Design of Experiment Applied to Transmission Lines in Radio Frequency Network Simulations

摘要

Design of experiment is a method where the relation between input factors and outputs can be studied. In practice, a number of experiments are conducted and the input(s) are changed between each experiment. Gained information can then be used to find out how to improve the process under study. It is applicable to many areas from cooking to radio frequency (RF) simulations. This thesis focuses on the effects of transmission line lengths and their effect to different RF parameters. Study is applied to a long term evolution frequency division duplexing (LTE-FDD) mobile front end. The purpose is to find out the applicability of DOE to RF design process.To be able to start final simulations it is required that layout is completed. When layout is finished, accurate parameter values can be used to receive reliable results. For example, transmission line lengths are acquired from the layout. However, there may be situations where the layout is not entirely finished. Therefore, it would be an advantage if limits for the length of a transmission line length could be defined without compromising reliability. In this thesis DOE is applied to search for suitable limits for the transmission line lengths. If applicable boundaries are found, simulations could be done before layout is completed.To find out the acceptable boundaries, existing simulation models are used to study the effects of transmission line lengths to different RF parameters. Chosen transmission lines are then varied in length with desired limits. Acquired results, using the limits, are then compared to a nominal case, where no transmission line variation is done. A set of different percentual limits are used. Studied RF parameters are insertion loss and return losses in each port.DOE was utilized on two RF (LTE-FDD) front ends. LTE-FDD bands 2 and 12 were chosen to cover two unique cases. Though only LTE-FDD front ends are investigated, the information received could also be applied on other RF transmission lines in other types of front end, such as GSM or WCDMA front ends.iiThe study revealed that DOE can be used as tool to evaluate whether a transmission line length, within a limit, is applicable to continue simulation process. In some situations the case might be that no applicable limit is found. If the limit is not usable, simulation process cannot be continued without compromising the accuracy of the results.