In this paper, a localization algorithm for mixed near-field and far-field sources by an interlaced nested array is proposed. The fourth-order cumulants (FOCs) of the received data are used to construct a FOC matrix, by which the angles of all signals can be estimated. Then, an effective method is driven to separate the directions of arrival (DOAs) of near-field and far-field sources without extreme value search. The ranges of the near-field sources can be estimated by one-dimensional (1D) search. Compared with existing nested array-based algorithms, the proposed algorithm can distinguish more sources and has higher estimation accuracy. Some simulation results are shown to certify the superiority of proposed algorithm.

A miniaturized rectangle-shaped complementary split ring radiating element with an offset-fed microstrip line is reported for multiband operations. The fabricated antenna with a compact size of 19×19×1.6 mm³ is designed on an FR-4 substrate with loss tangent tanδ = 0.02 and dielectric constant (ε_r) of 4.4. Multiband and antenna miniaturization are achieved by a complementary split ring radiating element, and it produces an impedance bandwidth of 40 MHz resonance at 3.03 GHz, 40 MHz resonance at 3.66 GHz, and 1470 MHz resonance at 5.5 GHz. The passband behaviour of the complementary split ring radiating element is studied in detail for obtaining multiband abilities of the miniaturized antenna. The metamaterial property of the complementary split ring radiating element is analyzed, by which the negative permittivity (ε) existence and the new resonance frequency are confirmed. The fabricated antenna shows optimum performance at the measured radiation characteristics.

This work presents the novel design and development of a WC-281 circular waveguide terminator or termination for microwave plasma interaction experiments. Final waveguide terminator is designed by using the quad wedge of FR4, cone of resistive material Kanthal and Teflon discs. Kanthal is a composition of aluminium, chromium, and iron. Wedge shape geometry helps in gradually changing the impedance and thus decreasing the return loss, while resistive material Kanthal attenuates the field before reaching the receiving end. This makes it suitable for use as the finest microwave termination. Simulation is carried out by CST microwave studio. The final model of terminator decreases the reflection coefficient (S₁₁) up to -40 dB while reduces the transmission coefficient (S₂₁) immensely up to -63 dB at 2.85 GHz.

This paper presents a very compact quintuple band bandpass filter utilizing multimode stub loaded resonator. A single symmetric resonator is loaded with a short ended stub at the middle along with four pairs of open-ended stubs. The open-ended stubs are folded towards each other in order to make the design more compact and improve the selectivity of the bandpass filter. Because of symmetry, the circuit is analyzed with the help of even-odd mode analysis. The proposed bandpass filter operates at GSM-900, LTE2300, WiMAX (3.5 GHz), WLAN (5.4 GHz), and RFID (6.8 GHz). The operating mid frequencies of quintuple-band BPF are 0.96 GHz, 2.22 GHz, 3.58 GHz, 5.41 GHz, and 6.64 GHz, and the corresponding 3 dB Fractional Bandwidths are 36.03%, 20.95%, 7.27%, 8.57%, and 3.37%, respectively. The implemented resonator is analyzed in detail, and the formulation is developed in this regard. The proposed filter is developed based on the analysis and is simulated and fabricated. The simulation and measurement responses agree very well.

In fusion reaction, plasma parameters such as the density and temperature of electrons should be diagnosed continuously. There are various methods to diagnose plasma parameters. In these, reflectometry systems are widely used to measure the electron density and plasma physics study. In reflectometry systems, antenna plays an important role as a transmitter/receiver element. This paper presents the design of a D-band (110-170 GHz) corrugated horn antenna suitable for reflectometry system. The simulated results for antenna are compared with that of the measurements. Further, different structures are proposed to ease fabrication complexities and reduce cost.

The design of conventional stepped-impedance microstrip line low pass filter (LPF) is based on high (Z_H) to low impedance (Z_L) ratio. The width of Z_H line, for Z_H > 100 Ω, becomes critical and challenging, especially on high dielectric constant substrates. A concept of air-filled recessed ground plane below a microstrip line is introduced in this paper. The effect of dimensions of recessed ground on characteristic impedance, attenuation and propagation constant of a microstrip line are first studied. This simple approach is utilized to design the Z_H line of stepped-impedance microstrip line LPFs. Prototypes of recessed ground stepped-impedance microstrip line LPFs with Z_H/Z_L (keeping Z_L constant as 20 Ω)ratio in the range 6 to 10 are designed and developed on Rogers 4350B of height 0.508 mm with ε_r = 3.66 at 3 GHz. For LPF with Z_H/Z_L = 10, the measured 3-dB cutoff frequency (f_c) is achieved at 3.12 GHz with return loss (RL) > 12 dB and insertion loss (IL) < 0.28 dB in its passband whereas the stopband attenuation (SBA) is better than 38 dB. In comparison to recessed ground LPF, the simulated results of conventional LPF with Z_H/Z_L = 10 (critical width of Z_H line =) are as follows RL > 10 dB and IL < 1.07 dB in passband at f_c = 3 GHz. The size of recessed ground LPF is reduced by 25%, when Z_H/Z_L is increased to 10 from 6. The approach of recessed ground microstrip line avoids the fabrication issues, reduces size, and improves the performance of LPF, which in turns confirms the advantages of recessed ground over conventional microstrip line.

This paper amalgamates two uncorrelated techniques namely finite difference time domain technique (FDTD) and nonlinear autoregressive with exogenous input (NARX) neural network to achieve a faster computation of radar cross section (RCS). It generates only a limited number of FDTD data and uses them to train a NARX neural network. The data beyond this limited number for the FDTD come from the NARX prediction. Comparison of the performance of FDTD-NARX hybrid with other methods indicates good matching with better timing for RCS of electrically larger objects.

In this paper, design of a novel broadband Canonical Tetra Sleeve Cage Antenna is presented. This antenna is designed using distributed antenna matching techniques. It has canonical shaped antenna elements and coaxial sleeves. The designed antenna operates over a wide frequency range in UHF band with omnidirectional characteristics. The proposed antenna is simulated in CST Microwave Studio, fabricated, evaluated, and the results are presented. The simulated and measurement results are in agreement. It has VSWR < 1.9:1 in frequency bands 270-330 MHz and 930-1670 MHz. The maximum value of VSWR in 250-1850 MHz is 3.3:1. The measured gain of the antenna varies from 0.6 to 5.5 dBi in the frequency range of 250 MHz to 1850 MHz. The implementation of distributed matching techniques by using canonical shaped antenna elements and tetra sleeves results in reduction of the length of the antenna by 59.86% compared to the length of a half wave dipole antenna designed at the lowest frequency. The proposed antenna finds applications in defence and wireless communication systems as a transceiver antenna.

This paper presents a stacked rectangular dielectric resonator antenna design. In this structure, two sapphires having the same dielectric constant and different dimensions piled over each other have been used for designing the proposed antenna. The designed antenna exhibits two frequency bands from 7.41 GHz to 8.21 GHz and 9.11 GHz to 12.65 GHz and impedance matching of 50 ohms. The proposed antenna design is a fine choice for subterranean and rugged communication, in addition, owing to sapphires unique features viz. durability, endurance, and aversion to physical change. The antenna structure is aperture coupled. Due to the advantage of aperture coupled feed mechanism such as good isolation between antennas and feed networks it has been employed. The antenna prototype has been fabricated, measured, and tested using Vector Network Analyzer and Anechoic Chamber to validate the proposed antenna design. The simulation results obtained indicate close proximity of tested result.

This paper presents a single layer, dual polarized 2.4 GHz microstrip patch antenna based on monostatic radiator. Microstrip-T (MS-T) feeds have been used for DC isolated Tx-Rx ports. It deploys differential feeding for receive mode operation to achieve high interport RF isolation. The differential feeding acts as a signal inversion technique to suppress the in-band self interference (SI) for simultaneous transmit and receive (STAR) operation at same frequency. The implemented single layer, dual polarized, compact patch antenna provides better than 78 dB isolation between DC isolated Tx- Rx ports at centre frequency of 2.393 GHz. Moreover, the implemented antenna achieves better than 64 dB interport isolation for 10 sdB-return loss bandwidth of 50 MHz (2.37 GHz to 2.42 GHz). The measured interport RF isolation is around 70 dB for 25 MHz bandwidth (2.385 GHz to 2.41 GHz). To the best of our knowledge, these are the highest levels of RF isolation reported for single layer, dual polarized microstrip patch antenna with DC isolated ports.

Plane wave diffraction by a finite number of metal cylindrical rectangular strips (patches) periodically placed on a dielectric rod (DR) surface in azimuth direction is considered. The problem is solved by the Method of Moments (MoM) in the spectral domain using PieceWise Sinusoidal (PWS) basis functions. Topologies with a highly resonant behavior of the patch currents in both azimuth and longitudinal directions are considered. This includes topologies with 1, 2, or 3 patches that are nearly touching, in which case one can also view the topology as a slotted metal cylinder. For these slotted cylinders with one and two slots it is shown that 2D approximate analytical solutions based on the rigorous Riemann-Hilbert approach yield a good agreement with 3D MoM solutions for the natural frequency of the half wavelength resonance until the slot width reaches 40˚. It is found that in the 3D case the natural frequency of the half-wavelength resonance for gap coupled patches tends to zero when the slot is vanishing. The radar cross-section versus frequency, resonant current distributions on the patches and far fields are presented.

An interference on a concurrent 4.5-/8.5-GHz-band operation has been effectively suppressed by applying a duplexer technique to high-efficiency GaN HEMT power amplifiers. Each harmonic was also suppressed by a harmonic reactive termination used for a high-efficiency operation. The developed concurrent dual-band amplifier delivered a 73% drain efficiency and a 61% power-added-efficiency (PAE) with 32 dBm output power at 8.24 GHz and a 69% drain efficiency and a 64% PAE with 37 dBm output power at 4.70 GHz. Undesired cross-modulation and intermodulation signals at nearby bands occurring due to dual-band interaction have been successfully suppressed to less than -41 dBc.

Due to the high power conversion efficiency, high efficiency and energy saving, wide voltage regulation range and light weight, switching converters are widely used in many fields such as industry, military, and medicine. However, strong electromagnetic interference can affect the normal operation of switching power supply and also has a negative impact on the external environment. Based on this phenomenon, we focus on the electromagnetic compatibility of switching power supply, and a high-frequency model for PSFB circuit is proposed. At last, a set of verification tests are conducted to verify the validity of the proposed model in this paper.

This paper proposes an approach for estimating the spatial and polarization angles of mixed-targets in bistatic MIMO radar. Mixed-targets mean the combination of uncorrelated, partially correlated, and groups of coherent targets. The approach resolves rank deficiency of received signal covariance matrix and then exploits the ESPRIT-based method for estimating the angles of direction-of-departure (DOD) and direction-of-arrival (DOA). This paper also presents an analytical review and necessary conditions for resolving the rank deficiency under various scenarios of the MIMO radar. Simulation results show the effectiveness of the proposed approach.

A novel wideband circularly polarized (CP) cross-dipole with wide 3 dB axial-ratio (AR) beamwidth is presented. To generate CP radiation, the cross-dipole is fed by a Wilkinson power divider which can provide 90° phase difference. The gain beamwidth and 3 dB AR beamwidth can be widened by the bent arm structures of cross-dipole and four vertical parasitic elements. As a result, the 3 dB AR beamwidth and gain beamwidth of the proposed antenna can achieve over 210° and 105°, respectively. It is observed that the impedance bandwidth (|S₁₁| ≤ -10 dB) of the proposed antenna is 1.2~2.0 GHz, and the AR bandwidth (AR ≤ 3 dB) is 1.28~1.76 GHz. The simulated and measured results are in good agreement, which shows that the proposed antenna is a good candidate for the application of satellite communications.

This paper presents the design of an X-band stepped lens-loaded flat reflector (STLR) using reflectarray unit cell approach. A flat reflector of size 15×15 cm², loaded with a 10×10 dielectric unit cell array, centre-fed by a horn antenna, is evaluated by simulation and measurement. The simulated performance of the proposed structure is compared with a smooth lens loaded plane reflector (SMLR) and microstrip reflectarray (RA), of equivalent cross section. The results are in good agreement for SMLR, whereas a fair match is observed only in the main lobes of RA. It is worth to note that the reported STLR has a reduced thickness compared to SMLR. Furthermore, a simulation-based study is carried out on the effect of tapering of the dielectric structure in the proposed design, and a similar performance to when stepping is used is noted.

The goal of this study is to conduct an analytical study of the properties (permittivity and permeability or refractive index) of a dispersive time-dependent linear isotropic medium interacting with electromagnetic fields. It is found that the permittivity and permeability of the time-dependent dispersive medium may either have an exponential profile or a sinusoidal profile. The permittivity and permeability can vanish or can be negative as in metamaterials. Therefore, the refractive index can vanish, so the electromagnetic wave can propagate at an infinite speed (c ≫ 3·10⁸ m/s). It is also shown that the permittivity and permeability can simultaneously be negative as in left-handed metamaterials (LHM). The general electric field and magnetic field solutions are derived, and the electric and magnetic flux densities are evaluated. The wave dispersion relation is also analysed. The obtained solutions can be used to validate experimental results by applying the initial and boundary conditions which are appropriate to the experimental setup. ε

Aiming at the problem of crosstalk in high-speed interconnects, a non-crosstalk scheme based on coupled transmission lines-channel transmission matrix (CTL-CTM) is proposed. In this scheme, the transmitted signals are linear combination transformed at the transmitting end of the interconnect lines where the transmission signals among the interconnect lines constitute an orthogonal mode. After the signals have synchronously transmitted to the receiving end, second linear combination transformation is performed to restore the transmitted signals. Simulation results show that this low cost circuit proposed is capable of improving the quality of eye diagram and eliminating the crosstalk obviously.

Radio tomographic imaging (RTI) is a main method in device-free localization (DFL) that can locate a target by analyzing its shadowing effect on wireless links, while removing the requirement of equipping the target with a device. The accuracy of RTI method closely depends on the accuracy of shadowing weight model, which represents the relationship between the shadowing effect of the target on wireless links and target location. However, most existing models have not been accurate enough for many applications since they cannot explain some phenomena observed in DFL practices. To overcome the shortcoming of the existing weight model, this paper proposes a gradual-changing weight model to enhance the imaging quality of RTI. Meanwhile, a foreground target detection algorithm based on the shape feature of the target image is proposed to reduce the negative impact of background noises and pseudo-targets, thereby further enhancing the localization accuracy. The indoor and outdoor experimental results highlight the advantages of using the proposed method in improving the imaging quality and the positioning accuracy.

The negative refractive property of a meta-material medium modeled by an array of localized elements is demonstrated numerically using the iterative method based on the wave concept. This property is used to show the channeling and control of the electromagnetic beam inside the triangular shaped meta-material supports that are interfaced with the conventional positive refractive index supports. WCIP was used to view the electromagnetic behavior of a source placed in a right-hand medium interfaced with another left-hand medium in order to present the properties of the negative refraction.