CST Software Research Articles

Highly Selective Ultra-wideband Filtenna with Triple Band Notch and Wide Stop Band Rejection for UWB Communication and Sensing Applications

A compact and highly selective monopole ultra-wideband (UWB) filtenna (UFA) having triple band notch is presented in this paper. The proposed UFA covers the UWB frequency range with good matching characteristics. Defected ground structure provides good impedance matching with return loss above 10 dB. A low pass filter with wide stop band rejection is integrated in the feed line to provide high selectivity and wide rejection band at upper edge of UWB. Three folded uniform impedance resonators are integrated with the UWB radiator to suppress the effect of interference experienced in the UWB spectrum from WiMAX, WLAN, and X-bands. The proposed UFA covers the frequency bandwidth from 2.5 to 11.1 GHz with above 3 dBi gain in all the pass bands and radiation nulls at notch bands. The proposed design has been simulated and analyzed using commercially available software CST Microwave Studio and the obtained results show good agreement between simulation and measurement. The performance of this UFA makes this a suitable candidate for UWB communication and sensing applications.

An ultra-wideband thin metamaterial linear cross-polarization conversion

This article presents the design of a novel ultra-wideband, thin metamaterial linear cross-polarization converter (CPC) operating at microwave frequencies. The CPC consists of two concentric deformed rings on a dielectric substrate backed by a metallic surface. It demonstrates co-polarization and cross-polarization reflection coefficients below − 11 and above − 1.1 dB, respectively, over a wide frequency range of 8.75–17.75 GHz, achieving a 68% bandwidth. Within this range, the polarization conversion ratio exceeds 90%, with three prominent peaks at 9.3 GHz, 13 GHz, and 17.4 GHz, reaching 99.5%, 99.8%, and 99.3% respectively. The unit cell dimensions are compact at 6.3 × 6.3 × 2 mm3. The CPC’s performance was analyzed under varying polarization and oblique incidence angles, and the surface current distributions were studied to elucidate the polarization conversion mechanism. Simulations using CST and FEKO demonstrated substantial agreement, also equivalent circuit is determined and compared to CST software. The compact, thin, and ultra-wideband design makes this CPC a promising candidate for applications in advanced communication systems such as radar cross-section reduction and electromagnetic interference suppression. The results are validated further by experimental measurements of the fabricated CPC.

Parameter study of a 5G array antenna at 28 GHz

In this paper a 5G compact antenna is investigated at 28 GHz. The structure is based on Quasi-Yagi antenna comprising a director, driver, and reflector. The SIW technology is utilized to feed the antenna because of its numerous benefits. The antenna array is designed and simulated and the S11, E pattern, and H pattern are analyzed for both single-element and array antennas. Moreover, the effects of various parameters such as the number of stubs, the length of the director, the distance between the director and driver, the length of the driver, and the distance between the driver and reflector on S11 are studied. The HFSS and CST software are used for all analyses. Additionally, for the array antenna the effects of increasing the number of directors on S11 and antenna gain, change in antenna length, and variations in distances between elements are evaluated.

16-Elements Ring Shaped MIMO Antenna Design for 5G Wireless Communication

The most popular area of study in wireless communication is Fifth Generation (5G). In this paper, a 5G MIMO antenna with a wide bandwidth, large gain, and compact structure is designed. The suggested design has two input and two output ports, with eight octagonal randomly shaped patches designed with Rogers RT5880 substrate in a building from the front and stripped from the bottom sort of arrangement. On CST-Microwave Studio, the entire designing and simulation process is carried out. Several characteristic parameters have been determined in this research using CST software. Broadband from 32GHz to 35 GHz and -43.62 return losses achieved at 33.56 GHz frequency with the proposed design. More than 9.6 dBi gain is also achieved with the proposed antenna. The antenna is broadband, very compact, with high gain and efficiency.

Modelling of differential probing analysis for biomedical dielectric spectroscopy

AbstractTranscutaneous microwave dielectric spectroscopy holds promise as a modality for non‐invasive subcutaneous biomarker monitoring, such as blood glucose levels. Experimental studies have demonstrated a strong correlation between blood glucose concentration and blood permittivity using microwave signals. However, the sample volume of interest, blood vessels, is located underneath skin layers where the microwave signal interaction with other surrounding biomaterials is accumulated. Here, a computational study of the proposed method to mitigate the contribution of unwanted tissue and thereby increase the specificity of subcutaneous spectroscopy, using differential probing analysis (DPA), is presented. By exploiting the relationship between the diameter of an open‐ended coaxial probe (OCP) and the size of its protruding electric field, two OCPs with different sizes can sense different volumes beneath the skin. The proposed method computationally subtracts the effect of unwanted tissue, estimated with the smaller probe, from the effective contribution of both blood and unwanted tissue with the larger one. The method is validated by using simulated models and data from the full wave software CST Studio Suite across frequencies ranging from 1 to 10 GHz, achieving errors comparable to state‐of‐the‐art techniques.

A Generalized and Efficient Equivalent Circuit Model for Frequency Selective Surfaces

Owing to their excellent intuitiveness and simplicity, equivalent circuit models (ECMs) are widely used to investigate and design frequency selective surfaces (FSSs). However, the generalization and accuracy of ECM has been a contentious issue, especially with regard to the requirement for analyzing diverse and numerous FSSs versus the restrictions applied to it. To address this problem, a generalized and efficient equivalent circuit model (GE-ECM), characterized by the feasibility of dealing with multiple sizes, broadband, and large oblique incidences, is proposed in this study to design FSSs and analyze their electromagnetic performance. In contrast to related works, gap and width factors are accounted for in the proposed GE-ECM to recalibrate the reactance and susceptance of the physical model, respectively. Additionally, normalized sizes of structure periods are introduced to further extend its generalization. Good agreement is achieved between the frequency responses of the GE-ECM and the electromagnetic software CST. Furthermore, excellent adaptation to multiple sizes and broadband is achieved from 0 GHz to 20 GHz, with the average relative error of the resonant frequency being only 1.19% for all sizes. Fabrication and measurements were conducted to verify the practicability of the proposed GE-ECM, with all results confirming its accuracy and universality in interpreting electromagnetic performance, thus establishing a reliable theoretical guideline for designing more complex FSSs.

Millimeter wave MPA using Metamaterial-substrate Antenna array for Gain Enhancement

This paper presents a Millimeter wave Microstrip Patch antenna(MPA) with a metaplate which consists of Split Ring resonators(SRR) design. The gain and bandwidth of MPA are improved by using 4×3 array unit cells printed on both the sides of the metaplate. Simulation results show that the Gain of the antenna was increased by 4.82 dBi and 4.53 dBi, bandwidth was increased by 2.25% and 6.21% in CST and HFSS softwares respectively using the Metaplate along with the MPA. The center frequency of the proposed antenna is 28.5 GHz. Thus the proposed antenna has a very small size of 18×22 mm2 and is suitable for Millimeter wave applications.

Electromagnetic coupling evaluation of small metal enclosures with apertures using analytical, numerical and measurement analysis

We have presented an analytical analysis of the shielding effectiveness of small metal enclosures with apertures by the Roinson model based on the theory of transmission line circuits, as well as a numerical analysis by the finite-difference time-domain method (FDTD) and finite integgration technique (FIT) under the CST Software software, the results returned by these methods were compared with those provided by the measurement, the comparative study reveals a good agreement between the simulation and the measurement. The study carried out in this article has resulted in very significant results allowing to solve electromagnetic compatibilty (EMC) type problems related to the reduction of the electromagnetic field in an enclosure with apertrures.

RF NEMS switches based on graphene for low pull-in voltage and excellent RF performance

This study introduces a novel graphene RF NEMS capacitive switch and conducts an extensive analysis of its RF performance using CST and COMSOL Multiphysics software. The switch’s characteristic impedance matching is accomplished through a coplanar waveguide (CPW) structure, incorporating a dielectric layer topped with conductive graphene beam electrodes. Simulation results reveal that the monolayer graphene RF NEMS switch maintains an insertion loss of 0.003 ~ 0.015 dB and an isolation greater than 40 dB across an ultra-wideband (UWB) frequency range of DC ~ 140 GHz. Moreover, the switch demonstrates a switching time of 4.03 ps at a pull-in voltage of 1 V. The performance of multilayer graphene RF NEMS switches was also evaluated. The study further investigates the operational mechanism of the graphene RF NEMS switch and performs finite element analysis on the proposed design. The graphene RF NEMS switch discussed herein offers significant advantages, including minimal size, lightweight, cost-effectiveness, low pull-in voltage, rapid response time, excellent RF performance, and reduced space consumption in circuitry. Its potential applications span a range from L to F bands, encompassing data storage, communication systems, sensors, remote sensing and military uses.

Impedance Matching Using Support Rod Rings in C-Band Helix TWT

A helical (Slow Wave Structure SWS) traveling wave tube (TWT) operating in the C bandwidth was designed using CST software. Based on modelling, TWT components were produced. Conductor support rod rings were used to matching the impedance line and provide ease of assembly. According to the modelling, the signal gain was determined as 30 dB. In addition, Time Domain Reflectometer (TDR) analyses were performed to observe the effect of mounting rings on impedance improvements with the help of software. As a result, it has been determined that the support rod rings, which have not been used before in C band helix TWT systems, positively affect the ease of assembly and impedance improvement.

A novel circularly polarized antenna array methodology for early identification of kidney tumors

Kidney cancer is a significant health concern worldwide, with early detection crucial for successful treatment outcomes. Recently, there has been an increasing focus on investigating affordable and non-intrusive methods for detecting cancer at its early stages. This proposed approach delves into the utilization of antenna arrays to identify kidney cancer. Specifically, antenna array with circular polarization has been crafted to identify tumors in the human kidney. This array design has been implemented using CST software, operating at 2.4 GHz. The antenna array having a dimension of 150 mm x 150 mm. The array consists of four-square patches each having a length of 30 mm and the spacing between the patches is preferred to be 20 mm for ensuring the mutual coupling. FR4 substrate is used with the relative permittivity 4.3 and 1.6 mm thickness. The axial ratio of the circularly polarized antenna is 0.9 dB at 2.4 GHz. The reflection coefficient S 11 = –30dB. The renal phantom in humans has been built with the kidney, adrenal gland, ureter, skin, fat, and muscle components to allow for precise simulation. Following that, four stages of cancer tumors were built employing all of the necessary qualities. For every stage of the cancer tumor, the reflection coefficient growth and resonance frequency shift are calculated. For the initial stages, the resonance frequency shift is very low. Consequently, the primary determinant of detection is the rise in S 11 . For 3rd and 4th stages of the tumor, there is a significant change in resonance frequency and increase S 11 , which facilitates identification. The calculated specific absorption rate (SAR) is a smaller amount than the safety thresholds, indicating that using this method is safe. Overall, this research points to a novel, easy-to-use method for kidney cancer screening. This method has the following benefits: it is non-invasive, safe, quick, affordable, and comfortable, and it emits no ionizing radiation during the measurement process. Furthermore, a range of output parameters such as gain, directivity, and polar radiation have been accurately computed.

Mobile-integrated SRR-based four-port MIMO antenna for broadband mm-wave 5G applications

ABSTRACT A low-profile, single-layered, compact-size, highly-isolated four-port MIMO antenna integrated within a 5 G smartphone has been proposed for a futuristic mm-wave broadband communication system. The proposed MIMO antenna configuration has been derived from a conventional inset-fed rectangular microstrip patch by introducing two parallel I-shaped slots on the patch surface for operating over a wide bandwidth of 4.91 GHz, that is, from 26.78 to 31.69 GHz. The antenna geometry has an overall dimension of 20.9 mm x 20.9 mm x 0.787 mm. The proposed configuration attained a maximum gain of 8.11 dBi and radiation efficiency of 90% at 28 GHz resonating frequency. The integration of the square-shaped SRR structure among closely packed antenna elements has significantly enhanced the overall isolation by 13 dB without compromising the antenna’s physical dimensions. The realisation of the S-parameters has also been carried out from the equivalent circuit model to agree with the results obtained from the electromagnetic simulation through CST software. The measured radiation patterns assured the minimal variation with simulated characteristics along the E and H planes. A comprehensive safety investigation of the proposed MIMO antenna has been carried out to assess power densities (<10 W/ m 2 ) across different usage modes, including data, reading, and talking in a mobile application perspective. Several diversity parameters, including ECC (<0.0001), DG (>9.999 dB), CCL (<0.12 bits/sec/Hz), MEG, and TARC, have also been evaluated as performance metrics. Furthermore, the linear transmission property of the proposed MIMO antenna has been validated through the variation of group delay (<0.5 ns) over operating frequency bands in the far-field region.

Design and Analysis of Wireless Power Transmission (2X1) MIMO Antenna at 5G - Frequencies for Applications of Rectenna Circuits in Biomedical

This research presents the design and analysis of a 5G harvesting energy Circuit (MIMO-rectenna) to receive wireless power at Sub-6 frequencies (5.6 GHz) as a power source for some medical devices carried by a patient and moved from one place to another, whether they are diagnostic or therapeutic devices. This concept aims (MIMO-rectenna) to increase the likelihood of obtaining electricity from the ambient field by harvesting energy at 5G- frequencies. The tiny MIMO (2x1) antenna measuring 30 by 40 mm2 is the antenna portion of this rectenna. It has been built and tested to operate at Sub-6 frequency, or 5.6 GHz, for wireless power transmission applications related to 5G technology. The MIMO antenna has parameters of E = 4.4, h = 1.6 mm, and tand = 0.025 when printed on an FR4 substrate. A significant section of the antenna's rear was removed to carry out the broadband process, and the material's front side was composed of a series of circular slits. In this antenna, the parasitic approach was employed to decrease the mutual coupling between two ports by creating an inverted T with precise dimensions. The CST software 2024 was used to assist with the design and simulation results of this MIMO antenna. It was discovered through the simulation that the mutual coupling for these ports, 𝑆12and 𝑆21, is equal to -51.476 dB, and that the S-parameters, 𝑆11, 𝑆22, equal -22 dB. That is, there is very little signal loss while switching from the first port to the second and vice versa. This antenna's rectifier comprised an AC-to-DC conversion circuit, a DC filter, and an impedance-matching network. With the use of ADS software 2024, this rectenna's design and simulation results were completed. The greatest conversion efficiency of this rectenna at the frequency of 5.6 GHz is determined to be between 65 % and 65.01% for load resistance between 12 KΩ and 15 KΩ at an input power of 14 dBm.

L-Valine solution sensing based on fano resonance of terahertz metasurface sensor

A terahertz metasurface sensor with the asymmetric double metal crosses structure is presented. By adjusting the position of vertical bar to generate Fano resonance, the dipole radiation can be greatly suppressed, thereby reducing the ohms and radiation losses of metal and enabling the sensor to achieve a high quality factor (Q factor). A simulation analysis using CST software revealed that the Q factor of Fano peak and Fano dip can reach 25 and 51, respectively. Furthermore, the sensitivity of Fano peak can reach up to 319 GHz/RIU when the thickness of the coating layer is 12.5 μm. Experimentally, a solvent mixture of water and glycerol with a volume ratio of 2:8 is utilized. The lower limit of detection by this method to detect the concentration of l-Valine solution is 5 mM. The concentration sensitivity of l-Valine solution can be quantified at 1.92 GHz/mM.

Design of a multi-carrier X-ray source for communication with energy modulation information.

X-ray communication is a kind of space communication technology which uses X-ray as information carrier. In order to improve the information transmission capacity, communication rate and anti-interference ability of X-ray communication, we proposes to design a novel multi-target X-ray source. The source is composed of a fast switching module of light channels based on FPGA technology and four photoelectric X-ray tubes with different target materials: Cr, Fe, Ni, and Cu. Using Geant4 software, we determined the optimal target thickness for each material, which enabled us to fully leverage the characteristic X-rays for multi-channel signal modulation transmission. Moreover, using CST software for particle trajectory simulation and optimization of the electron beam revealed that at a tube voltage of 20 kV, the focus area measures approximately 1.2 mm×1.2 mm. The simulations show that four kinds of spectra with high distinctiveness can be generated from the Cr, Fe, Ni, and Cu targets. Within a single modulation period, these spectra can be combined in various ways to create 16 different X-ray spectra signals, thereby increasing the number of communication elements and enhancing the information transmission rate.

Circular-ring tied arc loaded excellent metamaterial absorber for EMI shielding of Wi-Fi signal and impurity sensing of cooking oil

This paper demonstrates a unique symmetric structure excellent metamaterial absorber (MMA) loaded with circular-ring tied arcs. The FR4 substrate-based MMA can accomplish 98.88 % and 99.81 % absorption maximums at the Wi-Fi and 5G frequencies of 2.4 GHz and 5.0 GHz respectively. The unit cell dimension of 0.16λ0×0.16λ0×0.0128λ0 is considered where the wavelength, λ0 is calculated at 2.4 GHz. The performance of the absorber is analyzed through the electric field, magnetic field, surface current, and effective parameters. The dimensions are optimized through the parametric analysis of the developed model in CST software. The model exhibits stability up to 60° for Transverse electric and magnetic polarizations. During electromagnetic interference (EMI) shielding demonstration, it can achieve a high shielding effectiveness (SE) of 54.34 dB at 2.4 GHz and 77.96 dB at 5.0 GHz. For sensing operation, it can attain a quality factor (Q-factor) of 25.61, a sensitivity of 3.30 %, and a figure of merit (FoM) of 84.51. The prototype measurements of the MMA for EMI shielding and impurity sensing of oil samples have a strong correlation with the simulation performance. Because of the high SE, Q-factor, sensitivity, and FoM, the developed MMA can be a competitive candidate in EMI shielding and oil impurity sensing applications.

Coal-gangue recognition for top coal caving face based on electromagnetic detection

Identifying the coal-gangue mixing ratio during top coal caving is essential for automating the coal caving process efficiently. In this article, a block impression reconstruction method is proposed to create 3D models of coal-gangue mixtures with varying gangue ratios and morphological distributions, based on real coal-gangue blocks that reflect actual coal-falling conditions. These 3D models are then input into CST software for electromagnetic forward simulation. The relationship between electromagnetic signal propagation characteristics and gangue ratio is analyzed, resulting in the creation of a coal-gangue mixture electromagnetic signal dataset. An Optuna-XGBoost-based model is then designed to identify the coal-gangue mixing ratio and the recognition performance is firstly verified by using the electromagnetic forward simulation data. Finally, to verify the method’s practicality, a microwave detection test bench for top coal caving is set up and some comparative experiments are conducted. The experimental results indicate that the electromagnetic signals of coal and rock with different gangue contents exhibit significant differences, and the proposed coal-gangue identification model has significant advantages in accuracy and overall performance compared to other competing models.

Design and electromagnetic shielding of Bi0.5Na0.5TiO3 ceramics as meta-surface absorber for high-frequency microwave application

EMI shielding reduces ambient electromagnetic (EM) radiation by reflecting and absorbing EM waves. Rapid technological growth has increased electronic gadgets and EM radiations, threatening the environment. Microwave materials with high absorption power and cheap cost are crucial for eliminating electromagnetic difficulties in stealth technologies. This study used a conventional solid-state reaction technique to prepare Bi0.5Na0.5TiO3 (BNT) solid solutions and examined their structural, ferroelectric, dielectric, and shielding characteristics. This research describes an EMI shielding material that efficiently absorbs EM wave-induced radiation. Characterizations have been done to evaluate material behavior to support EMI shielding and confirm its absorbing nature. Field emission scanning electron microscopy (FESEM), Raman spectroscopy, and X-ray diffraction (XRD) were employed to examine the surface morphology, local lattice deformation with ionic configuration, and crystal structure. BNT exhibited a rhombohedral structure with R3c symmetry space group with crystallize size 81.5 nm and showed eight Raman active modes with an average grain size of 1.67 μm. The high dielectric constant, reduced dielectric tangent loss, and enhanced polarization value make BNT ceramic a good choice for electrical devices and microwave applications. BNT ceramics showed EMI shielding owing to absorption (SET ∼ −23.65 dB, SEA ∼ −18.91 dB) at 9.2 GHz in the X-band (8.2–12.4 GHz). Meta-surface-based BNT absorbers were designed and simulated in the CST software. The peak depicted the absorption at 9.2 GHz with absorptivity of 91.56 %, 85.03 %, 84.36 %, and 64.6 % for designs 1, 2, 3, and 4, respectively. BNT ceramics have exceptional dielectric absorption properties, and dielectric and magnetic losses, which make them suitable for EMI shielding and absorption applications in the microwave region.

Terahertz wide-band wide-angle absorber and polarization converter based on VO2 metamaterial

In this study, a Terahertz wide-band wide-angle absorber and polarization converter based on VO2 metamaterial is proposed. The device is simulated by using full-wave electromagnetic computing software CST. The device functions as a wide-band absorber while VO2 is in the metallic mode. In the 1.82 THz to 4.27 THz band, the absorption efficiency exceeds 90% and the relative bandwidth reaches 81.4%. The absorption mechanism is analyzed bying equivalent circuit theory. Additionally, the absorber can work at large polarization angle and incident angle. While VO2 is in the insulated mode, the design can convert the incident y-polarized terahertz wave into the x-polarized state and realize the transformation of linear polarization. Polarization conversion efficiency (PCR) exceeds 90% in the band of 1.57 THz to 3.82 THz, with a relative bandwidth of 83.5%. The device also supports large incidence angle tolerances. These results show that the disigned metamaterial device has potential applications in absorption, polarization conversion and imaging.

Wideband LP to CP Converter Using a Reflectarray Based on Modulated Admittance Surfaces Capable of Wide‐Range Beam‐Scanning for Ku/K Band Applications

AbstractThis study provides the design and demonstration of a Ku/K band horn‐fed linear polarization (LP) to circular polarization (CP) converter using a reflectarray antenna based on the holographic technique and the generalized law of total reflection without any iterative algorithms. The proposed hologram performs wide‐range frequency beam scanning with minimum gain losses and cross‐polarization levels. It comprises 2,500 diagonal slotted octagonal subwavelength metasurfaces with a periodicity of 0.266λ0 = 4 mm at 20 GHz as the center frequency. Two equations are defined to compute Y11 of the proposed unit cell regarding its dimensions for TE(0,0) and TM(0,0) Floquet modes. They significantly simplify the coding procedure and reduce the computational time for synthesizing the hologram. The antenna is simulated using the CST software from 14 to 25 GHz. As a confirmation, a prototype is manufactured and measured at 16, 18, 20, 22, and 24 GHz to verify its performance. The simulated and measured results are well‐matched. The presented hologram achieves 40% 1.8‐dB axial ratio (AR) bandwidth (16–25 GHz), 40% 3.3‐dB gain bandwidth (16–24 GHz), and above 30% 2‐dB gain bandwidth (16–22 GHz). Moreover, the antenna can perform beam scanning from 42° to 24° by changing the frequency from 16 to 24 GHz with peak gain values greater than 20.33 dBi. The LHCP pencil beams are at least 24° off‐broadside, so the proposed hologram avoids the feed blockage. These achievements make the hologram one of the best candidates for satellite communications, radar applications, short‐range communication, and point‐to‐point communication.