Design of a Compact Planar Transmission Line for Miniaturized Rat-Race Coupler With Harmonics Suppression

This paper presents an elegant yet straightforward design procedure for a compact rat-race coupler (RRC) with extended harmonic suppression. The coupler’s conventional ?/4 transmission lines (TLs) are replaced by specialized TL that offers significant size reduction and elimination capabilities in the proposed approach. is verified through theoretical, circuit, electromagnetic (EM) analyses, showing excellent agreement among different analyses measured results. circuit EM results show replicates same frequency behaviour of one at 1.8 GHz while enables suppression up to 7th 74%. According results, RRC has fractional bandwidth 20%, input insertion losses around 0.2 dB isolation level better than 35 dB. Furthermore, total footprint only 31.7 mm × 15.9 mm, corresponding 0.28 ? 0.14 ?, where guided wavelength GHz.