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HMC778 Evaluation Board some time the output power drops to -9dbm


We are using the HMC778 Evaluation board.  we have observed that some time we get  +9dbm output from the synthesizer board.  But many time we have seen that it drops to -9dbm.

Then we reset the synthesizer board  many times and again some time the output power comes back to +9dbm

This is random phenomena  we have observed. Is there any reason why sometime output power is drooping .

If its something to with grounding issues, then why just by resting the power, without  touching any hardware or cables it comes back to +9dbm again.

Please let us know what could be reason.



  • Hi Rajesh, 

    Haven't seen this before on this part. 

    Did you confirm that the synth is phase locked at +9 dBm and -9 dBm? Perhaps it's losing lock? 

    Maybe a poor solder joint on a capacitor or connector on output? 

    Maybe poor soldering to the eval board and it's heating up and shutting down? 

    Have you verified that the supply voltage 778 device and current isn't changing with the power fluctuation? If this is the case then take a close look at the LDO's and power supply section, quality of supply connections and current limit settings of power supply. 

    Best regards,