I have an ADL5519 evaluation board, and I noticed that, if I feed a low level signal (say 1GHz frequency, -120dBm up to -60dBm) into INHA (or terminate INHA in 50 ohms) I can see a recurring output glitch on OUTA (see scope captures below). As I increase the input power, the amplitude of the glitches decreases, but they do not disappear.
I am trying to use the detector to recover low frequency pulse train patterns, and this glitch is in the passband of the data I am trying to extract.
You are detecting noise from your enviornment. I tooka device into the lab and used a battery ( to eliminate power supply noise) and experienced a similar effect. Ithen took the device into a shielded room and the output was clear.