I can assume that your antenna has its dimensions longer than a half wavelength. Then you can use the same or a similar substrate to make the quarter-wave transformer as needed. Any handbook on striplines will give you the information of the line width defining lined impedance.
Having no information from you on the operating frequency, I can only suggest that impedance transformers can also be made with lumped elements and small size. As you do a project, you must study well everything you need to succeed.