Compact wideband and harmonic suppressed quadrature coupler using susceptance loaded coupled lines

Abstract

AbstractIn the paper, a novel type of quadrature coupler with the features of wideband, arbitrary harmonic suppression and small size is proposed, for the first time, by employing susceptance loaded coupled lines. Design equations are derived using the even‐odd mode decomposition analysis. The discussions on arbitrary couplings and harmonic suppressions are also investigated. For demonstration, a prototype with a second harmonic suppression was fabricated and measured. The overall size is 0.19λg × 0.27λg, which is smaller than most of the reported wideband quadrature couplers. Measurement results show that the fractional bandwidth of 40% is obtained under the condition of 15‐dB return loss/isolation, 1‐dB amplitude imbalance, and 90° ± 5° phase difference. The proposed coupler can be a good candidate for wideband applications without using the multi‐cascading and complex miniaturization method.