For a unit current, this is then equal to the mutual inductance between the coupling loop and the nth mode.
Mutual inductance or the magnetic flux through the coupling loop plays an important role in the analysis of the coupling.
Some of the magnetic flux lines through the coupling loop do not couple with the [TE.
In the conventional cavity, several coupling methods such as: 1) two coupling holes at the upper end plate  and 2) two coupling loops in the middle of the cavity wall , etc.
Because the voltage induced into a coupling loop
is a function of the frequency, loop area, and circuit bandwidth, keep wide bandwidth loop areas small.
A second tuner is used for matching the coupling loop to 50 |ohms~.
The output coupling loop and the piston used for matching it were not accounted for in the model.
l1~ = the electrical length from the coupling loop short circuit to the start of coupling along the loop (rad)
beta~ = the propagation constant for the coupling loop as a TEM transmission line (rad/m)
This accounts for the coupling loop being substantially long at microwave frequencies and, therefore, for the loop to have a nonconstant current magnitude along the loop.
The self inductance of the coupling loop is modeled as a high impedance transmission line whose length is equal to that of the coupling loop L3.
s] value and diameter are known, the coupling loop
diameter for the input, output and interstages can be calculated.