Who dominated tank Q: Inductor or Varactor?

[neoflash]

In literature, authors stated that tank-Q is dominated by inductor loss. However, I found that series resistance with inductor is as small as a few tens of ohms, however, the series resistance associated with diffusion could be much greater.

Is there any theory or data, paper could help explain this?

 

[vfone]

Q = (ω*L) / Rs
So, there is not only the DC resistance (Rs) that affect the Q factor.
Increasing the inductance, theoretically Q is going higher, but there should be a compromise.
In the real world increasing the inductance you get higher Rs that will decrease the Q.

 

[khouly]

don't forget thatin RF range the skin depth of the RF signal in the inductor will increase the series resistance of the coil , and this also increase the Rs

about the varactor , by proper layout and fingring , the serise resistance and gate resistance can be minimized

khouly

 

[neoflash]

Khouly:

do you have rough number of Rs and varactor resistance?

Thanks,
Neo

don't forget thatin RF range the skin depth of the RF signal in the inductor will increase the series resistance of the coil , and this also increase the Rs

about the varactor , by proper layout and fingring , the serise resistance and gate resistance can be minimized

khouly

 

[khouly]

i don't have number right now

but check this file it is great



khouly