Stub Structure Research Articles

Horus : Accelerating Kernel Fuzzing through Efficient Host-VM Memory Access Procedures

Kernel fuzzing is an effective technique in operating system vulnerability detection. Fuzzers such as Syzkaller and Moonshine frequently pass highly structured data between fuzzer processes in guest virtual machines and manager processes in the host operating system to synchronize fuzzing-relevant data and information. Since the guest virtual machines’ and the host operating system’s memory spaces are mutually isolated, fuzzers conduct synchronization operations using mechanisms such as Remote Procedure Calls over TCP/IP networks, incurring significant overheads that negatively impact the fuzzer’s efficiency and effectiveness in increasing code coverage and finding vulnerabilities. In this paper, we propose Horus , a kernel fuzzing data transfer mechanism that mitigates the aforementioned data transfer overheads. Horus removes host-VM memory isolation and performs data transfers through copying to and from target memory locations in the guest virtual machine. Horus facilitates such efficient transfers through using fixed stub structures in the guest’s memory space, whose addresses, along with the guest’s RAM contents, are exposed to the host during the fuzzer’s initialization process. When conducting transfers, Horus passes highly-structured non-trivial data between the host and guest instances through copying the data directly to and from the stub structures, reducing the overall overhead significantly compared to that of using a network-based approach. We implemented Horus upon state-of-the-art kernel fuzzers Syzkaller , Moonshine and kAFL and evaluated its effectiveness. For Syzkaller and Moonshine , Horus increased their transfer speeds by 84.5% and 85.8% for non-trivial workloads on average and improved their fuzzing throughputs by 31.07% and 30.62%, respectively. Syzkaller and Moonshine both achieved a coverage speedup of 1.6× through using Horus . For kAFL, Horus improved specifically its Redqueen component’s execution speeds by 19.4%.

Gain-assisted magnetoplasmonic switching in metal–dielectric–metal plasmonic waveguides

Optical switches in metal–dielectric–metal (MIM) structures attracted much interest for chip-scale plasmonic modulator merging nanoelectronics and ultrafast photonics. The absorption switches employed gain modulations; thus, their switching speed is limited to the sub-gigahertz range because of the spontaneous lifetime of the transition. In this paper, we theoretically predicted that the function of the absorption switches is achieved employing magnetic field reversal and constant gain instead of gain modulations. We investigated analytically and numerically transmission in the presence of both gain and gyration and revealed that the transmission shift by the external magnetic field is maximized at a resonance value of gain. The switching speed can reach the THz range thanks to the large optical bandwidth in the MIM stub structures and the advanced magnetization switching technology. The MIM structure with combined gain and magnetoplasmonic properties enhances interaction between light and magnetic field on nanoscale and enables the device footprint down to the deep subwavelength scale λ2/50.

Design of a Dual Band-pass Filter Using Fork-type Open Stubs and SIR Structure

Design of a Dual Band-pass Filter Using Fork-type Open Stubs and SIR Structure

Ka-/W-Band Shared-Aperture Antenna Array Based on Stacked Continuous Transverse Stub

In this article, a planar Ka-/W-band shared-aperture antenna is proposed for millimeter-wave detection radars. This antenna is based on the stacked continuous transverse stub (SCTS) structure and the hybrid waveguide, which work as the slow wave waveguide at Ka-band and the pure imaginary characteristic impedance (PICI) waveguide at W-band. The proposed SCTS structure consists of an upper W-band CTS antenna and a lower Ka-band CTS antenna. The upper W-band antenna can operate without the downward leakage due to the PICI waveguide. For the Ka-band antenna, the high-frequency structure can be equivalent to an inductive surface at Ka-band to achieve better impedance matching. The advantages of low profile, high isolation, and high aperture efficiency at both bands can be achieved. The overall height of the antenna is only 7.5 mm, about 2.5 times the wavelength of the high frequency.

High-sensitivity refractive index sensors based on Fano resonance in a metal-insulator-metal based arc-shaped resonator coupled with a rectangular stub

A metal-insulator-metal (MIM)-based arc-shaped resonator coupled with a rectangular stub (MARS) structure is proposed. This structure can generate two tunable Fano resonances originating from two different mechanisms. The structure has the advantage of being sensitive to the refractive index, and this feature makes it favorable for application in various microsensors. The relationship between the structural parameters and Fano resonance is researched using the finite element method (FEM) based on the software COMSOL Multiphysics 5.4. The simulation reveals that the sensitivity reaches 1900 nm/refractive index unit (RIU), and the figure of merit (FOM) is 23.75.

Three port photonic and plasmonic demultiplexers based on Cross and U-shaped stub structures: Application for filtering and sensing

We propose the design of three port photonic and plasmonic demultiplexers where filtering toward the two outputs is based on the phenomena of Fano resonances and electromagnetically induced transparency (EIT). We use a Cross-shape resonator in one output and a U-shape resonator composed of two stubs in the other output. We give a theoretical demonstration of the geometrical parameters of both resonators in order to filter one wavelength in one output while leaving the other output unperturbed. These results are confirmed by experimental validation in the radio frequency domain and a numerical simulation in the infrared (IR) domain using plasmonic metal–insulator–metal waveguides. The Cross resonator in the first output can give rise to an EIT resonance, whereas the U-shaped resonator in the second output may exhibit both EIT and Fano resonances depending on the lengths chosen for the stubs. Therefore, different demultiplexing schemes can be proposed such as achieving a Fano resonance in one output and an EIT in the other, or EIT resonances in both outputs. The Fano resonance is obtained by bringing resonance close to transmission zero, whereas the EIT results from the squeezing of resonance between two transmission zeros. When the widths of the resonances tend to zero, they transform to trapped or bound states in the continuum with an infinite lifetime. We show that the crosstalk between the two channels can be reduced to −82 dB and the sensitivity can reach 2390.8 nm/RIU, RIU is the refractive index units. Finally, we highlight the performance of our design as a high sensitive filter and sensor in the IR domain. In this work, the analytical calculations and demonstrations are performed by using Green’s function approach, the experimental verifications are realized by means of coaxial cables operating in the radio frequency range and the numerical simulations are obtained using the finite element method via Comsol Multiphysics software.

All-optical frequency-dependent magnetic switching in metal-insulator-metal stub structures.

Many attempts to switch magnetization with optical pulses were based on free-space coupling schemes of circularly polarized light pulses, so-called all-optical helicity-dependent magnetic switching; however, waveguide coupling schemes are promising for on-chip all-optical magnetic switching. Metal-insulator-metal (MIM) stub structures provide a promising platform for highly integrated photonic circuits, thanks to their compact size, on-chip compatibility, and ease of fabrication. We found clockwise and counterclockwise ring-like modes in the MIM stub structure, which can act as effective magnetic fields with two opposite directions due to the inverse Faraday effect. Effective magnetic field spectra inside the MIM stub have dual resonant peaks at which the effective magnetic field intensity reaches its extreme values with opposite signs, corresponding to binary magnetic states. Switching between the binary magnetic states can be achieved by altering the optical pump frequency. The all-optical frequency-dependent magnetic switching in the MIM stub may provide a chip-compatible and ultracompact tool for ultrafast switching of magnetic order.

Design of an Analog RFID-Based Tag Antenna with Opened Circuited L-Shaped Stubs for Applications in Localization

This paper presents a new analog design for a radio-frequency identification (RFID) tag antenna with a long-read range oriented to localization applications. The actual work focuses on the analog input characterization of antenna impedance by studying the capacitive effect, created by the gaps, and the effect of the introduced opened circuited L-shaped stubs, on the RFID tag characteristics. Numerical and measured results confirm that proposed tag antenna performances are significantly improved by introducing gaps and stub structures and after optimizing their dimensions, such as length and width. The introduced stubs with optimum dimensions provide good impedance matching, and improved return loss values. Furthermore, two operating frequency bands have been created when the antenna is excited by a 50 Ω port: a low-frequency band around 837 MHz and a higher one around 927 MHz. These results have been validated by measured ones. The proposed RFID antenna is mainly composed of three split rectangular resonators (SRR) where introduced structures concern only the larger SRR. The optimized antenna has an area of 76 × 24.6 mm2 and is printed on the Taconic RF-60A substrate with a dielectric constant of 6.12, a thickness of 1.6 mm, and a loss tangent of 0.025. Simulation results show interesting communication performances, of the proposed tag antenna, with a return loss of −22.3 dB around 916 MHz and a long-read range up to 25 m when it is fed by an industrial Mping M730 chip with a power sensitivity of −24 dB and an output impedance Zchip = 16 − j194 (Ω) at 916 MHz

A liquid crystal leaky-wave antenna with fixed-frequency beam scanning and open-stop-band suppression

ABSTRACT In this article, a liquid crystal (LC) leaky-wave antenna (LWA) is presented with fixed-frequency beam-scanning property operating in millimetre-wave band. Two rows of periodic-perturbation stubs (PPSs) structure are employed on both sides of a microstrip line to generate radiation. The undesirable open stop-band (OSB) that deteriorates the broadside radiation of the LWA can be avoided, and a satisfactory broadside radiation is realised, by introducing a specific offset between the two rows of the PPSs, which is different from the existing methods and is fully studied in this paper. Furthermore, since LC material with tunable dielectric constant is loaded on the antenna substrate, the phase constant of the LWA can be manipulated by applying a controllable biasing voltage from 0 V to 20 V. Therefore, fixed-frequency beam scanning can be realised. The presented LWA is fabricated and measured, and the antenna performances have been verified by the measured results.

Integrated lowpass and C spectrum band pass filter using miniaturized stub based model

A stub-based model for a miniaturized lowpass circuit integrated with C spectrum bandpass response is developed in this brief. The proposed integrated filter structure has two sections, which consist of upper stub based lowpass model with 3 dB cut-off frequency of 3.03 GHz and lower inverted T shaped (ITS) stub structure having bandpass response within C band. The symmetrical stub sections along with an H shaped transmission line increases the lowpass suppression response. The passband of 5.56 GHz to –7.12 GHz is realized in the stopband region of the lowpass response. The final design provides a normalized circuit size of 0.037 λg2 with stopband noise rejection up to 25 GHz after the upper cut-off of the bandpass response. The in-band return loss of 20.6 dB is achieved using the half of quarter wavelength model of ITS. The fractional bandwidth of 24% is observed with out-band suppression of 25 dB. The lowpass and bandpass circuit geometry is optimized and explained individually. The proposed structure is fabricated and measured which is in admirable agreement with the simulated results. This compact stub-based lowpass-bandpass filter prototype can be used for C band satellite uplink communication applications.

Design of a new anti-metal RFID temperature tag antenna based on short-circuit stub structure

With the increasing maturity of the power Internet of things (pIoT), radio frequency identification technology (RFID), is more applied to the fault monitoring of power equipment, of which the temperature monitoring of power equipment is one of the focuses of fault monitoring. When the traditional RFID temperature measurement tag is applied to high-voltage electrical equipment, it often produces metallic interference to the RFID temperature measurement tag antenna because it is attached to the surface of metal conductor, such as large synchronous machine and high-voltage transmission line, which greatly shortens the identification range of the traditional RFID temperature measurement tag on the metal surface and even cannot work normally. To solve the problems above, a new anti-metal RFID temperature tag antenna is designed in this paper. The internal antenna of the RFID temperature measurement tag adopts the anti-metal design based on the short-circuit stub structure, so that the temperature measurement tag can achieve the purpose of good anti-metal performance. Finally, through the simulation of HFSS, this paper verifies that the designed RFID temperature measurement tag can not only resist metal effect, but also be well applied to complex metal environment.

Wide Band Meandered-Loop Ground Radiation Antenna for Biomedical Applications

The concept of wireless implantable medical devices (IMDs) is becoming more popular as the world’s population ages and concerns about public health grow. Implantable antennas have figured prominently in wireless communication among IMDs and external infrastructures, yet they have subsequently become a major study area. Among the most difficult aspects of building implantable antennas is to varied physical tissues and fluids act as dielectric stress on antenna, affecting its efficiency dramatically. Ground radiation antenna was particularly designed for the antenna size reduction. The features of the ground have an impact on it. There is variance in the radiation field with similar frequency and antenna length yet varied ground conductance. It has been discovered that when the ground conductance is low, the radiation field is minimal and the orientation of the radiation field modifies. A meandered-loop ground radiation antenna (MGRA) was designed by coupling the meandered-loop structure to the ground radiating plane using only one electrical element. The proposed antenna was studied for biomedical applications at ISM band in the range between 2.4 to 2.8 GHz. The overall size of antenna is 30×24 mm2 making it suitable for the implantable applications. The bandwidth of the MGRA was further improved by using stub structures. The single layer skin model simulation showed that |S11| parameter as −21.21 dB at the resounding frequency of 2.40 GHz. Major factors like impedance match gain, radiation effectiveness and Specific Absorption Rate (SAR) had also been evaluated in this study.

Design and Analysis of MIMO Dual Band Patch Antenna for 5G New Radio Applications in Mobile Terminals

This paper presents a dual-band MIMO antenna design with compact size for 5G communication under 6 GHz band frequency. The metallic monopole stub structure is used to miniaturization of antenna. The L-shape monopole antenna is modified by adding semi-circular element in radiating structure of monopole to obtain dual-band resonance. The High isolation is achieved by employing T-shaped stub in ground plane.It has compact size is 45 mm × 25 mm × 1.6 mm3. The proposed Dual Band MIMO antenna has been design on FR4 material with ɛr = 4.4 with 1.6 thickness. The proposed antenna has 5G application in the bands of 2.5 GHz (2.34 GHz-2.62 GHz) and 3.5 GHz (3.20 GHz-5.20 GHz). The bandwidth of antenna getting 320MHz and 2500MHz at 2.5GHz and 3.5GHz respectively. The Isolation (S21) of proposed antenna is -31.2 dB at 2.5 GHz and -19.5 dB at 3.5 GHz. VSWR is less than 1.06 for both the bands. The designed dual band MIMO antenna covers 5G bands of 2.3-2.4GHz (n30/n40), 2.4-2.5GHz (n7/n38/n41/n90), and 3.2-5.2GHz (n77/n78/n80). The experimental and simulated results observed good matching except some slight variation. This proposed dual band MIMO antenna is suitable for 5G mobile Communications.

A Review on Different Techniques of Mutual Coupling Reduction Between Elements of Any MIMO Antenna. Part 1: DGSs and Parasitic Structures

AbstractThis two‐part article presents a review of different techniques of mutual coupling (MC) reduction. MC is a major issue when an array of antennas is densely packed. When the separation between the antennas is <λ0/2, i.e., half of the free‐space wavelength, the antenna parameters suffer from the surface wave, and the space wave coupling effect between the antenna elements. To reduce the MC influence, several techniques have been discussed in the scientific literature. This part of the review paper will discuss strategies: antenna placement and orientation approach, Defected Ground Structures (DGSs), slots/slits‐etching approach, protruding ground stub structures, and parasitic elements/structures. This article concludes with feasibility, applications, and comparison of the techniques mentioned above. Simultaneously, the applications and possibilities of the remaining methods are discussed in part two of the article.

Coplanar waveguide‐serially‐connected coplanar strip dual stub structure for wideband bandpass filters

In this paper, a kind of coplanar waveguide (CPW)-fed series stub structure is proposed and its application in wideband bandpass filters (BPFs) is developed based on the coplanar strip (CPS) dual stubs. Compared with its conventional CPS dual-series-stub counterparts, the proposed one excited by even-mode CPW lines possesses enhanced immunity against unexpected resonance of the CPS-based series stubs. By virtue of this attractive performance, desired resonance can be well realized with predicted in-band characteristics. Subsequently, the application in its constituted wideband BPFs is investigated with synthesis design method. In final, one third-order and one fifth-order BPFs are designed, fabricated, and measured to verify the proposed structure. Measured results are found in reasonably good agreement with the synthesized and the simulated ones.

A Compact Cavity-Backed Slot Antenna Using Dual Mode for IoT Applications

This letter presents a compact cavity-backed slot antenna using dual mode for Internet of Things (IoT) applications. The proposed antenna has stub structures for generating additional resonant mode, by which two polarization components orthogonal to each other are realized within the impedance bandwidth. By the combination of the two modes, circularly polarized radiation is generated. The impedance bandwidth increase by the additional resonant mode, and the proposed stub structures act as a capacitive loading contributing to the miniaturization of the antenna. For validation of the proposed antenna, simulations were conducted, and the antenna was fabricated and measured. The fabricated antenna size is 0.23 $\lambda _{0}$ $\times\; 0.23\lambda _{0}$ $\times\; 0.04\lambda _{0}$ , showing a significantly compact size compared to the conventional structures. The measured results confirm that the antenna has a impedance bandwidth from 896 to 958 MHz, and 3 dB axial ratio (AR) bandwidth is about 5 MHz. The measured peak gain and AR at 915 MHz are 2.4 dBic and 0.6 dB, respectively.

Scaling Law, Confined and Surface Modes in Photonic Fibonacci Stub Structures: Theory and Experiment

We investigate both theoretically and experimentally the properties of electromagnetic waves propagation and localization in periodic and quasi-periodic stub structures of Fibonacci type. Each block constituting the Fibonacci sequence (FS) is composed of an horizontal segment and a vertical stub. The origin of the primary and secondary gaps shown in such systems is discussed. The behaviors and scattering properties of the electromagnetic modes are studied in two geometries, when the FS is inserted horizontally between two semi-infinite waveguides or grafted vertically along a guide. Typical properties of the Fibonacci systems such as the fragmentation of the frequency spectrum, the self-similarity following a scaling law are analyzed and discussed. It is found that certain modes inside these two geometries decrease according to a power law rather than an exponential law and the localization of these modes displays the property of self-similarity around the central gap frequency of the periodic structure where the quasi-periodicity is most effective. Also, the eigenmodes of the FS of different generation order are studied depending on the boundary conditions imposed on its extremities. It is shown that both geometries provide complementary information on the localization of the different modes inside the FS. In particular, in addition to bulk modes, some localized modes induced by both extremities of the system exhibit different behaviors depending on which surface they are localized. The theory is carried out using the Green’s function approach through an analysis of the dispersion relation, transmission coefficient and electric field distribution through such finite structures. The theoretical findings are in good agreement with the experimental results performed by measuring in the radio-frequency range the transmission along a waveguide in which the FS is inserted horizontally or grafted vertically.

Proposal of Coplanar Stripline Series Stub Structure for Wideband Bandpass Filters

In this article, a simple kind of coplanar stripline (CPS) open-circuited series stub structure and its application in wideband bandpass filters (BPFs) are proposed and developed. Compared with its conventional dual-shunted CPS series stub counterparts, the proposed one is capable of achieving desired characteristics as the specified transmission-line (TL) prototypes behave. Based on such equivalent prototypes, three types of CPS open-circuited series stubs are then investigated to reveal the immunity against unexpected resonance caused by the underlying surface-wave-like mode. For demonstration, two examples, a second-order and a third-order wideband BPFs, are synthetically designed for equal-ripple Chebyshev response with prescribed fractional bandwidth (FBW) and return loss (RL). Finally, these two proposed filters with a respective FBW of 49%/70%, an RL of 16.426 dB, and a central frequency of 2 GHz are synthesized, simulated, fabricated, and measured. Measured and simulated results are reasonably in good agreement with each other, thus firmly validating the flexibility of the presented CPS series stub structure in the application of wideband BPFs.

Multiwideband Bandpass Filter Based on Folded Quad Cross-Stub Stepped Impedance Resonator

A multiwideband bandpass filter (MW-BPF) using a quad cross-stub stepped impedance resonator (QC-SSIR) was simulated, fabricated, and measured. The proposed QC-SSIR is designed on a four-series arrangement of crossed open stub (COS) structures where each open stub is developed with a step impedance resonator (SIR) structure to generate a wide bandwidth. Compared to the COS resonator, the QC-SSIR has a wider fractional bandwidth and good transmission coefficients and is compact. ABCD matrix analysis is used to investigate the filter structure. Furthermore, the MW-BPF is designed on an FR4 microstrip substrate with εr = 4.4, thickness h = 1.6 mm, and tan δ = 0.0265. The results show that the proposed MW-BPF using a QC-SSIR achieves transmission coefficients/fractional bandwidths of −0.60 dB/49.3%, −1.49 dB/18.7%, and −1.93 dB/13.9% at 0.81 GHz, 1.71 GHz, and 2.58 GHz, respectively. Furthermore, to reduce the filter size, a folded QC-SSIR (FQC-SSIR) structure was also proposed. The results show that the proposed MW-BPF using an FQC-SSIR achieves transmission coefficients/fractional bandwidths of −0.57 dB/49.6%, −1.21 dB/17.7%, and −1.76 dB/12.5% at 0.82 GHz, 1.80 GHz, and 2.62 GHz, respectively. The size of the proposed MW-BPF using an FQC-SSIR is reduced by up to 46% compared with the MW-BPF using a QC-SSIR. Finally, the performance of the simulated MW-BPF based on the QC-SSIR and FQC-SSIR was in good agreement with the measurement results.

High figure of merit refractive index nanosensor based on Fano resonances in waveguide

Fano resonances based on circle-with-inner-core and stub structure are investigated using data derived from the finite element method and theoretically explained by the multimode interference coupled mode theory and the electric distribution in the system. The parameters of specific structure are modified to investigate the influence of different parts for this metal–insulator–metal system. Due to the high sensitivity to filled dielectric materials, the proposed structure can be applied as a refractive index sensor, whose performances are also explored. High sensitivity is gained as high as 1183.3 nm / RIU. And the figure of merit, a key parameter to describe the sensing characteristic, is achieved as 5.1115 × 104, which is better than most similar structures. Our work is significant for the sensitive refractive index nanosensor.