How to measure

I must plan the student work for extensive measuring set to obtain a data of tangens delta for different plastics in frequency range 400-400 000 MHz. If for lowest frequencies that is elementary, then 100-400 GHz I have no a least idea where to get a proper signal generator and how to measure those loss angle if no any VNA is produced for such range. May somene give a tick with a finger which direction to look for? In the case of totally impossible signal generator for uninterrupted frequencies, the series of fixed frequencies may be permitted, for example 100; 150; 200; 250 etc however seems the multitude may stand more costly.