suggestion to me subject for writing ISI journal paper

I want to work on a subject in the RF and analog circuit area, my approach is writing an ISI journal at last (IEEE journal) , please give me idea about good , new and virgin subject in this field
I just have ADS and HSpice software and itsnt possible for me to implemente the final circuit and just is simulation approach

I think, first choice would be, learn the subject that you wish, and then do some experiments/research on that area then after, you can publish your works in any journal

If you ask some title form here then it seems, you are going to write some essay ? (for publish)

Ex: You may start finding some solution for the difficulties that you faced during your simulation if any

You may try this one: International Journal of RF and Microwave Computer-Aided Engineering

But most good journals I know of don't accept papers without experimental data as verification. So the chance to publish just simulation results is slim if not impossible.