Parallel-plate Transmission Line Research Articles

Multi-channel current electro-optic isolated measurement and discharge current characteristics in a parallel plate transmission line driver

Multi-channel current electro-optic isolated measurement and discharge current characteristics in a parallel plate transmission line driver

Synchronous Trigger Technology and Discharge Characteristics of Multiparallel Gas Switches Based on Parallel Plate Transmission Lines

This article proposes a gas switch with a low inductance (31 nH), a wide operating coefficient (≥50%), a rapid breakdown (< 100 ns), and a high intensity of current (532 kA/7.8 C). We also design a synchronous trigger system for discharging multiparallel switches while ensuring significant scalability and low cost. The maximum amplitude of the outputs of 16 pulses under high-resistance loads was 77.1 kV/14 ns (10%–90% rise time). Following this, we built a 200-kJ compact pulsed power device by using parallel plate transmission lines. This device can reduce the overall inductance by 14% compared with the previous generation of devices. We also investigated the factors influencing synchronous discharge as well as the conditions for the synchronous discharge of 16 gas switches in parallel. At an operating voltage of 70 kV, the maximum amplitude of the short-discharge current was 5.5 MA (deviation was less than 3%) and the shortest rise time was around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 ~\mu \text{s}$ </tex-math></inline-formula> (10%–90% rise time). The stable operation of the device is important for physics research on the load.

A Microwave-Induced Atmospheric-Pressure Low-Temperature Linear Plasma Source Based on Parallel Plate Transmission Lines

This article presents a new type of microwave-induced atmospheric-pressure low-temperature dielectric barrier discharge source, based on the principle of parallel plate transmission lines (PPTLs). This source is a simple structure with small size, large plasma discharge area, and low discharge temperature. Experiments show that linear plasma discharge with width of 15 mm can be obtained with input power of only 25 W at 2.45 GHz. The temperature of sample placed 1 mm vertically away from the nozzle and treated for 3 min is about 45 °C even with 60-W microwave input power, which proved its thermal safety even for the biomedical applications. Emission spectroscopy diagnosis indicates that the electron density of plasma can be controlled easily by adjusting the discharge gap and the dielectric thickness. It makes this source available for various applications. This work provides a new approach to obtain uniform linear plasma.

A Relativistic and Electromagnetic Correction to the Ramo–Shockley Theorem

The classical Ramo–Shockley (RS) theorem gives the current induced on perfect conductors by the motion of nearby charges, assuming nonrelativistic motion of those charges in electrostatic fields. This article illustrates how relativistic and electromagnetic effects modify RS in some simple examples. Specifically, we present explicit, closed form analytic solutions of Maxwell’s equations for the induced current distribution on perfectly conducting plates due to the motion of a line charge moving parallel and perpendicular to the plates. The results have been verified by several methods, including particle-in-cell simulations. They are compared with the classical electrostatic theory used to derive RS. New insights into the limitation and validity of RS are provided. Electromagnetic shocks are explicitly calculated in closed form when the line charge strikes a parallel plate transmission line.

Frequency response analysis of dielectric materials in a parallel-plate transmission line

A transmission line allows different frequencies to conduct alternating current (AC). They are a peculiar type of wire that allows signal transmission while making it resistant to external noises. A parallel-plate transmission line is a type of transmission line designed with two parallel plates with a dielectric sheet material in the center, as the name implies. The parallel-plate transmission lines are usually used for a miniature setup in which the line prevents the signal from losing power. However, the line's frequency response is a varying setup in which a change in a parameter can fully change the frequency response of the line, and in turn trigger inefficiency. With this, different factors such as the conductor, the size, and the dielectric material of the parallel-plate transmission line can affect its frequency response. Specifically, the analysis of the transmission would test the various frequency responses when the dielectric sheet content is varied. The researchers will carry out experiments on air, Teflon, plexiglass, and E type glass dielectrics.

High-Q Switched Oscillator With Capacitive Voltage Divider for Generating Mesoband High-Power Microwave Pulses

The switched oscillator (SWO) is a quarter-wave oscillator capable of generating mesoband high-power microwave (HPM) pulses. This paper presents a novel high-quality factor ( Q) SWO with a capacitive voltage divider (CVD). Unlike conventional SWOs, the transmission line energy of the proposed SWO is gradually coupled with the output load through the CVD. Thus, the proposed SWO can produce a mesoband pulse with a much higher power spectral density within the coupling bandwidth of a target in HPM effect testing. The frequency-domain output-voltage equation of the proposed SWO was obtained through a theoretical analysis of the equivalent circuit of the SWO. Through a numerical analysis, the time-domain output waveform of the proposed SWO was demonstrated to have a high quality factor, and the circuit parameters of the equivalent circuit of the SWO were set to achieve a high quality factor. The circuit parameters selected in the numerical analysis were used in an electromagnetic simulation to determine the design parameters of the parallel-plate transmission line (PPTL)-based SWO with the CVD built on a printed circuit board. The proposed SWO was fabricated and its performance was assessed. For a breakdown voltage of 8.7 kV, the output voltage of the fabricated SWO showed a quality factor of 25, which is more than two times larger than the quality factors of conventional SWOs. Thus, the proposed SWO was demonstrated to produce high- Q mesoband HPM pulses, and it has the potential to be applied in HPM effect testing. Moreover, the proposed SWO improves operator safety by preventing the output load from being charged by a high-voltage power supply.

Energy Band Attraction Effect in Non-Hermitian Systems.

The energy band attraction (EBA) caused by the nonorthogonal eigenvectors is a unique phenomenon in the non-Hermitian (NH) system. However, restricted by the required tight-binding approximation and meticulously engineered complex potentials, such an effect has never been experimentally demonstrated before. Here by a suitable design of all-dielectric Mie resonators in a parallel-plate transmission line, we for the first time verify the photonic analog of the EBA effects both theoretically and experimentally. The evolution of the EBA effect in a two-level NH system from gapped bands to gapless bands to flat bands is observed by precisely tuning the loss of the Mie resonators. The transmission spectra can be theoretically connected to the eigenvalues and eigenvectors of the NH Hamiltonian. Furthermore we extend our methods to a graphenelike two-dimensional NH system. Our works show a metamaterial approach toward NH topological photonics and foster a deeper understanding of band theory in open systems.

Frequency Response Analysis of the Parallel-plate Transmission Line using Various Conductors

Frequency Response Analysis of the Parallel-plate Transmission Line using Various Conductors

Lens Antenna With Planar Focal Surface for Wide-Angle Beam-Steering Application

A new lens antenna for wide-angle beam-steering application is presented. The 2-D lens permittivity profile according to Luneburg is modified using transformation optics to obtain a planar focal surface, allowing for a simple cost-effective planar feed technology. A slice of the lens is confined between two metallic surfaces forming a parallel-plate transmission line, enabling beam-steering in the plane containing the slice. Stacking up such slices result in a more focused beam and beam-steering capabilities in the perpendicular plane. As a result, full 2-D beam-steering becomes possible, with a very wide steering range of ±60° in one plane and a smaller steering range of ±15° in the orthogonal plane. The inhomogeneous dielectric slice is made of four dielectric materials with different permittivity, with a pattern of drilled holes of different diameters realizing a smooth gradient of the effective permittivity. The measured performance of the antenna prototype, operating at about 10 GHz includes 17.2 dB maximum directivity, a scan loss better than 0.8 dB, a sidelobe level better than 11 dB, and an aperture efficiency of 74%, outperforming any other reported beam steering antenna with planar focal surface.

Microstrip Center-Fed Bi-plane Printed Dipole Antenna Design and the Excitation Gap Contribution for Impedance Control

Source-antenna transition modeling differential feed of microstrip center-feed bi-plane printed dipole antenna is presented. Design considerations are focused on the feed mode of the studied antenna at its center by the means of ideal plane parallel-plate microstrip transmission line that supports a quasi-TEM mode of propagation. Numerical experiments of the excitation gap effects on the antenna peak resonant resistance were carried out. The calculations of the antenna input impedance using voltage and current wave formalism and the radiated field pattern using retarded potential approach for a given current distribution are performed. It is concluded that bi-plane printed dipole antenna exhibits excellent directional performances such as good selectivity, HPBW of 60° and large band-width of 22%.

Multipactor in parallel-plate transmission line partially filled with dielectric material

Due to the poor conductivity of the dielectrics, if an electron collides with the dielectric material, a charge will be deposited on the surface as a consequence of the secondary electron emission. Thus, the multipactor process in dielectric-loaded microwave devices differs from those in metallic devices. The objective of this paper is to study the self-extinguishing physical mechanism of the multipactor in parallel-plate transmission lines partially filled with dielectric layers by particle-in-cell simulation. The self-consistent field generated by the electrons in the simulation is assumed to be neglected, since there do not exist too many electrons in the self-extinguishing process. To illustrate the self-extinguishing phenomenon in a dielectric-loaded waveguide device, the strength of electric field in the vacuum area needs to be the same as that in a metallic device. When the input power is slightly higher than the multipactor threshold, the self-extinguishing phenomenon occurs after the initial electron multiplication while the number of electrons increases exponentially with the simulation duration in metallic device. Based on this fact, the physical mechanism of self-extinguishing phenomenon is investigated in detail. By analyzing the temporal evolution of the electrons and the average secondary electron yield (SEY), it can be concluded that the self-extinguishing phenomenon is caused by the electrostatic field generated by the charges deposited on the surface of the dielectric. Moreover, the average SEY of the dielectric tends to be one or greater than one when the number of electrons drops to nearly zero. Hence, it is necessary to further analyze the ability to continue accumulating charges on the dielectric surface when extra electrons are injected into the simulation region at the instant when the number of electrons is close to zero. For the former case, the charges deposited on the dielectric surface remain steady all along, while the charges reach to a stable state eventually as the number of injected electrons increases for the latter one. Both of them mean that the average SEY of the dielectric surface will be unity in the end. Since the electrostatic field generated by the charge deposited on the dielectric surface can reduce the risk of occurrence of multipactor, the electret material could be used in the design of the dielectric-loaded microwave devices to improve the multipactor threshold.

Cavity-Backed Angled-Dipole Antennas for Millimeter-Wave Wireless Applications

A cavity-backed angled-dipole antenna is proposed for millimeter-wave wireless applications. The angled-dipole radiator is built on both sides of an RT/Duroid 5880 substrate (εr=2.2) and fed by a parallel-plate transmission line. The cavity-backed reflector is utilized to improve the radiation characteristics of the angled dipole, such as gain, back-radiation, symmetric pattern, and similar 3 dB beamwidth in theE- andH-planes. The design, with a cavity aperture of0.5λ28-GHz×0.5λ28-GHz, results in aS11&lt;-10 dB bandwidth of 26.7–30.6 GHz, a gain of 6.6–8.0 dB, and a similar 3 dB beamwidth of approximately 70° for both theE- andH-planes. Eight-element linear arrays with the proposed antenna having a center-to-center spacing of 5.6 mm(0.52λ28-GHz)are characterized, fabricated, and measured. By applying nonuniform power distribution across excitations, the array achieves a scan angle up to 40° and a sidelobe level below −15 dB.

Broadband Planar 5:1 Impedance Transformer

This letter presents a broadband Guanella-type planar impedance transformer that transforms 50 $\Omega $ to 10 $\Omega $ with a 10 dB bandwidth of 1–14 GHz. The transformer is designed on a flexible 50 $\mu {\rm m}$ thick polyimide substrate in microstrip and parallel-plate transmission line topologies, and is inspired by the traditional 4:1 Guanella transformer. Back-to-back transformers were designed and fabricated for characterization in a 50 $\Omega $ system. Simulated and measured results are in excellent agreement.

Simulation computation and analytic modification of characteristic impedance of parallel-plate transmission line

Based on time domain reflection theory, a novel way to calculate the characteristic impedance of a parallel-plate transmission line is proposed. With CST microwave studio, a simulation model is established to calculate the accurate value of the characteristic impedance of the parallel-plate transmission line. Based on the results, the analytic formula for the characteristic impedance of the parallel-plate transmission line is modified. Furthermore, the effect of broadening of the bottom plate of parallel-plate transmission line on its characteristic impedance is researched. Considering the effect of broadening of bottom plate, a new formula for the characteristic impedance of the parallel-plate transmission line is proposed. The final formula could be applied to the calculation of the characteristic impedance of bounded-wave simulators and other electromagnetic pulse simulators with similar structure.

Development and Field Testing of a Parallel-Plate Transmission Line Moisture Sensor

Precisely and continuously monitoring the moisture content under pavements can provide significant information for pavement condition evaluation and maintenance. In this paper, a moisture sensor using a microwave parallel-plate transmission line is developed and prototyped. The moisture content is determined from the phase shift of waves propagating along the line. The sensor system was installed at an experimental field site, and the moisture contents in the pavement were monitored over a period of six months. Laboratory tests and field tests show that the moisture sensor system is sensitive and accurate. Compared with existing moisture sensors, the developed sensors are very small in size, easy to install, and durable.

Microwave spectroscopy of [formula omitted]-doublet transitions in the ground state of CH

The Λ-doublet transitions in CH at 3.3 and 0.7GHz are unusually sensitive to variations in the fine-structure constant and the electron-to-proton mass ratio. We describe methods used to measure the frequencies of these transitions with Hz-level accuracy. We produce a pulsed supersonic beam of cold CH by photodissociation of CHBr3, and we measure the microwave transition frequencies as the molecules propagate through a parallel-plate transmission line resonator. We use the molecules to map out the amplitude and phase of the standing wave field inside the transmission line. We investigate velocity-dependent frequency shifts, showing that they can be strongly suppressed through careful timing of the microwave pulses. We measure the Zeeman and Stark effects of the microwave transitions, and reduce systematic shifts due to magnetic and electric fields to below 1Hz. We also investigate other sources of systematic uncertainty in the experiment.

Monte-Carlo method of computing multipactor threshold in microwave devices

In order to find a rapid and accurate numerical method to compute the multipactor threshold in microwave device, three enhanced Monte-Carlo (MC) methods are proposed which are single particle-multiple collision MC, multiple particle-single collision MC and multiple particle-multiple collision MC method. The three MC methods all give the random nature of the secondary electrons, including their initial energies, phases and angles. And in all of the methods, the electron trajectory is computed with Runge-Kutta method and the secondary electron yield (SEY) per collision is computed with Furman model. The effective SEY is taken as the criterion to judge whether multipactor occurs, the definition of which is a little different from those of the three MC methods. As a verification, the multipactor in a parallel plate transmission line is investigated with the presented MC methods and the traditional MC method. The numerical results of the four MC methods are compared with the results of the statistical theory. It is demonstrated that the single particle-multiple collision MC method has the smallest error and the best stability.

Precise Measurement Using Coaxial-to-Microstrip Transition Through Radiation Suppression

This paper presents a study about the radiation problem of coaxial-to-microstrip launchers and suggests their improvement with a novel design. The proposed solution is based on a coaxial-to-microstrip transition enclosed in a parallel-plate transmission line that has its cutoff frequency above the working frequency band of interest. Any radiated field is quickly attenuated because it is propagating inside a subcritical parallel-plate transmission line. The proposed method is extensively analyzed in the CST Microwave Studio, and simulation results are verified on fabricated test-fixture by multiple measurements. The proposed solution improves the accuracy and reduces the uncertainty during measurements on a microstrip.

Design of Parallel-Plate Transmission Line Feeding Differentially Driven Patch Antenna for GPS application

In this paper a newly developed patch antenna, designated as the parallel-plate transmission line feeding differentially driven patch antenna is presented. The parallel-plate transmission line will not introduce inductance to the input impedance of a patch antenna, thus the height of the patch can be largely increased. Measurements show that the 3-dB-gain bandwidth can be obtained to 65% (0.86–1.93 GHz), return loss is -20dB, VSWR is 1.3 and impedance is 51 ohm at resonant frequency of 1.58GHz. The radiation pattern is stable and this antenna is designed for GPS application.

Traceable electric and magnetic field calibrations of radiation monitors for amateur radio inside a parallel plate transmission line up to 30 MHz

Abstract. In many countries the electromagnetic field strength in the proximity of licensed amateur radio stations is limited to ensure public safety. If the station antenna(s) and/or the environmental situation are complex, only measurement results are acceptable as proof, and proper calibration of the field strength meters ("radiation monitors") is mandatory. A system and a procedure are described here, enabling calibration of such "radiation monitors" at a high quality level and traceable to the SI units, but with low-budget amateur equipment.