Parasitic Elements Research Articles

A Wideband High-Isolation Microstrip MIMO Circularly-Polarized Antenna Based on Parasitic Elements.

This work presents a wideband, all-side square-cut square patch multiple-input, multiple-output circularly-polarized (MIMO-CP) high-isolation antenna. The MIMO-CP antenna contains a two-port square cut on all corners of the square patch, and parasitic elements of 9 × 5 periodic square metallic plates are designed and operated. The outer dimensions of the antenna are 40 × 70 mm2, and the FR4 substrate height is 1.6 mm. The proposed antenna with the parasitic elements improves impedance matching and enhances S-parameters and axial ratio (AR). In the suggested MIMO-CP antenna, a parasitic element is designed and placed around the antenna periodically to reduce mutual coupling (MC) and improve CP. Simulated results show that the suggested antenna has a wide bandwidth (BW) from 4.89 to 6.85 GHz for S11 and was < -10 dB with AR ≤ 3 dB from 5.42 to 6.58 GHz, with a peak gain of 6.6 dB. The suggested antennas have more than 30 dB isolation and a low profile, are affordable, easily made, and are CP. To make a comparison with the measured and simulated results, a MIMO-CP antenna structure was fabricated and tested. The suggested antenna is better in terms of efficiency, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC). The proposed antenna is adequate for WLAN applications.

An ultra-wideband orthogonal-beam directional graphene-based antenna for THz wireless systems

In terahertz (THz) wireless systems, graphene shows a tremendous promise for the implementation of miniaturized and reconfigurable antennas due to its unique tunable property. This paper presents a wideband beam reconfigurable directional antenna for THz wireless communication systems. The antenna design concept is based on the Yagi-Uda antenna working principle. The proposed antenna consists of a centre-fed graphene-based driven dipole and three graphene-based parasitic elements on either side of the driven element. These graphene-based parasitic elements either act as directors or reflectors by controlling the surface conductivity of these elements. The surface conductivity of the elements is adjusted individually by applying a bias voltage via the chemical potential of the graphene. The main beam direction of the antenna can be reconfigured by controlling the chemical potentials of the graphene-based parasitic elements. Specifically, the proposed graphene THz antenna reconfigures the main beam into four orthogonal directions (0°, 90°, 180° and 270°) at an operational frequency 1.25 THz. The antenna achieves a directional symmetrical radiation pattern with 14 dBi gain and a front-to-back ratio of 15.5 dB. Furthermore, the proposed graphene THz antenna provides a stable reflection coefficient in four reconfigurable cases and an ultra-wideband of 10-dB impedance bandwidth of 120%. Therefore, this novel design technique of graphene-based ultra-wideband high gain beam reconfigurable THz antenna is promising for THz wireless systems.

An active clamp coupled inductor‐based soft‐switched quadratic boost converter

SummaryThis paper proposes a novel active clamp‐based quadratic boost converter to achieve a high gain output voltage. The converter combines a quadratic boost converter with a voltage doubler circuit using a coupled inductor. An active clamp circuit with an auxiliary switch is used to utilize the usually wasted energy of leakage inductance and clamp the voltage to a certain limit. The combination of leakage inductance and parasitic capacitance of the main switch provides the benefit of zero voltage switching (ZVS) in both MOSFETs. Similarly, output diodes operating under zero current switching (ZCS) improve the overall efficiency of the converter. Voltage doubler and active clamp circuitry reduce the voltage stress on solid‐state devices; hence, a low Rds,on device is selected. The converter model is simulated using PSIM software and calculated maximum efficiency of ~95% for 200 W and measured maximum efficiency of ~93% for 190 W power level including various parasitic elements.

Vivaldi antenna for early cancer detection based on THz spectroscopy: Comparison between response of breast and skin cancer

this paper suggests a Vivaldi antenna for the THz frequency range with a wide bandwidth (more than 120% bandwidth) for early cancer detection with dimensions of 1λ× 0.5λ× 0.034λ for 0.5 THz with special novel arrangement of photonic crystal and taper grating reflector. The photonic crystal walls are implemented on both sides of the antenna to make an electric shield to concentrate energy for increasing the gain and directivity of the antenna and reducing the side lobe. Front to back (F/B) ratio is another problem for this THz antenna where the grating parasitic elements are used as the reflector to reduce the back lobe of the basic antenna. This antenna covers 0.5–2 THz with a maximum gain of 8.8 dB in the broadside. The proposed antenna is used for detecting breast and skin cancers which are modeled by Debye’s second-order model. The reflection and transmission, pulse response, and phase variation for normal and tumor tissue are considered for the reorganization of cancers. The results show that reflection and transmission, pulse responses are not effective factors for breast cancer detection in comparison to skin cancer while the phase response is the best solution for this type of cancer.

Design of Crossed Dipole Yagi–Uda MIMO Antenna for Radar Applications

This work proposes, builds, and manufactures a small, high-gain MIMO antenna for radar applications. Using a Parasitic elements such as director & reflector show a simple method for increasing the gain and bandwidth of a Yagi-Uda Antenna. Using a Parasitic elements such as director and reflector show a simple method for increasing the gain and bandwidth of a Yagi-Uda Antenna. Using a nearby parasitic director and reflector. Also, it shows a simple method for increasing the gain and bandwidth of a Yagi–Uda antenna. A strip with a parasitic director is placed close to the top dipole element to improve the gain as well as bandwidth attributes of the Yagi–Uda antenna. The antenna performance parameters are investigated for 1 × 2 MIMO, cross dipole MIMO antenna (1 × 4), and an array configuration (two 1 × 4). It has high gain and operates in the S-band (2 GHz–4 GHz). This antenna supports three bands and has a highest maximum directive gain of 12.5 dBi at 2.5 GHz and a bandwidth of 0.21 GHz. It is made of FR4 substrate. The suggested structure is 120 mm × 70 mm in size. Due to its high gain and less return loss, this antenna is better suited to radar applications.

Flexible UWB and MIMO Antennas for Wireless Body Area Network: A Review

In recent years, there has been a surge of interest in the field of wireless communication for designing a monitoring system to observe the activity of the human body remotely. With the use of wireless body area networks (WBAN), chronic health and physical activity may be tracked without interfering with routine lifestyle. This crucial real-time data transmission requires low power, high speed, and broader bandwidth communication. Ultrawideband (UWB) technology has been explored for short-range and high-speed applications to cater to these demands over the last decades. The antenna is a crucial component of the WBAN system, which lowers the overall system's performance. The human body's morphology necessitates a flexible antenna. In this article, we comprehensively survey the relevant flexible materials and their qualities utilized to develop the flexible antenna. Further, we retrospectively investigate the design issues and the strategies employed in designing the flexible UWB antenna, such as incorporating the modified ground layer, including the parasitic elements, coplanar waveguide, metamaterial loading, etc. To improve isolation and channel capacity in WBAN applications, the most recent decoupling structures proven in UWB MIMO technology are presented.

A Filtering Antenna Using Transversal Coupling Topology

In this letter, a coupling scheme for the realization of filtering antennas is introduced. This coupling scheme allows the filtering antenna to realize a filter-like reflection coefficient using an all-radiator structure. Instead of cascading resonators one by one in a ladder manner, in a transversal filtering antenna (TFA), all the radiative resonators are coupled to the source simultaneously. The impedance and radiation behaviors of these subantennas (SAs) can be designed individually. So, the performance of these filtering antennas has much lower sensitivity to their physical structure than conventional cascaded designs, which makes the design of such a filtering antenna much easier. Besides, this topology can realize out-of-band gain zeros without using any parasitic elements or cross-coupling structures. The locations of these gain zeros can be controlled by simply changing the lengths of each SA. To the authors’ knowledge, this is the first time that a transversal filtering antenna with all resonators radiative is presented. For validation, some transversal filtering antenna designs with different coupling topologies are introduced to prove the concept and show their advantages. A third-order prototype is fabricated and measured for demonstration, showing good agreement between the simulated and measured results.

A Dual Wideband Compact Shared-Aperture Microstrip Patch/Fabry–Perot Resonator Cavity Antenna

In this article, a dual wideband compact shared-aperture microstrip patch/Fabry–Perot resonator cavity antenna is proposed. A reflective meshed patch is designed to conduct as the shared surface, which works as the radiator at the lower band but the partial reflective sheet (PRS) at the upper band. A transmissive meshed patch is designed as the parasitic element to broaden the lower bandwidth without influence on the upper band radiation. The shaped ground is used to improve the front-to-back ratio at the lower band while maintaining a compact size. Moreover, the reflective meshed patch, which is built by two complementary frequency selective structures (FSSs), shows a positive reflection phase gradient to broaden the bandwidth of the antenna at the upper band without influence on the lower band radiation. The measurements reveal that a common bandwidth of ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11(22)}\vert &lt; -10$ </tex-math></inline-formula> dB, gain reduction < 3 dB) 25.4% and 21.3%, an isolation higher than 40 and 22 dB, a peak gain of 9.01 and 16.6 dBi at UHF band and C-band are achieved, respectively. The above properties make the proposed antenna suitable for dual-band point-to-point line-of-sight (LOS)/non-LOS (NLOS) communication systems.

Gate-Source Voltage Analysis for Switching Crosstalk Evaluation in SiC MOSFETs Half-Bridge Converters

Measuring the gate-source voltages of wide bandgap (WBG) devices in half-bridge converters provides useful information about susceptibility to crosstalk, which can cause uncontrolled cross-conduction and excessive gate-oxide stresses. However, parasitic elements of the printed circuit board (PCB) and device packaging can compromise measurement accuracy, causing unreliable results. Here we describe how this shortcoming can be addressed using devices in packages that have a Kelvin source pin, allowing a more accurate analysis.

Isolation Enhancement of a Two-Monopole MIMO Antenna Array with Various Parasitic Elements for Sub-6 GHz Applications.

In this paper, a high-isolation multiple-input/multiple-output (MIMO) microstrip monopole antenna array is investigated. To reduce the mutual coupling between antenna elements, a novel composite parasitic element constituted by a T-shaped ground branch and an isolated branch was designed and analyzed. The proposed composite parasitic element is capable of generating a unique three-dimensional weak electric field, which can effectively suppress the mutual coupling between the antenna elements. To give an intuitive illustration about the design principle and decoupling strategy of the proposed antenna, the antenna design procedure was ingeniously divided into four steps, and three types of decoupling structures during the antenna evolution were meticulously analyzed at both the theoretical and the physical level. To validate the proposed decoupling concept, the antenna prototype was fabricated, measured, and evaluated. The reflection coefficient, transmission coefficient, radiation pattern, and antenna gain were studied, and remarkable consistency between the measured and simulated results was observed. The simulations showed that the antenna has a peak gain of 3.5 dBi, a low envelope correlation coefficient (ECC &lt; 0.001), and a high radiation efficiency (radiation efficiency &gt; 0.9). Parameters of the proposed MIMO antenna including electrical dimension, highest isolation level, and 20 dB isolation bandwidth were evaluated. Compared with the previous similar designs, the proposed antenna exhibits attractive features including compressed dimension (0.55λ0 × 0.46λ0), extremely high isolation level (approximately 43 dB), fabulous 20 dB isolation bandwidth (3.11-3.78 GHz, 19.4%), a high diversity gain (DG &gt; 9.99 dB), an appropriate mean effective gain (-3.5 dB &lt; MEG &lt; -3 dB), and low design complexity.

Wideband Circularly Polarized Microstrip-Slot Antenna with Parasitic Ground Planes

In this study, a new stacked microstrip slot antenna (MSA) with wideband circular polarization (CP) characteristics is proposed. The antenna consists of a square-loop feed configuration, four parasitic square patches, four parasitic vertical planes, and a square ground plane etched with four parasitic square slots. The corner-cut square-loop can excite a stable 270° phase difference by loading an arc-shaped strip into the square-loop. Square-patches, vertical planes, and square slots as parasitic elements are placed together at the side of the square-loop to stimulate two CP resonant points. Simulation and measurement are performed on the designed antenna prototype to demonstrate the design’s rationality. The measured results depict that the measured impedance bandwidth (IBW) for |S11| &lt; −10 dB is 36.4% (4.65 to 6.70 GHz) and the measured axial ratio bandwidth (ARBW) for AR &lt; 3 dB is 25.1% (5.01 to 6.45 GHz). Compared with other reported stacked CP antennas, the proposed antenna has significant advantages in CP bandwidth, which could occupy the wireless local area network ITS (5.8 GHz), (5.725–5.85 GHz), and WIFI (5.85–5.925 GHz) bands.

Comparative evaluation and analysis of GaN-based VSIs and CSIs

In this paper, a SPICE-based assessment platform for fast-switching Gallium Nitride (GaN) devices-based voltage source inverters (VSIs) and current source inverters (CSIs) is presented. VSI has long been the dominant topology for motor drive systems. The previous research found enormous problems caused by the direct replacement of WBG switches in VSIs. As a viable alternative, the intrinsic properties of CSI topology make it suitable for WBG-based devices. The GaN device is selected in this paper as one of the most promising candidates among all WBG devices. Tailored double pulse test (DPT) is used to characterize the GaN switch in VSI and CSI topologies. VSI-DPT and CSI-DPT printed circuit boards (PCBs) are fabricated to experimentally evaluate the GaN switch, and to further modify the SPICE model. Moreover, the way to realize a dedicated SVPWM modulation scheme for three-phase CSI is introduced. The parasitic elements associated with the DPT-PCB layout are considered for the purpose of accuracy. VSI and CSI circuits are built in LTspice with a modified SPICE model of the GaN switch, enabling more precise analysis of GaN-based VSI and CSI under a wide range of operating conditions.

Analysis of effects of MOSFET parasitic capacitance on non-synchronous buck converter electromagnetic emission

This paper aims to extract the correlation between parasitic capacitances of the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and its influence in Electromagnetic (EM) Emission level of non-synchronous buck converter. In order to validate the proposed concept, the non-synchronous buck converter is designed and validated with dissimilar kind of MOSFETs which have different parasitic specifications. The effect of parasitic capacitance in MOSFET switching and transient characteristics are analyzed with time domain waveforms and the resultant electromagnetic emission due to those switching transients are analyzed and correlated with practical electromagnetic radiated and conducted emission results. The analysis and testing results shows the significant role of MOSFET parasitic capacitances in determining MOSFET switching transients, controlling the magnitude of electromagnetic emission and determining the frequency of EM noise propagation. Along with the time domain and frequency domain analysis the near field Electromagnetic scanning also performed to prove the proposed concept and reason for targeting MOSFET parasitic elements alone to control the EM emission level of the converter. The obtained results provide the evidence of controlling Electromagnetic emissions is possible with optimal selection of MOSFET parasitic capacitances without any additional control or filter circuits.

A compact four states radiation-pattern reconfigurable monopole antenna for Sub-6 GHz IoT applications

A simple design of a compact radiation-pattern reconfigurable monopole antenna with different states is proposed. The antenna switches between four radiation patterns by introducing two parasitic elements, which can be controlled by activating or deactivating two p-i-n diodes. The antenna presents two opposite-direction unidirectional modes, one bidirectional mode, and one omnidirectional mode. Few lumped components are used in the DC bias network, reducing the fabrication cost and antenna complexity. An antenna prototype is fabricated and tested to validate the proposed approach. The common operating frequency band measured realized gain and realized efficiency ranging from 3.36 GHz to 3.6 GHz, 2.13 dBi to 4.93 dBi, and 62% to 82%, respectively. The antenna presents the benefits of a low profile, simple DC bias, and the ability to suppress radiations in unwanted directions. Therefore, the antenna can be easily integrated and used in different wireless systems requiring pattern diversity, for instance, in Sub-6 GHz Internet of Things (IoT) Applications.

Possibilities of cryosurgery in the treatment of the abdominal cavity diseases

Aim. To study the immediate results of the use of cryosurgical instruments and ultra-low temperature liquid nitrogen in diseases of abdominal organs.Materials and research methods. The article presents the results of surgical treatment using ultra-low temperature liquid nitrogen (196oC) for 308 patients with diseases of the abdominal organs in the Department of Liver and Pancreas Surgery of the Institute of Gastroenterology of the Republic of Tajikistan from 2016 to 2022.The results and discussion. The authors proposed an algorithm for the use of the ultra-low temperature of liquid nitrogen in the treatment of diseases of the abdominal organs after the development of the latest cryogenic equipment. It turned out that the resulting cryodestruction leads to the death of parasitic elements of alveococcosis, echinococcosis, and liver tuberculosis, as well as to cytolysis of atypical calls in hepatocellular carcinoma. The most important advantage of liver cryosurgery, especially in concomitant chronic viral hepatitis and liver cirrhosis, is a reliable parenchymal haemo-and cholestasis, a decrease in intraoperative blood loss, an increase in the radicality of an operation, and reliable prevention of intraoperative dissemination of malignant and parasitic diseasesConclusion. The accumulated experience of surgeries for various diseases of the abdominal organs using ultra-low temperature liquid nitrogen allows concluding that cryosurgery of the abdominal organs has an undoubted prospect. The positive characteristic of using cryotechnology in the treatment of severe diseases of abdominal organs suggests that it is advisable to introduce the method into clinical practice on a wide scale.

Gastrointestinal Helminths in Horses in Serbia and Various Factors Affecting the Prevalence.

Data on gastrointestinal infections in horses in Southeastern Europe are limited; thus, this study aimed to add to the existing knowledge on this topic by reporting on the prevalence of intestinal parasites of horses in the territory of the Republic of Serbia. In the period from April 2017 to December 2018, parasitological examination of 548 samples from horses of different breed, age and sex from four regions and 18 districts of the country was performed. Coprological diagnostic was done by using qualitative methods without concentration and qualitative methods with concentration of parasitic elements. Quantification of the obtained results was performed using semi-qualitative faecal egg count. Four helminthoses were detected in the examined samples: P. equorum (8.57%), O. equi (3.65%), strongylid eggs (71.17%) and Anoplocephala spp. (0.91%). The total prevalence of helminthoses was 77.19%. Monoinfections were significantly more present 70.07% compared to coinfections (7.12%). The highest prevalence of helminthoses was detected in free-ranging horses (93.10%-27/29), in autumn 86.67% (117/135) and winter 79.71% (165/207), in Šumadija and West Serbia region (100%), and in the youngest category (100%). Significant difference (p < 0.001) was detected in the prevalence of monoinfections by strongylids and O. equi and also coinfections by strongylid/P. equorum between horses of different age categories. Obtained results are of great contribution to clinical parasitology and pathology, especially from the aspect of animal health, welfare and preservation of horse population.

Design and analysis of broadband circularly polarized compact planar antennas for 2.45 GHz RFID handheld reader applications

AbstractIn this article, an innovative design of a broadband circularly polarized compact planar antenna for RFID (radio frequency identification) receivers is presented. The suggested structure used the concept of slots loaded parasitic element printed underneath a coplanar waveguide-fed radiator to achieve the circularly polarized (CP) radiation and size reduction. A parasitic element loaded with F-slot and L-slot, and a window-type slotted ground plane was used to achieve resonance at 2.45 GHz with right-handed circularly polarized radiation for RFID handheld reader application. Experimental results confirmed that the designed antenna of size 16.5 × 14.8 × 1.6 mm3 attained a −10 dB impedance bandwidth of 15.8% (from 2.330 to 2.716 GHz) and 3 dB AR bandwidth of 3.43% (from 2.410 to 2.494 GHz). An axial ratio of 0.43 dB was achieved in the boresight of the antenna at the 2.45 GHz RFID band. The concept of electric field distribution on the antenna was used to elaborate the excitation of CP radiation in the antenna.

RF choke based methodology for flange effect mitigation and antenna isolation improvement in bistatic radars of aerospace vehicles

This paper presents a novel technique for mitigation of flange effect and antenna transmit to receive isolation improvement methodology using RF choke for the bistatic radars of aerospace vehicles. The presence of flange causes variation in antenna radiation pattern, by an increase in sidelobe level, decrease in gain and dip in roll pattern, thereby degradation in the performance of the antenna. An RF choke adjacent to the waveguide wall is introduced to nullify the undesirable effects of the flange. This Paper demonstrates through simulation and experimentation that this choke effectively suppresses the surface wave and can be applied in many types of antennas to improve the radiation pattern deteriorated by parasitic elements. It is also demonstrated through measurements that the isolation from transmit to receive antenna is improved by introducing choke, with this technique antenna isolation is enhanced by 23 dB with 11 dB antenna gain. The gain and sidelobe improvement of the antenna with RF choke is 2 dB, and 6 dB, respectively. The proposed array antenna is fabricated with and without choke, measurements are performed and test results are presented. The isolation test between transmit & receive antenna is performed in an anechoic chamber and test results are presented.

Isolation Improvement of Parasitic Element-Loaded Dual-Band MIMO Antenna for Mm-Wave Applications.

A dual-band, compact, high-gain, simple geometry, wideband antenna for 5G millimeter-wave applications at 28 and 38 GHz is proposed in this paper. Initially, an antenna operating over dual bands of 28 and 38 GHz was designed. Later, a four-port Multiple Input Multiple Output (MIMO) antenna was developed for the same dual-band applications for high data rates, low latency, and improved capacity for 5G communication devices. To bring down mutual coupling between antenna elements, a parasitic element of simple geometry was loaded between the MIMO elements. After the insertion of the parasitic element, the isolation of the antenna improved by 25 dB. The suggested creation was designed using a Rogers/Duroid RT-5870 laminate with a thickness of 0.79 mm. The single element proposed has an overall small size of 13 mm × 15 mm, while the MIMO configuration of the proposed work has a miniaturized size of 28 mm × 28 mm. The parasitic element-loaded MIMO antenna offers a high gain of 9.5 and 11.5 dB at resonance frequencies of 28 GHz and 38 GHz, respectively. Various MIMO parameters were also examined, and the results generated by the EM tool CST Studio Suite® and hardware prototype are presented. The parasitic element-loaded MIMO antenna offers an Envelop Correlation Coefficient (ECC) &lt; 0.001 and Channel Capacity Loss (CCL) &lt; 0.01 bps/Hz, which are quite good values. Moreover, a comparison with existing work in the literature is given to show the superiority of the MIMO antenna. The suggested MIMO antenna provides good results and is regarded as a solid candidate for future 5G applications according to the comparison with the state of the art, results, and discussion.

Circularly Polarized MIMO Antenna with Wideband and High Isolation Characteristics for C-Band Communication Systems.

This paper presents a circularly polarized (CP) multiple-input multiple-output (MIMO) antenna using a microstrip patch and parasitic elements. The proposed design exhibits wideband characteristics for both impedance and axial ratio bandwidths. Especially, the mutual coupling between the MIMO elements is significantly depressed without using any decoupling network. To achieve these features, parasitic elements are positioned nearby and in different layers to the radiating elements. The measured results demonstrate that the proposed MIMO CP antenna has a wideband operation of 11.3% (5.0-5.6 GHz), which is defined by an overlap between -10-dB impedance and 3-dB axial ratio bandwidths. Across this band, the realized gain is better than 6.0 dBi, and the isolation is greater than 32 dB with the highest value of 45 dB. The MIMO parameters such as the envelope correlation coefficient, diversity gain, and channel capacity loss are also investigated thoroughly, which are found to be good on the scale of diversity standards.