High rejection L-resonator notch filter with flexible electromagnetic coupling and second harmonic suppression using high dielectric overlays

摘要

The recent technique of electromagnetic (EM) coupling is used here for the microstrip notch filter It employs the normal lambda(g)/2 L-shaped microstrip resonator as a transmission type rejection filter for 2.4 GHz with its lambda(g)/4 arm coupled electromagnetically to the 50 Omega transmission line exactly under it. The L-resonator and feed line are on two separate TMM4 (epsilon(r) = 4.5) substrates. The well-known flexibility of EM coupling can be used in various ways, e.g., for coupling many resonators to a single line. In addition, to allow a wider and symmetric pass band second-harmonic suppression has also been employed, using different dielectric overlays (TMM4 and Al2O3). The overlay thickness is adjusted to effectively equalize the even- and odd-mode phase velocities. The overlay of Al2O3 with epsilon(r) higher than that of substrates is found to give better results. The experimental and simulation results are in good agreement.