The sequence of Schumann resonances is unique for each celestial body with an ionosphere, since these resonances are determined by the dimensions of the planet/satellite and the corresponding atmospheric conductivity profile. Detecting these frequencies in an atmosphere is a clear proof of electrical activity, since it implies the existence of an electromagnetic energy source, which is essential for their creation and maintenance. In this paper, an analysis procedure for extracting weak resonances from the responses of electromagnetic systems excited by electric discharges is shown. The procedure, based on analysis of the late-time system response, is first checked using an analytical function and later applied to the vertical electric field generated by the computational simulation of Earth's atmosphere using the TLM (Transmission Line Matrix) method in order to extract the weak Schumann resonances contained in this electric field component.

In this paper we will report on the optical performances of submicron planar lensless pixels arranged in the 2 x 2 Bayer cell configuration, the basic element of CMOS colour image sensors. The 2D microlens array placed in front of each pixel in commercial devices has been replaced by a 2D array of submicron holes realised on a thin metal film. Each pixel has been designed to present a lightpipe inside its structure acting as an optical waveguide that confines the light up to photodiode surface. This pixel design is fully compatible with large scale industry production since its fabrication involves only standard lithographic and etching procedures. Simulations of the light propagation inside the lensless pixel has been performed by using full 3D electromagnetic analysis. In this way it was possible to determine the optical performances of the Bayer cell in terms of the normalized optical efficiency and crosstalk effects between adjacent pixels that result to be up to 30% and a factor 10, respectively, better than those ones obtained for the microlens counterpart. The significant increase of the achievable values of the normalized optical efficiency and crosstalk can foresee the possibility to reduce the pixel size down to 1 μm, i.e., beyond the limit imposed by the diffraction effects arising in microlens equipped pixel.

This paper describes the use of the correlation maps in the Ground Penetrating Radar (GPR) for the detection of near surface objects. This method is based on the definition of bi-dimensional maps that describe the level and the nature of coherence between the received electromagnetic signals. The technique proposed provides the detection of objects, reducing the impact of the clutter and improving the image contrast by an appropriate combination of the information collected in the variance and time coherence of the received signals. The method has been tested in GPR developed by ourselves and described in detail. The implemented GPR system features a high dynamic vector network analyzer (VNA) and a mechanically scanned Vivaldi antenna; the scanning is bi-dimensional, so that A, B and C scans are available.

In this paper, a high selectivity quadruple-mode bandpass filter (BPF) with source-load coupling is proposed. This filter uses two short-circuited stubloaded stepped-impedance resonators (SIRs) which have the same type but different size. Two SIRs can generate four operating modes, which can be approximately adjusted individually. Owing to the special design of the filter, the coupling of two resonators is weak. In each resonator, the even-mode frequency can be flexibly controlled by changing the length of the short stub, whereas the odd-mode one remains stationary. Due to the source-load coupling, two transmission zeros are close to the cut-off frequencies of the passband, which leads to high selectivity. Simulated results show that central frequency is 2.27 GHz with 3-dB fractional bandwidth of 22.9%. The measured and simulated results are well complied with each other.

A compact ultra-wideband (UWB) bandpass filter (BPF) with simultaneous narrow notched band and out-of-band performance improvement is presented. The UWB BPF is built up using the hybrid microstrip and coplanar waveguide (CPW) structure. By employing split-ring resonator (SRR) defected on the lower plane, the narrow notched band was introduced. The center and bandwidth of the notched band can be controlled by adjusting the length and width of the SRRs. A novel cross-shape patch is constructed to implement transmission zeros in the upper out-of-band so as to suppress the spurious passband. The measured results show that insertion loss is less than 1.7 dB, the return loss is more than 13 dB and the variation of group delay is less than 0.2 ns. Furthermore, the width of narrow notched band is about 0.15 GHz and the attenuation is more than 18 dB at the center frequency of 5.76 GHz. The upper stopband is up to 15.2 GHz with rejection greater than 20 dB.

A design procedure for a dual-band CPW-fed linearly and circularly polarized (CP) antenna based on the L-shaped slot antenna is presented in this paper. The slot antenna and the feeding structure are fabricated on the same plane of the substrate so that circuit processes and position alignment can be simplified. By shortening the length of one arm of the L-slot, an additional mode with two orthogonal electrical fields with a phase difference of 90 degree is excited, so that the circularly polarized wave can also be excited. The enhancement of the resonant bandwidth is achieved by utilizing a stub-protruded feedline, adding one finger slit at the other arm slot, and tuning the dimension of the ground plane. A bandwidth of 22.0% (2.23-2.78 GHz) is achieved with an axial ratio < 3 dB for the optimized case.

While a radar target is illuminated under the condition of spherical wave, two-dimensional ISAR image can be obtained in near field, and the wavefront curvature must be compensated. A novel two-dimensional mathematical model is set up, and a 2D-ESPRIT super-resolution algorithm based on matrix pencil is applied to estimate the accurate locations of the scattering centers in near field. Numerical simulations are conducted in different distances as well as with different SNRs. It is proved that the method can revise the spherical wavefront curvature with a high accuracy. Finally, near field ISAR imaging experiments were done outdoor, and raw data were processed with this super-resolution method, which verify that 2D-ESPRIT algorithm based on matrix pencil can compensate the spherical wavefront curvature effectively in near field.

A generalized coupled-line circuit is introduced to construct a wide-stopband low-pass filter in this paper. This circuit configuration includes two-section coupled lines and a connected transmission-line stub. Due to the symmetry of this proposed structure, closed-form equations for scattering parameters are investigated. The transmission zeros and poles locations for different circuit parameters are discussed, and the corresponding design curves are given. For theoretical verifications, four typical numerical examples are designed, calculated and illustrated. Furthermore, two single-stage low-pass filters (LPF 1 and LPF 2) with the 1-dB cutoff frequencies of 0.72 GHz and 1.45 GHz are fabricated and measured. The implemented LPF2 has 19-dB stopband rejection in the range of 2.05 to 6.36 GHz. Finally, two LPF cells (LPF 1 and LPF 2) and an additional connected transmission line are used to construct a new two-stage low-pass filter (LPF 3) with extended stopband. The measured 16-dB stopband of LPF 3 is up to 7.5 GHz while the 1-dB passband range is from DC to 0.67 GHz. The advantages of this proposed low-pass filter are avoiding any lumped elements and compact layout structure.

The motivation behind fusing multimodality, multiresolution images is to create a single image with improved interpretability. In this paper, we propose a novel multimodality Medical Image Fusion (MIF) method, based on Ripplet Transform Type-I (RT) for spatially registered, multi-sensor, multi-resolution medical images. RT is a new Multi-scale Geometric Analysis (MGA) tool, capable of resolving two dimensional (2D) singularities and representing image edges more efficiently. The source medical images are first transformed by discrete RT (DRT). Different fusion rules are applied to the different subbands of the transformed images. Then inverse DRT (IDRT) is applied to the fused coefficients to get the fused image. The performance of the proposed scheme is evaluated by various quantitative measures like Mutual Information (MI), Spatial Frequency (SF), and Entropy (EN) etc. Visual and quantitative analysis shows, that the proposed technique performs better compared to fusion scheme based on Contourlet Transform (CNT).

In this paper we analyze the dependence of the resonance wavelength and mode formation of an optical gold nanorod antenna on its geometrical parameters in the wavelength range 500-1400 nm. In particular, we prove that nanoantennas differ from RF counterparts, since the minima and maxima, i.e., nodes and anti-nodes, of the resonant modes do not go to zero and show very intense peak at the corners due to non-negligible thickness. Moreover, FDTD simulations reveal that the usually considered linear relation between the resonant wavelength and the nanorod length has to be modified when the nanorod thickness is taken into account.

This paper considers adaptive array beamforming using signal cyclostationarity. Due to the effect of using finite data samples, there exists an estimation error in computing the weight vector required by performing cyclic beamforming. To deal with this problem, we formulate a cost function consisting of a posteriori information of the received signal and a priori information regarding the probabilistic distribution of the error. By minimizing the cost function, we obtain a weight vector with a diagonal loading data covariance matrix under a white Gaussian estimation error. An analytical solution for determining the loading factor is further derived. Simulation results for showing the effectiveness of the proposed method are provided.

A new design of dual-band antenna for DCS/ PCS/ UMTS/ WLAN/ WiMAX applications is proposed. Using two metamaterials omega-shaped structures, a good impedance matching the dual-band mode is obtained. The proposed prototype antenna is fabricated on a 1.5mm thick FR4 epoxy substrate with a relative dielectric permittivity ε_r= 4.4, and loss tangent tanσ = 0.02. Good monopole-like radiation patterns and antenna gains over the operating bands have also been observed. Effects of each omega particle on the antenna performance and their coupling are all examined and discussed.

To improve the impaired azimuth resolution of the novel Terrain Observation by Progressive Scans (TOPS) mode, a new multi-channel single phase center multiple beam (SPCMB) TOPS mode is proposed in this paper for high-resolution wide-swath (HRWS) imaging. However, the progressive azimuth beam scanning leads to the Doppler spectrum aliasing and both beam center time and Doppler centroid varying with the target's azimuth location. Challenges may arise for processing the SPCMB-TOPS SAR data from these problems. In this paper, an efficient full aperture imaging approach is proposed to process the raw data. The sketch of the proposed imaging approach is described in detail. Simulation results of point targets validate the proposed imaging approach.

The mutual conversion of the TM_mn and TE_mn waves (m, n ≠ 0) in periodic and aperiodic (fractal-like) stratified waveguide structures composed of dense metal-strip gratings is studied. The stopbands and passbands conditions of Bloch waves, the reflection and transmission spectra of the periodic structure are examined versus the gratings parameters. Peculiarities of the wave localization, selfsimilarity and scalability of both reflected and transmitted spectra of the fractal-like structure are investigated. The appearance of additional peak multiplets in stopbands is revealed and a correlation of their properties with the parameter of grating filling is established.

The present paper is a work on fluorescent tube performing the function of a monopole plasma antenna. In the construction, the needed power supply to the fluorescent tube is controlled by an IC 555 timer. In the experiments the supply frequency varies from 25 Hz to 200 Hz. By using a vector network analyzer it is shown that the persistence of plasma developed inside the tube persists for longer duration with increase in supply frequency. It is also found that the stability of resonant frequency increases with the increase in frequency of the AC power supply measured up to 200 Hz. Result shows that the effective part of a fluorescent tube functioning as Monopole plasma antenna is about 60% of the total length of the tube.

In this paper, we have proposed a shell type dielectric microsphere resonator in order to enhance its quality factor. In this work we have assumed that the radius of dielectric microsphere is 12 μm and that the interior metal layer radius is 11.5 μm. We have obtained analytic equations for Vector potentials, characteristic equation, quality factor, resonance frequency and resonance location of TE modes. We have plotted these characteristics by MATLAB software and compared them with the normal microsphere characteristics.

A novel bandpass filter design method of achieving different selectivity based on E-shaped dual-mode resonator is presented. The characteristic of the E-shaped dual-mode resonator is investigated. The technique of utilizing capacitive and inductive input-output cross-coupling to generate two adjustable transmission zeros at stopband is explored intensively. Advantages of this type of filter are not only its dual-mode resonator and miniaturization, but also its controllable transmission zeros. The coupling scheme is presented to model the operations of these filters. Four dual-mode microstrip BPFs have been designed, fabricated, and measured. Both the simulated and measured results are presented. The exemplary filters verify the feasibility of the new design method.

The feasibility of designing a compact-size beam-switching dielectric lens antenna (DLA) with improved angular (scanning) characteristics is investigated numerically using inhouse software based on the Muller boundary integral equations and hybrid genetic algorithm. It is demonstrated that joint optimization of the lens shape and feeding array parameters enables one to minimize the directivity degradation for off-axis feeds which is a well-known drawback of conventional extended hemielliptic DLAs fed by focal arrays. The key to success is found in proper shaping the lens profile and using arrays of non-identical feeds.

A planar W-band single balanced mixer is designed and measured in this paper. This mixer is realized by using two novel IF-block, a rat-race ring with the fifth port, two beamlead GaAs Schottky diodes and two RF chokes. The novel IF-block which designed the first time in W-band is employed to provide reflection points for IF signal and to provide low loss path in wide bandwidth for the RF and LO signals. To our knowledge, the mixer shows the best conversion loss at 95\,GHz and the highest 1\,dB power compression (P_-1dB) point among the W-band planar hybrid microwave integrated circuit (HMIC) mixers.

By means of a three-step linear optical transformation method, material parameters of a three-dimensional diamond-shaped electromagnetic concentrator composed of tetrahedral homogeneous blocks has been derived in this paper. The performance of the concentrator has been confirmed by full-wave simulation. The designed concentrator can operate in a wide bandwidth due to the line transformation. It represents an important progress towards the practical realization of the metamaterial-assisted concentrator.