Pls help to find an unlocking issue in PLL ckt using AD4156 and HMC587 VCO.It became unlock b/w the temperature range of +17 to +20 C.Freq is 5.5GHZ.It is working fine above and below this range.
Can you isolate the problem to see if it is the ADF4156 or the HMC587 that is failing?
At these temperature , V TUNE voltage from AD4156 varies entire range and VCO sweeps frequency form 3 GHZ to 8 GHZ but not locking to the desired frequency.The mux out pin configured as lock detector and it is not becomes high at these temperature range.After this particular temperature window,it automatically locks and will get a stable output.Phase comparison for AD4156 given thru 16MHZ crystal osc.Also I replaced this ,but still problem is there.Pls suggest some solution,Sir.
Finally I could find out the problem.The pad of LNA detached (very very small portion) from the body.The image attached is taken using a magnifier having 110 zoom.HMC 587 output is divided using stripline power divider and given to ADF4156 and LNA.When particular temperature window some mismatch happening and reflects the power from that point and it reduces overall power level.At that particular time ADF4156 is not getting sufficient level.Replaced LNA and solved the issue.
Thank you for the suggestions and feedback