A miniaturized wideband four‐way filtering power divider (FPD) is presented in this article. It is composed of unequal‐width three‐coupled‐lines (TCLs), stepped‐impedance open‐circuited stubs, and isolation resistors. By using two groups of the unequal‐width TCLs and the stepped‐impedance open‐circuited stubs, size reduced four‐way FPD with wideband filtering responses and out‐of‐band rejection is realized. Besides, good output ports matching and isolation are obtained by inserting two types of air‐bridge resistors. In the theoretical analysis section, the impedance matrix of the unequal‐width TCL is introduced, for the first time, and rigorous closed‐form design equations for the proposed FPD are also derived. Moreover, the methodology for computer‐aided design is given based on the design equations. For demonstration, a prototype operating at 1.5 GHz is designed, fabricated, and measured. The measured results validate the 80% bandwidth with more than 17 dB out‐of‐band rejection, more than 14 dB isolation and more than 15 dB return loss at all output ports. Compare with the reported four‐way FPD with similar bandwidth, a size reduction of 74% is obtained.

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In 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 0.19λ g  0.27λ g , 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 AE 5 phase difference. The proposed coupler can be a good candidate for wideband applications without using the multi-cascading and complex miniaturization method.