Another broadband matching approach may use a tapered line transformer with continuously varying
characteristic impedance along its length (characteristic impedance varies continuously in a smooth
fashion).
In this case, the design obtains reflection coefficients lower than a specified tolerance at frequencies
exceeding a minimum value.
· The required length of the taper section should be about 0.5 to 1.5 of wavelength.
A different narrow-band approach involves the insertion of a shunt imaginary admittance on the line.
Often, the admittance is realized with a section (or stub) of transmission line and the technique is
commonly known as stub matching. The end of the stub line is short-circuited or open-circuited, in
order to realize an imaginary admittance.
A second narrow-band example involves the insertion of series impedance (stub) along the line.