors without any extra modification to the conventional structure of WPDs. The analysis, design procedure, and mathematical expressions are presented for arbitrary design frequencies, and arbitrary power split ratio. For verification purposes, a 1:2 dual-frequency, a 1:2 tri-frequency, and a 1:2 quad-frequency WPDs are designed and fabricated. The measured results show good agreement with those obtained using the presented design methodology and with full-wave simulated results.

To measure the phase of signal with very high working frequency such as THz, and optics band is still a challenging problem. In this paper, based on the relationship between radiating current and measured intensity of electrical field a novel phase retrieval algorithm has been developed. As opposed to the existing approaches of phase retrieval where usually the Fourier coefficients of measured data will be firstly reconstructed, the proposed approach is to reconstruct the so-called radiating currents, with more physical meaning than the former. It has a much smaller number of freedoms of radiating current than that of measurements, which means that the obtained equations are over-determined. Thus one can efficiently model the intensity of measured electric field via the radiating part, and reconstruct it quickly and stably. The novelty is that this physical consideration 1) leads to efficiently avoiding false solutions due to the ill-posedness of phase retrieval problem, and 2) offers a good initial guess for inverse scattering based imaging algorisms. Importantly, a closed-form formulation of phase retrieve also has been derived when the intensity of incident wave is much stronger than one of the scattered wave, for example, for the weak scattering objects. Finally, several numerical experiments are provided to show the high performance of proposed algorithm.