A Star-Shaped Decoupling Network With No Crossovers for Broadband Monopole Arrays

A star-shaped decoupling network (DN) is proposed to reduce mutual coupling between broadband array elements. The novel architecture avoids meandering or jumper wiring in crossover DN and reduces the number of lumped components. Moreover, the proposed DN can be applied to both square and triangular manifolds. Taking a rectangular 3×3 monopole array as an example, it achieves an operating bandwidth of 3.3–4.1 GHz, which covers major 5G mid-bands. Within this frequency range, the isolation between the array elements is improved by 14 dB on average, and the average total efficiency of the array is also increased by ~12%. This architecture is readily expanded to larger arrays, such as8 × 8or larger layouts. Taking compact 4×4 and 8×8 triangular monopole arrays as examples, an operating bandwidth of 3.4–4.1 GHz was achieved, which is almost the same as the3 × 3one with identical array elements. Within this band, the isolation between adjacent elements improved by an average of 7 dB, while the average efficiency increased by ~6%. Those results validate the effectiveness of the proposed star-shaped DN, which supports various potential applications in 5G massive multiple-input–multiple-output (mMIMO) systems.