EV-ADF41513SD2Z lock problem

Hi,

Has the loop filter been designed for this 20MHz reference frequency? If the same filter has been used as for the 100MHz, there may be an instability issue. If the default on-boards 100MHz reference is used, is it working ok?

If this external 20MHz reference is used, ADISimPLL can be used to design an appropriate loop filter. 

Another consideration would be to ensure that your reference frequency is within the necessary amplitude range. 

Thanks,

Kieran 

Hi kieranb

I have found that the reason for the unlocking problem is caused by the VCO - HMC733LC4B on the EVB

at some frequencies the VCO Oscillate at half frequency. This phenomena causing the the Synth on the EVB to be unlocked.

Hi,

Yes that was an issue that was highlighted previously. Below is a detailed explanation on the issue: 

Behaviour of HMC733 that seem to be out-of-specs - Q&A - RF and Microwave - EngineerZone

As a work around the ADF5709 can be used. This is based on the HMC733, with a redesigned output buffer.

Regards,

Kieran