Poster GP1.029 Comparison of Four Multifrequency Traveling Wave Tube Models a

Wöhlbier et al. – DPP 2000 – 1 As the bandwidth of Traveling Wave Tubes (TWTs) continues to increase and the use of TWTs in communication systems continues to increase, it becomes ever more important to understand the wideband nonlinear behavior of the device. For example, phenomena such as signal capture, cross modulation, and harmonic injection would benefit from more thorough fundamental theoretical explanations. As a part of a general multifrequency TWT program, we intend to review TWT modeling and search for a way to describe the above phenomena. En route to the broader goal we have identified three multifrequency TWT models which have their origins in a Lagrangian “disk ” model. The models are named: i) Affine, ii) Standard Map, iii) Multifrequency Collective Variables. In this presentation we discuss all four models and compare them based on analytic tractability, computing speed, and computing accuracy. Wöhlbier et al. – DPP 2000 –

Paper O2B4 Finite Bandwidth and Space Charge Effects in the MUSE Model a,b

a See Friday morning mini-course poster session for more detail and discussion

On the Physics of Harmonic Injection in a Traveling Wave Tube

Abstract—The physics of signal injection to shape the output spectrum in a traveling wave tube (TWT) is studied using an analytic solution to the approximate nonlinear S-MUSE model and with the large signal code LATTE. The results verify the long-standing conjecture that a frequency canceled by signal injection is composed of a component due to the injected signal and a component due to the nonlinearity of the TWT. Furthermore, the structures of the solutions are exploited to explain and predict behavior for various signal injection schemes. The scenarios studied include second harmonic injection to reduce the second harmonic and enhance the fundamental, multiple harmonic injection to eliminate the sensitive output power dependence on injected phase, second harmonic injection to reduce intermodulation distortion, and multiple signal injection to reduce the intermodulation spectrum. Insights are given regarding the effectiveness of an injection depending on whether the injected signal is within or outside the linear gain bandwidth of the TWT. Index Terms—Harmonic injection, intermodulation, traveling wave tube (TWT)

• The Hamiltonian is:

nonlinearities in multitone helix traveling wave tube amplifier

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 30, NO. 3, JUNE 2002 1063 The Multifrequency Spectral Eulerian (MUSE)

We derive from Eulerian electron beam equations the multifrequency spectral Eulerian (MUSE) model, a new onedimensional (1-D) nonlinear multifrequency model of a traveling wave tube (TWT). We also derive from the same equations a Lagrangian "disk" model, LATTE, so that MUSE may be directly compared to a Lagrangian approach. The models are compared to the large signal code Christine 1-D on a set of TWT parameters which are based on a single section of the Hughes 8537H L-band TWT. Aspects of the physics, nonlinearities, and simulation dimensions of the MUSE model are discussed, as well as its relation to the method of collective variables. A simplified MUSE model S-MUSE useful for analysis is also presented and its applications are discussed