Computational optimization of RF and overall efficiency in TWTs with simulated annealing

Summary form only given. An RF phase velocity taper in the output section of a TWT slow-wave circuit is commonly used to increase RF power efficiency. In order to determine the optimal phase velocity profile, a simulated annealing algorithm has been developed and coded into the NASA 2.5-Dimensional TWT Computer Model. The advantage of simulated annealing over most optimization techniques is that it allows a solution to escape from a local extremum towards the ultimate global optimum. With the incorporation of this algorithm, the model can now be used to optimize any calculated output characteristic in terms of any combination of input parameters. The algorithm was first tested on a paper design for a 60-GHz coupled-cavity TWT. The lengths of the cavities at the end of the output section were optimized for center-frequency RF efficiency. The resulting nonlinear taper showed a computed increase in efficiency form 7.2% to 13.5%.