Another technique (overkill for this though) is to use a phase-locked-loop (PLL). You arrange a voltage-controlled oscillator that covers the frequency range linearly for your voltage signal and let the PLL lock onto the input signal. It's control voltage to the oscillator becomes your analog voltage output... As I said over-complex 
Or put another way a PLL converts a voltage->frequency converter into the inverse frequency->voltage converter (hiding a lot of detail).