Design of a compact microstrip coupler with harmonics suppression using resonator and meandered lines

Abstract

In this paper, a new coupler is designed using proposed resonator cell and meandered lines. The proposed coupler correctly works at 1 GHz operating frequency. The compact size of the presented resonator is only 10 mm x 6.8 mm (0.31λx0.46λ). The presented resonator creates two 2 GHz and 3 GHz transmission zeros with high attenuation level. By proposing this structure second and third harmonics of the proposed coupler are suppressed with high attenuation level. The insertion loss parameters for two output ports of the proposed coupler are less than 0.1 dB. The S14 and S11 parameters are below -20 dB at operating frequency. The proposed design can suppress second up to fifth harmonics with high attenuation level. The overall occupied size of the proposed coupler is only 34.2 mm x 33.4 mm (0.141λx0.142λ), which is only 33% of the typical coupler size at 1 GHz.