how to increase q of a coil
oasis4355 said:
Hi all,
I'm wondering how to increase Q factor of an LC tank,
If i change the reactance of the LC tank, won't be this affecting the frequency of interest?
Thanks in advance
Adjusting value on L and C affect frequency, but not if you make lower resistance in circurit, Q = reactance/resistance
Only way to make higher Q-value is make lowest possible resistance in inductance (capacitance have already low loss in most case, but use High Q-capacitanse if you can)
air-winding inductance with round copper wire can give Q around 200-300 as best.
if you wind inductance with copper folie (ex. 2-3 mm wide 35 um strip take from unetched PCB) you can make around Q = 1000 - 1500 depend of thin thickness and wide area 'wire' make lower skin effect loss in inductance. we talk now of 10-20 turns single layer inductance - not multilayer.
in high valued inductance (many nH ) with many multilayer turns, you must using litz-thread (expensive...)
you can also using inductance with magnetic core to shorten legth of copper wire, but in this case is always compromissing between usable frequency range, size, risk for magnetic saturate in core, non liniarity and loss in core.