Wideband Millimeter‐Wave Balun‐Diplexer Based on a Novel Coupled Marchand Architecture for Compact Footprint and Phased‐Array Integration

ABSTRACT This letter presents the first reported wideband balun‐diplexer for mm‐wave applications, designed for shared‐aperture full‐duplex array systems. By integrating balun and diplexer functionalities in a single component, we enable per‐element self‐interference suppression, while also facilitating the interface between the balanced feed of the antenna and the unbalanced ports found in many beamformer chips. A novel coupled Marchand topology enables a compact footprint compatible with the strict lattice constraints of grating‐lobe‐free phased arrays, and facilitates integration with the multilayer stackups commonly used in phased‐array systems. The component targets K/Ka‐band SatCom applications, with two 3.5‐GHz‐wide bands centered at 19 and 29 GHz, respectively. Fabricated on a Megtron 6 substrate, the prototype achieves a minimum TX–RX isolation of 20 dB, insertion losses of 1.5 and 2.3 dB in the lower/higher bands, respectively, and a common‐mode rejection ratio exceeding 19 dB in both bands. The results confirm the feasibility of the proposed concept and demonstrate the first realization of a compact, mm‐wave balun‐diplexer for high‐frequency phased‐array integration.