The present work is devoted to the clarification of the conditions necessary for step-by-step justification of the possibility of reduction of the homogeneous system of linear algebraic equations for the spectral problems of 2-D photonic crystals by the plane waves method. The issues related to the algorithms and the numerical solutions of these spectral problems are analyzed. The possibility of analytical regularization is investigated, and the ways to improve the convergence of the obtained results are identified.

This paper addresses the CFAR target detection in FM-based passive bistatic radars as a composite hypothesis testing problem, using the mixed signal model. The corresponding generalized likelihood ratio test (GLRT) is derived. It has less computational requirements with respect to the conventional GLRT-based detector, previously developed in the literature, due to the decrease in the row dimension of the interference matrix. The proposed detector is computationally efficient for tracking or short-range-radar applications in which a few range cells are surveyed. The theoretical and simulation-based analysis of detection performances and a thorough discussion on the computational complexity compared with that of the existing detectors are also provided.

A portable radio transceiver with rubber ducky antenna emitting at 446 MHz with an output power of 5 W was considered as near-field source of electric (E) and magnetic (H) field components when being used in the proximity of the user's face. By taking into account the significant content of ferromagnetic nanoparticles recently identified to reside in the human brain, we assessed the specific absorption rate (SAR) of energy deposition due to H-component penetrating a presumptive forebrain. H-component SAR contribution to the total SAR is for the first time estimated in such a case, based on an original idea inspired from knowledge on magnetic fluids hyperthermia.

In order to improve the focusing and imaging effects of conventional spiral zone plates (SZPs), we design a new type of spiral photon sieve (SPSs) apodized by a robust Bessel-like window. The design principle and numerical simulation results show that the Bessel-like window has a better modulation effect on the main lobe compression and side suppression of the point spread function (PSF) than other traditional window. Taking advantage of the robustness of Bessel-like windows, the proposed SPS can achieve a higher spatial resolution and lower side lobe noise than the conventional SPS and SZP. The practical effects have also been demonstrated by image experiments on the micropore. Our work may find some potential applications in laser alignment, optical trapping, optical communication and edge enhancement imaging fields.

In this paper, a novel W-band substrate integrated waveguide (SIW) power combiner/divider is analyzed theoretically and demonstrated experimentally/numerically, based on the antipodal fin-line SIW-rectangular waveguide (SIW-RW) transition and longitudinal slot coupling techniques. This antipodal fin-line SIW-RW transition can work at the frequency band of 86.4 GHz-106.1 GHz with return loss larger than 15 dB and inserting loss less than 2 dB. By combining the antipodal fin-line SIW-RW into the four-way longitudinal-slot SIW coupling structure, a novel back-to-back power dividing/combining system is achieved, which can operate at the frequency band of 92.8 GHz-93.8 GHz with return loss more than 10 dB and insertion loss less than 3.9 dB. Such a design can be used in future for spatial power amplifier applications.

A novel concept of using slotted ground structure and a single circular split ring resonator (SRR) to achieve multiband operation from a miniaturized UWB antenna is presented in this paper. Initially a miniaturized volkswagen logo ultawideband (UWB) antenna having -10 dB impedance bandwidth of about 124% (2.9-12.4 GHz) in simulation and 116.7% (3.1-11.8 GHz) under measurement is designed. This miniaturization leads to about 10% increment in -10 dB reflection coefficient bandwidth and about 66.71% reduction in volume of the proposed UWB antenna as compared to the conventional circular antenna. In order to reconfigure the proposed UWB antenna to operate it at 1.5 (GPS), 3.5 (WiMAX), 5.2 and 5.8 GHz (WLAN) frequency bands, slotted ground structure with metamaterial is used. The proposed metamaterial is a circular split ring resonator (SRR) consisting of single circular ring and is placed on the slotted ground structure of the proposed antenna to achieve 1.5 GHz band. The proposed configuration has a volume of 0.290λ₀×0.290λ₀×0.015λ₀ (30×30×1.6 mm³) at lower resonating band of 2.9 GHz and is fabricated on a widely available FR4 substrate with a loss tangent of 0.02 and dielectric constant of 4.4. Simulated and experimental results shows that the proposed design yields S₁₁<-10 dB at the targeted frequencies. Good impedance matching, stable radiation characteristics with cross-polarization level less than -15 dB (both in E and H planes), VSWR<2, average gain of 3.09 dBi and radiation efficiency of more than 85% are observed at the designed band when the antenna is fabricated and tested.

A compact microstrip lowpass filter with ultra-wide stopband characteristics and high suppression level is presented. To achieve compact size and wide stopband suppression along with improved impedance matching, symmetrically loaded resonant patches, open stubs and stair shaped high impedance stub is introduced in the filter. The measurement results show good agreement with the simulations. The 3 dB cutoff frequency of the filter is 2.44 GHz. The stopband with attenuation level better than 22 dB is extended from 2.84 GHz to 16 GHz, hence an ultra wide stopband with 6th harmonic suppression is achieved. The proposed filter has low insertion loss and high return loss in the passband, together with compact size of 0.257λ_gx0.148λ_g, where λ_g is the guided wavelength at cutoff frequency. The relative stop bandwidth of the proposed design is identified to be 139.5%.

A novel compact unidirectional UWB antenna is presented in this paper. First a novel planar omnidirectional UWB antenna with CPW-feed is designed. The antenna is composed of a half-elliptical disc with a small ground plane. A slot is inserted on the patch as a novel technique to improve the gain bandwidth of the antenna at higher frequencies is presented. The omnidirectional antenna shows UWB matching and gain bandwidth of 2 GHz to 6.5 GHz. Furthermore, to make the radiation pattern of the omnidirectional antenna unidirectional, a rectangular shape metallic reflector without bottom wall is used on the backside of the antenna. The unidirectional antenna with a total dimension of 0.52λ_m x 0.33λ_m x 0.18λ_m (λ_m wavelength of the minimum operating frequency) has a matching bandwidth of 1.5 GHz to 7.7 GHz with a gain of 5 dBi to 10.2 dBi over 1.7 GHz to 6.5 GHz, and flat group delays of less than 1 nsec. To validate the proposed design, the antenna is fabricated, and measured results are compared with simulations.

A modified star-shaped dual-mode microstrip loop resonator with a triangular patch is proposed to design compact narrow band bandpass filters with transmission zeros. The triangular patch is used as perturbation element to couple degenerated modes. The position of transmission zeros can be tuned by varying the size and location of the perturbation element. The coupling mechanism (inductive or capacitive) and the type of input/output feed (orthogonal or non-orthogonal) determine the type of filter response like symmetric or asymmetric. Three highly selective two-pole narrow band bandpass filters are designed using a modified star-shaped resonator with tunable transmission zeros. First, two filters with non-orthogonal feed lines have an asymmetric response with transmission zeros on one side of the passband, whereas the third filter with orthogonal feed lines exhibits symmetric frequency response with transmission zeros on both sides of the passband. Even and odd mode analysis is applied to the dual mode filters to calculate the position of transmission zeros. Filters are realized using a low loss dielectric substrate, and measured results are in good agreement with the theoretical and simulated ones.

A sharply rejected dual notch band UWB monopole antenna is presented in this paper. The proposed antenna consists of maple leaf shaped radiating element, a 50 Ω microstrip feed line and truncated ground plane. The proposed antenna shows the UWB operation in the frequency range (1.7 GHz-11.1 GHz) with VSWR<2 except the notch bands and two band notches centered at 4.3 GHz and 7.7 GHz. The band notches are achieved by introducing a meandered slot in the radiating element and U-shaped slot in feed line. The substrate used for designing of UWB antenna is low loss Rogers 5880 having relative permittivity of 2.2. The novelty of the proposed antenna is its shape and ability to support UWB bandwidth requirements, and it also rejects two bands to avoid possible interference with existing communication system. Good agreement between the simulated and measured results is observed. The proposed antenna has good gain and efficiency at pass bands.

We introduce a 212 GHz LO source which could be used to drive sub-harmonic mixer in the radiometer front-end. It mainly includes a phase-locked dielectric resonator, a 71 GHz power source and a 212 GHz tripler. Actually, design of 212 GHz tripler is the key technology in the LO chain because the research on W band source is relatively mature. Based on our former research work, there is a great improvement in the design of 212 GHz tripler. At room temperature, the measured efficiency is more than 9% in 208~218 GHz, and the maximum efficiency is about 14.5% at 215.5 GHz when being driven with 21.8 dBm of input power. Besides demand on the main technical specifications, the stability of each module is also extremely important since the front-end is designed to keep working for three months.

This paper presents the effect of solar illumination on the differential potential generated on the surfaces of spacecraft body in space. Two geometrical cases are considered: 1) Cylindrical symmetry and 2) Tilted metallic plates forming an angle with the adjacent side. The capacitance required for estimation of the body potential is computed by Method of Moment. Nonuniform triangular meshing is used for both the geometrical structures. The differential potential generated on surfaces of a geometrical body due to photoelectric effect results in electrostatic discharge. In the case of the tilted plates, the differential potential at various tilt-angles is computed along with the capacitance computation. In the case of the cylindrical object, the estimation of potential at the day-night interface is shown. The variation in the potential for different incident angles of the solar photons and the changing (h/r) ratio is analyzed. The validity of the analysis is established with that obtained in open literature.

A new approach for position and shape reconstruction of both penetrable and impenetrable objects from the measurements of the scattered fields is introduced and described. The approach takes advantage of the fact that for perfect electric conductors the induced currents are localized on the boundary, and equivalent sources also placed on the surface of the scatterers can be considered in the case of dielectric targets by virtue of the equivalence theorem. Starting from these considerations, a new inversion approach is formulated in order to retrieve the location and the boundary of unknown objects. Examples with both numerical and experimental data are given to demonstrate and assess the effectiveness of the method.

Every generation of mobile communication has been associated with higher data rates than the previous generation. So 5G new spectrum radio access should support data rates exceeding 10 Gbps in most of its applications. An Ultra Wide Band (UWB) ultrahigh data rate full six-port receiver architecture up to 6.7 Gbps for 5G new spectrum is presented in this paper. The proposed structure is constructed using one UWB ultrahigh data rate Wilkinson power divider/combiner and three UWB ultrahigh data rate two-stage branch line couplers which are the essential components of any full six-port structure. The design procedure, optimization and implementation of these two UWB essential components in 21-30 GHz are completely done to achieve the optimum performance of final six-port. The final fabrication results show the average of -14 dB of input matching, -20 dB of isolation of isolated Ports, -4.2 dB of coupling in output ports (considering 2 SMA connectors and transitions in each path), and linear phase variation of outputs in the whole bandwidth of 21-30 GHz. To analyze and qualify the UWB six-port structure in any specific application in 5G and other UWB high data rate applications, a new analytical formulation with a new six-port structure of non-ideal UWB six-port circuit is presented. With this new analytical model and new configuration, there is no need to calibrate the outputs of in-phase and quad phase of the six-port receiver outputs. Based on the final fabricated essential components and the new analytical model, the final full six-port structure is constructed and analysed using UWB-OFDM with QPSK and 16QAM demodulation schemes in its sub-bands. To complete and verify the new analysis and to validate the final constructed UWB six-port structure and its essential components in ultrahigh data rate application in 5G new spectrum, the UWB-IR impulse radio with modulated ultrahigh data rate signal up to 7 Gbps and in 21-30 GHz bandwidth is completely discussed. The results show that all clusters of demodulated constellations are very well positioned and individualized in whole bandwidth in all modulation schemes. Also this new design and configuration of six-port receiver improves the dynamic range of the RF input signals up to 60 dB which is valuable. During the design procedure, a very useful method to choose the suitable laminate based on the time, frequency and two dimensional Wigner-Vile Distribution methods is presented. Also, some practical issues in design and implementation of the UWB microstrip component such as transitions are considered to achieve the best results.

In this paper, a 2 x 1 duplex antenna array with small frequency space and high isolation between transmitting and receiving bands is presented. The duplex antenna array element consists of a pair of radiating patches for bidirectional radiation, a set of microstrip resonator and H-slot resonator coupled to the patches for transmitting, and the other set of microstrip and H-slot resonators coupled to the patches for receiving. The H slots are designed for the operations of coupling and the elements of the bandpass filters. The two antenna elements of the 2 x 1 array are connected by transmitting and receiving channels microstrip power-split resonators. The array achieves a compact size and high performances in terms of high isolation and small Tx-Rx frequency space. Higher than 30 dB and 40 dB ports isolation at 1.94-1.99 GHz and 2.43-2.52 GHz is realized. And the Tx-Rx frequency space Δf=(f_r-f_t) is smaller than 0.23 times of the central frequency (f_r+f_t)/2.

This paper presents the design of a compact E-plane waveguide diplexer with wide stopband characteristics of high rejection level. This is achieved by utilizing a unique E-plane waveguide filter comprising rectangular apertures located along the waveguide's E-plane. The upper and lower sections of the aperture in the septum insert have periodic comb-like ridges. The effect of the septum is (i) to slow the propagating wave that helps to reduce the filter's size, and (ii) widens its stopband property. Dimensions of the periodic ridges of the aperture enable the center frequency of the filter to be controlled without compromising its bandwidth. In addition, the proposed E-plane waveguide filter provides a high isolation between the two diplexer channels, which is necessary to prevent significant cross-talk between the channels. The performance of the proposed design was verified through measurements. There is excellent agreement between the simulated and experimental results.

In this paper, an effective numerical method based on a new surface impedance model is applied to the accurate calculation of the radar cross section of lossy conducting targets. The problem of determining the scattered electromagnetic fields from rectangular lossy conducting strips is presented and treated in detail. This problem is modeled by the method of moments to resolve integral equations of the first kind of surface current density with an accurate choice of basis and test functions. The illustrative computation results of complex surface impedance, surface current density and radar cross section are given for several cases. The accuracy of the method presented in this paper is verified by comparison with other methods, including the general-purpose full-wave simulators HFSS and CST.

Soliton solutions of a cubic-quintic Ginzburg-Landau equation (CQGLE) are computed and analyzed on a parametric plane, specifically across the transitional zones that separate regions associated with different types of solitons. The transformations of behaviors in these transitional zones between stationary and pulsating regions are characterized by the total pulse energy and its maximum value. It is also found that the initial pulse waveform has little effect on bifurcation and the valid range of initial amplitude.

An electrically small half-loop antenna (ESHLA) embedded with Foster elements is analyzed using the characteristic mode (CM) theory. The resonant frequency and radiation characteristics of the ESHLA are mainly determined by the resonant mode (Mode 1). The characteristic currents of resonant mode (Mode 1) and non-resonant mode (higher order mode) prove the parallel resonance of the ESHLA. However, owing to the modal significance (MS) of the resonant mode varying fast with frequency, the proposed ESHLA has a narrow bandwidth. Analysis shows the MS of the resonant mode and the higher order mode are changed by tuning the Foster element, leading to a negative admittance variation slope in accordance with the non-Foster behavior. By replacing the Foster capacitor with the non-Foster network, both the characteristic currents and the MS are changed over a wide bandwidth. As a consequence, the introduced non-Foster network turns Mode 1 from the narrowband resonant mode into a continuous resonant mode with its radiation pattern kept invariant over a wide bandwidth. The proposed ESHLA with its non-Foster network is fabricated and measured. The measured 6-dB return loss bandwidth is about 12.7% (11.45-13 MHz), with its reflection coefficient curve being an envelope of those of Foster elements embedded ESHLA.

The communication `blackout' in the reentry stage of a space mission is a serious threat to the reentry vehicle. The terahertz (THz) technology is supposed to be a potential solution to the `blackout' problem in the recent decade. In the present paper, the relation between the THz waves' transmission in the reentry plasma sheath and the angle of attack (AOA) of the vehicle is investigated. A three dimensional numerical model is introduced in order to obtain the plasma parameters in the reentry plasma sheaths. The computation results show that both the electron density and the electron collision frequency vary with the AOA. As results, the transmission rates for the THz waves vary with the AOA as well. According to the analysis, microwave communication system is very likely to suffer from the `blackout' in the reentry stage. The THz scheme is an effective solution. The fluctuation of AOA may weaken the signal strength received by the onboard antenna. On the other hand, keeping the AOA in an appropriate range is helpful for strengthening the received THz signals. Also, the AOA for the best THz communication quality is obtained according to the analysis.