How to select the the external inductor at Low RF frequency, 80 MHz ~ ?
VCO frequency is 80MHz *2*2 = 320MHz
Select inductor (Lext) is about 13nH ?
Is it correct ?
Datasheet say following,
"The second VCO, the external inductor VCO, uses an external inductor as part of its LC tank and supports the RF
operating band of 80 MHz to 650 MHz."
Figure 37. Direct RF Output vs. Total External Inductance
Figure 6. ADF7020-1, ADF7021, and ADF7021-N Frequency vs. LEXT (L3) Using EVAL-ADF7020-1DBZx , EVAL-ADF7021DBZx, or EVAL-ADF7021-NDBZx Layout