[SOLVED] What is "ASIC impedance measured with a 50 ohm souce" meaning?

[kent5566007]

Hi all,

I just confuse while I trying to design a matching antenna.

First of all, there are two impedance information according to ASIC spec.
1. Chip impedance (915MHz) : a-bj (Ω), with remark "Measured with a 50 Ω source impedance directly on the chip"
2. Typical assembled impedance (915MHz) : c-dj (Ω), with remark "The antenna shall be matched to this impedance"

My question is =>
A. If I design an antenna by HFSS simulation, which setup with 50Ω excitation terminal re-normalizing impedance. Therefore, I assume I should match with a-bj rather than c-dj.
B. If so, does assembled impedance is figure out by calculation?
Please correct me if I am wrong.

Thanks

 

[G4BCH]

a-bj is measured directly on the silicon.
c-bj is what you get when packaged and mounted on a pcb; match to this impedance.

 

[dick_freebird]

On-chip sounds like a VNA and appropriate Z-matched
probes (like GSG pad cage) and "assembled" adds series
R, L from wire bonds or bumps, and PCB routing to some
"boundary point". So of course the match will change,
by that.

Question is, which of the two (or neither) best matches
(heh) your physical reality.

 

[D.A.(Tony)Stewart]

http://anlage.umd.edu/Microwave%20Measurements%20for%20Personal%20Web%20Site/a_guide_to_successful_on_wafer_rf_characterisation.pdf

This is show why it is different.
G= Gnd layer
S= Sig. layer
GSG = Stripline, GS=Microstrip

The ground layer(s) adds capacitance dependant on area/ gap.
The series conductor geometry determines inductance/mm