Coaxial Mode Research Articles

Numerical simulation of the effect of coaxial and cross-axis injection modes on pulverized coal combustion in the raceway of blast furnace tuyere

The aim of this study is to investigate the influence of the angle of the pulverized coal (PC) injection lance on the combustion characteristics of fuel in the raceway of blast furnace tuyeres. Using FLUENT software, a Euler-Lagrange three-dimensional numerical model was constructed to analyze the influence of different positions of blast furnace tuyere coal powder injection lance (coaxial and cross-axis) on key parameters such as temperature distribution, gas flow, and combustion efficiency. The results demonstrate that adjusting the angle of the injection lance significantly modifies the average and peak temperatures in the raceway, while the composition of gas components remains relatively stable. When the injection lance angle is 10°, the average temperature and peak temperature in the raceway are 2294 K and 2747 K, respectively. When the injection lance angle is 12°, the combustion efficiency of the PC reaches 80.8%. This study reveals the significant impact of the injection lance angle on the combustion process. Especially at an angle of 12°, the combustion efficiency of the blast furnace significantly improves. With coaxial injection, the combustion rate increases as the distance between the injection lance tip and the tuyere increases. This paper is instructive for the optimization of the blast furnace combustion system, which improve fuel utilization efficiency and reduce environmental emissions. This paper provides practical recommendations for adjusting blast furnace operational parameters, offering insights for achieving more efficient and environmentally friendly industrial production.

Design and Reconfiguration Analysis of the Trunk Mechanism for a Reconfigurable Wheeled Mobile Platform

Abstract This paper proposes a reconfigurable wheeled mobile platform (RWMP) consisting of two two-wheeled mobile robots and a reconfigurable trunk. The reconfigurable trunk is a 6R multi-mode single-loop mechanism (SLM) that is obtained by inserting two revolute (R) joints with intersected axes into a planar rhombus 4R mechanism. The 6R mechanism has reconfigurable characteristics owing to changes in the wrench system. All six motion modes and their constraint equations of the 6R mechanism are obtained by solving the closed-loop equation based on the D-H transformation matrix. The analysis shows that the mechanism has six single-DOF motion modes, including a planar rhombus 4R mode, two overconstrained spatial 6R modes, and three coaxial 1R modes. The motion characteristics of the six motion modes are identified using screw theory. The six transition configurations among different modes are identified by combining the constraint equations of each mode. The locomotion modes of the RWMP are designed based on the reconfiguration analysis of the trunk mechanism. The locomotion effect of the RWMP under two confined spaces is verified by simulation analysis and prototype experiment.

Electromagnetic design of 402 MHz normal conducting coaxial window for SNS facility

RadiaBeam has developed a novel design of MW-class high-power RF windows to be used in high-power proton accelerators, such as SNS. This design is based on the utilization of a coaxial window between two waveguides to coaxial transitions, instead of a ceramic window in a uniform cylindrical waveguide, which provides several significant benefits. In this paper, we will present the RF and engineering design of this window.

A 3D coaxial transition with continuous ground wall fabricated by a 12-inch wafer-level packaging method for radio frequency applications

Purpose This paper aims to realize the vertical interconnection in 3D radio frequency (RF) circuit by coaxial transitions with broad working bandwidth and small signal loss. Design/methodology/approach An advanced packaging method, 12-inch wafer-level through-mold-via (TMV) additive manufacturing, is used to fabricate a 3D resin-based coaxial transition with a continuous ground wall (named resin-coaxial transition). Designation and simulation are implemented to ensure the application universality and fabrication feasibility. The outer radius R of coaxial transition is optimized by designing and fabricating three samples. Findings The fabricated coaxial transition possesses an inner radius of 40 µm and a length of 200 µm. The optimized sample with an outer radius R of 155 µm exhibits S11 < –10 dB and S21 > –1.3 dB at 10–110 GHz and the smallest insertion loss (S21 = 0.83 dB at 77 GHz) among the samples. Moreover, the S21 of the samples increases at 58.4–90.1 GHz, indicating a broad and suitable working bandwidth. Originality/value The wafer-level TMV additive manufacturing method is applied to fabricate coaxial transitions for the first time. The fabricated resin-coaxial transitions show good performance up to the W-band. It may provide new strategies for novel designing and fabricating methods of RF transitions.

Study on Time Domain Electromagnetic Remote Boundary Detection Method for Multi-component Well Logging

Borehole time-domain electromagnetic remote detection realizes reservoir scale formation boundary measurement. There is a strong correlation between the abnormal response signal of borehole time-domain electromagnetic pure quadratic field and the distance of formation boundary. The greater the boundary distance, the later the abnormal extreme point appears. The response characteristics of the secondary field of the coaxial and coplanar multi-component measurement modes are just "opposite" at different dip angles. Using borehole time-domain electromagnetic measurement information, the formation dip and remote borehole boundary detection can be directly calculated.

W-Band Low-Loss Eight-Way Radial-Waveguide Power Divider Based on Coaxial Mode Transition

W-Band Low-Loss Eight-Way Radial-Waveguide Power Divider Based on Coaxial Mode Transition

Design of a Broadband Transition from a Coaxial Cable to a Reduced-Height Rectangular Waveguide

For miniaturization, rectangular waveguides with a reduced height are often required, along with a coaxial transition for signal launching. We present a simulation-based design of a broadband transition from a coaxial cable to a rectangular waveguide with the height(b)-to-width(a) ratio b/a ranging from 0.125 to 0.375. The proposed transition consists of a coaxial probe with a cylindrical head or a disk and two symmetrically placed tuning posts. To extend the operating frequency range, three sections of the rectangular waveguide are employed with properly chosen dimensions. Design examples are presented for the WR75 waveguide transition with a b/a of 0.125, 0.25, and 0.375, having a bandwidth of 83.4%, 92.7%, and 84.4%, respectively. Compared with previous works, our design offers the largest bandwidth in a right-angle coaxial-to-rectangular waveguide transition employing the aforementioned structure.

Multi-Conductor Cable Modeling With Inclusion of Measured Coaxial Wave Propagation Characteristics

The prediction of voltage stresses in transformer and machine windings requires the ability to calculate pulse propagation effects on the feeding cable with sufficient accuracy. The use of commonly available cable models in electromagnetic transient (EMT) programs can lead to voltage wave fronts with too weak damping at very high frequencies. This work shows a method for improving the accuracy of such models by usage of measured coaxial mode propagation characteristics. The information is introduced into a wide-band multi-conductor cable model at high frequencies by a merging procedure, with only a minor impact on the non-coaxial modes of propagation. The application of the developed model is demonstrated for cases where the metallic sheaths are grounded at one end only, or are cross-bonded.

A 100–180-GHz Coaxial Frequency Tripler Based on Copper Additive Manufacturing

This article presents a wideband coaxial D-band frequency tripler fabricated by copper additive manufacturing (AM). The central part of the tripler consists of two waveguide–coaxial transitions, a coaxial low-pass filter, an antiparallel Schottky diode chip, and an output impedance matching network. Most constitutions, except for the diode chip, are monolithically fabricated in one piece. The diode chip with additional thermal paths is specially designed to obtain a good thermal performance and better power handling. To facilitate the measurement, a waveguide fixture is also designed to convert the ports to standard waveguide ports (WR-19 and WR-6.5). The measurements show that the maximum output power of the tripler is 9.44 mW with about 182 mW of input power at 147 GHz and its 3-dB bandwidth is 45.2% from 108 to 171 GHz. Additionally, the tripler delivers <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 1.87 mW of output power and better than 10 dB of return loss over the 100–180-GHz range. To the best of authors’ knowledge, this is the first AM coaxial ultra-wideband frequency multiplier reported in the open literature.

Design of Ka‐band, broadband, omnidirectional, with a top metal disk antenna

AbstractIn this report, a Ka‐band, broadband, omnidirectional, with a top metal disk antenna is proposed. The antenna is fed by an air waveguide. The TE10 mode of the waveguide can efficiently be converted into an air coaxial TEM mode by a compact waveguide air coaxial transition. After matching and adjusting, the dielectric substrate is loaded and then transited to the metal radiation structure loaded with a top metal disc to obtain omnidirectional electromagnetic waves efficiently converted to free space. By optimizing the sizes of waveguide to air‐coaxial transition structure and disk, and so on, a good broadband omnidirectional antenna performance is finally achieved. The measured fractional impedance bandwidth is larger than 30% with the reference of S11 dB, which fully verifies the rationality of the design. In addition, measured patterns at the plane of different azimuth angles almost coincide with each other, which shows an excellent omnidirectional pattern.

Extending orbital angular momentum multiplexing to radially high orders for massive mode channels in fiber transmission.

Orbital angular momentum (OAM) beams with different angular indices l have the potential to greatly increase communication capacity. However, the finite aperture of optical systems limits the value of the angular index. In order to fully use the orthogonal mode channels supported in the fiber for high-capacity communications, we propose extending the radial indices p of OAM modes as an additional multiplexing dimension. In this paper, we introduce spatially discrete multiple phase planes to multiplex the angular and radial OAM modes simultaneously. Due to the orthogonal property of the central symmetric OAM modes, a two-dimensional (2D) input Gaussian beams array can be converted to coaxial OAM modes through Cartesian to log-polar coordinate transformation by inverse design. For a proof-of-concept demonstration, a 10-mode multiplexer for high-order radial OAM modes was designed using five phase planes. The fabricated multiplexer generated high-quality multiplexed OAM modes with a loss of less than 5.4 dB. The multiplexed OAM modes were coupled into a specially designed ring-core fiber by mode-field matching, achieving stable mode transmission in 2 km fiber. The approach provides a scalable technology to increase the number of transmission channels and could lead to the practical applications of OAM multiplexing in communication.

Design and experiment of broadband electric field sensor for high-power sub-nanosecond pulse measurements

This paper briefly introduces the structure and working principle of the electric field sensor. And a conductive electric field sensor for measuring sub-nanosecond voltage pulse is designed. The sensor consists of coaxial transition section and integrated electric field probe. N-type connector and SMA connector are selected for input/direct output port and coupling output port respectively. The equivalent antenna area of electric field sensor measured by vector network analyzer is about 0.035cm2, and the 3dB bandwidth is more than 5GHz. The results show that the sensor can accurately measure the time-domain voltage pulse produced by the sub-nanosecond solid-state sources.

Space-Borne System-in-Package Based on High Reliability Microwave Interconnections

With the increasing demand for multi-function and highly integrated space-borne microwave products, a three-dimensional heterogeneous integration based on special substrates and other systems-in-package has difficulty with meeting the requirements of high reliability in space. Through simulation, the thermal-deformation resistance of traditional interconnections meets the requirements of high reliability, but its transmission performance at high frequency is poor. Based on the above, a novel microwave horizontal coaxial transition structure with good thermal-deformation resistance and excellent microwave characteristics is proposed. The design formula of the structure is derived, and the basic size of the structure can be quickly calculated. The transition structure and a vertical matching structure can realize microwave interconnection by combining microstrip impedance transformation and gold-ribbon interconnection. The complex microwave circuit is laid out and partitioned in a three-dimensional way, and thus a space-borne microwave metallic system-in-package method based on high reliability microwave interconnections is implemented. A Ka-band receiving system-in-package is used as an example to carry out the actual test and validation. The better characteristics of the Ka-band receiving channel on the satellite are obtained, and its excellent reliability is verified by the temperature cycle and mechanical vibration test.

Intelligent self calibration tool for adaptive few-mode fiber multiplexers using multiplane light conversion

Space division multiplexing (SDM) is promising to enhance capacity limits of optical networks. Among implementation options, few-mode fibres (FMFs) offer high efficiency gains in terms of integratability and throughput per volume. However, to achieve low insertion loss and low crosstalk, the beam launching should match the fiber modes precisely. We propose an all-optical data-driven technique based on multiplane light conversion (MPLC) and neural networks (NNs). By using a phase-only spatial light modulator (SLM), spatially separated input beams are transformed independently to coaxial output modes. Compared to conventional offline calculation of SLM phase masks, we employ an intelligent two-stage approach that considers knowledge of the experimental environment significantly reducing misalignment. First, a single-layer NN called Model-NN learns the beam propagation through the setup and provides a digital twin of the apparatus. Second, another single-layer NN called Actor-NN controls the model. As a result, SLM phase masks are predicted and employed in the experiment to shape an input beam to a target output. We show results on a single-passage configuration with intensity-only shaping. We achieve a correlation between experiment and network prediction of 0.65. Using programmable optical elements, our method allows the implementation of aberration correction and distortion compensation techniques, which enables secure high-capacity long-reach FMF-based communication systems by adaptive mode multiplexing devices.

Type synthesis of reconfigurable single-loop mechanisms based on planar rhombus mechanisms

This paper deals with the type synthesis of reconfigurable single-loop mechanisms (RSLMs) using screw theory. A novel approach is proposed to synthesize RSLMs by inserting two or four revolute joints to a planar rhombus 4R mechanism. Using the proposed approach, four types of wrench systems of RSLMs are obtained. The reconfiguration analysis of an RSLM with a constraint force system is then carried out using the kinematics close-loop equation and screw theory method. By locking the R joints, it can be found that the mechanism can realize a 1-DOF planar 4R mode, a 1-DOF Bricard mode, a 2-DOF serial mode, a 1-DOF coaxial mode, a 1-DOF Bennett mode, and a 2-DOF spatial 8R mode. Furthermore, four transition configurations among different modes are identified. To verify motion modes of the mechanisms, serval 3D printed models are also presented. This work provides a framework for further study of type synthesis reconfigurable mechanisms from overconstrained single-loop mechanisms.

Quadrupole Antenna and Diagnostic Complex for Ion Cyclotron Plasma Heating and Current Drive at the L-2M Stellarator

—A quadrupole antenna has been designed and produced at the L-2M stellarator for experiments on ion cyclotron plasma heating and current drive. Using a power meter of the incident and reflected waves, the first measurements of the radiation resistance of the antenna have been performed in the ohmic heating regime. The radiation resistance of the antenna has been measured as a function of the mean plasma density. It is shown that the fraction of absorbed power ensured by the coaxial modes is 25%. The created quadrupole antenna can also be used for current drive. The proposed method is based on the conversion of fast magnetosonic waves to slow magnetosonic waves with their subsequent absorption by plasma electrons, which is accompanied by current drive processes.

Broad band waveguide to coaxial transition for HOM suppression in RF cavities for future synchrotron light sources

In the modern storage ring light sources, exploiting multi-bunch beams, the longitudinal and transverse coupled bunch instabilities are predominantly driven by higher order modes (HOM) of the accelerator RF cavities. In order to suppress the HOM to a harmless level, we propose using a modified broadband waveguide to coaxial line transitions placed on the cavity body, similar to those used for the DAΦNE collider RF cavities. Such a solution has a simple design that avoids the application of the ferrite materials under the ultra-high vacuum and dissipates the HOM power on the external loadings. Different from DAΦNE with a single cavity per ring, where the damping waveguides are placed laterally on the cavity body, we consider the possibility of allocating the waveguides vertically. Since the modern synchrotron light sources require using more RF cavities to compensate for the synchrotron radiation losses, such a solution helps to save the occupied space when placing the cavities in a row next to each other. This paper describes the design optimization process and discusses the obtained results concerning the effectiveness of the HOM suppression and minimization of the impact of the transitions on the fundamental mode parameters.

An X-band high-power and high-efficiency coaxial relativistic klystron oscillator with four-gap buncher and three-gap extractor

Because of the scaling invariance, the over-mode ratio of the coaxial resonator can be increased to increase the power handling capability. However, as the over-mode ratio increases, the characteristic impedance and external quality factor decrease, which causes the modulation of the electron beam to be weakened. Moreover, when the output microwave power increases, the double-gap output cavity will suffer from severe radio frequency breakdown. Therefore, an X-band high-power and high-efficiency coaxial relativistic klystron oscillator with a four-gap modulation cavity and a three-gap extraction cavity is proposed. First, a four-gap modulation cavity can increase the modulation depth of the electron beam to improve the beam-wave conversion efficiency. The operating mode of the modulation cavity is the 3π/4 mode of the coaxial TM01 mode. Second, a three-gap extraction cavity is adopted to enhance the microwave extraction energy and reduce the RF field strength. The simulation results show that when the diode voltage is 650 kV, the beam current is 15.4 kA, and the guiding magnetic field is 0.48 T, the device outputs a microwave power of 4.2 GW, a frequency of 8.4 GHz, and an efficiency of 42%.

Optical orbital angular momentum multiplexing communication via inversely-designed multiphase plane light conversion

Multiplexing and demultiplexing of optical orbital angular momentum (OAM) are critical operations in mode-division multiplexing communications. Traditional Dammann gratings, spiral phase planes, and optical geometric transformations are regarded as convenient methods for OAM mode (de)multiplexing. However, crosstalk between the different modes and the difficulty of mode multiplexing greatly limit their application to mode-division multiplexing communications. Here, using a set of inversely-designed phase planes, we demonstrate an OAM (de)multiplexer based on multiphase plane light conversion that can enable perfect OAM multiplexing communication. The sorted patterns are Gaussian-like and can be coupled easily into single-mode fiber arrays. Inputs from the fiber array are turned into coaxial OAM modes after the phase planes. OAM mode crosstalk generated by the multiplexer is less than − 20 dB , with insertion loss of less than 2.6 dB. OAM modes are sorted by the demultiplexer with mode crosstalk below − 10 dB , and the sorting results are coupled to the fiber array. OAM modes carrying 10 Gbit/s on–off keying signals were transmitted in a 5 km few-mode fiber. The measured bit-error-rate curves have power penalties of less than 10 dB. The proposed configuration is highly efficient and convenient and will be beneficial for potential applications in quantum information, information processing, and optical communications.

Operation and Qualification of Coaxial Plasma Gun Modes With a Gas Puff Inlet

We describe the design, operation, and qualification of a coaxial plasma gun (CPG) in a low-pressure environment with a gas puff inlet. This infrastructure enables a CPG to operate in the deflagration mode followed by snowplow plasma sheath formation. These modes inject radially expanding and axially propagating plasma sheaths into a low-pressure residual background. This manuscript details the pulse power delivery circuit, including automatic logic control of subcircuits. High-speed camera images (12800 frames/s) of the formed plasma elucidate the ionization of an axially propagating plasma. Long-exposure images (1.3 s) capture the full propagation distance of the plasmoid. Rogowski coil current diagnostics elucidate the timing of a self-crowbar discharge that delineates between deflagration and snowplow modes. An empirically determined 50-ms gas puff duration resulted in a maximum plasma propagation distance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 23$ </tex-math></inline-formula> cm. Shorter durations did not ionize a sufficient amount of gas for elongated axial propagation, whereas longer durations suppressed axial plasma sheath expansion. This type of gas injection CPG device is now qualified for use in CPG experiments that require the snowplow mode and maximum mean free path of fast ions resulting from various plasma heating mechanisms. These include CPG operation within external magnetic fields in which significant plasma propagation distance is required, including solar physics experiments and space propulsion development.