s82223
Newbie level 3
Hi all,
I recently studied about the PLL and synthesizer and got a LMX2531 EVM.
When measuring the tuning voltage vs output frequency, I found that the frequency decreasing as tuning voltage rises i.e. negative Kvco. And the result is in the following figure.
To the best of my knowledge, typical Kvco is positive because the capacitance of varactor diode is reduced as the tuning voltage increasing which will increase the oscillation frequency.
What is the possible reason for this result?
I recently studied about the PLL and synthesizer and got a LMX2531 EVM.
When measuring the tuning voltage vs output frequency, I found that the frequency decreasing as tuning voltage rises i.e. negative Kvco. And the result is in the following figure.
To the best of my knowledge, typical Kvco is positive because the capacitance of varactor diode is reduced as the tuning voltage increasing which will increase the oscillation frequency.
What is the possible reason for this result?