If it is something like the K6BEZ antenna analyzer you will need a dds/frequency generator module that can run at higher frequency.
You will probably also need to design the reflection bridge for higher frequency if you want to go all the way up to 2m. 2m can be done with a SI570 but then the arduino code will have to be changed.
6m is a bit simpler you can use a AD8951 that will go up to about 70MHz but have some harmonics.
Have a look at hamradio 360 page,
http://www.kj6vu.com/?p=1014. I have buildt this one and it is working as a charm, but the code is a bit slow. There are several versions of the code font on internet that will run better.