HMC863ALC4 Performance issue: Output power 3 dB less than specified


we currently design a radar using HMC863ALC4.

The problem is that we could not get the spefied output power. It is about 3 dB less.

@24GHz with 6V we should see 28dBm bt could only measure 25dBm.

Is anybody out there who has experience with this device?

Is the a reference design, to get the specified values?

Any comment is highly appriciated!