MAX2606 VCO for FM modulation
I am using MAX2606 as the VCO of my FM modulator project after I got lot of suggestions to use it from edaboard members.
For frequency stability there is a PLL in this modulator. But this VCO has a single fixed oscillation frequency which is determined by the external inductance connected to pin #1.
Since my FM modulator has more channels (This is achieved from the programmable divided by N counter of the PLL) I need more than single fixed oscillation frequency. So how can I achieve range of frequency from MAX2606? Any suggestions?
Vary the voltage on the Vtune pin... that's the *Voltage Controlled* Part of the VCO acronym.
Hi! Thanks for the reply.
I have another problem. How I insert the modulating signal for modulation?
If you add a small modulating signal over tuninig voltage AND if you adjust the PLL filter as low as possible so that frequency daviation by modulating signal won't be sensed by PLL, you can
modulate the VCO in certain limits.
OR
You can lock the PLL for a while then leave th VCO in -free running- for a while, in this method you can modulate the VCO in this blind slot.So, transmitting can be done like
PLL-Blind(Modulation)-PLL-Blind(Modulation)-....
This is used in DECT system.Each slot is 864us but you can select these time slots as you wish.( This is valid for speech data and low rate video data)