Testing a differential antenna using network analyser

[Avala Lokesh]

Hi,

I designed an on chip antenna in CMOS for 20G. Now I just want to test it. As it is on chip I wanted to use gsg probes for testing with network analyser. Can anyone help me by telling what kind of probe(gsg or gssg or etc ) can be used to measure a dipole antenna with differential input to test with network analyser. I want to measure the S11 and radiation pattern of the antenna.

Any help will be appreciated.
Thanks,

 

[volker@muehlhaus]

If you measure the differential antenna with a single ended GSG probe, without having a balun on chip, you will get incorrect results because radiation from the probe ground will become part of the antenna behaviour. I recently had a similar case (PCB, not on chip) and it was difficult to get meaningful results because any change in coax feed (touching coax ground etc) was changing everything. Problem solved completely by adding a balun.

You really should ensure differential excitation. I don't know if the GSSG probe configuration can do this (power splitter and 180° delay line, to create signals with 180° phase difference) or if you better add a balun to the chip.