Divider-by-2 purpose in Synthesizer

[dtz_lou]

Hi all,

Just a general question of my knowledge of dividers.

So far, I know that a "divider-by-2" (when the VCO freq is high, the divider by 2 is analog) is needed because its output signal gives 50% duty cycle and also the programmable digital divider (prescaler) can functions better with lower frequencies.

Are there any other benefits in frequency synthesizers using divider by 2?

Thanks

 

[biff44]

it also halves the frequency bandwidth width that the divider components have to work over.

it does a lot of bad things too, like potentially screwing up the synthesizer phase noise by 6 dB, adding spurs, adding possible instabilities, adding leakage signals that can be a radiational problem, etc.

 

[sophiante]

It is widely used i simplex transceivers. A fast transition between receiver and transmitter is possible if TX VCO is in lock on RX frequency x2. Receiver does not hear its own transmitter VCO until the divider is turned on.

 

[dtz_lou]

Hi sophiante,

Thanks for your reply. I have not thought about this. Could you be more specific or is there any paper or book from which I can have a look at it?

Thanks