a problem about GPS Front-end match,thx.
see the PIC i uplaoded.
anybody can explain this RF match method. and whether other method will be better?
the simulation result is show as follow with Agilent ADS
the 22 pf cap act as RF short circuit in this band , so its effect is minimal in the matching , u can say it is DC blocking cap , the most effective are L and 1.8 pF C
to check the matching performance , u need to get the input impedance of the IC , and simulate it with the matching circuit
khouly
I think the 1.8pf is too large to match 1.57G gps signal.
You know the purpose of matching is to get 50Ohm input impedance, and 10nH is necessary for matching to 1.57Ghz with on chip inductor and parasitic capacitor.
So I think the external 1.8pf is not essential.
Added after 4 minutes:
Usually the output impedence of filter is 50Ohm. and 1.8pf impendence is about 50Ohm, so the total input impendence should be less than 50Ohm.
Beside, as the result showed, S11 is too large. and it should be less than -10dB at 1.57GHz.
Try to realize this S11.
Added after 4 minutes:
22pf is empleyed for ac couple, so I think it is too small.
I think it should large than 200pf.
R=1/(2*pi*Fin)
it should be less than 1% of 50Ohm.