I'm attempting to design a circuit that will determine the frequency ratio between a known reference frequency \$f_\text{ref}\$, and an unknown signal frequency \$f_\text{sig}\$. The signal frequency can vary dynamically between 1 GHz and 2 GHz. The goal is to use a reference frequency of about 100 MHz such that the frequency ratio can be easily represented with an eight bit counter.
My current thinking is to use a T-flip flop to create a gate signal from \$f_\text{ref}\$ such that the positive duration of the gate pulse equals the reference period. At that point there appear to be a couple of approaches that seem viable. The first is to AND the gate pulse derived from \$f_\text{ref}\$ with \$f_\text{sig}\$, then feed the output into a counter. This is a direct measure of the frequency ratio. The second option is to use the gate pulse as the enable signal into a counter. This is the approach I'm leaning towards. After determining the frequency ratio, I'd like to use this frequency ratio count to program the divider in a separate phase locked loop or direct digital synthesizer.
Ultimately I'm looking for help in finding a counter with the following capabilities. The first is the ability to accept a count enable that is driven by the gate pulse produced by the T-flip flop. Once the count is completed when the gate pulse goes low, I want to output the frequency count in the form of a binary output to program a separate divider before the gate pulse goes high again. It seem that a counter such as the 74HC590 with output registers would be a good candidate. But I'm also considering the benefits of using the timers of a microcontroller to compute the frequency ratio instead. It seems as using the microcontroller would make for a more efficient solution, as it could be used to compute the frequency ratio and then send the computed value to a PLL divider.
I hope my description of the problem is clear, and I would appreciate any insight on appropriate counters, or whether the microcontroller route is better.