VCXO - different voltage tuning mechanism
Well, you could generate a PWM signal digitally,then filter it and apply it to the tuning input.
Of course, this would be a monumentally bad idea, since the PWM frequency components which were not filtered out would modulate the oscillator output. Without knowing what your signal bandwidth is, there is no way to tell if this would be a problem - but it's hard to think of an application which would do well by this approach.* Or, you could make a very, very good filter - but if you're at the stage of &quot;the obvious way to vary voltage is with voltage dividers&quot; this is probably not a reasonable requirement.
But you could do it.
*For instance, you might be using your oscillator to produce a fairly low-resolution analog telemetry channel using a 2.3 to 2.5 GHz span to transmit -.5 to 4.5 volts. A possible example would be a single-channel data link for a model rocket. Since the voltage in/frequency out curve is not very linear, you wouldn't get much accuracy.
But you could do it.