oscillator - Sawtooth generator adjustable from 100MHz-500MHz

I need an easy circuit that will generate sawtooth waves at adjustable 100MHz-500MHz (preferably set by a resistor) from 0V going up to 5V. The waves themselves does not have to be perfectly linear, it can be an upside-down exponential wave (as with charging a capacitor).

There's no x55-type that go on this frequency, but I've read this can also be done with other oscillators or counters. Problem is I don't know which one to pick.

This is not for RF.

EDIT:

This is not for radio propagation.