CST

Periodic Eigenmode Simulation of a Travelling Wave Tube

This example demonstrates an eigenmode calculation using periodic boundaries in z-direction. The phase shift of the periodic boundary is defined as a parameter which is swept from 5 degrees to 175 degrees with a step size of ten degrees. CST MWS's Eigenmode solver is ideal for this task.


Geometry reduced to a single helix turn
Figure 1: Geometry reduced to a single helix turn

The frequency range is defined up to 10 GHz. The boundary conditions are set to "electric" except for the two boundary conditions in the z direction, which are defined as "periodic" in order to model the periodicity of the helix. A parameter "phase" is assigned to the periodic boundary, so that the phase shift can be used in a parameter sweep.


E, H fields and surface currents obtained from the periodic eigenmode solution
Figure 2: E, H fields and surface currents obtained from the periodic eigenmode solution

All Fields for periodic phase shift may be plotted as in figure 2 where the E and H Fields are shown.


Dispersion characteristics obtained from parameter sweep of the phase
Figure 3: Dispersion characteristics obtained from parameter sweep of the phase

Figure 3 shows the dispersion curves obtained from the parameter sweep via post-processing templates. The phase velocity is shown here as a function of  frequency. The eigenmode solver delivers any aribitrary number of desired modes, 3 of which are shown in the plot.


Pierce Impedance extracted via template-based post-processing of the parameter sweep results
Figure 4: Pierce Impedance extracted via template-based post-processing of the parameter sweep results

Figure 4 shows the Pierce Impedance obtained as a post-processing step. The powerflow in the tube is also an additional post-processing quantity that may be calculated.


CST Article "Periodic Eigenmode Simulation of a Travelling Wave Tube"
last modified 30. Apr 2013 9:56
printed 24. Feb 2017 6:47, Article ID 123
URL:

All rights reserved.
Without prior written permission of CST, no part of this publication may be reproduced by any method, be stored or transferred into an electronic data processing system, neither mechanical or by any other method.

Feedback

11 of 15 people found this article useful

Did you find this article useful?

Other Articles

Coupled EM-Thermal Modeling of Power Chokes

Coupled EM-Thermal Modeling of Power Chokes
Power chokes are used together with inverters (e.g. solar inverters) to reduce EMC issues. CST EM STUDIO® (CST EMS) can be used to calculate the electric losses in the choke winding of a power choke, and these losses can be used as a heat source to simulate temperature distributions using the thermal solvers in CST MPHYSICS® STUDIO (CST MPS). Read full article..

Optical Device Simulation Plasmonics and Nanophotonics

Optical Device Simulation Plasmonics and Nanophotonics Document type
Optical devices are already key components in many areas, such as communications, remote sensing, or medical applications, and their role will only increase in the future. Simulating such devices helps in optimizing their efficiency and in reducing cost of design and development. With its powerful solvers and user-friendly interface, CST® STUDIO SUITE® offers a unique platform for handling such challenges. Read full article..

Designing Building Structures for Protection against EMP and Lightning

Designing Building Structures for Protection against EMP and Lightning
This article will explore the use of electromagnetic simulation when hardening facilities against EMP and lightning. EMP is a high-intensity burst of electromagnetic energy that can potentially cause major disruption to vital infrastructure such as telecommunications, electrical power, banking and finance, emergency services, medical facilities, transportation, food and water supply. Lightning can cause significant damage by directly striking a building, when metallic structures such as electrical wiring provide return current flow in an attempt to equalize potentials. It is therefore essential to protect or “harden” critical facilities by stringent electromagnetic design, including shielding to block incident EMP fields, careful treatment of points of entry (POE) and diversion of lightning currents using down-conductors. This article shows how a simulation of the performance of EMP protection measures at the point of entry, such as filtering and clamping, can be set up and carried out. The simulation of a lightning strike to a building structure is also demonstrated, to show how the induced current return paths can be visualized in order to characterize the possible effect of the lightning strike on systems inside the building. This includes an investigation of cable system positioning inside the building and the prediction of induced shield and internal load currents and the analysis of lightning protection system (LPS), taking into account the effect of down-conductor type and grounding impedance. Read full article..

PCB and package codesign and cooptimization

PCB and package codesign and cooptimization
The drive for higher performance leads to increasing complexity and miniaturization of electronic circuit on-chip, more functionality on package level and high density PCB boards. PCB/Package designers are therefore taking the electrical environment via Co-Design and Co-Optimization into account. This webinar addresses the challenges in modeling and simulation for PCB package Co-Design and Co-Optimization. Read full article..

A Small, Efficient, Linear-polarized Omni-directional Antenna

A Small, Efficient, Linear-polarized Omni-directional Antenna
Nearly full-sized performance from a spherical coil only 1/6th as long in the E-plane normal direction as a half-wave dipole antenna. Read full article..
Back Back  

Your session has expired. Redirecting you to the login page...