[Yokogawa, Sugimoto, Enomoto]
(work on Oct 12 and today)
We measured the frequency noise (or equivalently phase noise) of one of the prototype low noise VCOs, S1809060.
The following plot shows the ASD of the frequency noise.
This is not as good as I expected but better than that of G&H's by a factor of 10.
= How we measured =
Basically it is same as we did in 5416.
Output of the VCO was comapred with stable 80 MHz signal with the PFD. The output of the PFD was sent to a common mode servo (PLL ver) and its output was fed back to Vtune port of the VCO. The output of the common mode servo was around 1.5 V (see 6544).
We measured the ASD of the output of the common mode servo, and by just multiplying the actuator efficiency of 0.42 MHz/V to it, calculated the ASD of frequency noise. (Measured UGF of this phase lock loop was 10 kHz, so this calculation is valid).
= Note =
We did this measurement on last friday, but I noticed that the operating point of the VCO was not good (~ 0.8V) so I repeated the measurement with the operating point of 1.5 V today.