A compact circularly polarized microstrip ring antenna is presented for Global Navigation Satellite systems (GNSS) application in this paper. The antenna consists of a ring-shaped slotted ground and a radiation patch which is fed by a T-like coupling feedline. The radiation patch is a square ring strip embedded within two inverted L-shaped strips and a rectangular strip. The overall size of the proposed antenna is 0.38×0.38×0.038λ_g³ (λ_g is the guide wavelength at the frequency of 1575 MHz). The measured -15 dB |S₁₁| bandwidth, 3 dB axial ratio (AR) bandwidth, and gain bandwidth of larger than 5 dBi are in the frequency range of 1552-1623 MHz, which can fully cover the operating frequency band of BDS B₁, GPS L₁, and GLONASS L₁.

This paper proposes a new method of calculating currents in three-phase overhead medium and high voltage networks by measuring the magnetic fields generated in the close vicinity of the power line conductors. A mathematical model for magnetic fields is presented in the form of second order partial differential equations that are derived from Maxwell's equation. The analysis of the magnetic field surrounding overhead conductors is performed using Finite Element Method. The least squares method is used for the formulation of equations for estimating currents from the measured magnetic fields for each phase. A computational program for detail analysis is developed in MATLAB. A plan for measurement points is developed for triangular arrangement of conductors. Field measurement with increased number of measuring points gives better results than those with the single points.

In this paper, in order to meet the requirements for miniaturizing a microwave frequency conversion module, an L-band filter with narrow band and high out-of-band rejection is designed based on LTCC technology. The values of each element in the simplified schematic diagram are used with Chebyshev type function being the prototype, and the shapes and layout of the elements are reasonably designed for effectively utilizing the electromagnetic coupling effect inside the structure. The actually processed filter has a bandwidth of 20 MHz, and its out-of-band rejection reaches 39 dB and 42 dB at 1 GHz and 1.6 GHz, respectively.

A method is proposed for calculating the radiation characteristics of a reflector antenna in the resonant wavelength range. The method uses the solution of the problem of electromagnetic field scattering from a well-conducting non-closed screen of finite thickness. This problem is solved by an E-field integral equation and on approximate boundary conditions by Leontovich, which are applied onto a surface of a well-conducting screen.

An optimized microfluidic sensor for extracting volume ratio of binary mixture comprising of ethanol and methanol using electrical resonance technique has been presented in this work. In order to detect small changes in composition of binary mixture, a split-ring resonator structure with enhanced sensitivity was designed to operate around 2.5 GHz. A resonator was designed using HFSS, which possessed enhanced sensitivity. A novel algorithm for optimization was devised for binary mixture of the two liquids. The resonator was fabricated and tested for validation of results. Samples of ethanol and methanol mixture in different volume ratios were prepared and filled in micro-capillary tubes. These tubes were placed inside the resonant structure to perturb electric field. Variations in resonant properties due to change in volume ratio of liquid mixtures were analyzed. Resonant frequency, s-parameters and quality factor of structure were measured. It was observed that change in volume fraction as small as 1/100 resulted a shift of 0.25 MHz in resonant frequency (relatively high level of sensitivity). Measured results were utilized by mathematical model to compute volume fraction of liquid in these mixtures.

Through-the-Wall Imaging systems are a promising method for on-line applications,especially in disaster areas, where victims are buried under collapsed walls. These applications require such systems to identify the shape of thetarget. The foremost step while performing the task of shape recognition of stationary targets behind a wall is to first detect the target position, its approximate shape and size, and then, subsequent processing of these images with the use of signal processing techniques for the shape recognition of targets. For determining highly accurate information about target location and its approximate shape, a high-resolution image of the target is required. In literature, various imaging algorithms have been reported, some of which are back projection, delay sum, and frequency-wavenumber imaging algorithm. However, the use of these algorithms for shape detection of the target has not been explored so far. Therefore, it becomes essential to explore the use of these algorithms on TWI data to select an effective imaging algorithm for detecting approximate shape and size of the target. For this purpose, an experiment has been performed. The performances of these imaging algorithms have been analyzed and evaluated. The detected target images do not correspond to the actual shape and size of targets; therefore, a novel methodology using an artificial neural network has been presented for predicting the actual shape of the target. From the experimental data, the retrieved result of shape has been found in good agreement with the target original shape.

In order to obtain the carrier frequency (CF) and direction-of-arrival (DOA) estimation, a uniform linear array (ULA)-based modulated wideband converter (MWC) discrete compressed sampling (CS) digital receiver system is proposed. It can achieve sub-Nyquist sampling, save the storage space and specially obtain the CF and DOA estimation by processing the CS data directly. However, the existing method for this system needs more branches to get better performance. In this paper, a compressed uniform linear array (CULA)-based MWC discrete CS digital receiver system is proposed. First, a compression matrix is used to reduce the number of branches behind the antennas. Then, the MWC discrete CS structure is used to reduce the data volume. Finally, the multiple signal classification (MUSIC) algorithm is used to jointly estimate the CF and DOA by processing the CS data directly. The simulation results validate the effectiveness of the proposed system and the proposed method for the joint CF and DOA estimation.

A wideband low-profile dual-polarized antenna based on the use of an artificial magnetic conductor (AMC) reflector is proposed. The AMC reflector consists of 9×9 square patches. In order to obtain wide impedance and gain bandwidths, the antenna consists of four printed dipoles: two dipoles are used as a radiator of horizontal polarization, and two dipoles are used as a radiator of vertical polarization. A simple excitation scheme without balun is used for dipoles feeding. A low profile of 0.068λ_L is realized (λ_L is the wavelength at the lowest operating frequency). Simulation and measurement results show that the proposed antenna has a 40% impedance bandwidth, a 40% 3-dB gain bandwidth, and a port isolation of less than -30 dB.

A metamaterial absorber in the Terahertz (THz) range is simulated and experimentally investigated in this work. The desired absorption frequency, efficiency and bandwidth can be tuned by changing the metal and dielectric geometric parameters. An absorption greater than 85% for TM polarized light with an incident angle up to 70˚ at any azimuthal direction is observed in a circular disc THz metamaterial structure. By adjusting the dielectric silicon dioxide (SiO₂) thickness to 4 μm, an optimal absorption greater than 95% can be achieved at a resonance frequency of 0.97 THz. The experimental results also indicate that using Titanium (Ti) as a metamaterial metal layer provides four times broader absorption bandwidth than Aluminium (Al). This study, which works on polarization-insensitive and wide-angle metamaterial absorbers, can be fundamentally applied tomany THz applications including THz spectroscopy, imaging, and detection.

Greater design flexibility and newer miniaturization techniques are highly sought after by the commercial antenna industry and researchers. Micro-Strip Patch Antenna (MSPA) is finding huge applications in various fields of communication. In the present paper, the novel idea of Double-Elliptical Micro-strip Patch Antenna (DEMPA) is proposed for antenna miniaturization and higher design flexibility. The Double-Elliptical Patch (DEP) is made as the combination of two half-elliptical patches having the same minor axis and different semi-major axes or the same major axis and different semi-minor axes. A DEP with different lengths of horizontally arranged semi-major axes and centrally given feed was considered here. The length of semi-major axis for right half-elliptical patch was varied while keeping the length of semi-major axis for left half-elliptical patch fixed. Design of DEMPA was carried out using Ansoft HFSS software, and the antenna has been fabricated and tested. The measured results were in good agreement with the simulated ones. The percentage reduction in effective patch area was found to be 8.33 for DEMPA compared to the corresponding elliptical patch antenna. The DEMPA covered the entire frequency range of Ultra Wide Band (UWB). With this novel shape, greater design flexibility along with miniaturization is achieved. The axial ratio analysis showed that the resulted antenna was of linear polarization.

A novel compact Ultra-Wideband Multiple Input Multiple Output (UWB-MIMO) antenna with enhanced bandwidth is proposed. The bandwidth of the designed antenna ranges from 1 to 30 GHz which covers L, S, C, X, Ku, K bands and some part of Ka-band. A square slot & inverse L-shaped strip is used to improve the isolation amid antenna elements. The suggested antenna achieves Mutual Coupling and Envelope Correlation Coefficient below -17 dB and 0.15 respectively. MIMO performance parameters like Mean Effective Gain is around 0 dB, and Total Active Reflection Coefficient is less than -10 dB. The Channel Capacity Loss and Effective Diversity Gain are less than 0.3 bits/s/Hz and 9.2 dB, respectively. The radiation efficiency of the designed antenna is around 80% over the complete frequency range. The overall dimensions of designed antenna are 27× 17 × 1.6 mm³.

A single semicircle shape Complementary Split Ring Resonator (CSRR) is designed to enhance isolation by suppressing mutual coupling between MIMO antennas. Furthermore high level of mutual coupling by introducing circular slot in-between patch antennas on the substrate which creates additional coupling path between the patch antennas also opposes the some leakage signals coming back from the opposite coupling path after CSRR is etched from ground plane. The proposed patch antenna dimensions are chosen as 37.26 x 28.13 mm for operating at 2.51 GHz frequency, and the low-cost dielectric material, FR-4 (ε_r = 4.4), is chosen as the dielectric substrate with 1.6 mm height. The S parameters of proposed antenna prototype are characterized by using VNA. The measured return loss (S₁₁) and isolation (S₂₁) are -23.13 dB & -56.8 dB respectively. The results show that by introducing semicircle CSRR and circular slot, the structure provides a 33.2 dB improvement in mutual coupling for MIMO antenna. Hence, the proposed structure provides a better isolation between two antennas without affecting antenna performance.

Aiming at the problems of low gain, low efficiency at lower frequency and warping in pattern at higher frequency of 10-meter high frequency (HF) whip antenna, the whip antenna is loaded and matched with the network in different bands using Grasshopper Optimization Algorithms (GOA) and antenna reconfiguration technology, so a new frequency reconfigurable broadband whip antenna is designed in this paper. According to the electrical characteristics of 10-meter HF whip antenna, this paper divides short wave frequency into three bands and designs its radiation structure, loading, and matching network for each band of antenna, respectively. GOA is introduced into the research and design of antenna to optimize the component parameters of loading network and matching network. The results show that the antenna in lower frequency band can be improved at most, the maximum gain growth up to 5.8 dB (from -10.3 dB to -4.5 dB) and the maximum efficiency growth up to 8.5% (from 3% to 11.5%); the gain and efficiency in high frequency band are greatly improved too, and the phenomenon of warping in the pattern is effectively avoided.

The magnetic field distribution of an axially magnetised cylinder with elliptical profile is analytically modelled and analysed in this paper. An accurate and fast-computed semi-analytical model is developed, based on the charge model and geometrical analysis, to compute the three components of the magnetic field generated by this elliptical cylinder in three dimensional space. The accuracy of the model is verified using Finite Element Analysis. The analytical expressions are efficient for calculating the implementation of the magnetic field, taking less than one millisecond to execute on a modern PC. Using the fast-computed analytical model, the distribution of the magnetic field of an axially magnetised cylinder with different elliptical profiles is studied and compared with that of a circular cylinder. The variations in magnetic field strength of axial, azimuthal and radial components can be used in novel sensing applications. The derived analytical model can be extended to calculate the magnetic field of arc-shaped elliptical and circular cylinders with axial magnetization, which can be used in Halbach arrangements.

A low-profile, decoupled two-monopole system with its two parasitic grounded strips conjoined, forming a very compact structure is demonstrated. Each of the two identical antennas comprises a driven coupling strip and a parasitic grounded strip, operating respectively in the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands. The two parasitic strips are further joined together, becoming a central, grounded T monopole. By loading a capacitor between the T monopole and the antenna ground, the mutual coupling in the 2.4 GHz band can be reduced by about 12 dB. The capacitor in this design is used to control Ant2 monopole mode to cancel out opposite-phased currents of the dipole mode on the T monopole when Ant1 is excited, such that isolation enhancement can be attained. The proposed two-monopole system occupies a compact size of 5 mm × 40 mm (about 0.04λ × 0.32λ at 2.4 GHz) and is favorable for applications in the narrow-bezel notebook computers owing to its low profile of 5 mm.

The effects of both anisotropy in the substrates and the superconducting films on the resonant frequencies and radiation patterns of an equilateral triangular patch are investigated theoretically. Our proposed method is based on the modified cavity model in conjunction with the electromagnetic knowledge. The validity of the proposed method is tested by comparing the computed results of the resonant characteristics with the experimental data. Results show effects of the superconducting patch thickness as well as the anisotropy in the substrate on resonant frequency and the radiation pattern of the triangular patch. The effects of the antenna parameters on the resonant frequencies and radiation patterns are also presented and discussed. At higher substrate thicknesses, numerical results indicate that the radiation pattern is drastically changed. The resonant frequency, on the other hand, decreases with high equivalent permittivity of the anisotropic substrate. The proposed method is very fast, simple, and compatible well with CAD.

This paper presents a high-selectivity dual-mode dual-band bandpass filter with good cutoff signal rejection. The high-selectivity dual-mode dual-band bandpass filter is designed by an asymmetrical transmission zero (TZ). The asymmetrical transmission zeros next to the upper sideband of the first resonant filter and the TZ at the lower sideband of the second passband filter are combined to form a dual-mode dual-band filter. The locations of the TZ are designed at the side passbands of the filters in order to filter out unwanted signals, obtain good cutoff rate in the stopband, and give much improved signal selectivity for the dual-band bandpass filter. One dual-mode filter is designed at the center frequency of 1.8 GHz and the other's desired performance at 2.4 GHz. The two filters can be combined using the coupled feed lines in which these coupled feed lines present a simple structure of dual-mode dual-band bandpass filter. The insertion loss of the dual-mode dual-band bandpass filter is less than 1.2 dB, and the rejection between two transmission bands is about 18 dB from 1.9 to 2.35 GHz. This high-performance dual-mode dual-band bandpass filter can be used in many wireless communication systems.

A planar wideband circularly-polarized (CP) antenna array is designed for an X-band CubeSat. The design is a two-level sequential phase architecture, consisting of a 4 × 4 element array composed of sequentially rotated of 2 × 2 subarrays. Each subarray consists of sequentially rotated 2 × 2 antennas using metasurface. These antenna elements are incorporated with a two-level sequentially rotated phase network in order to obtain wideband characteristic and high gain. The final prototype with a size of 100 mm × 100 mm × 2.032 mm yields a measured |S₁₁| < -10 dB bandwidth of 50% (6-10 GHz) and measured axial ratio < 3-dB bandwidth of 40.7% (6.45-9.75 GHz). Additionally, the proposed design achieves a good broadside right-hand CP radiation with a peak gain of 17.0 dBic, 3-dB gain bandwidth of 20.4% (7.5-9.2 GHz), and radiation efficiency of > 82%. With these features, the proposed antenna can be compatible with any CubeSat standard structure, as well as other small satellites.

The paper presents simulated and measurement results of a planar antenna structure at 2 GHz center frequency. The antenna has two ports implemented into the same conductive body. The antenna shows measured -10 dB impedance bandwidth from 1.87 GHz to 2.18 GHz with average 41.3 dB isolation between the antenna ports over the studied frequency bandwidth. Antenna is used to measure transmitted WCDMA FDD signal leakage to the receiver with a presence of blocker signal, which is transmitted over the air. The system measurements show that the RF filtering requirements can be relaxed based on 3GPP standard by using highly isolated antenna structure. Application areas can be found at the both ends of the mobile communications system, mobile devices and small cell base stations.

A modified feed line Wideband Circularly Polarized Dielectric Resonator Antenna (CPDRA) operating at 24 GHz is proposed in this paper. Deminiaturisation of design is achieved by operating antenna at higher order mode TE₁₁₇. The antenna structure consists of a rectangular DRA with three rectangular slots. One at the centre and other two inclined orthogonally with respect to centre slot. The bottom surface of substrate contains the modified feed structure in which two stubs of the same dimensions are connected orthogonally to main microstrip line to provide a phase difference of an odd multiple of λ/2 for circular polarization. DRA with excitation through modified aperture coupled feed structure provides the simulated and measured impedance bandwidths of 16.28% (22-25.9 GHz) and 15.06% (22.1-25.7) GHz. The antenna provides the simulated and measured gains of 8.4 dB and 7.9 dB. The antenna is deminiaturised by 61% by operating antenna at higher order mode. The designed antenna has potential for millimeter wave and 5G applications.