What cause the modulation spectrum poor when pressing shieldcan?

[John_li]

Dear friends,
I measured the modulation spectrum of mobile,it is ok without pressing the shielcan .But when i pressed sheidcan or use the jig(ABS material) press the shiedcan for fixing mobile PCBA test,modulation spectrum is poor of +/-200KHz.I do not know what is the root cause.Anybody can kindly help me?
Thanks,

 

[biff44]

Re: What cause the modulation sprctrum poor when pressing shieldcan?

shield can no longer making good ground contact when you press it.

 

[John_li]

Re: What cause the modulation sprctrum poor when pressing shieldcan?

I touched the shielcan(transceiver IC with PA IC) tenderly,also can cause this case.It is normal?Also when the jig that fix(ABS material jig) the PCBA of mobile can cause this case.I used another model mobile,it is ok with the same operation.

 

[tony_lth]

Or you can put some absorb materials on the inner top of the shieldcan.

 

[FvM]

post #3 suggests your talking about a mobile phone, but nothing is said clearly. If it's a mobile phone, I assume it's broken.

 

[John_li]

post #3 suggests your talking about a mobile phone, but nothing is said clearly. If it's a mobile phone, I assume it's broken.

It is mobile phone test.PA and transceiver are in the same shieldcan,pressing tenderly top of shieldcan or test jig(ABS material),modulation spectrum is poor of +/-200KHz.i do not know whether it is enough?