Difference between revisions of "Q Factor"
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The quality factor, also known as the "Q factor", "Q value", or just "Q", is a dimensionless parameter that characterizes the energy loss of a resonating cavity with respect to the energy stored in the cavity. | The quality factor, also known as the "Q factor", "Q value", or just "Q", is a dimensionless parameter that characterizes the energy loss of a resonating cavity with respect to the energy stored in the cavity. | ||
See the [[Wikipedia:Q factor|Wikipedia entry]] for a more general and detailed description. | See the [[Wikipedia:Q factor|Wikipedia entry]] for a more general and detailed description. | ||
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There are multiple, incompatible ways to measure this parameter, and there has been considerable debate on the NSF forums as to which is most appropriate for the EM Drive. | There are multiple, incompatible ways to measure this parameter, and there has been considerable debate on the NSF forums as to which is most appropriate for the EM Drive. | ||
| − | + | Publicized experiments have so far reported the [[#Unloaded Q factor|unloaded Q factor]]. | |
| + | However, the [[#Loaded Q factor|loaded Q factor]] is generally considered the standard technique for measuring the Q factor or closed resonant cavities outside of the EM Drive research community.{{Citation needed|{{subst:DATE}}}} | ||
There is no standard notation to distinguish between the method used. | There is no standard notation to distinguish between the method used. | ||
Revision as of 12:41, 26 August 2015
The quality factor, also known as the "Q factor", "Q value", or just "Q", is a dimensionless parameter that characterizes the energy loss of a resonating cavity with respect to the energy stored in the cavity. See the Wikipedia entry for a more general and detailed description.
There are multiple, incompatible ways to measure this parameter, and there has been considerable debate on the NSF forums as to which is most appropriate for the EM Drive. Publicized experiments have so far reported the unloaded Q factor. However, the loaded Q factor is generally considered the standard technique for measuring the Q factor or closed resonant cavities outside of the EM Drive research community.Template:Citation needed
There is no standard notation to distinguish between the method used. We use "Ql" to explicitly denote the loaded Q factor and "Qu" to denote the unloaded Q factor.
Loaded Q factor (Ql)
This is typically used for resonant cavities.
Method
Measure the S12 or S21 2-port return loss. See http://docs.lumerical.com/en/diffractive_optics_cavity_q_calculation.html.
Unloaded Q factor (Qu)
This is typically used for antennas.
Method
Measure the S11 return loss at the 3bd down bandwidth.
