GPS Antenna Power leaking into GPS input

Hello,

I am using SIM808 in my design and I am using a active GPS antenna.
I feed the antenna via a 10 Ohms resistor and a 27 nH inductance, just as described in the Datasheet (HW reference, page 55, Figure 49).

Although this was working well with one device (consuming about 30 mA with the Antenna attached), I have another device exactly buildup alike and it consumes 500 mA and they are directly going into SIM808 (I disconnected everything else, so this has to be the sink).

Why is that? Am I missing something?

Thanks in advance.

Are you designing a PCB?

Yes i did. Thanks for your answer

Well, how many layers do you have in your PCB? How have you arranged them? Perhaps you should change the location of you layers? I am a beginner in PCB design and can’t help you but you need to provide more details so that someone who has designed PCBs before can help you.

Thanks for your response. I have a six layer board and the other boards (exactly the same) work well. Unfortuanetly I cannot exchange the SIM808 on the board. There is also no short circuit, when I measure resistance when the modem is off it is in the MegOhm Range.

Maybe a faulty modem? I think ill leave it for now if this stays a single issue