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.

The design, development and characterization of broadband (1-30 GHz) microelectromechanical systems (MEMS) based electrostatically driven lateral switching networks are presented in this paper. Initially, single switch performances are optimized, and later it is used to develop different switching networks like single-pole-double-throw (SPDT), single-pole-three-throw (SP3T), and single-pole-six-throw (SP6T). All switches are extensively characterized including reliability testing. Switching networks demonstrate measured return loss of better than 21 dB (11.4 dB) with worst case insertion loss of 0.67 dB (~5 dB) and isolation of better than 31 dB (17.7 dB) at 3.5 GHz (28 GHz) for 5G communications. Switching networks tested for > 1 billion cycles with 1 W of RF power are found to be operational. Maximum fabricated switch (SP6T) area is ~0.7 mm² including bias lines and pads.

In this paper, a novel passive antenna cancellation technique for a full-duplex system is presented. This includes three patch antennas with a developed coupler that are constructed and integrated with the feed network to reduce the self-interference signal without the need for other components, thus achieving a complete antenna cancellation method. Computer Simulation Technology (CST) microwave studio is utilized to simulate the design model. A prototype was fabricated and tested practically to validate the proposed design. The computed results are compared with measurements. The proposed technique provides up to 68 dB cancellation at the operating frequency 2.45 GHz, and this decreases to 40 dB at 70 MHz bandwidth, and to 36 dB at 100 MHz bandwidth.

This paper examines an efficient low phase noise oscillator using a high Q resonator and harmonic suppression filter. The oscillator is designed using a combined bandpass filter (BPF), which is used as a feedback element to an amplifier. The filter consists of an embedded spur line filter in the L-shaped input and output section which encloses a perturbed square ring. All of these sections are assembled to form a combined BPF which gives an excellent suppression of second and third harmonics. Low phase noise oscillator results are evaluated at 2 V power supply. The measured results show the fundamental frequency at 2.4 GHz, total output power of 14.92 dBm, phase noise -130.7 dBc/Hz at 1 MHz offset frequency, figure of merit (FOM) -175.64 dBc/Hz, reduction in 2nd and 3rd harmonics to below -45 dBm and DC-to-RF efficiency of 51.73%.

This article proposes an advanced methodology to deal with the complexity of composite materials modeling up to 60 GHz. For radiofrequency (RF) requirements, it has been demonstrated that the distribution of conductive inclusions plays a major role. Since their locations are intrinsically subject to uncertain assumptions, the Monte Carlo (MC) technique is considered as a golden standard. Unfortunately, the computational costs involved by coupling full-wave electromagnetic (EM) simulations and MC remains prohibitive. The aim of this proposal is to demonstrate the interest of stochastic reduced order method (SROM) to tackle computational constraints, jointly with the statistical precision needed for a realistic description of RF composites.

A two-step method combining the algorithms of iterative Fourier transform (IFT) and differential evolution (DE), called IFT-DE, is proposed in this paper for the low sidelobe synthesis of a uniform amplitude planar sparse array (PSA). Firstly, the entire aperture of the array is divided into a set of square lattices that a respaced at half wavelength. Then the elementsare forced to be located on the lattices through performing IFT, so that a planar thinned array (PTA) is formed across the aperture. Undoubtedly the interval between adjacent elementsof the PTA is an integer multiple of half wavelength. In the second step, for each column of PTA the elements spaced greater than or equal to a wavelength are selected as the candidates whose locations need to be optimized by DE procedure, as long as the renewed inter-element spacing is not less than half wavelength. Consequently, a PSA with reduced sidelobe level may be obtained. According to the aforementioned selection rule, only a small part of elements that account for the total number need to be relocated, which denotes thatthe number of individual parameters waiting for optimizing by DE is decreased considerably, and thereby greatly accelerates the convergence speed of the algorithm. A set of synthesis experiments for PSA ranging from small to moderate size are presented to validate the effectiveness of the proposed method.

In this work, a dual-band microwave absorber is proposed with periodic array of unit cells which has of dual-split ring geometry on the top of a metal-backed dielectric substrate. The dual-split ring resonators on the top plane is electrically excited by co-polarized component of incident EM wave and gives two absorption peaks at Wi-MAX (3.5 GHz) and WLAN (5.8 GHz) band due to two resonance modes. These two-resonance modes are named as mode 1 and mode 2 for low and high frequency peaks, respectively. The surface current distributionson the top and bottom planes arestudied to gain insight of dual mode resonance for dual band absorption of the structure. Some parametric studies are also performed on key design parameters i.e., split gap, stub length and split angle for further analysis of the design. The measured results are verified with the simulated ones to test its performance and found to be similar.

This study investigates the sensitivity of L-band (1.41 GHz) polarimetric brightness temperature signatures to oriented permittivity patterns, which can occur for example in the case of row and interrow soil moisture differences in agricultural fields. A field experiment and model simulations are conducted to verify the effects of such patterns on all four Stokes parameters. We find that for an artificial target resembling idealized model conditions, permittivity patterns lead to systematic brightness temperature modulations in dependency of the azimuthal look angle. For the specific field setup, modulations reach amplitudes of ~4 K and mostly affect h-polarized brightness temperatures as well as the first, second and third Stokes parameters. Simulations of soil moisture patterns under idealized model conditions indicate even higher amplitudes (up to 60 K for extreme cases). However, the effects occur only for permittivity layer widths of up to 8 cm (given the observing wavelength of 21 cm), which is lower than the row and interrow widths typically observed in agricultural settings. For this reason, and due to the idealized model geometry investigated here, future studies are needed to transfer the findings of this study to potential applications such as the sensing of oriented soil moisture patterns. Particular interest might lie in radiometry and reflectometry in lower frequency ranges such as P-band, where according to the threshold established here (8/21 wavelengths), permittivity layer widths of up to ~45 cm could be observed.