Hi,

I am designing a LNA for 4GHz band. I am having a problem with inductor of lets say 5nH value which i am using as DC short. With ideal inductor the LNA circuit gives accurate results as i expect. But when i replace ideal inductor with real inductor i get in to problem. To analyze the inductor, i simulated it separately. Plotted its impedance vs Frequency graph and it clearly shows me that at frequency of interest inductor is actually behaving more like a capacitor rather than inductor. Inductor resonant frequency is around 10 GHz but around 4 GHz it gets a small dip and than it starts rising again (Like an inductor impedance should with increase in frequency) till 10 GHz and then falls again. Also, its Q factor is really low at 4 GHz.

1-If any one can suggest how to make inductor behave like an inductor at my desired 4 GHz frequncy and improve its Q value ?

2- My second question is related to layout design rules. If anyone can point me to any post/document where i can read about rules and best practices about how to place components from RFin to RFout to make sure that parasitics does not effect the circuit RF performance a lot. It would be really nice.


Really looking forward to some good feedback from the folks here.

/SC

Hi,

Thanks a lot. I will try the things you have mentioned next week. If i still couldnt solve it. I will post the inductor layout along with its response. Thanks a lot for the help. Paper looks really helpful.

/SC