X-band Applications Research Articles

DGS based miniaturized wideband MIMO antenna with efficient isolation for C band applications

Abstract A wideband multiple-input multiple-output (MIMO) antenna for C-band applications is presented in this paper. It consists of 2 × ${\times}$ 1 hexagonal motifs which serves as radiating elements. The side of each hexagonal element is 5.73 mm and the overall dimension of the proposed MIMO antenna is 30 × ${\times}$ 20 × ${\times}$ 1.6 mm3. The hexagonal motifs are embedded on inexpensive FR-4 lossy substrate. Thereafter, a circle with radius 1 mm is etched at the center of each hexagonal motif. Inverted L-shaped stubs are employed to attain efficient isolation between the nearby antenna elements. Four inverted L-shaped stubs are included to further enhance the isolation and eliminate the antenna size increment simultaneously, by suppressing the surface waves. Before using the decoupling approach, the MIMO antenna had an impedance bandwidth of 6.7 GHz and an isolation of −20 dB. The suggested antenna’s impedance bandwidth and isolation are 5.83 GHz and −52 dB, respectively, after using a decoupling approach (inverted L-shaped stub). The proposed MIMO antenna had a peak gain and radiation efficiency of 3–7 dBi and better than 90% (with decoupling), 2.75 to 6 dBi and greater than 60% (without decoupling). To verify the proposed design, a prototype was developed to compare the simulated parameters with the measured one. The envelope correlation coefficient (ECC) was less than 0.05, and channel capacity loss (CCL) less than 0.3 was achieved with DGS. Besides, scattering matrix such as return loss S 11 and transmission coefficient S 21 between two elements, radiation pattern, and current distribution was also favorable. Thus, the proposed MIMO antenna is advantageous to be used for C-band applications such as developing new generation air-borne and space-borne radars, as well as X-band applications.

Compact Four-Port Circularly Polarized MIMO X-Band DRA.

A circularly polarized (CP) multi-input multioutput (MIMO) dielectric resonator (DR) antenna (DRA) with compact size and four ports is implemented. CP radiation was achieved using the deformed DR geometry excited with aperture coupled feeding. A CPDRA with a single and two ports is investigated. The defected ground structure (DGS) was incorporated into the antenna for improving the isolation between the ports. The DGS was incorporated in such a way that the required phase difference between the generated orthogonal degenerate modes is preserved. This concept could be utilized in implementing a compact four-port CP antenna. The MIMO antenna provides a 10 dB impedance bandwidth of 38% (8.5–12.5 GHz) and a 3 dB AR bandwidth of 9.32% (9.2–10.1 GHz). The gain of the implemented antenna was around 6 dBi in the band where CP radiation was achieved. The MIMO performance parameters were calculated, and their values remained within the acceptable limits. The implemented antenna could suitably be used in X-band applications.

Printed Monopole Antenna with Tree-Like Radiating Patch and Flower Vase-Shaped Modified Ground Plane Useful for Wideband Applications

A novel design for the planar monopole antenna presented in this article consists of a patch resembling a tree and a modified ground plane resembling a flower vase. The proposed antenna is planned, designed, and made by utilizing FR4 substrate. The proposed antenna contributes to a computer simulation and tested S11 bandwidth of 9.4 GHz (144.62%) and 9.3 GHz (136.76%), respectively. A peak tested gain of 6.5 dBi and peak efficiency of 77.51% have been achieved. The measured results of the fabricated antenna are compared with the simulated results and are found to be in good agreement. The proposed antenna has a low general volume of 38 × 20 × 1.6 mm<sup>3</sup> . The antenna can be used in C-band and X-band application.

Flexible interconnected 4-port MIMO antenna for sub-6 GHz 5G and X band applications

A flexible 4-port 4-element interconnected MIMO antenna is proposed for Sub-6 GHz 5G and X-band applications. The 4-element structure attains a low profile of 0.612λ2 (at 3.34 GHz) through careful placement of antenna elements. The elementary antenna top side is formed of an inverted E and inverted L-shaped conductive structure attached to both sides of the central feed line. Two hollow tilted square-shaped assemblies are added horizontally with the inverted L for performance enhancement. The bottom plane consists of a truncated ground with a vertical stub on the side for achieving wideband performance. The MIMO configuration along with polarization diversity is attained by positioning the elementary antenna symmetrically in a sequential rotational manner. The interconnection between ground planes is ensured by placing an I-shaped strip which is further modified by adding a slotted rectangular stub on the central vertical line for better isolation. The flexible antenna demonstrated minimum efficiency and maximum gain of 70% and 4 dBi, respectively in addition to accomplishing a bandwidth of (40%) 3.34–5.01 GHz and (3.31%) 8.9–9.2 GHz while satisfying the MIMO diversity performance in terms of envelope correlation coefficient (ECC) < 0.17. Finally, the antenna performance in terms of S-parameters and MIMO diversity parameters are tested by bending the antenna along the X and Y axis that demonstrated decent performance thus making the MIMO antenna worthy for its use in Sub-6 GHz 5G and X Band Applications with tight space requirements.

Surrogate-Based Design Optimization of Multi-Band Antenna

In this work, design optimization process of a multi-band antenna via the use of artificial neural network (ANN) based surrogate model and meta-heuristic optimizers are studied. For this mean, first, by using Latin-Hyper cube sampling method, a data set based on 3D full wave electromagnetic (EM) simulator is generated to train an ANN-based model. By using the ANN-based surrogate model and a meta-heuristic optimizer invasive weed optimization (IWO), design optimization of a multi-band antenna for (1) 2.4–3.6 GHz for ISM, LTE, and 5G sub-frequencies, and (2) 9–10 GHz for X-band applications is aimed. The obtained results are compared with the measured and simulated results of 3D EM simulation tool. Results show that the proposed methodology provides a computationally efficient design optimization process for design optimization of multi-band antennas.

Miniaturized multi-band frequency selective surface with angular and polarization independent characteristic

Abstract This paper presents a miniaturized multi-band frequency selective surface for band-stop applications. The proposed design is evolved from a modified swastik structure with L-shaped arms printed on FR4 substrate. The structure is designed to operate at 2.4, 5.8, 8.6, and 10.8 GHz covering Wifi, WiMAX, and X-band applications. The proposed quad-band FSS has an overall unit cell size of 0.084 λ0 × 0.084 λ0, where λ0 is the wavelength of the lower operational frequency. The symmetric FSS structure provides the advantage of polarization independency. It also exhibits a stable frequency response up to 60° for both the horizontally polarized EM waves (Transverse Magnetic Mode) and the vertically polarized EM waves (Transverse Electric Mode). Moreover, measurement results obtained from the fabricated prototype are compared with the simulation results and are found to be in close agreement with each other. Single layer structure, compact, and coverage of multiple applications are the advantages of the proposed multiband FSS.

Circularly Polarized High Gain Coaxial Line Leaky Wave Antenna With Backfire Radiation

This communication presents a leaky wave antenna based on a standard rigid coaxial cable showing circular polarization (CP) in the backfire direction. Here, CP is achieved by using a sequential rotation scheme. Periodic slots are cut on the outer conductor of the cable leading to radiation from the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n = -1$ </tex-math></inline-formula> th fast space harmonic. The circular geometry of the coaxial cable allows to easily obtain space quadrature by rotating the successive slots by 90° about the cable axis. The required time quadrature for CP is obtained by slot-to-slot separation along the propagation direction. The antenna is designed and fabricated for X-band applications using a low-cost coaxial cable and is excited using a standard SMA connector. The measured gain is 20.26 dBic with 3 dB beamwidth of 14° at 10.26 GHz. The measured axial ratio of the left-handed CP antenna is below 1.8 dB in the backfire direction.

An FSS Based Broadband Elliptical Tree Shaped Antenna with Augmented Gain for Wireless Applications

This research presents a coplanar waveguide fed elliptical-based second iterative antenna for dual-broadband applications. The antenna radiator is formed after implementing two iterations of an elliptical-shaped patch in a tree-shaped manner and a modified semi-elliptical CPW plane. The antenna provides a bandwidth of 1.87 GHz (2.49–4.36 GHz) in the lower resonating band and 1.96 GHz (7.96–9.92 GHz) in the upper resonating band with peak gains of 2.84 and 6.15 dBi, respectively. An augmented gain of 9.48 dBi is obtained by implementing a single-layer FSS (frequency selective surface) beneath the designed antenna. The simulated and experimental results of the antenna with and without FSS are very similar regarding gain, impedance bandwidth, and directional radiation patterns. The antenna described in this article is simple, inexpensive, and low profile in nature. It can be used for Wi-MAX, lower sub-6 GHz 5G (n78), and x-band applications.

An effective metasurface-based linear and circular polarization converter for C- and X-band applications

In this study, a reflection-mode metasurface-based linear and circular polarization converter is designed for common microwave frequencies (C-band (5.85–8.20 GHz) and X-band (8.20–12.40 GHz)). The proposed polarization converter possesses a right-handed circular polarization (RHCP) capability in the 5.35–5.94 GHz frequency range and a left-handed circular polarization conversion (LHCP) capability in the 8.88–12.03 GHz frequency range. Besides its circular polarization converter capability, it demonstrates linear polarization transformation in the 4.61–4.85 GHz and 6.86–7.78 GHz frequency ranges with a polarization converter rate (PCR) greater than 90%. The design provides an oblique incidence performance up to 45° with 80% PCR value in linear polarization. The CST Microwave Studio (a commercial 3D electromagnetic simulator) was used to obtain simulation results of the design. For validation, the designed converter was first fabricated using the conventional circuit-board method, and then its reflection coefficient was measured by a microwave measurement setup calibrated by the thru-reflect-line method. A good agreement was observed between simulated and experimental results. Finally, the proposed converter design was compared with other converter designs in the literature to examine its effectiveness.

A low‐profile ultrawideband circularly polarized slot antenna array based on artificial magnetic conductor array reflector

A broadband circularly polarized (CP) slot antenna unit that is composed of a sector-shaped radiator and an irregular pentagon slot ground plane is initially investigated. The CP characteristics are realized based on unbalanced feeding and loading of irregular slot structure. To increase the gain and yield ultrawideband operation, a 2 × 2 antenna array with a sequential rotational feeding method is introduced. To further reduce the total profile of the proposed antenna array to 0.15λ0, an artificial magnetic conductor array reflector is loaded between the antenna array and the feeding network. The measured 10-dB impedance bandwidth of the proposed antenna array was 82.6% (8.31–20.0 GHz), and its corresponding CP bandwidth was 65.4% (8.61–16.98 GHz), and the radiation efficiency of the antenna is also higher than 80%. Besides exhibiting very good axial beams across the wide CP bandwidth, a peak gain of up to 11.1 dBic is also achieved. Thus, it is suitable for X-band and Ku-band satellite communication applications.

An Oval-Square Shaped Split Ring Resonator Based Left-Handed Metamaterial for Satellite Communications and Radar Applications.

Development of satellite and radar applications has been continuously studied to reach the demand in the recent communication technology. In this study, a new oval-square-shaped split-ring resonator with left-handed metamaterial properties was developed for C-band and X-band applications. The proposed metamaterial was fabricated on 9 × 9 × 0.508 mm3 size of Rogers RO4003C substrate. The proposed metamaterial structure was designed and simulated using Computer Simulation Technique (CST) Microwave Studio with the frequency ranging between 0 to 12 GHz. The simulated result of the proposed design indicated dual resonance frequency at 5.52 GHz (C-band) and 8.81 GHz (X-band). Meanwhile, the experimental result of the proposed design demonstrated dual resonance frequency at 5.53 GHz (C-band) and 8.31 GHz (X-band). Therefore, with a slight difference in the dual resonance frequency, the simulated result corresponded to the experimental result. Additionally, the proposed design exhibited the ideal properties of electromagnetic which is left-handed metamaterial (LHM) behavior. Hence, the metamaterial structure is highly recommended for satellite and radar applications.

On Microstrip Array Antenna with Enhanced Bandwidth and Gain Using Modified Ant Lion Optimization for X-Band Applications

This article furnishes the design and analysis of three concentric circular array antennas (CCAAs) of point sources and a linear microstrip patch array antenna (LMPAA) employing a newly developed hybrid optimization algorithm, the modified ant lion optimization (MALO). The optimum CCAAs employing MALO offer better radiation patterns in terms of the reduction in peak side lobe level, null depths, first null beam width, and directivity considering the same apertures, compared to some other popular optimization algorithms available in the literature. In the other hand, the LMPAA with optimized rectangular ring shaped slots in its ground plane using MALO enhances its bandwidth (BW), gain, and directivity. A prototype of the proposed LMPAA is fabricated, which offers measured values of BW, gain, directivity, and radiation efficiency of 907.1 MHz, 10.26 dBi, 12.19 dB, and 84.16%, respectively. The LMPAA is compared with some previously available designs in the literature to highlight its significance and hence to validate the process of employing optimization algorithms in design and analysis of real antennas.

Numerical Investigation of Frequency Reconfigurable Antenna with Liquid Metamaterials for X-band

In this paper, a frequency reconfigurable liquid metamaterial microstrip-based radiating structure is proposed and it is an attempt toward achieving reconfiguration in liquid metamaterial-based microstrip radiating structures. Reconfigurable antenna design is superstrated with five liquid metamaterial layers based on a distilled water split-ring resonator. Superstrate layers give enhancement from 6.5 dB to 13.1 dB in gain of the proposed antenna. A patch is reconfigured through PIN diodes as RF switches. Switching ‘on’ and ‘off’ states of PIN diodes are used for reconfiguration of frequency and radiation patterns. Analysis in terms of reflection coefficient, gain (dBi), radiation pattern, bandwidth (BW), and half-power beamwidth (HPBW) is obtained in switch-off and switch-on state. The proposed design provides enhanced gain, reflection coefficient, and multiband characteristics in the 8-12 GHz range suitable for X-band satellite and radar applications. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

The Ba(Mg1/3Ta2/3)O3 ceramic based X-band filter

The microwave dielectric Ba(Mg1/3Ta2/3)O3 ceramics with different sintering temperatures were prepared by conventional solid-state reaction synthesis method. The ordering degree and lattice distortion related to high quality factor were investigated systematically with XRD. In accordance with the observed morphology and grain distribution, compact and uniform microstructure with large grain size has a good effect on the high Q × f value. Surprisingly, in the case of the 1:2 ordered structure, the shorter bond length associated to Mg-O at 1670 ℃ also contributes to the high-Q, as compared with that of samples sintered at low temperature. Finally, Ba(Mg1/3Ta2/3)O3 ceramic based filter (center frequency: 10.29 GHz, bandwidth: 216 MHz, insertion loss: 0.86 dB) was designed for X-band high frequency application.

A highly-directive hybrid-fractal radiator-based printed array for X-band amateur radio applications

This article provides a 4-elements planar array of fractal patch antennas for X-band wireless communication, especially amateur-radio (10.00–10.50 GHz) applications. The single constituent of the indicated array is a freshly designed hybrid-fractal antenna with a modest gain and low cross-pol. level along the primary beam's path. The exhibited hybrid-fractal design was created using the Minkowski iteration, followed by a scaling to a square geometry in the next stride. The compact planar array structure incorporates the Wilkinson power divider-based corporate feed network. The solo antenna built resonates at 10.02 GHz and offers 10.67 dBi of massive gain and 0.395 GHz of return-loss bandwidth, respectively. At 10.05 GHz resonating frequency, the array prototype gives 16.54 dBi absolute gain and 0.318 GHz impedance bandwidth. Printed prototypes achieved radiation efficiency of and , respectively. Both prototypes had computed aperture efficiency of and , respectively. There is a great deal of agreement between the prototypes' measured and simulated findings.

Bridging the Gap between Physical and Circuit Analysis for Variability-Aware Microwave Design: Modeling Approaches

Process-induced variability is a growing concern in the design of analog circuits, and in particular for monolithic microwave integrated circuits (MMICs) targeting the 5G and 6G communication systems. The RF and microwave (MW) technologies developed for the deployment of these communication systems exploit devices whose dimension is now well below 100 nm, featuring an increasing variability due to the fabrication process tolerances and the inherent statistical behavior of matter at the nanoscale. In this scenario, variability analysis must be incorporated into circuit design and optimization, with ad hoc models retaining a direct link to the fabrication process and addressing typical MMIC nonlinear applications like power amplification and frequency mixing. This paper presents a flexible procedure to extract black-box models from accurate physics-based simulations, namely TCAD analysis of the active devices and EM simulations for the passive structures, incorporating the dependence on the most relevant fabrication process parameters. We discuss several approaches to extract these models and compare them to highlight their features, both in terms of accuracy and of ease of extraction. We detail how these models can be implemented into EDA tools typically used for RF and MMIC design, allowing for fast and accurate statistical and yield analysis. We demonstrate the proposed approaches extracting the black-box models for the building blocks of a power amplifier in a GaAs technology for X-band applications.

Improved X-Band Performance and Reliability of a GaN HEMT With Sunken Source Connected Field Plate Design

The world class performance and reliability of a high-power density AlGaN/GaN high electron mobility transistor (HEMT) with an innovative sunken source connected field plate (SCFP) is reported. The optimized HEMT structure implements a novel sunken SCFP design that has significant advantages over the conventional field plated GaN HEMT. The new design reduced parasitic capacitances (C_gs and C_gd) whilst suppressing the peak electric fields in the drift region to improve breakdown voltage and reliability. This sunken SCFP demonstrates the improved RF performance and reliability with respect to leading GaN HEMT devices for x-band applications. The fabricated device produces 10 GHz performance with saturated output power &#x003E;10 W/mm, linear gain &#x003E;18 dB and PAE &#x003E; 60&#x0025; &#x0040; 50 V. The improved gain is a direct result of the reduction in Cgs and Cgd, by 15&#x0025; and 60&#x0025;, respectively. The increased power is achieved from lower trapping and increased drain voltage rating of 25&#x0025;. Accelerated RF-driven reliability testing is shown to determine the expected lifetime of the device was &#x003E;6E7 hours at 225&#x00B0;C junction temperature. This is a more than 2 orders of magnitude increase over the conventional field plate design.

3-D Printed Radar Absorber with Meta-material Features for X-band Application

This paper presents a structured radar absorber with metamaterial features based on graphite SLS composite. The unit cell of the proposed design was simulated on COMSOL Multiphysics to determine its frequencydependent absorption characteristics and fabricated using low-cost selective laser sintering 3-D printing technology. The measurement and simulation results showed an effective absorption bandwidth of 1.04 GHz and 2.08 GHz respectively. The optimized structure however, revealed broadband absorption in a frequency range between 8.35 to 12.20 GHz (X band) under normal incidence. Besides, the absorption performance under different polarizations and incident angles were investigated. Results indicated that the absorber exhibits polarization indifference and high absorptivity at a wide angle of incidence. The advantages of low cost, ultra-broad operating band, wide-angle feature, and polarization insensitivity made the proposed absorber a promising candidate in military and civilian applications.

A Tri-band Planar Inverted-F Antenna with Complementary Split Ring Resonator and Reactive Impedance Surface for Wireless Application

In this paper, a compact, tri-band Planar Inverted-F Antenna (PIFA) using Complementary Split Ring Resonator (CSRR) and Reactive Impedance Surface (RIS) is presented for multiband application. The structure of the PIFA consists of a metallic CSRR and 5×6 periodic unit RIS cells, which accomplishes miniaturization and improves bandwidth and multiband. The RIS metamaterial plane lies between two substrates and acts as a loading function, reducing the volume of the antenna. The measured and simulated results are consistent for a manufactured prototype. The overall size of the antenna is 22.71×3.451×1mm. The PIFA shows a tri-band with an S11 &lt; −10dB bandwidth of approximately 17.08% (2.26-2.67GHz), 5.14% (6.85-7.21GHz) and 19.44% (7.44-9.19GHz) under measurement. The antenna radiates a wave in a preset direction with realized gains ranging from 3.21 to 8.1dbi. The CSRR and RIS improve the performance of the antenna for WLAN, C-band, and X-band applications.

Design and implementation of a beam-steering antenna array using butler matrix feed network for X-band applications

This article proposes the design, simulation, fabrication and testing of a beam steerable antenna array using a 4 × 4 Butler Matrix feed network technique. The proposed antenna is developed to operate at the X band frequency range. The integrated antenna array and the Butler Matrix feed network operating at 10 GHz has a bandwidth of approximately 2 GHz with an achieved gain of 12 dBi. The main beam pattern of the antenna array is switched between four directions (+10°, −38°, +38°, −10°) providing an effective coverage of over 100°. The proposed antenna has the advantages of low cost, easy fabrication, and simplicity.