Although the system is not perfectly symmetric due to the orientations of the open matching stubs
, the coupling coefficients [S.sub.12] and [S.sub.13] are almost equal to each other.
Series, as well as shunt matching stubs
, can be realized and used to reduce the size of planar passive elements.
Finding the impedance [Z.sub.s] = [R.sub.s] + j[X.sub.s] by its real and imaginary parts, [R.sub.s] and [X.sub.s] respectively, is made by applying the method of matching stubs
on the antenna feedline.
The quarter-wavelength RF traps introduce a substantial mismatch for the LO signal so additional LO matching stubs
are always required.