# Quality factor of an inductor (Sonnet)

#### omar32s

Oct 5, 2022
1
When I create a series (floating) 2-port inductor in sonnet I know it is equivalent to a pi model where we have a series R and series L and shunt components at the 2 ports.

after eming the inductor using sonnet, I knew that inductance 2 represents the series inductance and same for resistance 2 also represents series resistance.

1) I wanted to know what is the quality factor of that (series/floating) inductor, as Q represents quality factor if port 2 is grounded and Q3 represents quality factor for differential inductor, but how to calculate quality factor for the floating inductor ?

2) After I emmed an inductor I found that resistance 2 has negative value at some frequencies is that even possible or did I do something wrong ?
I have added a photo at which resistance 2 has a negative value with frequency, and would it be in that case the quality factor (w*L2/R2) even if R2 has a negative value ? or what should be the quality factor of a 2 port floating inductor ?

#### Attachments

• inductor.PNG
7.5 KB · Views: 3
• pi.PNG
2.5 KB · Views: 3
• Q.PNG
14.9 KB · Views: 3

#### walishahid333

Nov 1, 2022
8
The Q factor can be applied to an inductor just as it can to a resonant circuit containing inductance, capacitance and resistance.

An inductor Q is a valuable quantity. Often inductors may be thought of as having a pure inductance, whereas in reality they have some resistance.

This resistance causes energy loss and hence the inductor Q is reduced. In fact the inductor resistance is one of the major performance limiting factors for an inductor.

As a result the level of the inductor Q gives a good indication of the overall performance of the component, and it is a factor that is widely used within RF design.

#### JayBS

Feb 19, 2023
1
I think what you're measuring is the shunt capacitance to ground of your inductor. Best measure the Q by connecting it shunt to ground, not floating.

Replies
1
Views
1K
Replies
2
Views
1K
Replies
4
Views
1K
Replies
3
Views
1K
Replies
3
Views
498